Dissertations / Theses on the topic 'Internal Combustion Engine - Piston'

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 143-147).
Ever-increasing demand for reduction of the undesirable emissions from the internal combustion engines propels broader effort in auto industry to design more fuel efficient engines. One of the major focuses is the reduction of engine mechanical losses, to which the friction of the piston skirt is one important contributor. Yet there lacks a sufficient understanding of the skirt lubrication behavior to effectively optimize the piston skirt system in practice. The ultimate goal of this work is to develop a comprehensive model to advance the predictability of the skirt friction while integrating all the dynamic behavior of the piston secondary motion and the structural deformation of the piston skirt and cylinder liner. Major contributions of this work are analysis of and development of a model for the oil transport and exchange of the piston skirt region and its surroundings. The new oil transport model is composed with two elements. First, the oil scraped into the chamfer region by the oil control ring during a down-stroke is tracked and its accumulation and release to the skirt region are modeled. Second, oil separation and re-attachment are allowed in the skirt region, breaking conventional full-attachment assumption in lubrication studies. The new oil transport model together with hydrodynamic and boundary lubrication model were coupled with piston secondary motion and structural deformation of the piston skirt and cylinder liner. For numerical efficiency and physics clarity, we used different discretization for the lubrication from the structural deformation. The final model is robust and efficient. The discussion of the model results is focused mainly on the oil transport. There exist a general pattern in available oil for skirt lubrication, namely, skirt tends to be starved when it travels at the upper portion of a stroke. Comparison with visualization experiment for oil accumulation patterns show consistency between model prediction and observation. This work represents a major step forward to realistically predicting skirt friction and the influence of all the relevant design and operational parameters. However, oil supply to the region below the piston skirt can largely influence the outcome of the friction prediction and its mechanism is system dependent. Additionally, simple treatment of the oil transport in the current model is merely a first step to modeling the complex fluid problems involved. Improvements of this model based on application and further analysis will make it a more powerful engineering tool to optimize the skirt system to minimize its undesirable outputs.
by Dongfang Bai.
Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2020
Cataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages 120-121).
The piston pin joins the piston and the connecting rod to transfer the linear force on the piston to rotate the crankshaft that is the eventual power outlet of the engine. The interfaces between the piston pin and the pin bore as well as the connecting rod small end are one of the most heavily loaded tribo pairs in engines. Piston pin seizure still occurs often in the engine development and the solution often comes from applying expensive coatings. Furthermore, it has been found that the friction loss associated with the pin can be a significant contributor to the total engine mechanical loss. Yet, there lacks a basic understanding of the lubrication behavior of the pin interfaces. This work is aimed to develop a piston pin lubrication model with consideration of all the important mechanical processes. The model predicts the dynamics of the pin and the lubrication of the interfaces between the pin and pin bore as well as small end.
The model couples the dynamics of the pin with the structural deformation of the mating parts, the hydrodynamic and boundary lubrication of all the interfaces, and oil transport. The model is successfully implemented with an efficient and robust numerical solver with the second order accuracy to compute this highly stiff system. The preliminary results applying the model to a gasoline engine show that the boundary lubrication is the predominant contributor to the total friction. As a result, the interface with more asperity contact tends to hold the pin with it. Thus, the pin friction loss is coming from the interface with less contact. Solely from friction reduction point of view, ensuring efficient hydrodynamics lubrication in one interface is sufficient.
Furthermore, as the heavy load is supported in several small areas, mechanical and thermal deformation of all the parts are critical to load distribution, oil transport, and the generation of hydrodynamic and asperity contact pressure, providing the necessity of the elements integrated in the model. This work represents the first step to establishing a more comprehensive engineering model that helps the industry understand the pin lubrication and find cost-effective solutions to overcome the existing challenges.
by Zhen Meng.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering

Thesis (M.S.)--West Virginia University, 1998.
Title from document title page. Document formatted into pages; contains x, 82 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 69-70).

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 88-91).
With the increasing interest in decreasing the environmental impact from internal combustion engines as well as increasing the fuel efficiency has led to deeper investigation into the components of the engine. The mechanical friction in an engine is a major concern, any improvements or reductions in friction can have large implication on the' efficiency of the engines. This thesis focuses on the piston/ ring pack assembly and its contribution to friction. It investigates several key components and trends in friction for the piston/ ring pack assembly, specifically the trends related to the oil control ring and the liner surface. The Floating Liner Engine is used in this study to isolate results from different components. The data collected can be used for comparative analysis and to identify trends in the friction trace. The thesis starts with describing the Floating Liner Engine system at MIT in detail. Both the data collection and the hardware systems are described as well as the test capabilities of the Floating Liner Engine. The results used in the thesis have been collected using the motoring condition. The oil control ring plays a key role in controlling the supply of oil to the top two rings and hence has a higher tension that the top two rings. This leads to the oil control ring having a significant contribution to the total friction of the system. The two most prevalent oil control rings used in the industry are the twin land oil control ring (TLOCR) and the three piece oil control ring (TPOCR). The thesis investigates the effect of changing liner roughness on the friction of the TLOCR. A comparison between the TLOCR and the TPOCR is also performed using the same liner surfaces. The results from these studies show a marked difference between the friction traces from the two oil control rings.
by Sarthak Vaish.
S.M.

Internal combustion (IC) engines used in road transport applications employ pistons to convert gas pressure into mechanical work. Frictional losses abound within IC engines, where only 38- 51% of available fuel energy results in useful mechanical work. Piston-bore and ring-bore conjunctions are fairly equally responsible for circa 30% of all engine friction - equivalent to 1.6% of the input fuel each. Therefore, reduction in piston assembly friction would have a direct impact on specific performance and / or fuel consumption. In motorsport, power outputs and duty cycles greatly exceed road applications. Consequently, these engines have a shorter useful life and a high premium is placed on measures which would increase the output power without further reducing engine life. Reduction of friction offers such an opportunity, which may be achieved by improved tribological design in terms of reduced contact area or enhanced lubrication or both. However, the developments in the motorsport sector are typically reactive due to a lack of relative performance or an ad-hoc reliance, based upon a limited number of actual engine tests in order to determine if any improvement can be achieved as the result of some predetermined action. A representative scientific model generally does not exist and as such, investigated parameters are often driven by the supply chain with the promise of improvement. In cylinder investigations are usually limited to bore surface finish, bore and piston geometrical form, piston skirt coatings and the lubricant employed. Of these investigated areas newly emerging surface coatings are arguably seen as predominate. This thesis highlights a scientific approach which has been developed to optimise piston-bore performance. Pre-existing methods of screening and benchmarking alterations have been retained such as engine testing. However, this has been placed in the context of validation of scientifically driven development. A multi-physics numerical model is developed, which combines piston inertial dynamics, as well as thermo-structural strains within a thermoelastohydrodynamic tribological framework. Experimental tests were performed to validate the findings of numerical models. These tests include film thickness measurement and incylinder friction measurement, as well as the numerically-indicated beneficial surface modifications. Experimental testing was performed on an in-house motored engine at Capricorn Automotive, a dynamometer mounted single-cylinder 'fired' engine at Loughborough University, as well as on other engines belonging to third party clients of Capricorn. The diversity of tests was to ascertain the generic nature of any findings. The multi-physics multi-scale combined numerical-experimental investigation is the main contribution of this thesis to knowledge. One major finding of the thesis is the significant role that bulk thermo-structural deformation makes on the contact conformity of piston skirt to cylinder liner contact, thus advising piston skirt design. Another key finding is the beneficial role of textured surfaces in the retention of reservoirs of lubricant, thus reducing friction.

In questo lavoro di tesi mi soffermerò, inizialmente, sul possibile futuro dei motori a combustione interna e sulle tecnologie innovative già presenti sul mercato (HCCI, VCR, ecc.). Mi concentrerò, poi, sull’analisi di due sistemi innovativi come gli Opposed Piston Engine (OPE) e gli Split Cycle Combustion Engine (SCCE).

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.
Page 172 blank.
Includes bibliographical references (p. 129-130).
A model was developed to study engine oil vaporization and oil vapor transport in the piston ring pack of internal combustion engines. With the assumption that the multi-grade oil can be modeled as a compound of several distinct paraffin hydrocarbons, a set of equations governing the oil vapor density variations were derived by applying the mass conservation law to the amount of oil vaporized from the piston and the amount of oil vapor transported within the piston ring pack. The model was applied to a heavy-duty diesel engine. First, the case with the maximum oil supply to all the piston regions was studied and the results showed that, under this condition, the oil consumption from vaporization alone was far greater than the typical oil consumption value measured in the engine. Then, to show the contribution of oil vaporization to oil consumption and the dependence of vaporization on oil supply to different regions, different lubrication conditions for the high temperature regions of the piston were studied. Finally, a liquid oil transport model was integrated with this oil vaporization model in order to investigate the change of oil composition on the crown land with each engine cycle and the contribution of liquid-phase oil and vapor-phase oil to the total oil consumption under a fixed liquid oil supply rate to the crown land.
by Yeunwoo Cho.
S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.
Includes bibliographical references (p. 113-115).
Piston ring friction losses account for approximately 20% of the total mechanical losses in modern internal combustion engines. A reduction in piston ring friction would therefore result in higher efficiency, lower fuel consumption and reduced emissions. The goal of this study was to develop low-friction piston ring designs to improve engine efficiency, without adversely affecting oil consumption, blowby, wear, or cost. These are desirable objectives for today's engine manufacturers as they strive to improve engine performance while trying to meet increasingly stringent emissions regulations. Using an existing piston ring friction and lubrication model, the main contributors to friction in modern internal combustion engines were identified as the top ring around top dead center of the compression/expansion strokes and the oil control ring throughout the engine cycle. Model predictions indicated that the top ring friction could be reduced by implementing a skewed barrel profile design or an upward piston groove tilt design, and oil control ring friction could be reduced by decreasing ring tension. An increase in groove wear was predicted to occur with the upward piston groove tilt design, which could be eliminated by the introduction of a positive static twist on the top ring. An increase in oil consumption was predicted to occur with the low-tension oil control ring design, which could be mitigated either by the introduction of a negative static twist on the second ring, or by the implementation of the skewed barrel top ring design. Model predictions indicated that by combining the low-friction designs, a reduction in piston ring pack friction of 30-35% could be achieved, without an increase in blowby, wear, or oil consumption.
(cont.) Experimental results conducted on a full-scale natural gas power generation engine supported the model predictions for the low-tension oil control ring design. The predicted reduction in piston ring friction would translate to a 0.5-1% increase in brake thermal efficiency, which would result in a significant improvement in fuel economy and a substantial reduction in emissions over the life of the engine.
by Grant Smedley.
S.M.

