Dissertations / Theses: 'SI-engine'

1

Westin, Fredrik. "Accuracy of turbocharged SI-engine simulations." Licentiate thesis, KTH, Machine Design, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1491.

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This licentiate thesis deals mainly with modelling ofturbocharged SIengines. A model of a 4-cylinder engine was runin both steady state and transient conditions and the resultswere compared to measured data. Large differences betweenmeasurements and simulations were detected and the reasons forthis discrepancy were investigated. The investigation showedthat it was the turbocharger turbine model that performed in anon-optimal way. To cope with this, the turbine model containedparameters, which could be adjusted so that the model resultsmatched measured data. However, it was absolutely necessary tohave measured data to match against. It was thus concluded thatthe predictivity of the software tool was too poor to try topredict the performance of various boosting systems. Thereforemeans of improving the modelling procedure were investigated.To enable such an investigation a technique was developed tomeasure the instantaneous power output from, and efficiency of,the turbine when the turbocharger was used on the engine.

The projects initial aim was to predict, throughsimulations, the best way to boost a downsized SI-engine with avery high boost-pressure demand. The first simulation run on astandard turbocharged engine showed that this could not be donewith any high accuracy. However, a literature study was madethat presents various different boosting techniques that canproduce higher boost pressure in a larger flow-range than asingle turbocharger, and in addition, with smallerboost-pressure lag.

Key words:boosting, turbocharging, supercharging,modelling, simulation, turbine, pulsating flow, unsteadyperformance, SI-engine, measurement accuracy

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2

Renberg, Ulrica. "1D engine simulation of a turbocharged SI engine with CFD computation on components." Licentiate thesis, KTH, Machine Design (Div.), 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9162.

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1D engine simulations of turbocharged engines are difficult to

Techniques that can increase the SI- engine efficiency while keeping the emissions very low is to reduce the engine displacement volume combined with a charging system. Advanced systems are needed for an effective boosting of the engine and today 1D engine simulation tools are often used for their optimization.

This thesis concerns 1D engine simulation of a turbocharged SI engine and the introduction of CFD computations on components as a way to assess inaccuracies in the 1D model.

1D engine simulations have been performed on a turbocharged SI engine and the results have been validated by on-engine measurements in test cell. The operating points considered have been in the engine’s low speed and load region, with the turbocharger’s waste-gate closed.

The instantaneous on-engine turbine efficiency was calculated for two different turbochargers based on high frequency measurements in test cell. Unfortunately the instantaneous mass flow rates and temperatures directly upstream and downstream of the turbine could not be measured and simulated values from the calibrated engine model were used. The on-engine turbine efficiency was compared with the efficiency computed by the 1D code using steady flow data to describe the turbine performance.

The results show that the on-engine turbine efficiency shows a hysteretic effect over the exhaust pulse so that the discrepancy between measured and quasi-steady values increases for decreasing mass flow rate after a pulse peak.

Flow modeling in pipe geometries that can be representative to those of an exhaust manifold, single bent pipes and double bent pipes and also the outer runners of an exhaust manifold, have been computed in both 1D and 3D under steady and pulsating flow conditions. The results have been compared in terms of pressure losses.

The results show that calculated pressure gradient for a straight pipe under steady flow is similar using either 1D or 3D computations. The calculated pressure drop over a bend is clearly higher1D engine simulations of turbocharged engines are difficult to using 1D computations compared to 3D computations, both for steady and pulsating flow. Also, the slow decay of the secondary flow structure that develops over a bend, gives a higher pressure gradient in the 3D calculations compared to the 1D calculation in the straight pipe parts downstream of a bend.

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3

Niekamp, Troy S. (Troy Steven). "Translation of dilution tolerance for gasoline SI engine." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/81616.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 69-70).
There are a variety of fuel improvement strategies being developed for spark ignition engines which use dilution. Many of these technologies use a combination of different diluents. It is impractical in optimizing these technologies to test every possible combination of diluents. The purpose of this study was to determine a relationship between the various diluents and combustion related output parameters. One of these key outputs was determining the dilution tolerance for an engine. In order to achieve this goal, the fundamental of combustion were studied. The results from this study will be useful in developing more aggressive engine control strategies. Dilution has been studied extensively in previous research. Its effects are well known. Primarily, it reduces peak combustion temperatures. This can be used as an effective means to reduce losses and hazardous emissions. Too much dilution, however, and the combustion stability is compromised. To facilitate this project, an engine was fully instrumented. Experiments were performed for a variety of operating conditions and diluents. Results were then used to correlate the diluent properties and quantities to combustion outputs. Adiabatic flame temperature was first attempted as the key metric for correlation. This metric proved to be unsuitable for developing correlations. Later, a new metric was computed by taking a linear combination of diluents. This was found to offer superior results. Using this metric along with other basic engine measurements, correlations were developed between the diluents and engine output parameters. These output parameters include dilution tolerance, exhaust temperature, NOx emissions, and combustion bum durations.
by Troy S. Niekamp.
S.M.

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4

Frisk, Erik. "Model-based fault diagnosis applied to an SI-Engine." Thesis, Linköpings universitet, Fordonssystem, 1996. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-141630.

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A diagnosis procedure is an algorithm to detect and locate (isolate) faulty components in a dynamic process. In 1994 the California Air Resource Board released a regulation, called OBD II, demanding a thorough diagnosis system on board automotive vehicles. These legislative demands indicate that diagnosis will become increasingly important for automotive engines in the next few years. To achieve diagnosis, redundancy has to be included in the system. This redundancy can be either hardware redundancy or analytical redundancy. Hardware redundancy, e.g. an extra sensor or extra actuator, can be space consuming or expensive. Methods based on analytical redundancy need no extra hardware, the redundancy here is generated from a process model instead. In this thesis, approaches utilizing analytical redundancy is examined. A literature study is made, surveying a number of approaches to the diagnosis problem. Three approaches, based on both linear and non-linear models, are selected and further analyzed and complete design examples are performed. A mathematical model of an SI-engine is derived to enable simulations of the designed methods.

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5

Tidefelt, Henrik. "Applied Output Error Identification: SI Engine Under Normal Operating Conditions." Thesis, Linköping University, Department of Electrical Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2380.

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This report presents work done in the field of output error identification, with application to spark ignition (SI) engine identification for the purpose of air to fuel ratio control. The generic parts of the project consist mainly in setting out the basis for the design of output error identification software. Efficiency issues related to linear state space models have also been explored, and although the software design is not made explicit in this report, many of the important concepts have been implemented in order to provide powerful abstractions for the application to SI engine identification.

The SI engine identification data was obtained under normal operating conditions. The goal is to re- estimate models without utilizing a virtual measurement which has been used successfully to estimate models in the past. This turns out to be a difficult problem much related to the lack of excitation in the system input, shortcomings of the fuel dynamics model and the unknown and hard to estimate exhaust sensor characteristics. Indeed, the larger of the previously estimated models are found not to be identifiable in the present situation. However, trivial restrictions of the models (not meaning restriction to trivial models) avoid that problem.

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6

Goldwitz, Joshua A. (Joshua Arlen) 1980. "Combustion optimization in a hydrogen-enhanced lean burn SI engine." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/27061.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.
Includes bibliographical references (p. 95-97).
Lean operation of spark ignition (SI) automotive engines offers attractive performance incentives. Lowered combustion temperatures inhibit NO[sub]x pollutant formation while reduced manifold throttling minimizes pumping losses, leading to higher efficiency. These benefits are offset by the reduced combustion speed of lean mixtures, which can lead to high cycle-to-cycle variation and unacceptable engine behavior characteristics. Hydrogen-enhancement can suppress the undesirable consequences of lean operation by accelerating the combustion process, thereby extending the "lean limit." Hydrogen can be produced onboard the vehicle with a plasmatron fuel reformer device. Combustion optimization experiments focused on three key areas: the ignition system, charge motion in the inlet ports, and mixture preparation. The ignition system tests compared a standard inductive coil scheme against high-energy discharge systems. Charge motion experiments focused on the impact of turbulence patterns generated by conventional restrictor plates as well as novel inlet flow modification cones. The turbulent motion of each configuration was characterized using swirl and tumble flow benches. Mixture preparation tests compared a standard single-hole pintle injector against a fine atomizing 12-hole injector. Lastly, a further series of trials was also run to investigate the impact of high exhaust gas recirculation (EGR) dilution rates on combustion stability. Results indicate that optimizations of the combustion system in conjunction with hydrogen-enhancement can extend the lean limit of operation by roughly 25% compared against the baseline configuration. Nearly half of this improvement may be attributed to improvements in the combustion system.
(cont.) An inductive ignition system in conjunction with a high tumble-motion inlet configuration leads to the highest levels of combustion performance. Furthermore, hydrogen enhancement affects a nearly constant absolute improvement in the lean misfire limit regardless of baseline combustion behavior. Conversely, the amount of improvement in the point of peak engine NIMEP output is inversely related to the level of baseline performance.
by Joshua A. Goldwitz.
S.M.

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7

Westling, Joel, and Haris Subasic. "Effects and Models of Water Injection in an SI Engine." Thesis, Linköpings universitet, Fordonssystem, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-148952.

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Downsizing and turbocharging is a popular combination nowadays in cars inorder to decrease the fuel consumption. However, the boost pressure increasesthe risk of engine knock, limiting the engine in high-load operating points. Inthe current engines, fuel is used to cool the engine in these operating points,leading to a higher fuel consumption. Water injection is an effective method tomitigate knock and enable a more aggressive ignition. It enables the engine toproduce more power and cools the exhaust, thereby protecting the turbochargerand the catalyst from wear. In this thesis, the effects of injecting water in anengine is investigated and a further development of a cylinder pressure model,with a model that takes the water into account, is presented and validated. Themodel can be used to estimate the cylinder pressure in several operating points.

