Dissertations / Theses on the topic 'Direct injection diesel fuel jets'

Recent imaging studies have provided a new conceptual model of the internal structure of direct injection diesel fuel jets as well as empirical correlations predicting jet development and structure. This information was used to create a diesel cycle simulation model using C language including compression, fuel injection and combustion, and expansion processes. Empirical relationships were used to create a new mixing-limited zero-dimensional model of the diesel combustion process. During fuel injection five zones were created to model the reacting fuel jet: 1) liquid phase fuel 2) vapor phase fuel 3) rich premixed products 4) diffusion flame sheath 5) surrounding bulk gas. Temperature and composition in each zone is calculated. Composition in combusting zones was calculated using an equilibrium model that includes 21 species. Sub models for ignition delay, premixed burn duration, heat release rate, and heat transfer were also included. Apparent heat release rate results of the model were compared with data from a constant volume combustion vessel and two single-cylinder direct injection diesel engines. The modeled heat release results included all basic features of diesel combustion. Expected trends were seen in the ignition delay and premixed burn model studies, but the model is not predictive. The rise in heat release rate due to the diffusion burn is over-predicted in all cases. The shape of the heat release rate for the constant volume chamber is well characterized by the model, as is the peak heat release rate. The shape produced for the diffusion burn in the engine cases is not correct. The injector in the combustion vessel has a single nozzle and greater distance to the wall reducing or eliminating wall effects and jet interaction effects. Interactions between jets and the use of a spray penetration correlation developed for non-reacting jets contribute to inaccuracies in the model.

Thesis (M.S.)--West Virginia University, 1999.
Title from document title page. Document formatted into pages; contains x, 96 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 61-62).

Computational fluid dynamics methodologies have been achieving in the last decades remarkable progresses in predicting the complex physical process in internal combustion engines, which need to be continuously optimised to get the best compromise between fuel economy, emissions and power output/drivability. Among the variety of computational tools developed by researchers to investigate the multi-Phase flow development from high-pressure fuel injection systems for modem diesel and gasoline direct injection engines, the Eulerian-Lagrangian stochastic methodology, which models the air/vapour mixture as continuous phase and the liquid droplets as the dispersed one, has become standard among the developers of commercial or in-house university CFD codes due to its intuitive assumptions and simple implementation. It is generally recognised that this method is specifically suitable for dilute sprays, but it has shortcomings with respect to modelling of the dense sprays present in the crucial region close to the nozzle exit of fuel injection systems. Moreover, the mathematical formulation of the Eulerian-Lagrangian models is intrinsically related to critical numerical issues, like the difficulty of correctly estimating the initial conditions at the nozzle hole exit required by spray modelling calculations and, furthermore, the dependency of the results on the spatial and temporal discretisation schemes used to solve the governing flow equations. To overcome some of these difficulties, a modified Lagrangian methodology has been developed in this study. The interaction between the Eulerian and the Lagrangian phases is not treated on the cell-to-parcel basis, but using spatial distribution functions, which allow for distribution of the spray source terms on a number of cells located within a distance from the droplet centre. The end result is a numerical methodology which can handle numerical grids irrespective of the volume of the Lagrangian phase introduced. These improvements have been found to offer significant advances on Lagrangian spray calculations without the need to switch to Eulerian models in the near nozzle region. Besides these fundamental numerical issues, the present study offers some new insights on the physical processes involved in evaporating sprays under a wide range of operating conditions typical of advanced diesel and gasoline direct injection engines. Attention hag been directed on the topic of liquid droplet vaporisation modelling, which has been addressed by implementing and discussing different models published in the literature. Topics of particular emphasis include phase equilibrium, quasi-steadiness assumption, fuel composition, physical properties correlation, droplet shape and energy and mass transfer in the liquid and gas phases. The models have been implemented and validated against an extensive data base of experimental results for single and multi-component droplets vaporising under suband super-critical surrounding conditions and then implemented in the in-house GFS code, the multi-phase CFD solver developed within the research group over the last decade. A variety of physical sub-models have been assessed against comprehensive experimental data, which include the effect of thermodynamic, operating and physical parameters on the liquid and vapour penetration of diesel sprays. In particular, the effect of liquid atomisation, evaporation, aerodynamic drag, droplet secondary break-up and fuel physical properties has been thoroughly tested. The sensitivity of the predictions on the numerical treatment of the multi-phase interaction has been investigated by identifying and properly modelling the numerical parameters playing the most crucial role in the simulations. Finally the validated code has been used to investigate the flow processes from three high-pressure injection systems for direct injection spark-ignition engines. These have included the pressure swirl atomiser, the multi-hole injector and the outward-opening pintle nozzle. These investigations have enlightened the crucial role of the accurate modelling of the link between the internal nozzle flow prediction and the characteristics of the forming sprays in term of the successive multi-phase flow interaction, as function of the design of the fuel injection system used.