A rolling piston engine, operating according to a novel thermodynamic cycle is designed. Thermodynamic and structural analysis of this novel engine is carried out and thermodynamic and structural variables of the engine were calculated. The losses in the engine, friction and leakage were calculated and their effects on the engine were demonstrated.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 169-173).
Characterizing the piston ring behavior is inherently associated with the oil consumption, friction, wear and blow-by in internal combustion engines. This behavior varies along the ring's circumference and determining these variations is of utmost importance for developing ring-packs achieving desired performances in terms of sealing and conformability. This study based on straight beam model was already developed but does not consider the lubrication sub-models, the tip gap effects and the characterization of the ring free shape based on any final closed shape. In this work, three numerical curved beam based models were developed to study the performance of the piston ring-pack. The conformability model was developed to characterize the behavior of the ring within the engine. In this model, the curved beam model is adopted with considering ring-bore and ring-groove interactions. This interactions include asperity and lubrication forces. Besides, gas forces are included to the model along with the inertia and initial ring tangential load. In this model we also allow for bore, groove upper and lower flanks thermal distortion. We also take into account the thermal expansion effect of the ring and the temperature gradient from inner diameter (ID) to outer diameter (OD) effects. The piston secondary motion and the variation of oil viscosity on the liner with its temperature in addition to the existence of fuel and the different hydrodynamic cases (Partially and fully flooded cases) are considered as well. This model revealed the ring position relative to the groove depending on the friction, inertia and gas pressures. It also characterizes the effect of non-uniform oil distribution on the liner and groove flanks. Finally, the ring gap position within a distorted bore also reveals the sealing performance of the ring. Using the curved beam model we also developed a module determining the twist calculation under fix ID or OD constraint. The static twist is an experimental characterization of the ring during which the user taps on the ring till there is a minimum clearance between the ring lowest point and the lower plate all over the ring's circumference but without any force contact. Our last model includes four sub-models that relate the ring free shape, its final shape when subjected to a constant radial pressure (this final shape is called ovality) and the force distribution in circular bore. Knowing one of these distribution, this model determines the other two. This tool is useful in the sense that the characterization of the ring is carried out by measuring its ovality which is more accurate than measuring its free shape or force distribution in circular bore. Thus, having a model that takes the ovality as an input is more convenient and useful based on the experiments carried out to characterize the ring.
by Mohamed Aziz Bhouri.
S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 169-173).
Characterizing the piston ring behavior is inherently associated with the oil consumption, friction, wear and blow-by in internal combustion engines. This behavior varies along the ring's circumference and determining these variations is of utmost importance for developing ring-packs achieving desired performances in terms of sealing and conformability. This study based on straight beam model was already developed but does not consider the lubrication sub-models, the tip gap effects and the characterization of the ring free shape based on any final closed shape. In this work, three numerical curved beam based models were developed to study the performance of the piston ring-pack. The conformability model was developed to characterize the behavior of the ring within the engine. In this model, the curved beam model is adopted with considering ring-bore and ring-groove interactions. This interactions include asperity and lubrication forces. Besides, gas forces are included to the model along with the inertia and initial ring tangential load. In this model we also allow for bore, groove upper and lower flanks thermal distortion. We also take into account the thermal expansion effect of the ring and the temperature gradient from inner diameter (ID) to outer diameter (OD) effects. The piston secondary motion and the variation of oil viscosity on the liner with its temperature in addition to the existence of fuel and the different hydrodynamic cases (Partially and fully flooded cases) are considered as well. This model revealed the ring position relative to the groove depending on the friction, inertia and gas pressures. It also characterizes the effect of non-uniform oil distribution on the liner and groove flanks. Finally, the ring gap position within a distorted bore also reveals the sealing performance of the ring. Using the curved beam model we also developed a module determining the twist calculation under fix ID or OD constraint. The static twist is an experimental characterization of the ring during which the user taps on the ring till there is a minimum clearance between the ring lowest point and the lower plate all over the ring's circumference but without any force contact. Our last model includes four sub-models that relate the ring free shape, its final shape when subjected to a constant radial pressure (this final shape is called ovality) and the force distribution in circular bore. Knowing one of these distribution, this model determines the other two. This tool is useful in the sense that the characterization of the ring is carried out by measuring its ovality which is more accurate than measuring its free shape or force distribution in circular bore. Thus, having a model that takes the ovality as an input is more convenient and useful based on the experiments carried out to characterize the ring.
by Mohamed Aziz Bhouri.
S.M.

During the course of this project, a digital radio telemetry system has been designed and shown to be capable of measuring parameters from the piston of an internal combustion engine, under load. The impetus for the work stems from the need to sample the appropriate data required for oil degradation analysis and the unavailability of system to perform such sampling. The prototype system was designed for installation within a small Norton Villiers C-30 industrial engine. This choice of engine presented significant design challenges due to the small size of the engine (components and construction) and the crankcase environment. These challenges were manifest in the choice of carrier frequency, antenna size and location, modulation scheme, data encoding scheme, signal attenuation, error checking and correction, choice of components, manufacturing techniques and physical mounting to reciprocating parts. In order to overcome these challenges detailed analysis of the radio frequency spectrum was undertaken in order to minimise attenuation from mechanisms such as, absorption, reflection, motion, spatial arrangement and noise. Another aspect of the project concerned the development of a flexible modus operandi in order to facilitate a number of sampling regimes. In order to achieve such flexibility a two-way communication protocol was implemented enabling the sampling system to be programmed into a particular mode of operation, while in use. Additionally the system was designed to accommodate the range of signals output from most transducer devices. The sampling capabilities of the prototype system were extended by enabling the system to support multiple transducers providing a mixture of output signals; for example both analogue and digital signals have been sampled. Additionally, a facility to sample data in response to triggering stimuli has been tested; specifically a sampling trigger may be derived from the motion of the piston via an accelerometer. Ancillary components, such as interface hardware and software, have been developed which are suitable for the recording of data accessed by the system. This work has demonstrated that multi-transducer, mixed signal monitoring of piston parameters, (such as temperature, acceleration etc.) using a two-way, programmable, digital radio frequency telemetry system is not only possible but provides a means for more advanced instrumentation.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000.
Includes bibliographical references (leaves 100-101).
The reciprocating motion of the piston of an internal combustion engine in the vertical plane is referred to as its primary motion, and it is this primary motion that produces power in the engine. Due to the fact that there is a clearance between the piston and the liner, and that certain forces on the piston have components in the horizontal direction, there exists some lateral motion of the piston and also some rotational motion about the wrist pin axis. This motion is referred to as secondary motion. Secondary motion has significant implications for oil transport past the piston ring-pack, engine friction and engine noise. For these reasons a comprehensive numerical model of secondary motion is a valuable tool for engine designers and development engineers. This work involves the development of a comprehensive and robust computer model of piston secondary motion, which can be easily run on a desktop computer. The model is applicable to both conventional mono-piston assemblies and also to articulated piston assemblies. The modeling approach involves treating the piston assembly as a set of independent rigid bodies, and formulating and solving the equations of motion for each body. The hydrodynamic skirt-liner interaction force is computed by solving the Reynolds equation for the oil film and integrating the computed pressure. This essentially one dimensional calculation is performed at several circumferential locations on the piston, and the results are integrated to yield a single force in the main thrust-anti thrust direction. The model is first developed with a basic form of this hydrodynamic calculation, which is later improved to include a solution for the wetted region and a complete pressure distribution on the piston. Results using both forms of the model are compared and analyzed, and the final model is used to perform several parametric studies involving various engine operating parameters.
by Conor P. McNally.
S.M.

The emissions control regulations introduced by governments are set to improve the quality of the engines and reduce the impact automobiles have on the planet. The regulations imposed on the manufactures have proven very difficult to meet, with some of the leading names in the industry investing significant part of their funding in research and development. Their goal is to reduce the fuel consumption and exhaust emissions while increasing the engine performance and durability. The piston-ring and cylinder-liner interaction is the major source of frictional losses for reciprocating internal combustion engines. The failure of the piston-rings to effectively control the transportation of oil from the sump onto the cylinder walls results among others to lubricant consumption. The objective of this project is to assist with the investigation of phenomena that occur in the cylinder liner and piston ring interaction under different operating conditions. To achieve these the following investigations have been carried, flow and cavitation visualisation in a model lubricant rig, and cavitation visualisation in a newly designed optical engine. The main focus of the project was the design, manufacturing and assembly of an optical internal combustion reciprocating engine. The new engine has been based on the design of a 450cc Ricardo Hydra, where many parts had to be redesigned or modified. The engine was fitted with a custom cylinder liner designed to accommodate custom made windows that covers almost the full length of the liner over a width of 25mm; this visibility allows access not only into the contact point over the entire length of the liner, but also provides access to the combustion chamber to allow for flow visualisation and flow field measurements. The cooling system was modified to allow for the accurate control and maintaining of the engine temperature. The control of the engine is performed with a new custom engine management system build in LabView which allowed for the precise control of the engine and of all the auxiliary systems such as fuel, ignition, sensors and optical equipment. The new control system and the optical engine were tested successfully up to 3000 RPM with the same specification as the unmodified engine in terms of in cylinder pressure and maintaining the original engine tolerances. The design of the new optical engine was a great success and it would offer a useful and valuable testing device that would allow further investigation to be carried out. In parallel to the design of the engine, a parametric experimental study was undertaken and performed on 6 lubricant samples of different formulations at two lubricant flow rate of 0.02 and 0.05 L/min, three speeds at 100, 300 and 600 RPM, and two different temperatures at 30oC and 70oC. The study was performed on an existing test-rig to visualise lubricants cavitation using two high speed cameras coupled with three ARRI high intensity light sources. This optical test device is a quick, efficient and effective way to test different lubricant samples and compare their in-between performance. The captured video images were processed through a custom build algorithm designed around the lubrication rig. This algorithm allowed for the extraction of matrices such as cavity length, cavity width, area of cavitation and number of cavities present in the area between the piston ring and the cylinder liner interaction. This parametric study offered a set of valuable results from which the performance of each lubricant can be assessed and a direct link between the lubricant formulation and the operating conditions can be established. Cavitation visualisation of the lubricant in the new optical engine was performed under motorised and firing condition up to an engine speed of 300 RPM and produced high quality images from the usually inaccessible piston ring and cylinder liner interaction. This unique design allowed to investigate a number of phenomena around that specific area like cavitation, blow-by, fuel spray, flame propagation and oil transportation. The parametric study results investigated in the test-rig have been linked with those obtained in the conventional internal combustion engines while providing a very useful and very powerful piece of software.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.
Includes bibliographical references (p. 239-241).
Internal combustion engines dominate transportation of people and goods, contributing significantly to air pollution, and requiring large amounts of fossil fuels. With increasing public concern about the environment and the reliability of oil supplies, automotive companies are pushed to improve engine design in order to reduce engine emissions and fuel consumption. This project aims to develop a numerical model of piston dynamics and lubrication in internal combustion engines, enabling prediction of friction generation at the piston -cylinder bore interface, and oil transport in the power cylinder system. It is currently estimated that the piston - cylinder bore friction accounts for up to 25% of the power loss in a typical engine, while oil transported to the combustion chamber by the piston and ring-pack contributes significantly to engine emissions. A dry piston model was first developed to allow fast calculation of approximate piston dynamics. An elastohydrodynamic lubrication model was then developed to allow direct numerical simulation of the effect of piston tooling marks, and comparison with results obtained using an Average Reynolds equation with flow factors. The lubrication model was incorporated into the piston dynamics model, enabling more accurate evaluation of friction and oil transport. Comparison between the dry and lubricated model results demonstrate the effect of oil film thickness on piston lateral motion, tilt, friction generation and oil transport.
by Fiona McClure.
Ph.D.