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Kapadia, Bhavin Kanaiyalal. "Development Of A Single Cylinder SI Engine For 100% Biogas Operation." Thesis, Indian Institute of Science, 2006. https://etd.iisc.ac.in/handle/2005/283.

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This work concerns a systematic study of IC engine operation with 100% biogas as fuel (as opposed to the dual-fuel mode) with particular emphasis on operational issues and the quest for high efficiency strategies. As a first step, a commercially available 1.2 kW genset engine is modified for biogas operation. The conventional premixing of air and biogas is compared with a new manifold injection strategy. The effect of biogas composition on engine performance is also studied. Results from the genset engine study indicate a very low overall efficiency of the system. This is mainly due to the very low compression ratio (4.5) of the engine. To gain further insight into factors that contribute to this low efficiency, thermodynamic engine simulations are conducted. Reasonable agreement with experiments is obtained after incorporating estimated combustion durations. Subsequently, the model is used as a tool to predict effect of different parameters such as compression ratio, spark timing and combustion durations on engine performance and efficiency. Simulations show that significant improvement in performance can be obtained at high compression ratios. As a step towards developing a more efficient system and based on insight obtained from simulations, a high compression ratio (9.2) engine is selected. This engine is coupled to a 3 kW alternator and operated on 100% biogas. Both strategies, i.e., premixing and manifold injection are implemented. The results show very high overall (chemical to electrical) efficiencies with a maximum value of 22% at 1.4 kW with the manifold injection strategy. The new manifold injection strategy proposed here is found to be clearly superior to the conventional premixing method. The main reasons are the higher volumetric efficiency (25% higher than that for the premixing mode of supply) and overall lean operation of the engine across the entire load range. Predictions show excellent agreement with measurements, enabling the model to be used as a tool for further study. Simulations suggest that a higher compression ratio (up to 13) and appropriate spark advance can lead to higher engine power output and efficiency.

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Kapadia, Bhavin Kanaiyalal. "Development Of A Single Cylinder SI Engine For 100% Biogas Operation." Thesis, Indian Institute of Science, 2006. http://hdl.handle.net/2005/283.

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This work concerns a systematic study of IC engine operation with 100% biogas as fuel (as opposed to the dual-fuel mode) with particular emphasis on operational issues and the quest for high efficiency strategies. As a first step, a commercially available 1.2 kW genset engine is modified for biogas operation. The conventional premixing of air and biogas is compared with a new manifold injection strategy. The effect of biogas composition on engine performance is also studied. Results from the genset engine study indicate a very low overall efficiency of the system. This is mainly due to the very low compression ratio (4.5) of the engine. To gain further insight into factors that contribute to this low efficiency, thermodynamic engine simulations are conducted. Reasonable agreement with experiments is obtained after incorporating estimated combustion durations. Subsequently, the model is used as a tool to predict effect of different parameters such as compression ratio, spark timing and combustion durations on engine performance and efficiency. Simulations show that significant improvement in performance can be obtained at high compression ratios. As a step towards developing a more efficient system and based on insight obtained from simulations, a high compression ratio (9.2) engine is selected. This engine is coupled to a 3 kW alternator and operated on 100% biogas. Both strategies, i.e., premixing and manifold injection are implemented. The results show very high overall (chemical to electrical) efficiencies with a maximum value of 22% at 1.4 kW with the manifold injection strategy. The new manifold injection strategy proposed here is found to be clearly superior to the conventional premixing method. The main reasons are the higher volumetric efficiency (25% higher than that for the premixing mode of supply) and overall lean operation of the engine across the entire load range. Predictions show excellent agreement with measurements, enabling the model to be used as a tool for further study. Simulations suggest that a higher compression ratio (up to 13) and appropriate spark advance can lead to higher engine power output and efficiency.

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10

Gustafsson, Karin. "Ion Current Dependence on Operating Condition and Ethanol Ratio." Thesis, Linköping University, Department of Electrical Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8053.

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This masters thesis investigates the possibility to estimate the ethanol content in the fuel using ion currents. Flexible fuel cars can be run on gasoline-ethanol blends with an ethanol content from0 to 85 percentage. It is important for the engine control system to have information about the fuel. In todays cars the measurements of the fuel blend are done by a sensor. If it is possible to do this with ion currents this can be used to detect if the sensor is broken, and then estimate the ethanol content until the sensor gets fixed. The benefit

of using ion currents is that the signal is measured directly from the spark plug and therefore no extra hardware is needed. To be able to see how the ethanol ratio affects the ion currents, the dependencies of the operating point have been investigated. This has been done by a literature review and by measurements in a Saab 9-3. Engine speed, load, ignition timing, lambda and spark plugs effects on the ion currents are especially studied. A black box model for the ion currents dependence on operating point is developed. This model describes the engine speed, load and ignition timing dependencies well, but it can not be used to estimate the ethanol ratio.

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11

Argolini, Roberto, and Viviana Bloisi. "On optimal control of the wastegate in a turbocharged SI engine." Thesis, KTH, Reglerteknik, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-106241.

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The project aims to improve positive torque transient response through more advanced wastegate controllers than what are used today. All controllers are developed for a standard General Motors turbocharged engine. In many turbocharged SI engines, a wastegate is used for preventing the turbine to overrun and to decrease the pumping loss. Today, the wastegate is controlled by a PI controller, which tries to fulfill a compromise between fuel consumption and torque response by regulating the wastegate position. A nonlinear Mean Value Engine Model (MVEM) of this engine, with 13 states and linearized in 45 different working points, is used. The original model, implemented in Matlab/Simulink, has been enriched with new features, like lambda and spark advance efficiencies and the related exhaust temperature correction. The project aims to do a theoretical analysis to find the optimal control of wastegate position, investigating also spark retard and fuel enrichment during a positive torque transient. First a solution for achieving optimal wastegate control is designed, based on Linear Quadratic (LQ) approach. Since the optimal control strategy is expected to vary quite much for different working points, a gain scheduling architecture has been investigated. An independent lambda controller has been developed, in order to maximize the lambda efficiency and quicken the torque response during transient. Since the system operates near a constraint boundary, another solution based on Model Predictive Control (MPC) of the wastegate has been investigated. The MPC design has been extended also to a MIMO formulation, adding the throttle and the air to fuel ratio as control inputs, and the trade off between fast torque response and fuel economy is analyzed. A complete realtime MPC implementation, with the capability for automatic code generation in the dSpace microAutobox environment, requires the model, now with 13 states, to be reduced to a minimum state space order. The extent of model reduction that is required and the possible performance deterioration have been investigated.

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12

Etheridge, Jonathan Edward. "Modelling the SI-HCCI transition in a GDI internal combustion engine." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609621.

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13

Summers, Tim. "Fast-response FID measurement of SI engine residual gas hydrocarbon concentration." Thesis, University of Cambridge, 1996. https://www.repository.cam.ac.uk/handle/1810/272772.

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14

Coates, Barnaby Paul. "Investigation of engine design parameters on the efficiency and performance of the high specific power downsized SI engine." Thesis, Brunel University, 2012. http://bura.brunel.ac.uk/handle/2438/12404.

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This study investigates the impact of employing the Miller cycle on a high specific power downsized gasoline engine by means of Early Intake Valve Closing (EIVC) and Late Intake Valve Closing (LIVC). This investigation assesses the potential for the Miller cycle to improve fuel economy at part load points, as well as high load points with significantly elevated boost pressures (Deep Miller) of up to 4 bar abs. The impact of geometric Compression Ratio (CR) and Exhaust Back Pressure (EBP) has also been investigated. The knock mitigating qualities of Deep Miller have been assessed, and its ability to increase maximum engine load explored. Low Speed Pre-ignition (LSPI) and autoignition tendencies with reduced coolant flow rates and with aged and new fuels have also been studied. This study comprises both experimental and analytical studies. A Ricardo Hydra single cylinder thermodynamic engine was developed and used for the experimental component of the study. This engine features a high specific power output (120kW/l) cylinder head from the Mahle 1.2l 3 cylinder aggressively downsized engine. The analytical component was carried out using a 1-dimensional GT-Power model based on the Ricardo Hydra experimental engine. A Design of Experiments (DoE) based test plan was adopted for this analytical study. The experimental study found that EIVC was the optimal strategy for improving fuel economy at both part-load and high-load conditions. LIVC yielded a fuel economy penalty at part-load operations and a fuel economy improvement at high-loads. The unexpected part-load LIVC result was attributed to the engine breathing dynamics of the experimental engine. The analytical study found moderate LIVC to be the optimal strategy at lower speeds, unless compensation for the increased degree of scavenging experienced with EIVC was compensated for, in which case EIVC was optimum. At higher speeds EIVC was found to be optimum regardless of whether or not compensation for scavenging was employed. It was generally found that less sensitivity to EBP was exhibited the more extreme the EIVC and LIVC. It was also found that a higher geometric CR could be tolerated with extreme EIVC and LIVC, and a fuel economy benefit could be obtained through the elevation of Geometric CR.

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15

Rosén, Anna. "Air/Fuel Ratio Control of an SI-Engine Under Normal Operation Conditions." Thesis, Linköping University, Department of Electrical Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2448.