The temporal and spatial distribution of fuel in cylinders is a key factor affecting the combustion characteristics and emission generation of a DI diesel engine. The airfuel mixing quality is critical for controlling ignition timing and combustion duration. Avoiding fuel-rich areas within the cylinder can significantly reduce soot formation as well as high local temperatures resulting in low NOx formation. The present investigation is focused on the effects of advanced fuel injections and air path strategies as well as the effects of piston geometry and fuel spray angle on air-fuel homogeneity, combustion process and their impacts on the performance and emission of the engine. A Ricardo Hydra single-cylinder engine in combination with AVL Fire CFD software was used in this investigation. An experimental analysis was conducted to assess the combustion characteristics and emissions formation of the engine under various injection strategies such as different injection timing, quantity, ratio, dwell angles between injections with various exhaust valve opening times and exhaust back pressures. A quan- titative factor named Homogeneity Factor (HF) was employed in the CFD code in order to quantify the air-fuel mixing and understand how the air-fuel homogeneity within the cylinder can influence the combustion and emissions of the engine. The investigation concludes that multiple injection strategies have the potential to reduce diesel emissions while maintaining meaningful fuel economy. Split injection can be used to improve the air-fuel mixture locally and control temperature generation during the start of combustion. Increased air-fuel homogeneity results in fewer fuel-rich areas within the cylinder and contributes to the reduction of soot emission. Extending the pre-mixed combustion phase has a direct effect on the reduction of soot formation while NOx generation is highly dependent on the scale of the primary fuel injection event.

The fuel pressure is one of the central control variables of a modern common-rail injection system. It influences the generation of nitrous oxide and particulate matter emissions, the brake specific fuel consumption of the engine and the power consumption of the fuel pump. Accurate control of the fuel pressure and reliable diagnostics of the fuel system are therefore crucial components of the engine management system. In order to develop for example control or diagnostics algorithms and aid in the understanding of how hardware changes affect the system, a simulation model of the system is desirable.  A Simulink model of the XPI (Xtra high Pressure Injection) system developed by Scania and Cummins is developed. Unlike the previous models of the system available, the new model is geared towards fast simulations by modelling only the mean flow and pressure characteristics of the system, instead of the momentary flow and pressure variations as the engine rotates. The model is built using a modular approach where each module represents a physical component of the system. The modules themselves are based to a large extent on the physical properties of the components involved, making the model of the system adaptable to different hardware configurations whilst also being easy to understand and modify.
Bränsletrycket är en av de centrala styrvariablerna i ett modernt common-rail insprutningssystem. Det påverkar utsläppen av kväveoxider och partiklar, motorns specifika bränsleförbrukning och bränslepumpens effektförbrukning. Nogrann reglering och tillförlitliga diagnoser av bränslesystemet är därför mycket viktiga funktioner i motorstyrsystemet. Som ett hjälpmedel vid utveckling av dessa algoritmer samt för att öka förståelsen för hur hårdvaruförändringar påverkar systemet är det önskvärt med en simuleringsmodel av bränslesystemet.  En Simulink modell av XPI (Xtra high Pressure Injection) systemet som utvecklats av Scania och Cummins har utvecklats. Till skillnad från de redan tillgängliga modellerna av systemet fokuserar denna modell på snabba simuleringsförlopp genom att enbart modellera medeltryck och medelflöden istället för de momentana trycken och flödena i systemet när motorn roterar. Modellen är uppbyggd av moduler som var och en representerar en fysisk komponent i systemet. Modulerna är mestadels uppbyggda kring de fysikaliska egenskaperna hos komponenten de försöker modellera vilket gör modellen av systemet anpassningsbar till olika hårdvarukonfigurationer och samtidigt lätt att förstå.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: This thesis comprises of the testing and evaluation of a modern diesel engine running on both biodiesel and mineral diesel on the upgraded Bio-fuels Testing Facility (BTF) at Stellenbosch University. The project was motivated by the need to install a modern diesel engine onto the existing BTF test rig for biodiesel testing. In this project, the BTF was re-designed to support a new Volkswagen 1.9L TDI engine. The capabilities of the BTF were then expanded further by the implementation of a low-cost pressure indicating system, utilising an optical pressure transducer. During the testing of biodiesel, it was found that the calorific value of the biodiesel was 14% lower than that of the tested mineral diesel. The ignition quality (cetane index) of the biodiesel was also lower than that of the mineral diesel. Even so, the engine only experienced a maximum power loss of 4.2%. During heat-release analysis, it was determined that there was no significant difference in the combustion process of biodiesel and that of mineral diesel. The conclusion could be made that biodiesel is suitable for use in modern TDI engines. Testing validated the operation of the upgraded test cell, and in trials it was determined that the test results are highly repeatable. The pressure indicating set proved to have some limitations. Only simplified heat-release analyses and reasonable indicated power calculations could be performed with the indicating set. Recommendations were made for improvement in future research.
Centre for Renewable and Sustainable Energy Studies