V rámci této práce byl vyvinut komplexní simulační nástroj, vycházející z výpočtového modelování fyzikálních a chemických dějů, který je doplněn vhodnými matematickými postupy. Výsledný software je schopen stanovit ztrátový výkon sady pístních kroužků pomocí účinků klíčových mechanismů a jejich vzájemné interakce při standardním provozu pístních kroužků. Simulační výstupy byly navrženy v souladu se zájmy průmyslové praxe, např. určení objemového toku plynů pístní skupinou, ztrátové výkony vlivem tření a spotřeba oleje, která je ovlivněna sadou pístních kroužků. Při vývoji simulačního modelu byly technické experimenty vykonány na tříválcovém zážehovém motoru za účelem získání vstupních dat a ověření výsledků. Možnosti navrženého simulačního nástroje jsou na tomto motoru dále demonstrovány v podobě parametrických studií, využitelných zejména při návrhovém procesu. Cílem dizertační práce bylo zaplnit mezeru ve výzkumné oblasti simulačních nástrojů, které mohou účinně propojit výpočtové modelování třecích ztrát a současně i spotřeby oleje, a podpořit tak výrobce pístních kroužků a vývojová oddělení spalovacích motorů.

Internal combustion engines are perhaps the most ubiquitous power source in the modern world. Their heavy use in the vehicle industry and the current impetus to improve efficiency whilst reducing emissions means that OEMs are driving research to provide cleaner and 'greener' engines. Though significant effort is being channelled into teasing out improvements in thermodynamic Efficiency by such methods as pressure boosting and power management. the nature of an engine means many moving parts contribute to parasitic frictional loss. Of these interfaces. the reciprocating contacts between cylinder. piston rings and skirt are arguably subject to the most demanding tribological conditions within an engine. required to seal against the high temperature' combustion gases whilst supporting the large side loading inherent to the system. Given that the piston of an engine may perform this action hundreds of millions of times in its lifespan. the lubrication strategy and component design is of key importance in minimising wear frictional losses. Though the use of numerical simulation tools for improving design has seen significant growth as computational capabilities improve and provide cost advantages to full scale testing. robust validation methods are required to guide the development of the underlying models. The aim of this project was to assess the suitability of an ultrasonic method to monitor the condition of lubrication at the aforementioned contacts by measuring film thickness. Though various techniques involving optical and electrical principles have been employed in the past they generally require the cylinder of the engine to be penetrated and implementation. for the most part. is limited to the test cell. The results of investigations at the piston ring contact have shown that the ultrasonic technique can be used to measure lubricant film thickness and have shown the influence of cylinder pressure and reciprocating speed. Measurements correlate well with work by other authors using the alternative methods mentioned. giving confidence in the robustness of the method. Film measurements at the skirt have been also been successful. not only in quantifying the minimum films present. but also in detailing the profile of the film over its surface and enabling some of the secondary motions of the piston to be deduced. It has been shown that the ultrasonic technique offers the ability and freedom to measure film thickness within an operational engine whilst having the distinct advantage of limiting the degree structural modification required. It shows promise as a research tool and with further development. offers the potential to be incorporated into a lubricant monitoring and control System to help reduce friction losses and emissions.

Automotive engine pistons are not normally expected to be made of plastics or even composites, but before now the latter have been applied to an Over Head Cam follower of an automotive engine. As such this research work sought to demonstrate that the composite Carbon fibre Phenolic composite of the grade used is suitable enough to be employed in a hybrid piston. This work covered three broad areas; Constitutive modelling, Optimization and Fatigue. Numerical/simulation and empirical methods were employed to accomplish the tasks involved. The design of the piston was presented and this design took into account the fact that a composite was involved. A contact analysis was carried out to analyse the stresses arising from the interference of the composite piston skirt and the aluminium cap just in case interference fit is adopted as the method of assembly. Empirical analyses of tubular carbon fibre composite samples as well as carbon fibre Phenolic composite prepregs were carried out to determine the tensile, compressive and flexural capabilities of the materials as the case may be. Young's and Shear modulus values as well Poisson's ratio values were deduced leading to the establishment of the constitutive model of the composite's lamina and consequently that of the laminate for the various samples that were deemed suitable based on the nature of their testing and preparation as well as a piston cap model. With the constitutive models worked out and the piston cap model developed, fatigue analysis of the structure and piston cap followed, and in other to get the best out of the structures or materials and the piston cap optimization followed after which yet more fatigue analysis was done for the optimization outcomes. To a great extent one of the Elastic Modulus values obtained empirically can be said to be sufficiently reliable as its empirical test was simulated numerically and it turned out satisfactory; the maximum stress value from the test was 158.5 MPa while that of the simulation was 158.267 MPa. All the results were almost the same apart from the strain values that were significantly divergent. The adopted Elastic Modulus value of 61049.6757 MPa stemmed from this empirical and numerical analyses and since these two differed only in the strain values and agreed in pretty much in all other the parameters it can be said that this adopted Elastic Modulus value was indeed sufficiently reliable. It also implies that the outcomes of all the other numerical analyses that were carried out with it can be trusted. In the Results and Discussion chapter numerical Crack Propagation was discussed for various crack lengths of a finite element model.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 135-136).
The consumption of lubricating oil in internal combustion engines is a continuous interest for engine developers and remains to be one of the least understood areas. A better understanding on oil transport is critical to an optimization of engine designs, and advanced analytical tools are essential to the achievement of reduced frictions without compromising oil consumption. Oil transport from piston lands to a liner, hereafter called "bridging", has been observed in engine tests. The additional oil transferred to the liner becomes a potential source of oil consumption through ring-liner interaction. Thus, it is important to develop more quantitative models to better analyze bridging. The objective of this work is to obtain a more in-depth understanding on the oil transport between piston lands and liner and provide quantitative models of the oil transport mechanisms. Multiphase Computational Fluid Dynamics (CFD) was employed together with analyses of experimental observations. Three categories of bridging were identified: assisted bridging, self-sustained bridging, and reverse bridging. While assisted bridging involves an axial oil flow across an entire piston land, the other two phenomena are localized and become prominent at low engine speeds. The mechanisms of each phenomenon were analyzed in this work. Correlations and theoretical models were developed to associate the risk of bridging with geometrical designs of a piston and operating conditions of an engine. Particularly, the theoretical model of self-sustained bridging contributes to the optimization of geometrical designs of the third land of a piston ring pack. This work constitutes a major step towards a further quantification of oil transport. Some findings and models presented in this work can readily contribute to providing optimal solutions to certain piston regions. Furthermore, the results of this work serve broader purposes in providing boundary conditions to other interactions in a piston ring pack.
by Tianshi Fang.
S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 215-218).
Fuel consumption reduction of more than 20% can be achieved through engine friction reduction. Piston and piston rings contribute approximately half of the total engine friction and are therefore central to friction reduction efforts. The most common method to reduce mechanical losses from piston rings has been to lower ring tension, the normal force providing sealing between the piston ring and the cylinder liner. However tension reduction can result in additional lubricant consumption. The objective of this thesis is to understand and model the physical mechanisms resulting in flow of oil to the combustion chamber in order to achieve optimal designs of piston rings. The optimal design is a compromise between friction reduction and adequate gas and lubricant sealing performance. To do so a multi-scale curved beam finite element model of piston ring is developed. It is built to couple ring deformation, dynamics and contact with the piston and the cylinder. Oil flow at the interfaces between the ring and the cylinder liner and between the ring and the piston groove can thus be simulated. The piston ring model is used to study the sealing performance of the Oil Control Ring (OCR), whose function is to limit the amount of oil supplied to the ring pack. The contributions of the three main mechanisms previously identified, to oil flow past the OCR are quantified: - Deformation of the cylinder under operating conditions can lead to a loss of contact between the ring and the liner. - Tilting of the piston around its pin can force the OCR to twist and scrape oil from the liner. - Oil accumulating below the OCR can flow to the groove and leak on the top of the OCR The OCR is found to be flexible enough to limit the impact of cylinder deformation on oil consumption. Both ring scraping and flow through the OCR groove can contribute to oil consumption in the range of engine running conditions simulated. Reduction of scraping is possible by increasing the ability of both OCR lands to maintain contact with the liner regardless of piston groove tilt. The flow of oil through the OCR groove can be reduced by designing appropriate draining of oil in the groove and an adequate oil reservoir below the OCR. The piston ring oil transport model developed in this thesis will be a valuable tool to optimize ring pack designs to achieve further ring pack friction reduction without increasing oil consumption.
by Camille Baelden.
Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 131-133).
Piston ring packs are used in internal combustion engines to seal both the high pressure gas in the combustion chamber and the lubricant oil in the crank case. The interaction between the piston ring pack and the cylinder bore contributes substantially to the total friction power loss for IC engines. The aim of this thesis work is to advance the understanding of the ring liner lubrication through numerical modeling. A twin-land oil control ring lubrication model and a top two-ring lubrication model are developed based on a deterministic approach. The models take into consideration the effect of both the liner finish micro geometry and the ring face macro profile. The liner finish effect is evaluated on a 3D deterministically measured liner finish patch, with fully-flooded oil supply condition to the oil control rings and starved oil supply condition to the top two rings. Correlations based on deterministic calculations and proper scaling are developed to connect the average hydrodynamic pressure and friction to the critical geometrical parameters and operating parameters so that cycle evaluation of the ring lubrication can be performed in an efficient manner. The models can be used for ring pack friction prediction, and ring pack/liner design optimization based on the trade-off of friction power loss and oil consumption. To provide further insights to the effect of liner finish, a wear model is then developed to simulate the liner surface geometry evolution during the break-in/wear process. The model is based on the idea of simulated repetitive grinding on the plateau part of the liner finish using a random grinder. The model successfully captures the statistic topological features of the worn liner roughness. Combining the piston ring pack model and the liner finish wear model, one can potentially predict the long term ring pack friction loss. Finally the thesis covers the experimental validation of the twin-land oil control ring model using floating liner engine friction measurements. The modeled ring friction is compared with the experimental measurement under different ring designs and liner finishes. The result shows that the model in general successfully predicts the friction force of the twin-land oil control ring/liner pair.
by Haijie Chen.
Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 71-72).
In the process of designing internal combustion engine, piston ring plays an important role in fulfilling the requirements of camber gas sealing, friction reduction and lubrication oil consumption. The goal of this thesis is to have a better understanding of the ring behaviors under different working conditions in a structural level. This thesis is an extension of existing ring design tool. A model is built up to simulate the processes of changing ring states from one to another such as free or fit the ring. It revealed the sensitive characters of the piston ring tip; it expanded the field of application of the existing piston ring design tool; it also investigated the ring bore interaction in more conditions. This work removed the symmetric assumption in the existing tool. A new method that calculates ring free shape and ring bore contact force from ring ovality data is introduced for the first time. The analysis of ring bore interaction is widened. The model was applied to an industry ring design case. In this case it shows the free and fit procedure in this model is physically and mathematically reversible. It shows these procedures are direction independent. The contact force distribution changes when the ring is moving within the distorted bore. It also changes when the wetting or roughness situation is different. This model can calculate the ring free shape from asymmetric measured ovality data. It can also retrieve the desired contact force from it. The piston ring design tool is updated and implemented with these highly appreciable new features. This complete package has high efficiency and a wider practical field.
by Dian Xu.
S.M.