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Emission from cars today is one of the biggest environmental issues, hence stringent government standards have been introduced to decrease emission. Car companies do not only have to satisfy government standards, but also meet consumer demands on increased fuel economy and good drivablility. This report will introduce controllers designed to control the air/fuel ratio in an SI engine. The engine model used is simplified. The engine components modelled include the inlet manifold, fuel dynamics, combustion and exhaust sensor.

Nonlinearities and delays are inherent in the engine dynamics and as such a Smith Predictor is utilised as the basis for controller structure to compensate for the delays. Here the Smith Predictor is combined with feedforwarding of the mass air charge, which is estimated from both the inlet and combustion models. Therefore different ways of merging the estimates are also explored.

A real engine was not accesible, thus simulators were implemented using data sets provided by General Motors. Model errors were introduced to test the controllers performance. The proposed methods should be tested on a real engine to ensure that this isa viable approach, as the simulations show it maybe promising to use in practice.

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16

Hadjiconstantinou, Nicolas G. (Nicholas George). "A model for conversting SI engine flame arrival signals into flame contours." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/35444.

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Bai, Yang. "Studies on SI engine simulation and air/fuel ratio control systems design." Thesis, Brunel University, 2013. http://bura.brunel.ac.uk/handle/2438/8342.

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More stringent Euro 6 and LEV III emission standards will immediately begin execution on 2014 and 2015 respectively. Accurate air/fuel ratio control can effectively reduce vehicle emission. The simulation of engine dynamic system is a very powerful method for developing and analysing engine and engine controller. Currently, most engine air/fuel ratio control used look-up table combined with proportional and integral (PI) control and this is not robust to system uncertainty and time varying effects. This thesis first develops a simulation package for a port injection spark-ignition engine and this package include engine dynamics, vehicle dynamics as well as driving cycle selection module. The simulations results are very close to the data obtained from laboratory experiments. New controllers have been proposed to control air/fuel ratio in spark ignition engines to maximize the fuel economy while minimizing exhaust emissions. The PID control and fuzzy control methods have been combined into a fuzzy PID control and the effectiveness of this new controller has been demonstrated by simulation tests. A new neural network based predictive control is then designed for further performance improvements. It is based on the combination of inverse control and predictive control methods. The network is trained offline in which the control output is modified to compensate control errors. The simulation evaluations have shown that the new neural controller can greatly improve control air/fuel ratio performance. The test also revealed that the improved AFR control performance can effectively restrict engine harmful emissions into atmosphere, these reduce emissions are important to satisfy more stringent emission standards.

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Thornberg, Nils, and Kraft Jonas Eriksson. "Physically Based Modelling for Knock Prediction in SI Engines." Thesis, Linköpings universitet, Fordonssystem, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-149020.

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The high demand for an increase in performance and at the same time loweringthe emissions is forcing the automotive industry to increase the efficiency of thevehicles. This demand lead to a problem called knock, which often is the limitingfactor when increasing the efficiency of the engine. Knock occurs when theunburned gases inside the combustion chamber self-ignites due to the increasingpressure and temperature.This thesis investigates if it is possible to predict knock with a physicallybased knock model. The model consist of several sub-models such as pressuremodel, temperature model and knock model. The models are built by using measureddata and the goal is to get an independent knock prediction model that canfind the limited ignition angle that will cause knock.The results shows that an analytic pressure model can simulate a measuredpressure curve. But when it comes to predicting knock, there is an uncertaintywhich can be improved by changing the modelling strategy and making the modelsmore accurate.

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Hashemzadeh, Nayeri Mohit. "Cylinder-by-Cylinder Torque Model of an SI-Engine for Real-Time Applications." Thesis, Linköping University, Department of Electrical Engineering, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5396.

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In recent years Hardware-in-the-Loop HiL, has gained more and more

popularity within the vehicle industry. This is a more cost effective research alternative, as opposed to the tests done the traditional way, since in HiL testing the idea is to test the hardware of interest, such as an electronic control unit, in a simulated (or partially simulated) environment which closely resembles the real-world environment.

This thesis is ordered by Daimler Chrysler AG and the objective of this thesis is the developing of a cylinder-by-cylinder model for the purpose of emulation of misfire in a four-stroke SI-engine. This purpose does not demand a precise modelling of the cylinder pressure but rather an adequate modelling of position and amplitude of the torque produced by each cylinder. The model should be preferebly computaionally tractable so it can be run on-line. Therefore, simplifications are made such as assuming the rule of a homogenous mixture, pressure and temperature inside the cylinder at all steps, so the pressure model can be analytical and able to cope with the real-time demand of the HiL. The model is implemented in Simulink and simulated with different sample rates and an improvement is to be seen as the sample rate is decreased.

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Kalian, Navin. "Investigation of CAI/SI operations ina a four-cylinder direct injection gasoline engine." Thesis, Brunel University, 2006. http://bura.brunel.ac.uk/handle/2438/5482.

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A four-cylinder, four-stroke, gasoline engine with direct injection fuel was commissioned and used to achieve CAI combustion. CAI combustion was achieved by employing short-duration, low-lift camshafts and early exhaust valve closure. Trapping sufficient volumes of exhaust residual provided the necessary thermal energy needed to initiate auto-ignition. The effects of valve opening durations on the CAI operation range were investigated at different air/fuel ratios, valve timings and injection timings. Furthermore the effect on engine performance, exhaust emissions, fuel consumption and combustion characteristics were also investigated. Methods which could be used for CAI combustion region enlargement were also studied. These included spark-assisted CAI at different EVC timings and valve durations, CAI operation at 2000 rpm and CAI combustion at late fuel injection timings

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Hardy, AliciA Jillian Jackson 1978. "Vehicle fuel economy benefit and aftertreatment requirement of an HCCI-SI engine system." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42986.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.
Includes bibliographical references (v. 2, p. 821-823).
This body of work dimensions the HCCI fuel economy benefits and required aftertreatment performance for compliance with emissions regulations in North America and Europe. The following parameters were identified as key factors influencing the benefit of implementing HCCI over driving cycle: * Power-to-weight ratio * Operation range of HCCI * Conditions of the driving cycle * Application of constraints that cause "un-natural" mode transitions * Application of transition penalties * Available after-treatment performance * Constraints imposed by emissions regulations This study shows that development priorities for attaining maximal fuel economy benefit during urban driving cycles differ greatly in North America and in Europe due to differences in emissions regulations. The combined effect of increasing power-to-weight ratio, increasing the operation range of HCCI, removing operational constraints on HCCI implementation, and reducing fuel penalties associated with transitions into and out of HCCI mode is shown to double the emissions-constrained fuel economy benefit of HCCI during the new European driving cycle. These factors are shown to have modest impact on fuel economy benefit of HCCI during the North American city driving cycle when compliance with the more stringent emissions regulations is required. In order to attain maximal fuel economy benefit and comply with emissions regulations in California, improving conversion efficiencies in the aftertreatment of lean engine exhaust must be a primary focus. Fuel economy benefit of HCCI during the highway driving cycles is shown to be most responsive to the amount of time the engine spends in the speed and load range of HCCI operation. Time spent in HCCI mode during these driving cycles is most heavily influenced by changes in power-to-weight ratio and upper load limit for HCCI.
by AliciA Jillian J Hardy.
Ph.D.

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22

Fox, Jonathan Wetmore. "Effects of fuel injection strategy on HC emissions during SI engine start-up." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13107.

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Grasreiner, Sebastian. "Combustion modeling for virtual SI engine calibration with the help of 0D/3D methods." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2012. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-90518.

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Spark ignited engines are still important for conventional as well as for hybrid power trains and are thus objective to optimization. Today a lot of functionalities arise from software solutions, which have to be calibrated. Modern engine technologies provide an extensive variability considering their valve train, fuel injection and load control. Thus, calibration efforts are really high and shall be reduced by introduction of virtual methods. In this work a physical 0D combustion model is set up, which can cope with a new generation of spark ignition engines. Therefore, at first cylinder thermodynamics are modeled and validated in the whole engine map with the help of a real-time capable approach. Afterwards an up to date turbulence model is introduced, which is based on a quasi-dimensional k-epsilon-approach and can cope with turbulence production from large scale shearing. A simplified model for ignition delay is implemented which emphasizes the transfer from laminar to turbulent flame propagation after ignition. The modeling is completed with the calculation of overall heat release rates in a 0D entrainment approach with the help of turbulent flame velocities. After validation of all sub-models, the 0D combustion prediction is used in combination with a 1D gas exchange analysis to virtually calibrate the modern engine torque structure and the ECU function for exhaust gas temperature with extensive simulations
Moderne Ottomotoren spielen heute sowohl in konventionellen als auch hybriden Fahrzeugantrieben eine große Rolle. Aktuelle Konzepte sind hochvariabel bezüglich Ventilsteuerung, Kraftstoffeinspritzung und Laststeuerung und ihre Optimierungspotentiale erwachsen zumeist aus neuen Softwarefunktionen. Deren Applikation ist zeit- und kostenintensiv und soll durch virtuelle Methoden unterstützt werden. In der vorliegenden Arbeit wird ein physikalisches 0D Verbrennungsmodell für Ottomotoren aufgebaut und bis zur praktischen Anwendung geführt. Dafür wurde zuerst die Thermodynamik echtzeitfähig modelliert und im gesamten Motorenkennfeld abgeglichen. Der Aufbau eines neuen Turbulenzmodells auf Basis der quasidimensionalen k-epsilon-Gleichung ermöglicht anschließend, die veränderlichen Einflüsse globaler Ladungsbewegung auf die Turbulenz abzubilden. Für den Brennverzug wurde ein vereinfachtes Modell abgeleitet, welches den Übergang von laminarer zu turbulenter Flammenausbreitung nach der Zündung in den Vordergrund stellt. Der restliche Brennverlauf wird durch die physikalische Ermittlung der turbulenten Brenngeschwindigkeit in einem 0D Entrainment-Ansatz dargestellt. Nach Validierung aller Teilmodelle erfolgt die virtuelle Bedatung der Momentenstruktur und der Abgastemperaturfunktion für das Motorsteuergerät