This master thesis covers the development of a high-pressure fuel system for compression ignitedfuels such as diesel and diesel-like fuels that will be deployed into a single cylinder test cell at AVLMTC Södertälje, Sweden. The test cell is used by AVL to conduct research and testing of new fuelsfor their customers and this new fuel system will widen the span of fuels able to be tested by theequipment.This thesis focuses on pumping and pressurizing of the fuel, ensuring that all ingoing materialsare non-corrosive in this environment and compatible with the necessary fuels and lastly a safetyanalysis of the system with respect to operator and process safety. Other aspects of the projectsuch as mass flow measurements and fuel conditioning is covered in a sister thesis Mass flowrate measurement of compression ignition fuels in high-pressure stand-alone pump unit for singlecylinder test cell written by C. Aksoy [1].The goal of this thesis project was to deliver a finished manufactured fuel system and if the timeallowed for it, also validate its performance and finally installing and incorporating it into the singlecylinder test cell. The development process started with the writing of a product specificationoutlining the requirements and request on the product in a specification of requirements matrix andrelate these to product properties of the system using a quality function deployment (QFD) matrix.This document was then used as a base for further advancement in developing concepts to solveeach product property and weighing these concepts against each other using Pugh’s matrices. Thechosen concepts were then further developed, a flow chart for the system was developed as well asfuel lines and other supporting components were analyzed and chosen.In the end the high-pressure fuel pump from Scania’s XPI fuel system were chosen as well asa pressure transducer in the HP1000 series from ESI. Within the time frame of this thesis, theproject did not end up getting finished to the degree planned, but due to time constraints werehalted before starting manufacturing of the system. Some minor component choices remained aswell as documentation such as drawings and finalizing the physical layout of the system remained.All information regarding the remaining work needed to finalize the project and deploying thesystem in the test cell were outlined and with more time, the fuel system should fulfill its purposeof allowing testing and research of compression ignited fuel to be possible in the test cell.
Kontentan för denna mastersavhandling är utvecklingsprocessen för ett högtrycksbränslesystemför kompressionsbränslen såsom diesel och diesellika bränslen som kommer att installeras i enencylindertestcell hos AVL MTC Södertälje, Sverige. Testcellen används av AVL för forskningoch testning av nya bränslen åt deras kunder och detta nya bränslesystem kommer att utöka typernaav bränslen som kan testas med utrustningen till att inkludera kompressionsantända bränslen.Denna avhandling fokuserar på utvecklingen av tillförseln och trycksättnigen av bränslet, säkerställnigenav att ingående material är icke-korrosiva i den avsedda miljön och kompatibla med allanödvändiga bränsletyper och slutligen en säkerhetsanalys av systemet med avseende på operatörsochprocessäkerhet. Andra aspekter såsom massflödesmätning och bränslekonditionering presenterasi systeravhandlingen Flödesmätning och konditionering av högtryckantända bränslen för encylindertestcellskriven av C. Aksoy [1].Målet med denna avhandling var att leverera ett färdigtillverkad bränslesystem och om tiden tillät,även validera systemets prestanda och slutligen integrera och installera systemet i testcellen. Utvecklingsprocesseninleddes med att skriva en produktspecifikation som innehöll en sammanställningav kundens krav och önskemål för produkten och relaterade dessa till produktegenskaper med hjälpav en quality function deployment (QFD) matris. Detta dokument användes vidare som en bas förfortsatt utveckling av produkten i konceptgenereringsprocessen och för att väga de olika konceptenmot varandra med hjälp av Pugh’s matriser. De valda koncepten blev sedan analyserade ytterligare,ett flödesschema för de ingående komponenterna framtaget och övriga sekundära komponenteranalyserade och valda.Till slut valdes högtrycksbränslepumpen från Scanias XPI system och en tryckgivare från HP1000-serien från ESI. Inom tidsramen för avhandlingen färdigställdes aldrig projektet till den grad somhade planerats, men blev istället avbrutet innan tillverkningen av systemet han påbörjas på grund avtidsbegränsningar. Vissa sekundära komponentval, dokumentation såsom ritningar och färdigställningav den fysiska layouten av systemet kvarstod vid avhandlingens slut. All information angåendeallt nödvändigt fortsatt arbete för att färdigställa projektet och integrera systemet i encylindertestcellendokumenterades och med mer tid borde bränslesystemet kunna uppfylla sitt syfte att möjliggöratestning och forskning av kompressionsbränslen i testcellen.