Hlavní cíl této práce je vyvinout pokročilý výpočtový model dynamiky pístové skupiny. Kontakt mezi pístem a válcem je zprostředkován skrz vrstvu maziva nebo pomocí kontaktu nerovností. To vede k různým režimům mazání, tudíž k různým silovým interakcím působících na plochy kontaktní dvojice. Během řešení hydrodynamiky a kontaktu nerovností, je nutné zahrnout deformaci pístu a válce do výpočtu—přirozeně iterační proces. Jelikož požadavky na výpočtovou síť kontaktních sil a deformaci těles se liší, byl navržen robustní mapovací algoritmus. Výsledky vyvinutého výpočtového nástroje jsou experimentálně verifikovány. Pro tento účel je uskutečněno měření sekundárního pohybu pístu pomocí laserových snímačů vzdálenosti. Měření je vykonáno na experimentálním motoru s bočním vedením ventilů a průhlednou hlavou válce, aby byl přítomen kompresní tlak ve spalovací komoře. Naměřený boční pohyb pístů je znehodnocen. Proto je další analýze potrobeno pouze úhlové natočení pístů. Shoda mezi naměřenými a vypočítanými výsledky variuje pro různé části pracovního cyklu. Dobrá shoda je dosažena během komprese a expanze. Naopak výrazné rozdíly nastávají, když boční síla dosahuje nízkých hodnot: sání a výfuk. Hlavní přínos této práce je vytvoření výpočtového nástroje, který je schopný zahrnout výše popisované jevy, které mají podstatný vliv na dynamiku pístové skupiny. Bohužel to vede k dlouhým výpočtovým časům, zvláště když je zahrnuta deformace. Tento problém řeší navržený paralelní výpočet. To je založeno na paralelizaci podprogramu během vyčíslování citlivostní analýzy. Tímto způsobem je řádově redukován výpočtový čas.

[ES] Con el aumento de la demanda de soluciones más amigables con el medio ambiente en la industria de la automoción, el motor de combustión interna alternativo (MCIA) enfrenta actualmente grandes desafíos para minimizar su consumo de recursos no renovables y especialmente, para reducir sus emisiones contaminantes. Debido a que el aporte de los MCIAs es fundamental para cubrir las necesidades de movilidad y de generación de energía alrededor de todo el mundo, y el hecho de que diferentes alternativas, como los motores eléctricos e hibrido, están y continuaran enfrentado múltiples obstáculos para su implementación masiva en el futuro cercano, la investigación continua en MCIA es fundamental para cumplir con los propósitos de reducción de emisiones. En este aspecto, una aproximación para el aumento de la eficiencia del motor y la reducción del consumo de combustible es mediante la implementación de alternativas dirigidas a reducir las pérdidas mecánicas por fricción. Estas alternativas tribológicas incluyen aquellas que requieren modificaciones en los componentes del motor, como materiales y acabados superficiales, y el uso de formulaciones de aceite lubricante de menor viscosidad o aditivos que mejoren las condiciones de lubricación del motor. Con la contante evolución y mejoras en el MCIA y las condiciones de trabajo cada vez más severas, también surgen nuevas alternativas tribológicas para enfrentar los nuevos desafíos del motor, y por tanto se requiere de investigaciones adicionales en este tema. Durante el desarrollo de esta Tesis, uno de los objetivos consistió en contribuir a la investigación del uso de aceites de baja viscosidad para el ahorro de combustible como un efecto conjunto con las condiciones de conducción del vehículo. Para llevar a cabo este objetivo, se desarrollaron ensayos experimentales bajo condiciones estacionarias en un banco de motor con formulaciones de aceite de diferente viscosidad HTHS, algunas de ellos con aditivo modificador de fricción para expandir el rango de reducción de fricción a condiciones de lubricación más severas. Los mapas de consumo de combustible resultantes de estos ensayos fueron utilizados en un modelo de simulación del vehículo para estimar su consumo de combustible como función del aceite y las condiciones de trabajo de tres ciclos de conducción. Con el objetivo de expandir los conocimientos en los fundamentos de lubricación de los MCIAs y tener la capacidad de evaluar otras alternativas para reducir las pérdidas por fricción, se consideró necesario enfocar la investigación en el conjunto pistón-camisa, que es el par tribológico con mayor aporte a las perdidas por fricción. Para conseguir este objetivo, durante esta Tesis se desarrolló una maqueta específica para el ensamble pistón-camisa, y un modelo teórico para simular la lubricación del segmento de compresión. Para la primera parte, la maqueta se desarrolló basada en el método de camisa flotante, en el cual la camisa fue aislada del resto del motor y la fuerza de fricción generada en la interfaz pistón-camisa pudo ser medida mediante sensores de fuerza. En esta instalación se desarrollaron diferentes ensayos los cuales permitieron llevar a cabo un análisis exhaustivo de los fundamentos de lubricación de este par tribológico como función de diferentes parámetros que tiene impacto en las condiciones de lubricación. Este estudio se complementó con el desarrollo de un modelo de lubricación para el segmento de compresión basado en el método de diferencias finitas. Finalmente, se llevó a cabo una comparativa de resultados experimentales y teóricos para el segmento de compresión, lo cual permitió validar los ensayos experimentales en la maqueta de camisa flotante, así como el modelo de simulación desde el punto de vista de datos de entrada, condiciones de contorno y supuestos.
[CA] Amb l'augment de la demanda de solucions més amigables amb el medi ambient en la indústria de l'automoció, el motor de combustió interna alternatiu (MCIA) s'enfronta actualment a grans desafiaments per minimitzar el seu consum de recursos no renovables i especialment, per reduir les seves emissions contaminants . Tenint en compte que l'aportació dels MCIA és fonamental per a cobrir les necessitats de mobilitat i generació d'energia arreu de tot el món, i el fet que diferents alternatives, com els motors elèctrics i híbrids, estan i continuaran enfrontat múltiples obstacles per a la seva implementació massiva al proper futur, la investigació contínua en MCIA és fonamental per complir amb els propòsits de reducció d'emissions. En aquest aspecte, una aproximació per a l'augment de l'eficiència del motor i la reducció de consum de combustible és mitjançant la implementació d'alternatives dirigides a reduir les pèrdues mecàniques per fricció. Aquestes alternatives tribològiques inclouen aquelles que requereixen modificacions de components del motor, com materials i acabats superficials, i l'ús de formulacions d'oli lubricant de menor viscositat o additius que milloren les condicions de lubricació del motor. Amb la constant evolució i millores en el MCIA i les condicions de treball cada vegada més severes, també sorgeixen noves alternatives tribològiques per enfrontar els nous desafiaments del motor, i per tant es requereix d'investigacions addicionals en aquest tema. Durant el desenvolupament d'aquesta Tesi, un dels objectius va consistir a contribuir a la investigació de l'ús d'olis de baixa viscositat per a l'estalvi de combustible com un efecte conjunt amb les condicions de conducció de vehicle. Per dur a terme aquest objectiu, es van desenvolupar assajos experimentals sota condicions estacionàries en un banc de motor amb formulacions d'oli de diferent viscositat HTHS, algunes d'elles amb additiu modificador de fricció per expandir el rang de reducció de fricció a condicions de lubricació més severes . Els mapes de consum de combustible resultants d'aquests assajos van ser utilitzats en un model de simulació del vehicle per estimar el seu consum de combustible com a funció de l'oli i les condicions de treball de tres cicles de conducció. Amb l'objectiu d'expandir els coneixements en els fonaments de lubricació dels MCIAs i tenir la capacitat d'avaluar altres alternatives per reduir les pèrdues per fricció, es va considerar necessari enfocar la recerca al conjunt pistó-camisa, que és el parell tribològic amb major aportació a les perdudes per fricció. Per aconseguir aquest objectiu, durant aquesta Tesi es va desenvolupar una maqueta específica per al acoblament pistó-camisa, i un model teòric per simular la lubricació del segment de compressió. Per a la primera part, la maqueta es va desenvolupar basada en el mètode de camisa flotant, en el qual la camisa va ser aïllada de la resta del motor i la força de fricció generada en la interfície pistó-camisa va poder ser mesurada mitjançant sensors de força. En aquesta instal·lació es van desenvolupar diferents assajos els quals van permetre dur a terme una anàlisi exhaustiva dels fonaments de lubricació d'aquest parell tribològic com a funció de diferents paràmetres que tenen impacte en les condicions de lubricació. Aquest estudi es va complementar amb el desenvolupament d'un model de lubricació per al segment de compressió basat en el mètode de diferències finites. Finalment, es va dur a terme una comparativa de resultats experimentals i teòrics per al segment de compressió, la qual cosa va permetre validar els assajos experimentals a la maqueta de camisa flotant, així com el model de simulació des del punt de vista de dades d'entrada, condicions de contorn i hipòtesis.
[EN] With the increasing demand for greener solutions in the automotive industry, the ICE is currently facing great challenges to minimize the consumption of nonrenewable resources and specially to reduce its harmful emissions. Given that the contribution of the ICE is fundamental to cover the actual mobility and power generation needs worldwide, and the fact that different power-train alternatives, such as electric and hybrid vehicles, are and will continue facing multiple obstacles for their large-scale implementation in the near future, the continuous research on the ICE is fundamental in order to meet the emissions reduction targets. In this regard, one approach to increase the engine efficiency and reduce the fuel consumption, is through the implementation of alternatives aimed to reduce the friction mechanical losses. These tribological alternatives include those that require modifications to the engine components, such as materials and surface finishes, and the use of lubricant oil formulation of lower viscosity or additives that improve the lubrication performance of the engine. With the ongoing evolution and improvement of the ICE and the increasingly severe working conditions, new tribological solutions also emerge to face the new challenges in the ICE, and therefore further research is required on this subject. During the development of this Thesis, one of the objectives was to contribute to the research on low viscosity engine oils for fuel economy as a joint effect with the driving conditions of the vehicle. To accomplish this, experimental tests were performed under stationary conditions in an engine bench test for oil formulations of different HTHS viscosity, some of them with friction modifier additive to expand the friction reduction effect to more severe lubrication conditions. The resultant fuel consumption maps were then employed in a vehicle model to estimate the fuel consumption of the vehicle as function of the oil formulation and the working conditions of the three driving cycles. With the aim of expanding the knowledge on the lubrication fundamentals of the engine and to have the capability to assess other alternatives to further reduce the friction mechanical losses, it was deemed necessary to focus the research on the piston-cylinder liner assembly, the tribo-pair of major friction share. In order to achieve this objective, a test rig was developed in this Thesis specific for the piston-liner assembly, and a theoretical model to estimate the lubrication of the piston compression ring. For the first part, the test rig was designed based on the floating liner method, where the cylinder liner was isolated from the rest of the engine and the friction force generated in the piston-liner conjunction could be measured by means of force sensors. Different tests were developed in this test rig which allowed a comprehensive analysis of the piston lubrication fundamentals as function of different parameters having an impact on the lubrication performance of this assembly. This study was complemented with the development of a piston compression ring lubrication model based on the finite differences method. A comparison of experimental and theoretical results was performed for the piston compression ring that helped to validate both the experimental tests in the floating liner and the simulation model from the point of view of input data, boundary conditions and assumptions.
Bastidas Moncayo, KS. (2021). Experimental and analytical study of the mechanical friction losses in the piston-cylinder liner tribological pair in internal combustion engines (ICE) [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/172188
TESIS