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24

Ayala, Ferran A. (Ferran Alberto) 1976. "Combustion lean limits fundamentals and their application to a SI hydrogen-enhanced engine concept." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38262.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.
Includes bibliographical references (p. 197-199).
Operating an engine with excess air, under lean conditions, has significant benefits in terms of increased engine efficiency and reduced emissions. However, under high dilution levels, a lean limit is reached where combustion becomes unstable, significantly deteriorating drivability and engine efficiency, thus limiting the full potential of lean combustion. Due to hydrogen's high laminar flame speed, adding a hydrogen-rich mixture with gasoline into the engine helps stabilize combustion, extending the lean limit. This work studies the fundamental behavior of lean combustion in a spark ignition (SI) engine, identifying the processes that determine the engine's efficiency curve, and studying practical solutions to extend the peak efficiency and the lean limit. Lean and hydrogen-enhanced combustion data in a SI engine were generated covering a wide range of operating conditions including different compression ratios, loads, types of dilution, types and levels of hydrogen enhancement, and levels of turbulence. Combustion simulations were then performed to quantify the components that determine the efficiency vs. dilution curve. Results showed how burn duration is the primary driver of lean combustion, with a limiting 10-90% burn duration at peak efficiency and a limiting 0-10% burn duration at the onset of rapid combustion variability.
(cont.) These two burn durations, while correlated, are affected differently by laminar flame speed and turbulence. Consequently the effect of hydrogen enhancement on combustion will depend on operating conditions. A flame entrainment combustion model was then used to fundamentally explain the observed criticalities in the experiments. The model properly captured the physics of the combustion process, accurately predicting the data and the basic trends. The model showed that the rapid increase in variability near the lean limit is due to the inverse dependence of the eddy-burning time on the laminar flame speed. This relationship causes the eddy-burning time to grow slowly and then rapidly with decreasing laminar flame speed, amplifying the baseline, normal, random variability associated with the flame initiation process. Due to the effect of initial conditions on combustion phasing, this increasing, but symmetric, variability during flame initiation will lead to asymmetrical variability in the main part of the combustion process. Modeling studies show how by reducing the eddy-burning time, the full burn duration curve can be shifted, extending the location of peak efficiency and the lean limit.
(cont.) This can be done by increasing turbulence, effectively decreasing its microscale structure or by increasing the laminar flame speed through hydrogen enhancement. Hydrogen enhancement using reformate shows diminishing returns at high loads and high compression ratios due to the detrimental effect of high pressures on laminar flame speed. As suggested by the model, reducing the engine's baseline combustion variability during flame initiation can also extend the lean limit. These conclusions are confirmed through experimental results.
by Ferrán A. Ayala.
Ph.D.

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25

Gerty, Michael D. "Effects of operating conditions, compression ratio, and gasoline reformate on SI engine knock limits." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32369.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
Includes bibliographical references (p. 133-135).
A set of experiments was performed to investigate the effects of air-fuel ratio, inlet boost pressure, hydrogen rich fuel reformate, and compression ratio on engine knock behavior. For each condition the effect of spark timing on torque output was measured. Knock limited spark advance was then found for a range of octane number (ON) for each of three fuel types; primary reference fuels (PRFs), toluene reference fuels (TRFs), and test gasolines. A new combustion phasing parameter based on the timing of 50% mass fraction burned, ternled "combustion retard", was found to correlate well to engine performance. Increasing air- fuel ratio increases the combustion retard required to just avoid knock for PRFs and has little effect for TRFs. Combustion retard also increases more with inlet pressure and decreases more with reformate addition for PRFs than for TRFs. Both fuel types responded similarly to increased compression ratio. The trends for gasoline are about halfway between PRFs and TRFs. Experiments were also performed to determine the response of mid-load indicated efficiency to air-fuel ratio, load, and compression ratio. At a compression ratio of 9.8:1, relative net efficiency improvement is about 2.5% per unit compression ratio. Efficiency peaks at about 14:1 with a maximum benefit of 6-7%. Detailed chemical kinetics were combined with a cylinder pressure based end-gas modeling methodology to successfully predicted the response of PRFs to compression ratio and air-fuel ratio, and the response of TRFs to boost. The difference between the response of PRFs and TRFs to air-fuel ratio was also captured.
(cont.) Constant volume chemistry modeling found that hydrogen slows alkane autoignition reactions by consuming hydroxy radicals in the end gas. Reforming 30% of the fuel entering an engine decreases the required fuel quality 10 ON or more, which would allow increased compression ratio or increased turbocharging without increasing combustion retard. A simplified analysis indicates that increasing compression ratio and downsizing the engine to maintain constant maximum torque would increase fuel efficiency by about 9%. Turbocharging and downsizing would increase fuel efficiency by about 16%.
by Michael D. Gerty.
S.M.

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26

Rezapour, Kambiz. "Exergy Based SI Engine Model Optimisation. Exergy Based Simulation and Modelling of Bi-fuel SI Engine for Optimisation of Equivalence Ratio and Ignition Time Using Artificial Neural Network (ANN) Emulation and Particle Swarm Optimisation (PSO)." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5386.

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In this thesis, exergy based SI engine model optimisation (EBSIEMO) is studied and evaluated. A four-stroke bi-fuel spark ignition (SI) engine is modelled for optimisation of engine performance based upon exergy analysis. An artificial neural network (ANN) is used as an emulator to speed up the optimisation processes. Constrained particle swarm optimisation (CPSO) is employed to identify parameters such as equivalence ratio and ignition time for optimising of the engine performance, based upon maximising 'total availability'. In the optimisation process, the engine exhaust gases standard emission were applied including brake specific CO (BSCO) and brake specific NOx (BSNOx) as the constraints. The engine model is developed in a two-zone model, while considering the chemical synthesis of fuel, including 10 chemical species. A computer code is developed in MATLAB software to solve the equations for the prediction of temperature and pressure of the mixture in each stage (compression stroke, combustion process and expansion stroke). In addition, Intake and exhaust processes are calculated using an approximation method. This model has the ability to simulate turbulent combustion and compared to computational fluid dynamic (CFD) models it is computationally faster and efficient. The selective outputs are cylinder temperature and pressure, heat transfer, brake work, brake thermal and volumetric efficiency, brake torque, brake power (BP), brake specific fuel consumption (BSFC), brake mean effective pressure (BMEP), concentration of CO2, brake specific CO (BSCO) and brake specific NOx (BSNOx). In this model, the effect of engine speed, equivalence ratio and ignition time on performance parameters using gasoline and CNG fuels are analysed. In addition, the model is validated by experimental data using the results obtained from bi-fuel engine tests. Therefore, this engine model was capable to predict, analyse and useful for optimisation of the engine performance parameters. The exergy based four-stroke bi-fuel (CNG and gasoline) spark ignition (SI) engine model (EBSIEM) here is used for analysis of bi-fuel SI engines. Since, the first law of thermodynamic (the FLT), alone is not able to afford an appropriate comprehension into engine operations. Therefore, this thesis concentrates on the SI engine operation investigation using the developed engine model by the second law of thermodynamic (the SLT) or exergy analysis outlook (exergy based SI engine model (EBSIEM)) In this thesis, an efficient approach is presented for the prediction of total availability, brake specific CO (BSCO), brake specific NOx (BSNOx) and brake torque for bi-fuel engine (CNG and gasoline) using an artificial neural network (ANN) model based on exergy based SI engine (EBSIEM) (ANN-EBSIEM) as an emulator to speed up the optimisation processes. In the other words, the use of a well trained an ANN is ordinarily much faster than mathematical models or conventional simulation programs for prediction. The constrained particle swarm optimisation (CPSO)-EBSIEM (EBSIEMO) was capable of optimising the model parameters for the engine performance. The optimisation results based upon availability analysis (the SLT) due to analysing availability terms, specifically availability destruction (that measured engine irreversibilties) are more regarded with higher priority compared to the FLT analysis. In this thesis, exergy based SI engine model optimisation (EBSIEMO) is studied and evaluated. A four-stroke bi-fuel spark ignition (SI) engine is modelled for optimisation of engine performance based upon exergy analysis. An artificial neural network (ANN) is used as an emulator to speed up the optimisation processes. Constrained particle swarm optimisation (CPSO) is employed to identify parameters such as equivalence ratio and ignition time for optimising of the engine performance, based upon maximising 'total availability'. In the optimisation process, the engine exhaust gases standard emission were applied including brake specific CO (BSCO) and brake specific NOx (BSNOx) as the constraints. The engine model is developed in a two-zone model, while considering the chemical synthesis of fuel, including 10 chemical species. A computer code is developed in MATLAB software to solve the equations for the prediction of temperature and pressure of the mixture in each stage (compression stroke, combustion process and expansion stroke). In addition, Intake and exhaust processes are calculated using an approximation method. This model has the ability to simulate turbulent combustion and compared to computational fluid dynamic (CFD) models it is computationally faster and efficient. The selective outputs are cylinder temperature and pressure, heat transfer, brake work, brake thermal and volumetric efficiency, brake torque, brake power (BP), brake specific fuel consumption (BSFC), brake mean effective pressure (BMEP), concentration of CO2, brake specific CO (BSCO) and brake specific NOx (BSNOx). In this model, the effect of engine speed, equivalence ratio and ignition time on performance parameters using gasoline and CNG fuels are analysed. In addition, the model is validated by experimental data using the results obtained from bi-fuel engine tests. Therefore, this engine model was capable to predict, analyse and useful for optimisation of the engine performance parameters. The exergy based four-stroke bi-fuel (CNG and gasoline) spark ignition (SI) engine model (EBSIEM) here is used for analysis of bi-fuel SI engines. Since, the first law of thermodynamic (the FLT), alone is not able to afford an appropriate comprehension into engine operations. Therefore, this thesis concentrates on the SI engine operation investigation using the developed engine model by the second law of thermodynamic (the SLT) or exergy analysis outlook (exergy based SI engine model (EBSIEM)) In this thesis, an efficient approach is presented for the prediction of total availability, brake specific CO (BSCO), brake specific NOx (BSNOx) and brake torque for bi-fuel engine (CNG and gasoline) using an artificial neural network (ANN) model based on exergy based SI engine (EBSIEM) (ANN-EBSIEM) as an emulator to speed up the optimisation processes. In the other words, the use of a well trained an ANN is ordinarily much faster than mathematical models or conventional simulation programs for prediction. The constrained particle swarm optimisation (CPSO)-EBSIEM (EBSIEMO) was capable of optimising the model parameters for the engine performance. The optimisation results based upon availability analysis (the SLT) due to analysing availability terms, specifically availability destruction (that measured engine irreversibilties) are more regarded with higher priority compared to the FLT analysis.