La législation sur les émissions de polluants des Moteurs à Combustion Interne (ICEs) est de plus en plus contraignante et représente un gros défi pour les constructeurs automobiles. De nouvelles stratégies de combustion telles que la Combustion à Allumage par Compression Homogène (HCCI) et l’exploitation de stratégies d’injections multiples sont des voies prometteuses qui permettent de respecter les normes sur les émissions de NOx et de suies, du fait que la combustion a lieu dans un mélange très dilué et par conséquent à basse température. Ces aspects demandent la création d’outils numériques adaptés à ces nouveaux défis. Cette thèse présente le développement d’un nouveau modèle 0D de combustion Diesel HCCI : le dual Combustion Model (dual - CM). Le modèle dual-CM a été basé sur l’approche PCM-FPI utilisée en Mécanique des Fluides Numérique (CFD) 3D, qui permet de prédire les caractéristiques de l’auto-allumage et du dégagement de chaleur de tous les modes de combustion Diesel. Afin d’adapter l’approche PCM-FPI à un formalisme 0D, il est fondamental de décrire précisément le mélange à l’intérieur du cylindre. Par consequent, des modèles d’évaporation du carburant liquide, de formation de la zone de mélange et de variance de la fraction de mélange, qui permettent d’avoir une description détaillée des proprietés thermochimiques locales du mélange y compris pour des configurations adoptant des stratégies d’injections multiples, sont proposés. Dans une première phase, les résultats du modèle ont été comparés aux résultats du modèle 3D. Ensuite, le modèle dual-CM a été validé sur une grande base de données expérimentales; compte tenu du bon accord avec l’expérience et du temps de calcul réduit, l’approche présentée s’est montrée prometteuse pour des applications de type simulation système. Pour conclure, les limites des hypothèses utilisées dans dual-CM ont été investiguées et des perspectives pour les dévélopements futurs ont été proposées
More and more stringent restrictions concerning the pollutant emissions of Internal Combustion Engines (ICEs) constitute a major challenge for the automotive industry. New combustion strategies such as Homogeneous Charge Compression Ignition (HCCI) and the implementation of complex injection strategies are promising solutions for achieving the imposed emission standards as they permit low NOx and soot emissions, via lean and highly diluted combustions, thus assuring low combustion temperatures. This requires the creation of numerical tools adapted to these new challenges. This Ph.D presents the development of a new 0D Diesel HCCI combustion model : the dual Combustion Model (dual−CM ). The dual-CM is based on the PCM-FPI approach used in 3D CFD, which allows to predict the characteristics of Auto-Ignition and Heat Release for all Diesel combustion modes. In order to adapt the PCM-FPI approach to a 0D formalism, a good description of the in-cylinder mixture is fundamental. Consequently, adapted models for liquid fuel evaporation, mixing zone formation and mixture fraction variance, which allow to have a detailed description of the local thermochemical properties of the mixture even in configurations adopting multiple injection strategies, are proposed. The results of the 0D model are compared in an initial step to the 3D CFD results. Then, the dual-CM is validated against a large experimental database; considering the good agreement with the experiments and low CPU costs, the presented approach is shown to be promising for global engine system simulations. Finally, the limits of the hypotheses made in the dual-CM are investigated and perspectives for future developments are proposed