La microgéométrie de la surface de la chemise joue un rôle très important dans les pertes par frottement et dans la consommation de l’huile dans un moteur à combustion interne. Une des texturations classiques de cette surface est celle créée par pierrage. Elle se compose de plateaux plus ou moins lisses et de profondes stries croisées. L’´épaisseur du film d’huile est influencée fortement par cette texturation. Un modèle simplifié du contact segment chemise a été créé en la présence de la microgéométrie. Puis, un code de calcul basé sur la méthode numérique multigrille a été développé. Ce code a été utilisé pour des études paramétriques avec des jeux de paramètres très variés. Les calculs quantifient l’influence de cette microgéométrie particulière sur la relation film d’huile - portance. Les résultats mettent en évidence deux mécanismes distincts de génération de portance selon le type du segment. Le segment parabolique porte par son convergent et les stries ne font que diminuer cette portance. Inversement, le segment plat ne porte pas et ce sont les stries qui génèrent la portance. Deux modèles de prédiction ont finalement été déduits, un pour les segments paraboliques et un pour les segments plats. Ces deux prédictions ont ensuite été validées par des calculs sur des surfaces mesurées
The liner microgeometry influences the friction losses and the oil consumption in IC engines. The cross-hatched texturing, created by the honing process, plays an essential part in the load carrying capacity - film thickness relation. This work studies the influence of the crosshatched groove parameters on the piston ring load carrying capacity. First, a simplified model of the hydrodynamic contact has been created. Thus a Multigrid based code was developed. Calculations with different sets of microgeometric parameters have been performed. These calculations quantify the load carrying capacity for both parabolic and flat rings. The results show that the load carrying capacity is generated differently in both cases. For the parabolic case, the pressure is build up by the wedge in the inlet zone and the grooves decrease the global load carrying capacity. In the flat case the grooves generate the total load carrying capacity. Finally, two prediction models were deduced for the parabolic ring and for the flat ring. These predictions were validated by measured surface calculations

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 87-88).
When decreasing of fossil fuel supplies and air pollution are two major society problems in the 21st century, rapid growth of internal combustion (IC) engines serves as a main producer of these two problems. In order to increase fuel efficiency, mechanical loss should be controlled in internal combustion engines. Interaction between piston ring pack and cylinder liner finish accounts for nearly 20 percent of the mechanical losses within an internal combustion engine, and is an important factor that affects the lubricant oil consumption. Among the total friction between piston ring pack and cylinder liner, boundary friction occurs when piston is at low speed and there is direct contact between rings and liners. This work focuses on prediction of contact between piston ring and liner finish based on 3D measured surface and different methods are compared. In previous twin-land oil control ring (TLOCR) deterministic model, Greenwood-Tripp correlation function was used to determine contact. The practical challenge for this single equation is that real plateau roughness makes it unreliable. As a result, micro geometry of liner surface needs to be obtained through white light interferometry device or confocal equipment to conduct contact model. Based on real geometry of liner finish and the assumption that ring surface is ideally smooth, contact can be predicted by three different models which were developed by using statistical Greenwood-Williamson model, Hertzian contact and revised deterministic dry contact model by Professor A.A. Lubrecht. The predicted contact between liner finish and piston ring is then combined with hydrodynamic pressure caused by lubricant which was examined using TLOCR deterministic model by Chen. et al to get total friction resulted on the surface of liner finish. Finally, contact model is used to examine friction of different liners in an actual engine running cycle.
by Qing Zhao.
S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 175-177).
The compromise between friction and lubricant consumption has been a long-lasting challenge for the design of the piston ring pack in internal combustion engines. In order to achieve a satisfactory compromise, a systematic understanding of the lubricant transport in the piston ring pack is of critical importance. In the context of increasingly stringent standards on engine emissions, there is a more urgent need for the knowledge on the lubricant transport. This work is focused on the lubricant transport in two non-contact regions in the piston ring pack: 1) the region near a piston skirt chamfer; 2) the region near a piston third land. While the Reynolds equation has been widely employed to model the contact interfaces, more general fluid mechanics has to be applied in the non-contact regions. This thesis is the first work to comprehensively apply Computational Fluid Dynamics (CFD) and theoretical modelling to the non-contact regions in the piston ring pack.
CFD was employed to fundamentally understand the lubricant transport, and theoretical models were developed to more efficiently quantify the lubricant transport. This work is a major step towards an accurate quantification of the lubricant leakage through the oil control ring (OCR) that can be critical to the lubricant consumption. The lubricant transport in a skirt chamfer region determines the pressure outside the contact interface between the lower flank of the OCR and its groove, and thus the lubricant flow rate into the OCR groove. A numerical model and a closed-form correlation were developed to efficiently predict the pressure. While the lubricant transport into the OCR groove had often been overlooked, this work revealed that this lubricant transport could be remarkable. In the region near a piston third land, two mechanisms of lubricant transport were studied: 1) high-speed bridging; 2) reattachment.
Both of them introduce additional lubricant to the ring/liner contact interfaces. The effects on the inlet conditions to the ring/liner contact interfaces were quantitatively studied. The existing knowledge on high-speed bridging was enhanced in a quantitative sense. The reattachment process was first discovered and studied.
by Tianshi Fang.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.
"June 2001."
Includes bibliographical references (p. 253-257).
Engine oil consumption is one of the primary interests for the automotive industry in controlling emissions and reducing service cost. Due to a lack of understanding of the mechanisms of oil transport along the piston, reducing oil consumption from the ring pack of internal combustion engines has been extremely challenging for engine manufacturers and suppliers. This work addressed the fundamental aspects of oil transport in the piston ring pack through experiments and modeling. A two-dimensional multiple-dye Laser-Induced Fluorescence (LIF) visualization system was successfully implemented in a diesel and a spark-ignition engine. Real time high resolution images of the ring pack oil distribution were acquired and analyzed for the entire range of operating conditions typically encountered by passenger car engines. Based on experimental observations, major oil flow patterns in the piston ring pack were identified and characterized. Physically based models were proposed to describe each individual oil transport process, such as, oil flows on the piston lands in both axial and circumferential directions and oil flows through the ring grooves and gaps. Modeling results showed good agreement with the experimental data.
(cont.) Then, using the individual oil transport models, the contributions of the different oil transport mechanisms to oil flow in and between the piston regions and the effects of piston and ring designs were analyzed. Finally, a global oil transport scheme was presented by integrating all major paths and mechanisms of oil transport along the piston. It highlighted that the rate at which oil is lost to the combustion chamber is mostly determined by the competing oil transport processes occurring on the piston lands. While the effect of the inertia force results in a net oil flow toward the top of the piston, the dragging action of the blow-by gases removes oil from the piston lands and recycles it to the crankcase. This work was the first comprehensive investigation of the mechanisms of oil transport in the piston ring pack of internal combustion engines. It constitutes a major step in the development of analytical tools for oil consumption reduction.
by Benoist Thirouard.
Ph.D.