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27

Filippou, Sotirios. "Virtual sensor for air mass flow measurement in an SI engine: Application of distributed lumped modelling in prediction of air mass flow into the cylinder of SI combustion engines." Thesis, University of Bradford, 2018. http://hdl.handle.net/10454/17450.

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After undergoing an extensive study about engine air mass flow measurement approaches as well as engine modelling for air mass flow prediction, a major problem found to exist is that engineers have still not found a suitable technique to accurately measure the air mass flow entering the cylinder of an internal combustion engine. The engine air mass flow is the most important parameter needed during engine development so the fuel control can be accurately calibrated and as a result increase performance and reduce emission output of an engine. The current methods used to determine the air mass flow lead to inaccuracies due to the large amount of mathematical assumptions and also sensor errors and as a result the mapping and calibration process of a new engine family takes approximately 2 years due to extensive modelling and testing required overcoming the above drawbacks. To improve this, the distributed lumped modelling technique (D-L) of the inlet manifold was chosen, where the intake system is separated into very small sections which are distributed continuously throughout the volume of the intake until entering the cylinder. This technique is validated against a CFD model of the engine’s intake system and real engine data as well as a 1D engine model.

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28

Lindén, Erik, and David Elofsson. "Model-based turbocharger control : A common approach for SI and CI engines." Thesis, Linköpings universitet, Institutionen för systemteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-70288.

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In this master’s thesis, a turbine model and a common control structure for theturbocharger for SI and CI-engines is developed. To design the control structure,simulations are done on an existing diesel engine model with VGT. In order tobe able to make simulations for engines with a wastegated turbine, the model isextended to include mass flow and turbine efficiency for that configuration. Thedeveloped model has a mean absolute relative error of 3.6 % for the turbine massflow and 7.4 % for the turbine efficiency. The aim was to control the intake manifoldpressure with good transients and to use the same control structure for VGTand wastegate. By using a common structure, development and calibration timecan be reduced. The non-linearities have been reduced by using an inverted turbinemodel in the control structure, which consists of a PI-controller with feedforward.The controller can be tuned to give a fast response for CI engines and a slowerresponse but with less overshoot for SI engines, which is preferable.

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29

Zheng, Jincai Cernansky N. P. Miller David L. "A study of homogeneous ignition and combustion processes in CI, SI, and HCCI engine systems /." Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/557.

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30

Alrayyes, Taleb. "The effect of ethanol-gasoline blends on SI engine energy balance and heat transfer characteristics." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/29749/.

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Ethanol is one of a group of hydrocarbon fuels produced from bio-mass which is attracting interest as an alternative fuel for spark ignition engines. Major producers of ethanol include Brazil, from sugar cane, and the USA, from com. Reasons for the growing interest in ethanol include economic development, security of fuel supply and the reduction of net emissions of carbon dioxide relative to levels associated with the use of fossil fuels. Unlike gasoline, which is a mixture of hydrocarbon compounds suited to meet a range of start and operating requirements, ethanol is a single component fuel with characteristics which make engine cold starting difficult, for example. Hence, ethanol is generally used in a blend with gasoline, accounting for <5% in EU pump-grade gasoline to 85% by volume for so called flex-fuel vehicles. Although ethanol is already available in the marketplace, there are aspects of its effects on engine behaviour that are unresolved, including its effects on engine thermal behaviour and heat transfer. These have been investigated in the experimental study presented in this thesis. The aims of this work included determining the effect of ethanol content in blends on combustion characteristics, energy balance, gas-side heat transfer rate and cylinder instantaneous heat transfer. This study covers a range of loads, speeds, spark timings, equivalence ratios and EGR levels representative of every day vehicle use, and has been restricted to fully warm operating conditions. The investigations have been carried out on a modern design of direct injection, spark ignition engine. The performance of different ethanol-gasoline blends has been compared at conditions of matched brake power output. The emissions data for NO, HC, CO and C02, which was used to calculate combustion efficiency, show a decrease in their levels proportional to the increase in ethanol content in the fuel blend. This is owing to an increase in combustion efficiency and change in chemical structure and physiochemical properties. Compared to gasoline, running on 85% ethanol produces slightly faster rates of burning in rapid burn stages of combustion. Typically, the reductions in rapid burn angle are 4%. Results show that the effects do not vary in proportion to the ethanol content in the fuel blend. This is attributable to the fact that, at low and medium ethanol content, the enhancement in combustion gained by oxygen availability is offset by its higher enthalpy of vaporisation and lower heat content. Energy balance data show an improvement in thermal efficiency proportional to the increase in ethanol ratio. This is due to improvement in combustion efficiency and a reduction in coolant and exhaust losses. Results for gas-side heat rejection show that a correlation developed for engines run on gasoline can be used without any modification. The heat rejection rate has been inferred from measurements of heat rejection to coolant adjusted to allow for the contribution of engine rubbing friction. The apparent insensitivity to ethanol content is attributed to a combination of factors. These include the increase in fuel flow rate for a given energy supply being offset in its effect on charge flowrate by a reduction in stoichiometric air/fuel ratio. Gas-side heat transfer results from both the exhaust port and the cylinder show a clear decrease when running on 85% ethanol compare to gasoline. This reduction was also observed in the total measured heat loss to coolant. The magnitude and phasing of instantaneous heat loss is not sensitive to the use of ethanol during combustion. However, as the combustion starts to terminate, lower heat loss for medium and high ethanol content was observed due to the reduction in the combustion product temperature. The results from the C 1 C2 correlation and instantaneous heat transfer are comparable.

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31

Lim, Bryan Neo Beng. "Computational simulations of fuel/air mixture flow in the intake port of a SI engine." Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310769.

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32

Luo, Kai Hong. "Experimental measurement and numerical simulation of induction port flow of a four-valve SI engine." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358318.

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33

Pischinger, Stefan. "Effects of spark plug design parameters on ignition and flame development in an si-engine." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14433.

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34

Gu, Jiayi. "Chemical kinetics modelling study of naturally aspirated and boosted SI engine flame propagation and knock." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/17356.

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Modern spark ignition engines are downsized and boosted to meet stringent emission standards and growing customer demands on performance and fuel economy. They operate under high intake pressures and close to their limits to engine knock. As the intake pressure is increased knock becomes the major barrier that prevents further improvement on downsized boosted spark ignition engines. It is generally accepted that knock is caused by end gas autoignition ahead of the propagating flame. The propagating flame front has been identified as one of the most influential factors that promote the occurrence of autoignition. Systematic understanding and numerical relation between the propagating flame front and the occurrence of knock are still lacking. Additionally, knock mitigation strategy that minimizes compromise on engine performance needs further researching. Therefore the objectives of the current research consist of two steps: 1). study of turbulent flame propagation in both naturally aspirated SI engine. 2) study of the relationship between flame propagation and the occurrence of engine knock for downsized and boosted SI engine. The aim of the current research is, firstly, to find out how turbulent flames propagate in naturally aspirated and boosted S.I. engines, and their interaction with the occurrence of knock; secondly, to develop a mitigation method that depresses knock intensity at higher intake pressure. Autoignition of hydrocarbon fuels as used in spark ignition engines is a complex chemical process involving large numbers of intermediate species and elementary reactions. Chemical kinetics models have been widely used to study combustion and autoignition of hydrocarbon fuels. Zero-dimensional multi-zone models provide an optimal compromise between computational accuracy and costs for engine simulation. Integration of reduced chemical kinetics model and zero-dimensional three-zone engine model is potentially a effective and efficient method to investigate the physical, chemical, thermodynamic and fluid dynamic processes involved in in-cylinder turbulence flame propagation and knock. The major contributions of the current work are made to new knowledge of quantitative relations between intake pressure, turbulent flame speed, and knock onset timing and intensity. Additionally, contributions have also been made to the development of a knock mitigation strategy that effectively depresses knock intensity under higher intake pressure while minimizes the compromise on cylinder pressure, which can be directive to future engine design.