碩士
國立臺北科技大學
車輛工程系所
100
Bio-alcohol fuels mixing with super diesel is the most top issue in the world, now. It can contribute to the combustion of diesel engine; some others with water have micro-explosion effect to improve combustion efficiency in diesel engine and reduce exhaust emissions to augment engine performance. According to researching about isopropyl alcohol used in diesel engine all over the world is barely uncover. So the study investigates the effect on diesel engines performance and exhaust emissions by adding high-purity isopropyl alcohol and water-contained isopropyl alcohol into the super diesel. The results show that the anhydrous mixed fuel has higher BSFC value, HC emissions, the smoke, NOx and exhaust gas temperature, however, is lower than those of super diesel; the mixed fuel with water which contains lower heating value also has higher BSFC value, but the smoke, NOx and HC emission levels as well as exhaust gas temperature are lower than those of anhydrous mixed fuel.

Thesis (M.S.)--University of Wisconsin--Madison, 1988.
Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 102-105).

碩士
國立臺北科技大學
車輛工程系所
100
With industrial developing, fossil energies are widely used; they produce some problems like a large number of exhaust pollutants and the greenhouse effect. In this study, we use the characteristics of the high oxygen content and low carbon content of the alcohol fuel to reduce the concentration of pollutants in the exhaust emissions from diesel engines. In the procedure, the super diesel fuel is added by 90 wt% with high-purity butanol additive and 5 wt% water-contented butanol additive in non-modified diesel engine, respectively. The results show that the butanol mixed fuel has higher BSFC value, higher HC emissions and lower BMEP value than super diesel fuel, however, the Smoke, NOx, exhaust gas temperature are lower than super diesel; the butanol mixed fuel with water-contented additive also has higher BSFC value and BMEP value, yet the Smoke, Nox, HC emission levels, and exhaust gas temperature are lower than the butanol mixed fuel without water.

碩士
國立臺北科技大學
車輛工程系所
100
Diesel engines have the advantage of high thermal efficiency, maximum torque output, cheap oil, stability and durability. So diesel engine has an important contribution in dynamic machine, such as vehicle, ship, agri-motor etc. It is effective contributions to develop world economy. But the contaminant of diesel engines, such as smoke, NOX and HC emissions will lead air pollution to damage respiratory disease. In order to reducing exhaust emission, the theme of theses analyze that super diesel fuels are added by 90% with high-purity methanol additive and 5% water-contented methanol additive in non-modified diesel engines, respectively. The results show that the anhydrous methanol mixed fuel has higher BSFC value, the smoke, NOX, HC emissions and exhaust gas temperature, however, is lower than super diesel; the methanol mixed fuel with water which contains lower heating value also has higher BSFC value, but the smoke, NOX and HC emission levels, as well as exhaust gas temperature are lower than the anhydrous methanol mixed fuel.

Emissions and performance of an HPDI single-cylinder diesel engine fueled by natural gas and by a mixture of hydrogen-natural were investigated. A DDC 1-71 engine with electronic controls was used. Natural gas or hydrogen-natural gas mixture was injected late in the compression stroke after a pilot quantity of a diesel was injected. Engine performance and emissions have been measured over a wide range of parameters: gas injection pressure, engine load, injection delay and mass flow percentages for the gaseous fuels. These results were compared with conventional diesel fueling. The purpose of this research was to investigate the potential for reducing the diesel exhaust emissions while maintaining high thermal efficiency. With HPDI of natural gas and hydrogen-natural gas, NOx emissions can be reduced to almost half of those with diesel fueling, by appropriately adjusting the injection timing. NOx concentration is observed to increase with gas injection pressure. For hydrogen-natural gas fueling, an increase of the hydrogen percentage produces an increase in NOx. This is attributed to the higher combustion temperature as the percentage of hydrogen increases. Thermal efficiency of HPDI of natural gas was greater than conventional diesel fueling at high loads but almost identical for medium and low loads. For HPDI of hydrogen-natural gas mixture the thermal efficiency is less than with natural gas fueling. The drop in thermal efficiency has not yet been explained. With hydrogen addition, the unburned hydrocarbons are greatly reduced, for almost all the engine loads. Carbon monoxide emission with HPDI was reduced for high and low loads.