Orientador: Janito Vaqueiro Ferreira
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-23T13:13:46Z (GMT). No. of bitstreams: 1 Bosso_AndreLuizAparecido_M.pdf: 7894502 bytes, checksum: 2052586d161cac58f608acb2945fbd48 (MD5) Previous issue date: 2013
Resumo: Este trabalho tem como objetivo principal desenvolver um sistema alternativo para impulsionar o pistão em um motor de combustão interna que aciona um gerador de energia elétrica operando a uma rotação fixa. O sistema biela-manivela é substituído por um sistema eixo-cremalheira-engrenagem, que é capaz de realizar a inversão de movimento do pistão no ponto morto superior e no ponto morto inferior, sem que ocorra uma inversão de velocidade instantânea nesses pontos. Para garantir a eficiência desse sistema, análises cinemática e dinâmica são realizadas utilizando a modelagem de múltiplos corpos rígidos e a modelagem geométrica. Uma análise termodinâmica é realizada com o auxílio de um modelo de simulação computacional desenvolvido para um motor de combustão interna, com ignição por centelha e movido a etanol. O programa inclui a combustão com duração finita, transferência de calor instantânea e processos de admissão e escape, porém não considera o equilíbrio químico e a dissociação. Com os resultados obtidos é possível construir as curvas características do motor estudado e determinar sua melhor rotação de operação
Abstract: The main focus of this work is to develop an alternative system to drive the piston in an internal combustion engine which drives an electric power generator operating at a fixed speed. The connecting rod-crankshaft system is replaced by an axle-rack-gear system that is capable of performing the inversion of the piston movement in the top and the bottom dead center, without occurring an inversion of the instantaneous velocity in these points. In order to ensure the efficiency of this system, kinematic and dynamic analyzes are performed using rigid body and geometric modeling. A thermodynamic analysis is performed using a computer simulation model developed for a conventional ethanol-powered internal combustion engine with spark ignition. The program includes combustion with finite duration, instantaneous heat transfer and intake and exhaust processes, but does not consider the chemical equilibrium and dissociation. With the results it is possible to obtain the typical curves of the engine studied and determine its best operating speed
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 107-109).
Nowadays, a rapid growth of internal combustion (IC) engines is considered to be a major contributor to energy crisis. About 20% of the mechanical loss in internal combustion engines directly goes to the friction loss between piston ring pack and liner finish. A twin-land oil control ring (TLOCR) deterministic model was developed by Chen et al. and it helps the automotive companies investigate the effects of liner finish, rings, and lubricants on friction and oil control of the TLOCR [2]. This work focuses on application of the TLOCR model and extension of the deterministic model to the top two rings. First, there are some practical challenges in the application of Chen's TLOCR deterministic model. Due to different wear condition on the same liner, surface roughness varies from spot to spot. A small patch of measurement cannot provide enough information and the change of plateau roughness makes the contact model unreliable. As a result, a multi-point correlation method was proposed to combine the information of different spots from the same liner and this method was shown to give better match to the experimental results. A top-two-ring lubrication cycle model was developed based on the multiphase deterministic model by Li. et al [30] and previous top-two-ring lubrication model by Chen. Et al [2][31]. The model is composed with two parts. First, the deterministic model is used to generate a correlation between the hydrodynamic pressure/friction and the minimum clearance with prescribed oil supply from the deterministic oil control ring model. It was found that within reasonable accuracy, the gas pressure effect on the hydrodynamic lubrication of the top two rings can be decoupled from the hydrodynamic lubrication. Thus, only single-phase deterministic model was needed to generate the correlation. This decoupling significantly reduces the computation time. Then, a cycle model was developed utilizing the correlation of hydrodynamic pressure/friction and the minimum clearance. The cycle model considers the effect of gas pressure variations in different ring pack regions as well as the dynamic twist of the top two rings. Finally, the models were used to examine the friction and lubrication of three different liner finishes in an actual engine running cycle.
by Yang Liu.
S.M.

O presente estudo descreve as alterações metalúrgicas e topográficas do cilindro de blocos de motor de combustão interna fabricados em ferro fundido cinzento, após a realização de testes de durabilidade em dinamômetro. O motor testado tem tecnologia Flex-Fuel, e pode ser operado com qualquer proporção de mistura gasolina comum/etanol. Um motor foi testado com combustível etanol e o outro com gasolina comum, buscando-se assim representar duas condições extremas de trabalho em termos de combustível. A pesquisa constituiu-se da revisão bibliográfica e da parte prática que envolveu: a realização de testes de durabilidade de motor em dinamômetro; a caracterização metalúrgica e topográfica do cilindro após teste com ambos os combustíveis, utilizando técnicas de microscopia eletrônica de varredura, metalografia por microscopia óptica, perfilometria e quantificação de parâmetros de rugosidade, entre outros; a análise crítica, discussão dos resultados e apresentação da conclusão.
The present study approaches the metallurgical and topographical alterations on the cylinder of an internal combustion engine block made of gray cast iron, after durability dynamometer tests. The tested engine has flexible fuel technology (Flex-Fuel), and is capable to work with both gasoline/ethanol fuels, in any mixture proportion. One engine has been tested with ethanol and another one tested with gasoline, and so representing two extreme conditions on which the engine may work in terms of fuel. The research has been developed basically through the conceptual approach by the bibliographic review and the experimental steps that involved: general engine durability test at dynamometer bench; metallurgical and topographic characterization analysis at laboratory, after the test with both fuels, applying Scanning Electronic Microscopy SEM, optical microscopy metallography, profilometer and roughness parameters quantification, and so forth; critical analysis on the results, discussion and final conclusion.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2004.
Includes bibliographical references (p. 191-194).
Faced with increasing concern for lubricating, oil consumption and engine friction, it is critical to understand the oil transport mechanisms in the power cylinder system. Lubricating oil travels through distinct regions along the piston ring pack before being consumed in the combustion chamber, with the oil distribution and dominant driving forces varying substantially for each of these regions. This experimental work focuses on specific regions in the piston ring pack. A detailed 2D LIF (Two Dimensional Laser Induced Fluorescence) study has been performed on the oil distribution observed with the LIF generated real time high-resolution images, as were changes in piston and ring design. The results reveal the third land, located between the second compression ring and the oil control ring, oil flow patterns and timing are consistent and predictable at each operating point. Speed and load variation alter the basic flow pattern and oil balance through a corresponding change in inertia and gas dragging effect respectively, with ring design variation instigating specific and repeatable phenomenon onto the consistent oil flow pattern. Second land, the region between the top two compression rings, geometric and flow patterns throughout the entire cycle of a single cylinder spark ignition engine. The impact of speed and load were experimentally changes were found to have a significant impact on inertia driven oil transport; however, their effects on oil consumption were not as clear. As the majority of lubricating oil consumed in the engine crosses the third land at some point, an understanding of the timing and magnitude of the oil transport processes will allow means to be specifically developed to reduce the net oil flow across the third land
(cont.) towards the combustion chamber. This work forms a foundation for developing oil control strategies for the third land and for identifying how and when oil reaches the upper piston ring pack regions that directly contribute to oil consumption. The ability to control, or impact, oil transport on the piston ring pack will have an impact on all engine classes, including engines in the maritime community. This experiment study is directly comparable to small marine engines, and can be used to help reduce maritime exhaust emissions related to lubrication consumption; additionally, this approach would be much more rugged and cost effective then other current technological improvements being investigated. Were a similar 2D LIF experiment to be performed on large slow speed diesel engifes, the annual savings per vessel, assuming only a 10% reduction in lube oil consumption was achieved, could amount to $30,000 as cylinder lube oil is one of the most expensive operating costs for large slow speed diesel engines.
by Adam Vokac.
S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
Includes bibliographical references (p. 139-143).
The performance of the piston ring-pack is directly associated with the friction, oil consumption, wear, and blow-by in internal combustion engines. Because of non-axisymmetric characteristics of the power cylinder system, the performance of a ring varies along its circumference. Investigating these variations is of great interest for developing advanced ring-packs, but is out of the capabilities of the existing two-dimensional models. In this work, three separate but closely related numerical models were developed to study the performance of the piston ring-pack. The model for static analysis was developed to facilitate the design of piston rings. In this model, a finite beam element model is adopted with incorporation of a physics-based sub-model describing the interaction between the ring and the bore as well as the ring and the groove. A step-by-step approach is adopted to calculate the ring/bore and ring/groove conformability if the free shape of the ring is given. A method that can be used to determine the free shape as to achieve a specific tension distribution is also developed. Model results revealed the complex ring/bore and ring/groove interaction. A three-dimensional model for ring dynamics and blow-by gas flow was developed to address non-axisymmetric characteristics of the power cylinder system. In this model, the rings are discretized into straight beam elements. 3-D finite element analysis is employed to address the structural response of each ring to external loads. Physics-based sub-models are developed to simulate each ring's interactions with the piston groove and the liner. The gas flows driven by the pressure difference along both the axial and circumferential directions are modeled as well.
(cont.) This model predicts the inter-ring gas pressure and 3-D displacements of the three rings at various circumferential locations. Model results show significant variations of the dynamic behavior along ring circumference. In the ring-pack lubrication model, an improved flow continuity algorithm is implemented in the ring/liner hydrodynamic lubrication, and proves to be very practicable. By coupling the ring/liner lubrication with the in-plane structural response of the ring, the lubrication along the entire ring circumference can be calculated. Model results show significant variations of lubrication along the circumference due to the non-axisymmetric characteristics of the power cylinder system. Bore distortion was found to have profound effects on oil transport along the liner. Particularly, it stimulates the occurrence of oil up-scraping by the top ring during compression stroke. Because the oil evaporation on the liner affects the liner oil film thickness, a sub-model for liner evaporation with consideration of multi-species oil is incorporated with the lubrication model. With consideration of oil transport along the liner, the prediction of evaporation is more precise. The combination of these models is a complete package for piston ring-pack analysis. It is computationally robust and efficient, and thus has appreciable practical value.
by Liang Liu.
Ph.D.

La modélisation numérique des écoulements dans les moteurs à pistons est un enjeu d'importance pour les industriels de l'automobile. Mathématiquement, cette modélisation se heurte a plusieurs difficultés: les écoulements sont faibles mach, compressibles et visqueux, les géométries sont compliquées à représenter et, de plus, elles se déforment dans le temps (le piston, les soupapes se déplacent). Dans cette thèse, nous modélisons ce type de problème par la méthode des volumes finis Galerkin sur des maillages non structures hybrides. Cette méthode robuste consiste à approcher les flux convectifs par volumes finis et les flux diffusifs par éléments finis

L'elaborato tratta di una strategia real time, utilizzata su motori ad elevata potenza specifica, al fine di aumentare le performance, senza sostanziali modifiche HW. Tale incremento viene raggiunto attraverso mappature più aggressive che portano il motore a lavorare in condizioni di funzionamento limite per l'affidabilità dei componenti. In particolare, per ottenere un maggiore rendimento di combustione, si è portato il motore a lavorare in condizioni detonanti, andando quindi a danneggiare maggiormente i componenti della camera di combustione. Dalle prime prove sperimentali si è constatato che i pistoni sono i componenti che per primi risentono del danneggiamento da detonazione. Pertanto, sono stati studiati più nel dettaglio i principali tipi di danneggiamento che portano alla perdita di funzionalità di questi componenti. Nel corso dell'attività sono poi state fatte delle prove di durata al banco, per quantificare il danneggiamento accumulabile dal motore senza perdere di Funzionalità. Questa ricerca è dovuta al fatto che l'aumento delle performance è strettamente legato al danneggiamento tollerabile. Infatti maggiore è il danno accumulabile, tanto più possono essere aggressive le condizioni di funzionamento che consentono l'incremento prestazionale. Fatta una prima stima del danno accumulabile dal motore utilizzato in questo studio, è stata fatta una prova di durata completa con il propulsore di riferimento per consuntivare l'effettivo danno accumulabile.