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35

Criscuolo, Ivan. "Optimization of SI and CI engine control strategies via integrated simulation of combustion and turbocharging." Doctoral thesis, Universita degli studi di Salerno, 2013. http://hdl.handle.net/10556/902.

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2010 - 2011
Combustion engines have been for a long time the most important prime mover for transportation globally. A combustion engine is simple in its nature; a mix of fuel and air is combusted, and work is produced in the operating cycle. The amount of combusted air and fuel controls the amount of work the engine produces. The engine work has to overcome friction and pumping losses, and a smaller engine has smaller losses and is therefore more efficient. Increasing engine efficiency in this way is commonly referred to as downsizing. Downsizing has an important disadvantage; a smaller engine cannot take in as much air and fuel as a larger one, and is therefore less powerful, which can lead to less customer acceptance. By increasing the charge density the smaller engine can be given the power of a larger engine, and regain customer acceptance. A number of charging systems can be used for automotive application, e.g. supercharging, pressure wave charging or turbocharging. Turbocharging has become the most commonly used charging system, since it is a reliable and robust system, that utilizes some of the energy in exhaust gas, otherwise lost to the surroundings. There are however some drawbacks and limits of a turbocharger. The compressor of a single stage turbo system is sized after the maximum engine power, which is tightly coupled to the maximum mass flow. The mass flow range of a compressor is limited, which imposes limits on the pressure build up for small mass flows and thereby engine torque at low engine speed. Further, a turbo needs to spin with high rotational speed to increase air density, and due to the turbo inertia it takes time to spin up the turbo. This means that the torque response of a turbocharged engine is slower than an equally powerful naturally aspirated engine, which also lead to less customer acceptance A two stage turbo system combines two different sized turbo units, where the low mass flow range of the smaller unit, means that pressure can be increased for smaller mass flows. Further, due to the smaller inertia of the smaller unit, it can be spun up faster and thereby speed up the torque response of the engine. The smaller unit can then be bypassed for larger mass flows, where instead the larger turbo unit is used to supply the charge density needed. In the dissertation, the value of engine system modeling has been discussed. It was shown how modeling in-cylinder processes and turbocharger can aid the development of the control strategies saving time and money efforts. All the developed models were experimentally validated and applied for optimization analysis or real-time control. Particularly the model based optimization of the engine control variables of an automotive turbocharged Diesel engine has been presented. The model structure is based on a hybrid approach, with a predictive multi-zone model for the simulation of in-cylinder processes (i.e. combustion and emissions formation) integrated with a control-oriented turbocharger model to predict intake/exhaust processes. Model accuracy was tested via comparison between measured and simulated in-cylinder pressure and engine exhaust temperature on a wide set of experimental data, measured at the test bench. Validation results exhibit a correlation index R2 equal to 0.995 and 0.996 for IMEP and exhaust temperature, respectively. The optimization analysis was aimed at minimizing NO emissions in four steady state engine operating conditions, selected among those of interest for the ECE/EUDC test driving cycle. Constraints were introduced to prevent from increase of soot emissions and low exhaust temperature which would have a negative impact on the efficiency of the after-treatment devices. The optimization results evidence a significant reduction of engine NO emissions by means of increased EGR rate and earlier main fuel injection. A model-based optimization was also applied for a CNG heavy-duty engine, equipped with turbocharger and EGR. The optimization analysis was addressed to design the set-points of engine control variables, following the implementation of an EGR system aimed at reducing the in-cylinder temperature and preventing from the thermal stress of engine components (i.e. head and valves). A co-simulation analysis was carried out by coupling a 1-D engine commercial code with a classical constrained optimization algorithm. The 1-D model accounts for intake and exhaust gas flow arrangement, comprehensive of EGR system and turbocharger, while an empirical formulation based on the classical Wiebe function was implemented to simulate the combustion process. An intensive identification analysis was performed to correlate Wiebe model parameters to engine operation and guarantee model accuracy and generalization even in case of high EGR rate. 1-D model and identification results were successfully validated against a wide set of experimental data, measured on the test bench. The results of the optimization analysis, aimed at minimizing fuel consumption while preventing from thermal stress, showed an increase of fuel economy up to 4.5% and a reduction of the thermal load below the imposed threshold, against five engine operating conditions selected among the most critical of the reference European Transient Cycle (ETC). Particularly, the effectiveness of the co-simulation analysis is evidenced in pursuing the conflicting goal of optimizing engine control while reducing the recourse to time consuming and expensive experiments at the test bed. This latter point is becoming more and more critical as the number of control variables is increasing with engine complexity. Both the presented optimization analyses evidenced the key-role of the turbocharger to face with energy and emissions issues. Particularly the impact of the turbocharger management via wastegate or VGT control was evidenced. Indeed, by acting on these components, the amount of exhaust gases evolving in the turbine can be managed thus regulating the supercharging degree and the boost pressure. This allows keeping the throttle valve fully open with significant decrease of pumping losses. The wastegate position is defined by a pneumatic actuator in which the pressure is regulated by a solenoid valve fed by a PWM signal. The drawback of this system is the dependence of the PWN signal, and afterwards of the performance, from the system supply voltage. During the thesis the development of a wastegate actuator model was carried out in order to compensate the actuator PWM signal to improve boost pressure control. The compressible flow equations were found to be sufficient to describe the actuator system mass flow and both discharge coefficient and static actuator chamber pressure were modeled using polynomials in PWM signal. Furthermore a simple friction model was implemented to simulate the actuator system. The boost pressure controller based on the developed compensator has shown to give limited undershoot and overshoot and is further able to reject the disturbance in supply voltage. The compensator was incorporated into a boost pressure controller and the complete control system has shown to reject system voltage variations and perform good boost pressure control in both simulations analyses and experimental tests on the engine test stand. Model simulations evidenced the need to ensure low enough vacuum pressure to enable fully closed and open actuator while a switch type controller was proved to be sufficient for vacuum tank pressure control. [edited by author]
X n.s.

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KHESHTINEJAD, HAMED. "Investigation Into Advanced Architecture and Strategies For Turbocharged Compressed Natural Gas Heavy Duty SI-engine." Doctoral thesis, Politecnico di Torino, 2017. http://hdl.handle.net/11583/2689169.

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CNG is at present retaining a growing interest as a factual alternative to traditional fuel for SI engine thanks to its high potentials in reducing the engine-out emissions. Increasing thrust into the exploitation of NG in the transport field is in fact produced by the even more stringent emission regulations which are being introduced into the worldwide scenario. Specific attention is also to be devoted to heavy duty engines given the high impact they retain due to the diesel oil exploitation and to the PM emissions, the latter issue assessing for the need to shift towards alternative fuels such as natural gas. A thorough control of the air-to-fuel ratio appears to be mandatory in spark ignition CNG engines in order to meet the even more stringent thresholds set by the current regulations. The accuracy of the air/fuel mixture highly depends on the injection system dynamic behavior and to its coupling to the engine fluid-dynamic. The amount of injected fuel should in fact be properly targeted by the ECU basing on the estimation of the induced air and accounting for the embedded closed-loop strategies. Still, these latter are normally derived from engine-base routines and totally ignore the injection system dynamics. Thus, a sound investigation into the mixing process can only be achieved provided that a proper analysis of the injection rail and of the injectors is carried out. The first part of the present work carries out a numerical investigation into the fluid dynamic behavior of a commercial CNG injection system by means of a 0D-1D code. The research has been focused on defining the set of parameters to be precisely reproduced in the 0D-1D simulation so as to match the injection system experimental behavior. Specific attention has been paid to the one component which significantly contributes to fully defining its dynamic response, i.e. the pressure reducing valve. The pressure reducer is made up of various elements that retain diverse weights on the valve behavior and should consequently be differently addressed to. A refined model of the pressure reducer has hence been proposed and the model has been calibrated, tested and run under various operating conditions so as to assess for the set-up validity. Comparisons have been carried out on steady state points as well as through out a vehicle driving cycle and the model capability to properly reproduce the real system characteristic has been investigated into. The proposed valve model has proved to consistently replicate the injection system response for different speed and load conditions. A few methodological indications concerning modeling aspects of a pressure regulator can be drawn from the present study. The model has been run in a predictive mode so as to inquiry into the response of the system to fast transient operations, both in terms of speed and load. The model outputs have highlighted mismatches between the ECU target mass and the actually injected one and have hinted at the need for dedicated and refined control strategies capable of preventing anomalies in the mixture formation and hence in the engine functioning. The second part of the present work aims at deeply investigating into the potentials of a heavy duty engine running on CNG and equipped with two different injection systems, an advanced SP one and a prototype MP one. The considered 7.8 liter engine was designed and produced to implement a Sigle-Point (SP) strategy and has hence been modified to run with a dedicated Multi-Point (MP) system so as to take advantage of its flexibility in terms of control strategies. More specifically, a thorough comparison between the experimental performances of the engine equipped with the two injection systems has been carried out at steady state as well as at transient operations. Better performances in terms of cycle-to-cycle variability were proved for the MP system despite poorer mixture homogeneity. Attention has also been paid to the different engine control strategies to be eventually adopted in compliance with the constraints set by the two different layouts. A 0D-1D model has also been built and validated on the experimental data set to be hence exploited for investigating into different strategies both for the SP and for the MP layout. An extensive simulation has been carried out on the effects of the injection phasing on the SP system performance referring to the engine power output and to the air-to-fuel ratio homogeneity amongst the cylinders. Finally, as far as the MP injection system is concerned, the innovative fire-skipping (DSF) or cylinder deactivation has been considered and deployed by means of the numerical model, assessing for an overall decrease in the fuel consumption of 12% at part load operations.