Yes
Dual-fuel HCCI engines allow a relatively small quantity of diesel fuel to be used to ignite a variety of fuels such as natural gas or methane in HCCI mode. The gaseous fuel is mixed with the incoming air, and diesel fuel is sprayed into the cylinder by direct injection. Mathematical modelling is used to investigate the effects of parameters such as premixed ratio (fuel ratio) and pilot fuel injection timing on combustion of a dual-fuel HCCI engines. A CFD package is used with AVL FIRE software to simulate dual-fuel HCCI combustion in detail. The results establish a suitable range of premixed ratio and liquid fuel injection timing for low levels of NOx, CO and HC emissions along with a reliable and efficient combustion. Dual-fuel HCCI mode can increase NOx emission with lower premixed ratios in comparison to normal HCCI engines, but it is shown that the NOx emission reduces above a certain level of the premixed ratio. Due to the requirement of homogenous mixing of liquid fuel with air, the liquid fuel injection is earlier than for diesel engines. It is shown that, with careful control of parameters, dual-fuel HCCI engines have lower emissions in comparison with conventional engines.

碩士
國立雲林科技大學
機械工程系
106
This study presents experimental examinations of a common-rail single-cylinder diesel engine, mixing three different kind of alcohols by pre-mixed the diesel with the same percentage heat value of alcohols which include Methanol、1-Butanol and 1-Octanol expecting that will not only increase the fuel to contain more oxygen but alter the fuels chemical and physical properties to improve combustion efficiency. And also explore the potentiality of alcohols to become an alternative fuels. This experiment focused on the measurement of torque and pollution emissions which contains CO、HC、CO2、NOX and Smoke. The results of the examinations witch using pure diesel fuel were be the base-line for this experiment. This study were used a single cylinder diesel engine CY 190 at various engine speed (1500rpm、1800rpm、2100rpm、2400rpm) and various energy value injection that define by the pure diesel at the engine equivalence ratio (Φd=0.2、0.3、0.4). The experiment were constant the injection timing at top dead center 19°CA and the fuel injection pressure is 500 bar. The result shows that it’s positive for the engine performance at non-high engine speed for all three kind of diesel/alcohols blends. It’s due to the alcohols containing more oxygen that cloud improve the combustion rate. At the emissions way, low engine speed would cause the HC、CO、Smoke emission increase, but the emissions decreased by increasing the engine speed till 2100rpm. The emission of NOX were depend on the type of additives, the diesel/Methanol blend compare to the base-line had a lower NOX emission at all condition, the diesel/1-Butanol blend and diesel/1-Octanol blend has a similar pattern of NOX emission. As the result we could find out that adding alcohols could increase the fuels oxygen containing rate to improve the combustion efficiency, but sort-chain alcohols has a lower CN value and higher Heat of Vaporization that were make the ignition timing late, cause a higher emissions. Conclude all the measure value, it has a best engine performance increase and emission reduce at 2100rpm with mid and high load.

碩士
國立臺北科技大學
車輛工程系所
94
High productivity and low cost biodiesels for the palm oil is especially suitable for diesel engine. But the palm oil has the characteristics of bad fluidity in atmospheric temperature; it has to do the transesterification reaction to be palm oil methyl ester (POME). Therefore, it can be used in the region above 15℃, such as the seasons of summer and autumn in our country. The fuel system, lubrication system and the piston ring have been caused harmful affections in diesel engines for the long-term use of pure POME. In order to improve the poor fluidity of POME fuel, this study blends the different proportion of POME with premium diesel (PD) to investigate the effect on engine performance, brake specific fuel consumption (BSFC), exhaust gas emissions and combustion characteristics in diesel engines. Experimental results demonstrated that the blending fuel of 20% POME with PD (POME20) and the blending fuel of 50% POME with PD can effectively reduce BSFC and the concentration of NOx. However, the concentrations of smoke and HC have been slightly increased as compared with pure POME under full load condition at the highest engine speed.