In the last decades, the focus of internal combustion engine development has moved towards more efficient and less pollutant engines. In a Diesel engine, approximately 30-40% of the energy provided by combustion is lost through the exhaust gases. The exhaust gases are hot and therefore rich of energy. Some of this energy can be recovered by recycling the exhaust gases into turbocharger. However, the energy losses in the exhaust port are highly undesired and the mechanisms driving the total pressure losses in the exhaust manifold not fully understood. Moreover, the efficiency of the turbine is highly dependent on the upstream flow conditions. Thus, a numerical study of the flow in the exhaust port geometry of a Scania heavy-duty Diesel engine is carried out mainly by using the Large Eddy Simulation (LES) approach. The purpose is to characterize the flow in the exhaust port, analyze and identify the sources of the total pressure losses. Unsteady Reynolds Averaged Navier-Stokes (URANS) simulation results are included for comparison purposes. The calculations are performed with fixed valve and stationary boundary conditions for which experimental data are available. The simulations include a verification study of the solver using different grid resolutions and different valve lift states. The calculated numerical data are compared to existent measured pressure loss data. The results show that even global parameters like total pressure losses are predicted better by LES than by URANS. The complex three-dimensional flow structures generated in the flow field are qualitatively assessed through visualization and analyzed by statistical means. The near valve region is a major source of losses. Due to the presence of the valve, an annular, jet-like flow structure is formed where the high-velocity flow follows the valve stem into the port. Flow separation occurs immediately downstream of the valve seat on the walls of the port and also on the surface of the valve body. Strong longitudinal, non-stationary secondary flow structures (i.e. in the plane normal to the main flow direction) are observed in the exhaust manifold. Such structures can degrade the efficiency of a possible turbine of a turbocharger located downstream on the exhaust manifold. The effect of the valve and piston motion has also been studied by the Large Eddy Simulation (LES) approach. Within the exhaust process, the valves open while the piston continues moving in the combustion chamber. This process is often analyzed modeling the piston and valves at fixed locations, but conserving the total mass flow. Using advanced methods, this process can be simulated numerically in a more accurate manner. Based on LES data, the discharge coefficients are calculated following the strict definition. The results show that the discharge coefficient can be overestimated (about 20 %) when using simplified experiments, e. g. flow bench. Simple cases using fixed positions for valve and piston are contrasted with cases which consider the motion of piston and/or valves. The overall flow characteristics are compared within the cases. The comparison shows it is impossible to rebuild the dynamic flow field with the simplification with fixed valves. It is better to employ LES to simulate the dynamic flow and associated losses with valve and piston motion.

QC 20131204

Основною метою розвитку сучасного двигунобудування є створення двигунів високої потужності, зі зменшеною питомою вагою на одиницю потужності, а також зі зниженою витратою палива, шкідливих викидів і шуму. Ці підвищені вимоги до двигуна, нерозривно пов'язані з найбільш відповідальною його деталлю - поршнем. Збільшення потужності двигуна означає для поршня вищі міцністні вимоги, насамперед жорсткість, забезпечення зниження тертя і шуму при роботі у складі двигуні, а також зменшення його ваги з одночасним підвищенням зносостійкості та жаростійкості.

This thesis reports original research on a novel internal combustion (IC) engine charge air system concept called Turbo-Discharging. Turbo-Discharging depressurises the IC engine exhaust system so that the engine gas exchange pumping work is reduced, thereby reducing fuel consumption and CO2 emissions. There is growing concern regarding the human impact on the climate, part of which is attributable to motor vehicles and transport. Recent legislation has led manufacturers to improve the fuel economy and thus reduce the quantity of CO2 generated by their vehicles. As this legislation becomes more stringent manufacturers are looking to new and developing technologies to help further improve the fuel conversion efficiency of their vehicles. Turbo-Discharging is such a technology which benefits from the fact it uses commonly available engine components in a novel system arrangement. Thermodynamic and one-dimensional gas dynamics models and experimental testing on a 1.4 litre four cylinder four-stroke spark ignition gasoline passenger car engine have shown Turbo-Discharging to be an engine fuel conversion efficiency and performance enhancing technology. This is due to the reduction in pumping work through decreased exhaust system pressure, and the improved gas exchange process resulting in reduced residual gas fraction. Due to these benefits, engine fuel conversion efficiency improvements of up to 4% have been measured and increased fuel conversion efficiency can be realised over the majority of the engine operating speed and load map. This investigation also identified a measured improvement in engine torque over the whole engine speed range with a peak increase of 12%. Modelling studies identified that both fuel conversion efficiency and torque can be improved further by optimisation of the Turbo-Discharging system hardware beyond the limitations of the experimental engine test. The model predicted brake specific fuel consumption improvements of up to 16% at peak engine load compared to the engine in naturally aspirated form, and this increased to up to 24% when constraints imposed on the experimental engine test were removed.

Orientador: Katia Lucchesi Cavalca Dedini
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-22T07:50:24Z (GMT). No. of bitstreams: 1 Reis_VitorLuiz_M.pdf: 22501479 bytes, checksum: 7dcc42bed756f7cd1dc28e2f763f91ed (MD5) Previous issue date: 2013
Resumo: Este trabalho apresenta o desenvolvimento de um modelo dinâmico para o mecanismo biela-manivela com folga na junta de revolução pino-pistão. As equações do movimento para este sistema são obtidas através do método de Lagrange e os efeitos relacionados ao contato, atrito e lubrificação que atuam nos elementos com folga são alvo de estudo. O modelo da força de contato utilizado baseia-se na formulação de Hertz, considerando a inclusão do efeito dissipativo associado ao impacto entre o pino e o pistão. A força de atrito adotada baseia-se no atrito de Coulomb, porém adaptada à abordagem da dinâmica multicorpos. Tais modelos são validados com os resultados encontrados na literatura recente. A pesquisa apresenta contribuição na avaliação do efeito introduzido pela lubrificação hidrodinâmica na junta com folga. Dois modelos de lubrificação hidrodinâmica são avaliados: o primeiro apresenta uma solução direta e de baixo custo computacional; o segundo modelo obtém uma solução numérica que leva em consideração o efeito da aceleração imposta ao fluido lubrificante pelo movimento do mecanismo. A resposta dinâmica é obtida sob a variação paramétrica do tamanho da folga e a velocidade de rotação da manivela. Ao final, agrega-se ao sistema um modelo simplificado de geração da curva de pressão para um motor de combustão interna típico. Observou-se que a inclusão do modelo de lubrificação proposto não garante a sustentação do pino-pistão em regime de lubrificação hidrodinâmica durante as simulações efetuadas. Desta maneira, faz-se necessário o desenvolvimento de um modelo de lubrificação hidrodinâmica e elastohidrodinâmica capaz de determinar o comportamento no contato pino-pistão de maneira mais realista
Abstract: This work presents the development of a dynamic model for the slider-crank mechanism with clearance on the piston-pin revolute joint. The equations of motion for this system are obtained by Lagrange's method and the effects related to contact, friction and lubrication at the elements that operate in the clearance are the targets of study. The contact force model used in this work is based on Hertz formulation, considering the inclusion of the dissipative effect associated with the impact between the pin and the piston. The frictional force adopted is based on the Coulomb friction but adapted to the multibody dynamics approach. Such models are validated with the results found in recent literature. The research presents contribution in evaluating the effect introduced by hydrodynamic lubrication in the revolute joint clearance. Two models of hydrodynamic lubrication are investigated: the first model presents a direct solution of low computational cost, the second model results in a numerical solution that consider the effect of the acceleration of the lubricant fluid imposed on the movement of the mechanism. The dynamic response is studied for different sets of parameters of clearance and rotational speed of the crank. Moreover, a simplified model of the generation of the pressure curve for a typical internal combustion engine was included in the system. It was observed that the present lubrication model does not guarantee the support of the pin-piston system for hydrodynamic lubrication in the present simulations. Therefore, it is necessary to develop a more realistic model of hydrodynamic lubrication and elastohydrodynamic lubrication that is capable of reproducing the behavior of the piston-pin contact
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica

The continued development of increasingly compact and efficient laser sources, advanced laser optics and optical techniques has provided the basis for significant steps forward in research towards practical proof-of-concept demonstration of LI in IC engines. Before this goal could be realised, however, research was needed to characterise the laser beam parameters required for LI under true engine conditions and to. demonstrate the feasibility of an optical system capable of delivering such laser beam parameters from the most' appropriate high power pulsed laser source available. This dissertation discusses research undertaken in the Department of Engineering at the University of Liverpool, in which a prototype laser ignition system has been developed and used to successfully ignite, and run for extended periods, one cylinder of a 4-cylinder petrol-fuelled IC test engine. The laser ignition system was based on a Q-switched lamp-pumped Nd: YAG laser operating at 1064 nm wavelength and with pulse duration configurable between 6ns and 15ns. The research was supported by the Department of Trade and Industry (DTI), through a 3Y2 year project 'Laser Ignition in IC Engines (LASIIC)' awarded under the Foresight Vehicle LINK initiative to partners Ford Motor Company, GSI Group and the University of LiverpooI. The experimental work has largely addressed the development and implementation of free-space (or direct) laser beam delivery in order to practically realise the prototype LI system, although optical fibre delivery was also addressed in part. The variation of several laser parameters and their effect on the control of engine performance are discussed, but primarily centring on the influence of pulse energy and focused beam waist· diameters at the combustion point. The engine performance was measured in terms of changes in Coefficient of Variation (COV) of mean and peak engine cylinder pressure values with laser input parameters. Laser pulse energies of up to 30 mJ at the cylinder were used to obtain power densities at the focused· beam waist of up to 4470 GWcm·2 • The minimum ignition energy (MIE) required for successful ignition (no misfires) was measured as 4 mJ for a pulse length of 6 ns, which compares to 30 mJ in I ms for a typical spark plug and suggests the likely ·laser and power supply requirements of a future laser ignition system. The power density required to be delivered into the combustion volume has a minimum value of 545 GW/cm2 , which gave comparable or better COVs, than conventional spark ignition. These power densities are significantly less than that required to produce dielectric breakdown in air, due to the high values ofpressure in the cylinder up to 20 bars, but are high enough to conclude that dielectric breakdown is the dominant mechanism ofLl in this case. One potential benefit of LI realised during the work has been the ability to vary the focal position within the combustion chamber, which is not available with spark ignition due to the fixed spark plug. Using a 'design, build and test' approach, the work therefore investigated the effect of varying the focal point position of the beam waist within the combustion volume through a number of configurations of the laser ignition system optics. Once stable combustion had been achieved, further investigations were carried out into optimising laser parameters for ignition control. Earlier work had suggested that laser-induced damage in optical media could affect the achievement of a robust LI system for continuous delivery of such high pulse energies and short pulse lengths, or at least detennine the most appropriate fonn of beam delivery for such high power pulsed laser sources. Hence, a study was also undertaken on laser parameters and beam conditions that could give rise to laser-induced optical damage in system components and the damage mechanisms involved. The work also considers a self-cleaning effect of the pulsed laser radiation and its role in preventing 'sooting' of optical window materials placed at the boundary of the combustion chamber, which has been one of the key problems in earlier LI studies. To complete the experimental work, the prototype laser ignition system was further developed for implementation on a spray guided direct injection (SGDI) test engine at Ford Motor Company's European test facility at Merkenich in Germany. The results obtained were both unique and publishable.