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37

Tippett, Esther Claire. "The effects of combustion chamber design on turbulence, cyclic variation and performance in an SI engine." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/28071.

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An experimental program of motored and fired tests has been undertaken on a single cylinder spark ignition engine to determine the influence of combustion chamber design on turbulence enhancement in the achievement of fast lean operation. Flow field measurements were taken using hot wire anemometry in the cylinder during motored operation. On line performance tests and in-cylinder pressure data were recorded for the operation of the engine by natural gas at lean and stoichiometric conditions over a range of speed and loads. Squish and squish jet action methods of turbulence enhancement were investigated for six configurations, using a standard bathtub cylinder head and new piston designs incorporating directed jets through a raised wall, a standard bowl-in-piston chamber and an original squish jet design piston. A non squish comparison was provided by a disc chamber. Peak Pressure and Indicated Mean Effective Pressure (IMEP), two parameters characterizing performance and cyclic variability, showed that enhanced turbulence by combustion chamber geometry is effective in improving performance at lean operation. The single jet action directed towards the spark was most effective in improving the efficiency at high speed and lean mixtures. The addition of jets to the single jet, or jet channels to the main squish action of the bowl- in-piston chamber, reduced performance and increased cyclic variability. Mass fraction burn analysis of the cylinder pressure data showed that squish action was most effective in the main burn period. Configurations with large squish area and centrally located spark produced the greatest reduction in both the initial and main burn periods. The potential for the squish jet action to improve engine drivability and increase the knock limit was exhibited in reduced coefficient of variance of IMEP and reduced ignition advance requirements. Directions for further research to exploit this potential for engines operated by alternative fuels are identified.
Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate

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38

Costanzo, Vincent S. (Vincent Stanley) 1979. "Effect of in-cylinder liquid fuel films on engine-out unburned hydrocarbon emissions for SI engines." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/65276.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2011.
"February 2011." Cataloged from PDF version of thesis.
Includes bibliographical references (p. 265-270).
Nearly all of the hydrocarbon emissions from a modern gasoline-fueled vehicle occur when the engine is first started. One important contributing factor to this is the fact that, during this time, temperatures throughout the engine are low - below the point at which all of the components of the gasoline can readily vaporize. Consequently, any fuel that enters the combustion chamber in liquid form can escape combustion and subsequently be exhausted as hydrocarbon emissions. An experimental study was performed in a firing engine in which liquid gasoline films were established at various locations in the combustion chamber and the resulting impact on hydrocarbon emissions was assessed. Unique about this setup was that it combined direct visual observation of the liquid fuel films, measurements of the temperatures these films were subjected to, and the determination from gas analyzers of burned and unburned fuel quantities - all with cycle-level or better resolution. An increase in the hydrocarbon emissions was observed with liquid gasoline films present in the combustion chamber. This increase depended upon both the location of the film and the temperature of that location, and correlated with estimates of the mass of fuel in the film. The largest impact was observed when the head near the exhaust valve was wetted; the smallest impact was observed when the piston on the intake side of the engine was wetted. In general, as engine temperatures increased the hydrocarbon emissions due to the liquid fuel films decreased. It was also identified when, in the exhaust event, fuel from the films was actually exhausted. The effect of the location of the liquid fuel film can best be understood in terms of the time before flame arrival at that location, the local flow over the film, and the extent to which the overall flow in the combustion chamber carries fuel from the film to the exhaust valve. The primary effect of wall temperature is to affect the amount of vaporization from the film: as temperature increases more vaporization occurs before flame arrival, resulting in less fuel that can vaporize post-flame as unburned fuel emissions.
by Vincent S. Costanzo.
Ph.D.

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39

Westin, Fredrik. "Simulation of turbocharged SI-engines - with focus on the turbine." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-216.

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40

Andersson, Henrik. "Model Based Control of Throttle, EGR and Wastegate : A System Analysis of the Gas Flows in an SI-Engine." Thesis, Linköpings universitet, Fordonssystem, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-140533.

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Due to governmental requirements on low exhaust gas emissions and the drivers request of fast response, it is important to be able to control the gas flow in a spark ignited engine accurately. The air into the cylinder is directly related to the torque generated by the engine. The technique with recirculation of exhaust gases (EGR) affect the air flow into the cylinder and increase the complexity of the control problem. In this thesis a mean value model for a spark ignited engine has been created. The basis was a diesel model from Linköping University that has been modified and parameterized with data from a test cell. The model has been used to study the gas exchange system with respect to the dynamic behaviors and nonlinearities that occur when the three actuators (throttle, wastegate and EGR-valve) are changed. Based on this analysis, some different control strategies have been developed and tested on the model. The presented results show that different control strategies give different behaviors and there is a trade-off between fast torque response and high precision for controlling the EGR-ratio. A control strategy is proposed containing two main feedback loops, prefiltering of the reference signal and a feedforward part.

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41

Ghauri, Ahmar. "An investigation into the effects of variable valve actuation on combustion and emissions in an SI engine." Thesis, University College London (University of London), 1999. http://discovery.ucl.ac.uk/1317999/.

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The work reported in this thesis was conducted to study the effects of variable valve actuation on combustion, emissions, and fuel economy in a modern design of 4-valve per cylinder SI engine. The use of statistically-based procedures for the design of experiments allowed a limited number of tests to be used to explore a wide region of each of the experimental variables. A series of steady-flow tests was conducted to assess the effects of valve lift on flow past the valves and the nature of any in-cylinder motion generated. Results from the former were incorporated into a filling and emptying model that allowed levels of trapped residuals and pumping work to be estimated for different valve strategies. The in-cylinder motion tests explored asymmetric valve lifts, that is to say where the two valves were opened by a different amount. These results allowed a pair of response surfaces to be established to model the intensity of both axial and barrel swirl within the cylinder over the range of valve lifts. Engine tests were conducted in two parts. The first explored the effects of changes in exhaust event phasing, intake event phasing, intake event duration, and peak intake valve lift. The design of the experiment allowed linear, quadratic, and interactions between the variables to be modelled using regression analysis. Statistical analysis allowed the most influential factors (both main effects and interactions) to be identified. Contour plots of the modelled response were used to draw conclusions about the nature of the response surface and to isolate the effects of valve opening and closure angles as well as overlap. The results were correlated with those from the steady-flow tests and from the computer model. The strategy for the second phase of tests was chosen after considering the previous results. The steady-flow tests indicated that there was considerable potential for enhancing in-cylinder motion by adopting a valve deactivation strategy and combining it with a low lift of the active intake valve. The second phase investigated the use of such a technique in conjunction with large overlaps over a range of duration of the intake valve event. The results from both phases of engine tests indicated possible strategies to reduce emissions from future engines.

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42

Hasan, Ahmad Omar. "Influence of prototype three way catalytic converter on regulated and unregulated emissions from gasoline HCCI/SI engine." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/2944/.

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Designing automotive catalysts for the effective control of NOx, HC (Hydrocarbon) and CO (Carbon Monoxide) emissions under both lean and stoichiometric engine operation is a challenging task. The research presented in this thesis assesses the performance efficiency of a three-zone prototype catalytic converter in reducing exhaust emissions from a gasoline engine, operating in HCCI (Homogeneous Charge Compression Ignition) and SI (Spark Ignition) mode under lean and stoichiometric conditions. The research was carried out using Jaguar V6 engine operating in SI and HCCI mode using commercial unleaded gasoline fuel. The catalyst efficiency in reducing the three pollutant emissions is closely related to the exhaust gas conditions (e.g. temperature and space velocity), oxygen content and composition i.e. NOx, CO and HC concentrations. As part of this study a quantitative and qualitative analysis of C1-C11 hydrocarbon compounds achieved before and after the catalytic converter. The results show that hydrocarbon species formation in the combustion process and destruction over the catalyst is primarily dependent on the engine operation and combustion mode (i.e. HCCI or SI). Alkane concentrations were found to be higher in the HCCI mode, while alkene species were mainly found in the engine exhaust under SI mode. The analysis showed that the HCCI exhaust contained heavier hydrocarbon species (e.g. toluene, p-exylene, naphthalene and methylnaphthalene) compared to the exhaust from the SI engine operation. Methane, Naphthalene and methylnaphthalene were the most resistant compounds while toluene was the most degradable compound over the catalyst.

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43

Hsin-wei, Chiu, and 邱信瑋. "Study of SI Engine System Dynamic Response Identification." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/74687644127291958964.

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碩士
大葉大學
車輛工程學系碩士班
94
This study used different system identification approach to establish the dynamic model for SI engine system response. The input signals are the throttle position opening in percentage and engine torque, and output signal are the engine speed and MAP. Different system identification methods were applied including ARX(Auto-Regressive Xogeneous), ARMAX(Auto- Regressive Moving Average Xogeneous), BJ(Box and Jenkins), OE(Output Error) and NN(Neural Network). The different model order and parameters for each method were used to compare the experimental data to find out the best engine dynamic model. From the system identification result, engine system dynamic model can be resolved quickly and it can provide helpful information for engineers. Research and development time and expense can be saved by this approach in developing future engine system controller.

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44

Lin, JianChen, and 林建成. "The Application of Methanol Fuel on SI Engine." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/81424213089424947664.