碩士
國立嘉義大學
生物機電工程學系研究所
94
This study is to compare the performances and exhaust emissions of a direct-injection diesel engine fueled separately by domestic biodiesel(B100), biodiesel blend(B50) and the petroleum diesel, without engine modification. They are all measured from the engine tests under varying loads from the engine at varying speeds. The experimental results show that (1)The maximum power output of the engine is 3.2% lower and the specific fuel consumption is 12.34~25.65% higher, when the engine operates with biodiesel than by petroleum diesel under varying loads from the engine in four values of speed. (2)At 536kPa, 655kPa and 715kPa of the brake mean effective pressure the smoke emissions produced by the biodiesel reduce 81.4%, 76.4% and 59.1% respectively than by petroleum diesel. In addition, the CO2 and CO emissions are also decreased. (3) The NOX emission produced by biodiesel is 17.6~54% higher than by petroleum diesel under varying loads and speeds from the engine, but the difference between the amount of NOX emission produced by both are getting smaller when the engine load increased.（4）The performances and exhaust emissions of the engine feeding with B50 are between those of the engine fueled by petroleum diesel and biodiesel.

Homogeneous Charge Compression Ignition (HCCI) combustion is an alternative combustion mode in which the fuel is homogeneously mixed with air and is auto-ignited by compression. Due to charge homogeneity, this mode is characterized by low equivalence ratios and temperatures giving simultaneously low nitric oxide (NOx) and soot in diesel engines. The conventional problem of NOx-soot trade-off is avoided in this mode due to absence of diffusion combustion. This mode can be employed at part load conditions while maintaining conventional combustion at high load thus minimizing regulatory cycle emissions and reducing cost of after-treatment systems. The present study focuses on achieving this mode in a turbocharged, common rail, direct injection, four-cylinder, heavy duty diesel engine. Specifically, the work involves a combination of three-dimensional CFD simulations and experiments on this engine to assess both traditional and novel strategies related to fuel injection. The first phase of the work involved a quasi-dimensional simulation of the engine to assess potential of achieving HCCI. This was done using a zero-dimensional, single-zone HCCI combustion model with n-heptane skeletal chemistry along with a one-dimensional model of intake and exhaust systems. The feasibility of operation with realistic knock values with high EGR rate of 60% was observed. The second aspect of the work involved three-dimensional CFD simulations of the in-cylinder process with wall film prediction to evaluate injection strategies associated with Early Direct Injection (EDI). The extended Coherent Flame Model-3Zone (ECFM-3Z) was employed for combustion simulation of conventional CI and EDI, and was validated with experimental in-cylinder pressure data from the engine. A new Uniformity Index (UI) parameter was defined to assess charge homogeneity. Results showed significant in-homogeneity and presence of wall film for EDI. Simulations were conducted to assess improvement of charge homogeneity by several strategies; narrow spray cone angle, injection timing, multiple injections, intake air heating, Port Fuel Injection (PFI) as well as combination of PFI and EDI. The maximum UI achieved by EDI was 0.78. The PFI strategy could achieve UI of 0.95; however, up to 50% of fuel remained trapped in the port after valve closure. This indicated that except EDI, none of the above-mentioned strategies could help achieve the benefits of the HCCI mode. The third part of the work involved engine experimentation to assess the EDI strategy. This strategy produced lower soot than that of conventional CI combustion with very short combustion duration, but led to high knock and NOx which is attributed to pool fire burning phenomenon of the wall film, as confirmed by CFD. An Optimized EDI (OptimEDI) strategy was then developed based on results of CFD and Design of Experiments. The Optim EDI consisted of triple injections with split ratio of 41%-45%-14% and advancing the first injection. This strategy gave 20% NOx and soot reduction over the conventional CI mode. Although this strategy gave encouraging results, there was a need for more substantial reduction in emissions without sacrificing efficiency. Hence, a novel concept of utilizing air-assisted Injection (AAI) into the EGR stream was employed, as this implied injecting very small droplets of fuel into the intake which would have sufficient residence time to evaporate before reaching the cylinder, thereby enabling HCCI. The fourth and final part of the work involved engine experimentation with AAI, and combination of OptimEDI with AAI. Results with 20% EGR showed that 5 to 10% of AAI gave further reduction in NOx but not in soot. With experiments involving 48% EGR rate, there was soot reduction of 75% due to combined AAI-EDI. NOx was negligible due to the high EGR rate. Thus, the significant contribution of this work is in proving that combining AAI with EDI as a novel injection strategy leads to substantial NOx and soot reduction.