The effect of charge stratification on the lean mixture combustion in a Ricardo E6 single cylinder, variable compression, spark ignition engine has been investigated. The charge stratification process involved injecting small amounts of pure methane gas into the engine cylinder through a modified spark plug just prior to ignition, at a relatively low pressure. Methane injection timing and methane injection duration (or injection rate) were controlled electronically and varied over a range of values. The charge stratification experiment was performed with two different types of inlet mixture. They were :- (1). gasoline fuel injected into the inlet manifold (2). methane gas carburetted through the inlet manifold To examine the effects of charge stratification, a few optimisation studies were undertaken prior to the main combustion experiments. A combustion chamber simulation was performed to visualise the effects of the velocity field on the injected methane gas. For this a constant volume bomb was built with the same bore as that of the Ricardo engine cylinder. A typical set of velocity fields around the spark plug gap location were established using hot wire anemometry, and relevant positions of the injected methane gas at different times from the injection point in the simulated velocity field were captured through Schlieren photography. The present work has led to the following conclusions:- (1). lean limit of the inducted fuel mixture is extended through the charge stratification process (2). effectiveness of charge stratification is well pronounced at lean air - fuel ratios (3). HC emission is higher with stratified charge combustion compared with base line operation (4). CO emission with stratified charge combustion is almost the same as or little lower than with base line operation, at leaner air - fuel ratios (5). the initially small and compact shape of the injected methane gas appearing in the Schlieren photographs could have a positive influence on the flame initiation phase.

This thesis traces and critically reviews recent developments in hydrogen fuelling of internal combustion engines. It reports the development of an improved fuelling system that has been tested on a Ricardo E6 variable compression spark ignition engine, in the Thermodynamics laboratory, Department of Mechanical Engineering at the University of Canterbury. The introduction of hydrogen to an internal combustion engine via the inlet manifold (external mixture formation), often results in the occurrence of pre-ignition. This is because hydrogen, with its low ignition energy and extreme lean limit of flammability, is easily ignited by residual gases or hot spots in an engine cylinder. If pre-ignition occurs before inlet valve closure, the mixture may burn back through pre-mixed gases in the inlet manifold. Another serious disadvantage with external mixture formation is that hydrogen displaces a large volume of air, effectively reducing the volumetric efficiency of the engine. To overcome these problems hydrogen may be injected directly into an engine combustion chamber during the compression stroke, although if injection commences too early in the stroke pre-ignition may still occur. It is thus considered that the most desirable system for fuelling an internal combustion engine on hydrogen is to employ direct gaseous injection at high pressure late in the compression stroke. There are a number of problems involved with the design and development of a suitable high pressure hydrogen direct injector. In particular the injector must actuate rapidly and be controllable to a high degree of accuracy to consistently meter precise quantities of fuel at each injection. Leakage of hydrogen through the injector when closed must be minimised in order to avoid unnecessary fuel wastage and to prevent the build up of a flammable pre-mixed mixture that could lead to pre-ignition. A suitable injector has been designed and tested. The injector is electromagnetically actuated for electronic control of injection timing and duration (control of injection duration being necessary to vary the quantity of fuel delivered). The injector has a nominal lift distance of 0.2 mm and can be opened for durations as short as 1 ms. A fluorocarbon elastomer Quad-ring was used in the seat of the valve to provide a leak free seal for the high pressure hydrogen. Engine testing was conducted to determine the performance of the valve. The engine was tested on hydrogen for compression ratios of 8:1, 10:1 and 12:1 over a range of operating conditions. Results of engine performance, complete with combustion chamber pressure traces and exhaust gas emission analysis are presented. The design concept has proven to be successful with satisfactory operation of the engine on hydrogen without any combustion related problems. The elastomeric seal, although providing leak free operation, had an average lifetime of about 30 minutes. Future injector development work should focus on devising a highly durable injector seat seal which minimises leakage.

Thesis (MScEng)--University of Stellenbosch, 2001.
ENGLISH ABSTRACT: Statistical experimental design techniques are powerful tools that are often approached with suspicion and apprehension by experimenters. The trend is to avoid any statistically structured and designed experimentation program, and to rather use the traditional method of following ones "gut feel". This approach, more often than not, will supply a satisfactory solution, but there is so much more information availablefor the same amount of effort. This thesis strives to outline the method and application of the Taguchi methodology of experimental design. The Taguchi method is a practical, statistical experimental design technique that does not rely on the designer's knowledge of the complex statistics typicallyneeded to design experimental programs, a fact that tends to exclude design of experiments from the averageengineers' toolbox. The essence of the statistical design of experiments is this: The traditional method of varying one variable at a time and investigating its effect on an output is no longer sufficient. Instead all the input variables are varied at the same time in a structured manner. The output trends resulting from each input variable are then statisticallyextracted from the data in the midst of the variation. Taguchi method achieves this by designing experiments where every level of every input variable occurs an equal number of times with every level of every other input variable. The experimental designs are represented in orthogonal arrays that are chosen and populated by the experimenter by following a simple procedure. Four case studies are worked through in this text and, where possible, compared to the "traditional" approach to the same problem. The case studies show the additional information and time savings availablewith the Taguchi method, as well as clearlyindicating the importance of using a stable system on which to do the experiments. The Taguchi method generated more information in fewer experiments than the traditional approaches as well as allowing analysis of problems too complex to analysewithout a statisticaldesign of the experimentation procedure.
AFRIKAANSE OPSOMMING: Statistiese eksperimentele ontwerptegnieke is besonder kragtige instrumente wat baie keer met agterdog deur ekspermenteerders beheen word. Die neiging is om enige statistiese gestruktureerde and ontwerpte eksperimentele program te vermy, en om liewer die tradisionele metode, wat op 'n mens se intuïsie staatmaak, te gebruik. Hierdie benadering sal baie keer 'n bevredigende oplossing gee, maar daar is veel meer inligting vir dieselfde hoeveelheid inspanning verkrygbaar, wanneer die Taguchimetode gebruik word. Hierdie tesis strewe om die metode en toepassing van die Taguchimetodologie van eksperimentele ontwerp voor te lê. Die Taguchimetode is 'n praktiese statistiese eksperimentele ontwerptegniek .wat nie op die ontwerper se kennis van komplekse statistiek om eksperimentele programme te ontwerp berus nie. Hierdie komplekse statistiek neig ook om eksperimentele ontwerp van die gemiddelde ingenieursvaardigehede uit te sluit. Die kern van statistiese eksperimentele ontwerp is die volgende: Die tradisionele metode van een veranderlike op 'n slag te varieer om die effek op die uitset te ondersoek, is onvoldoende. In plaas daarvan, word al die insetveranderlikes gelyktydig gevarieer in 'n gestruktureered manier. Die neigings van elke veranderlike is dan statisties ontleed van die data ten midde van die variasie van al die ander veranderlikes. Die Taguchimetode bereik die ontwerpte eksperimente deur elke vlak van elke insetveranderlik in 'n gelyke aantal keer met elke vlak van elke ander insetveranderlike te varieer. Hierdie is verteenwoordig deur ortogenale reekse wat gekies en gevul is deur 'n eenvoudige wisselpatroon te volg. Vier gevallestudies is deurgewerk en, waar moontlik, vergelyk met die tradisonele siening van dieselfde probleem. Die gevallestudies wys hoe toereikbaar die additionele inligting in die Taguchimethode toepassings is. Hulle beklemtoon ook die belangrikheid van 'n stabiele sisteem waarop die eksperimente berus. Die Taguchimetode het meer inligting verskaf met minder eksperimente as die tradisionele toenaderings, en ook toegelaat dat die analise van probleme, te kompleks om te analiseer sonder om 'n statistiese ontwerp van eksperimentele prosedure te volg, opgelos kon word.

The control system has been suggested to convert the nonlinear model to a linearized plant model. Therefore, we characterized the engine model based on certain aspects and analyzed it accurately to fit in the system. Simulations were performed using the PID controller to regulate and maintain the output response while rejecting any input disturbance. An engine model of a control system shows an essential role in defining the correct parameters. Hence, Idle speed control is the principal of the highest confrontations for the automotive industry and developers as they were addressing many issues concerning engine at rest position and fuel-saving economy. We keep many experiments with changing values of the PID control system. Through Simulink graphs, we compared different results and were able to find the correct value for the Idle Speed Control of the engine model. Hence, this system control predicts the control change in the system for stable equilibrium. Via manual tuning of PID control parameters, we were able to linearize the plant model and determine the correct parameters of the plant model. This study also presents an AFR control for the engine model. The main contribution is that AFR regulation is reformulated as a tracking control for the required injected fuel. To obtain a better response, the output measurement is added to a predefined AFR control. The parameter tuning is straightforward, while better AFR control response and reduction can be achieved compared to the PID control. The AFR control has been studied for internal combustion engines based on the mean value model. The control design method based on nonlinear feedback control and their control performance has been investigated for different cases. The simulation results show that the controller applying the nonlinear feedback control could give satisfactory AFR regulation performances for our engine model with specific load disturbance.

Abstract Large Eddy Simulation in internal combustion Engine Dipl.-Ing Matteo Ghel� The internal combustion (IC) engine simulation is nowadays one of the most difficult proceeding during engine development. Simultaneously this is one of the most important phase because it leads to better acknowledgment of in-cylinder phenomena and suggests new method of emission reduction and control.\\ Large Eddy Simulation (LES) can help this process because of its instationary nature, in perfect agreement with motion, injection and combustion, typical instationary components in this kind of study.\\ This work focuses on a method which includes all the phenomena happening during IC engine cycle in a LES. \\ The main purpose of this work is to include combustion on the simulation obtaining a complete engine cycle. The work concentrates in particular on models development and investigation of the perfect computational domain movement, necessary to reach an optimal resolution during all the engine cycle phases. \\

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.
Includes bibliographical references (leaf 36).
To meet the needs of forward deployed soldiers and disaster relief personnel, a mobile water distillation system was designed and tested. This system uses waste engine heat from the exhaust flow of an internal combustion engine to vaporize water for the purpose of removing impurities. The vapor is condensed back down to water in a finned condenser that experiences forced convection. The system pumps heat transfer oil through a 0.61 meter long, cross flow, annulus-type heat exchanger installed over a section of exhaust pipe where the oil experiences a AT of 7°C. The hot heat transfer oil is then piped to a boiler where it releases its heat to the water and returns to the exhaust heat exchanger to be reheated. Testing demonstrated that the system has a heat up time of 30 minutes, and a steady state distillation rate of 2 gallons per hour. In steady state, the system removes and transfers heat from the exhaust at a rate of 4600 Watts.
by Kevin S. Mears.
S.B.