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碩士
國立臺灣大學
機械工程學研究所
87
Methanol is an oxygenated compound. The exhaust of the engine running with the mixture of methanol and gasoline may thus be improved. In this work, the effect of various volume fractions of methanol (0%, 5%, 15%, and 25%) is explored. The control parameters of the work are the fuel mixture ratio (X), the speed (1000, 1500, 2000, and 2500rpm), load (10, 20, 30, and 40N-m), and the fuel/air equivalence ratio (ψ). The emissions of HC, CO, NOx in the exhausts, the temperature of the exhausts and the brake specific fuel consumption (bsfc) of the engine are measured. The results from the work are show: (1) When the engine speed and the load are increased, the CO concentration remains unchanged but the HC concentration is improved lightly. (2) The concentration of CO and HC increase and the exhaust temperature will decreases when we increase the fraction of methanol with the same value ofψ. (3) The engine’s thermal efficiency increases most at X=15 and X=25 with the same engine operation condition and ψ=1.The best ratio is X=15. (4) Increasing the load, we can get lower bsfc value and have a better economic effect. If the air/fuel ratio remains unchanged and using the gasoline-containing methanol, the exhausts have improved, but improvement is unstable. On the other hand, if the fuel/air equivalence ratio remains unchanged, the exhausts are not improved. This is a remark when using methanol in the place of pure gasoline should take into consideration.

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45

tseng, yuan-shiu, and 曾元旴. "Study on performance of small turbocharger SI engine." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/10899257290568969766.

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碩士
逢甲大學
材料與製造工程所
100
In this study, a small SI engine (Mitsubishi EY20D) is analyzed theoretically and select a small turbocharger (Hitachi HT06) for matching. The intake and exhaust pipe is designed, and the fuel mixture ratio, ignition timing and valve clearance are adjusted to complete the experimental equipment of a suck-through small carburetor gasoline single-cylinder turbocharged engine. The Nm and Brake Horse Power (BHP) are obtained by electric-dynamometer. The bsfc is determined in a fixed speed by the fuel consumption measurements. The CO (in %) and HC (in ppm) are determined by non-dispersive exhaust gas analyzer. The above experiments are recorded in tables, and the experiment steps are repeated to be compared with naturally aspirated engine and turbochargered for analyses and discussions. The technology of the small turbocharger SI engine is expected to be more advanced by means of the research.

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46

Boddez, Jason Bradley. "Evaluation of SI-HCCI-SI mode-switching using conventional actuation on a CNG engine." Master's thesis, 2011. http://hdl.handle.net/10048/1825.

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Homogeneous Charge Compression Ignition (HCCI) operation is desirable for its high thermal efficiency and low emissions of NOx and particulates. Difficulty with cold starting and maximum achievable speed/load highlight the desire for mode-switching to traditional spark ignition (SI) operation. Mode-switching between SI and HCCI is investigated using only actuation of throttle, CNG injector pulse width, and CNG injection timing on a single cylinder CFR engine. Open-loop control achieves a one cycle mode-switch between two adjustable IMEP levels. Sequences are repeatable as demonstrated by 10 mode-switches with the same inputs. Performance is evaluated using a developed mode-switch performance criterion (MSPC) by considering duration between steady-states of operation, smoothness of IMEP, and knock based on maximum rate of pressure rise. Comparing the results with subjective analysis (the current standard) reveals good correlation. Throughout development, mode-switching performance is shown to improve by a factor of 60.

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47

Rezapour, Kambiz, Byron A. Mason, Alastair S. Wood, and Kambiz M. Ebrahimi. "Bi-fuel SI Engine Model for Analysis and Optimization." 2014. http://hdl.handle.net/10454/10983.

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Yes
The natural gas as an alternative fuel has economical and environmental benefits. Bi-fuel engines powered by gasoline and compressed natural gas (CNG) are an intermediate and alternative step to dedicated CNG engines. The conversion to bi-fuel CNG engine could be a short-term solution to air pollution problem in many developing countries. In this paper a mathematical model of a bi-fuel four-stroke spark ignition (SI) engine is presented for comparative studies and analysis. It is based on the two-zone combustion model, and it has the ability to simulate turbulent combustion. The model is capable of predicting the cylinder temperature and pressure, heat transfer, brake work , brake thermal and volumetric efficiency, brake torque, brake specific fuel consumption (BSFC), brake mean effective pressure (BMEP), concentration of CO2, brake specific CO (BSCO) and brake specific NOx (BSNOx). The effect of engine speed, equivalence ratio and performance parameters using gasoline and CNG fuels are analysed. The model has been validated by experimental data using the results obtained from a bi-fuel engine. The results show the capability of the model in terms of engine performance optimization and minimization of the emissions. The engine used in this study is a typical example of a modified bi-fuel engine conversion, which could benefit the researchers in the field.

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48

Chou, Jun-Nan, and 周俊男. "A Study of Combustion Thermal Efficiency of SI Engine." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/64949760153157227841.

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碩士
大葉大學
機械工程研究所
88
In an engine cycle, combustion thermal efficiency is the most important factor to affect engine performance. How to convert the heat released from combustion into engine brake work efficiently is the main concern of an engine designer. This research looks into the conversion efficiency of an engine deeply by zero-dimensional model together with heat release analysis method. By changing the relevant parameters of engine combustion, such as efficiency parameter a, form factor m, crank angle of start of combustion, combustion duration angle and speed of engine, ratio of compression, air-fuel ratio etc, we can get the niche to increase the thermal efficiency of an engine. We can also understand the influence of each design parameter on engine performance.

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49

Lee, Ming-Chun, and 李明俊. "Ignition Timing on SI Engine Performance Effect by Acetone." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/92114003961167235874.

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碩士
國立彰化師範大學
車輛科技研究所
101
In recent years, the alternative fuels were respect to developed with environmental considerations and petroleum fuels price increase and global warming effect. In this study, using acetone as oxygen additive blended with unleaded gasoline, on four cylinder four stroke spark ignition engine control with variable ignition timing under wide open throttle to measure the effect on engine performance and exhaust emissions were investigated. The results showed that the HC、NOX would be decreased with increasing the ratio of an oxygen additive and retarding the ignition timing. On the engine power output, the blended fuels were similar to gasoline and increased with advance ignition timing. The amplitude of vibration was decreased with increasing the blended fuel ratio and the advance ignition timing. On brake special fuel consumption (BSFC), the blended fuels compared with gasoline were similar and decrease with advance ignition timing. In this study, we found that using acetone as additive with advance ignition timing, higher oxygen content and longer combustion stroke can to improve CO、HC、CO2 pollution emissions. Because the acetone fuel has a higher octane number and Latent heat of vaporization, the engine power output were similar to gasoline. Improve the engine’s performance and the exhaust emissions.

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50

Huang, Jun-Yi, and 黃俊逸. "MIMO System Identification of Four-Stroke SI Engine Dynamic Research." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/63012485262780081922.

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碩士
大葉大學
車輛工程學系碩士班
93
This study proposed a methodology to identify the dynamic characteristics of a four stroke SI engine which are important for system control and performance evaluation. Since the engine performance parameters are complicated correlated with the control parameters and operating variables, the engine system plant becomes a random, time-varying, nonlinear and multi-input and output dynamic relation. Engine simulation models used to explore the internal flow and thermal field are multidimensional complicated codes, which are not proper be used in engine real-time control purpose. This motivated study to establish proper engine plant models by MIMO system identification methods for engine performance evaluation and controller design. The experiments were compared under two different engine control modes, which are constant-load and constant-speed mode. The engine load was applied by an eddy current dynamometer, and the engine throttle position was controlled to maintained constant engine speed or load condition. This study also developed a graphic user interface for data acquisition and measurement monitor for different engine and dynamometer control operation modes. The measured data from dynamometer and engine sensors were acquired by user graphic interface and were used to find the system dynamic response behavior. The output performance variables including the engine speed, manifold absolute pressure were correlated with the input operating variables which were engine load and throttle position. The system identification process were adopted and compared by different approaches and validated by the same data sets taken at later acquisition time. The observed different engine dynamic performance during acceleration and deceleration were compared with the simulation identification results. System identification models from the measured dynamic performance data correlation can be used for future reference of the engine design and engine management controller settings. In order to improve the system identification model prediction result, several engine experiments and different simulations were validated and compared. The comparison showed that the measured engine data needs to have proper variation to get better system identification result. In addition, the identification range chosen the whole experimental data range attained better model predicted result than those partly chosen data to identified. This study used the parametric identification methods such as Automatic Regression eXogenious (ARX), Automatic Regressive Moving Average eXogenious (ARMAX), Output Error (OE), Box-Jenkins (BJ), etc., and nonparametric identification methods, such as frequency and impulse response model. Different system identification parameters and order effects on the identification results were compared and validated by the real engine experimental data. From these results, it was observed that the ARX model predictions were not diverged the MIMO engine dynamic response in most of the engine operating conditions. As for the accuracy, the OE predictions were validated to be the most effectively method to follow the engine step response. As mention to the identification order effects, results showed that not necessarily the higher order the better, by proper adjusting identification parameters might get better approximated model. Divergence and separation happened when the nonlinear MIMO engine plant models which were identified and transformed into linear transfer functions. In order to solve this problem, frequency response must be judged in advance and zero-pole plot be checked to assure system stability requirement. Among the two engine constant-load and speed control modes experiments, OE showed better fit result under engine higher throttle opening variation conditions. The constant-load mode results were fitted better than the constant-speed control mode cases. The engine data before using filter were used in the identification could derived more stable and not distorted result compared to those filter data. Although results showed that OE attained better fit while when the transfer function results were compared, ARX model gained best result, thus these two methods are suggested for the MIMO engine identification plant model.

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