In diesel engines the fuel injection system produces the spray, which directly affects the combustion of the fuel, which in turn determines the production of pollutants. In spite of this, the details of this causal re...In diesel engines the fuel injection system produces the spray, which directly affects the combustion of the fuel, which in turn determines the production of pollutants. In spite of this, the details of this causal relationship remain unclear. There is, however, a lack of quantitative experimental data for determining and visualizing the cavitation inside real size diesel injector nozzle. The present work is devoted to analyze analytically the flow pattern inside the nozzle of a diesel engine working with hydrocarbon fuel (Diesel fuel) and to predict the relationship between the various flow parameters and occurrence of fuel cavitation in such nozzles. Basic physical parameters affecting this phenomenon are identified and quantified while the effect of nozzle geometry, fuel injection pressure, and engine cylinder temperature upon the flow pattern and occurrence of cavitation in such nozzles are assessed. In this study, a commercial computational fluid dynamics (CFD) package (FLUENT-T grid) is used while a computational grid is generated for the real geometry of diesel injector nozzle using (ANSYS). The suitability of the generated computational grid to give reliable results is examined using the suitable procedures and techniques. The results indicated that, cavitation modeling has reached a stage of maturity and it can usefully identify many of the cavitation structures present in internal nozzle flows and their dependence on nozzle design and flow conditions. The qualitative distributions and comparison of cavitation inception and distribution as well as flow parameters at the nozzle exit are also studied.展开更多
External mixture formation (PFI) of a diesel fuel aerosol has employed to investigate the diesel HCCI engine combustion and emissions characteristics. The key to the external mixture formation with diesel fuel is the ...External mixture formation (PFI) of a diesel fuel aerosol has employed to investigate the diesel HCCI engine combustion and emissions characteristics. The key to the external mixture formation with diesel fuel is the proper fuel/air mixture preparation. A proposed intake diesel fuel aerosol system mainly consists of a small chamber, in which the diesel fuel is fully vaporized by means of fuel cavitation inside the diesel injector nozzle. Nozzle cavitation is mainly affected by the injection pressure and the fuel system temperature. Results obtained reveal that the proposed method determines the possibility of producing a complete homogeneous fuel/air mixture, which can be applied to the diesel HCCI engine. With this method, the combustion and emission behavior were entirely optimized and the engine is capable of running in HCCI combustion mode with nearly ideal mixture preparation. In the present investigation, a methodology for the HCCI combustion mode of the diesel aerosol/air mixtures based on the fuel cavitation inside the injector nozzle parameters (such as the injection pressure and the fuel system temperature where fuel premixed ratio, NOx, CO, CO2, and HC emissions) have analyzed. Based on the engine performance and emissions characteristics the fuel injection pressure and the fuel system temperature have optimized to produce a suitable fuel premixed ratio and the perfect fuel/air mixture homogeneity at different engine operating conditions. The optimal injection pressure ranges between 150 - 200 bars, while the fuel system temperature lies within 175℃ - 200℃. Loops of exhaust gas recirculation (EGR) are used to extend the engine load by controlling the combustion phasing.展开更多
文摘In diesel engines the fuel injection system produces the spray, which directly affects the combustion of the fuel, which in turn determines the production of pollutants. In spite of this, the details of this causal relationship remain unclear. There is, however, a lack of quantitative experimental data for determining and visualizing the cavitation inside real size diesel injector nozzle. The present work is devoted to analyze analytically the flow pattern inside the nozzle of a diesel engine working with hydrocarbon fuel (Diesel fuel) and to predict the relationship between the various flow parameters and occurrence of fuel cavitation in such nozzles. Basic physical parameters affecting this phenomenon are identified and quantified while the effect of nozzle geometry, fuel injection pressure, and engine cylinder temperature upon the flow pattern and occurrence of cavitation in such nozzles are assessed. In this study, a commercial computational fluid dynamics (CFD) package (FLUENT-T grid) is used while a computational grid is generated for the real geometry of diesel injector nozzle using (ANSYS). The suitability of the generated computational grid to give reliable results is examined using the suitable procedures and techniques. The results indicated that, cavitation modeling has reached a stage of maturity and it can usefully identify many of the cavitation structures present in internal nozzle flows and their dependence on nozzle design and flow conditions. The qualitative distributions and comparison of cavitation inception and distribution as well as flow parameters at the nozzle exit are also studied.
文摘External mixture formation (PFI) of a diesel fuel aerosol has employed to investigate the diesel HCCI engine combustion and emissions characteristics. The key to the external mixture formation with diesel fuel is the proper fuel/air mixture preparation. A proposed intake diesel fuel aerosol system mainly consists of a small chamber, in which the diesel fuel is fully vaporized by means of fuel cavitation inside the diesel injector nozzle. Nozzle cavitation is mainly affected by the injection pressure and the fuel system temperature. Results obtained reveal that the proposed method determines the possibility of producing a complete homogeneous fuel/air mixture, which can be applied to the diesel HCCI engine. With this method, the combustion and emission behavior were entirely optimized and the engine is capable of running in HCCI combustion mode with nearly ideal mixture preparation. In the present investigation, a methodology for the HCCI combustion mode of the diesel aerosol/air mixtures based on the fuel cavitation inside the injector nozzle parameters (such as the injection pressure and the fuel system temperature where fuel premixed ratio, NOx, CO, CO2, and HC emissions) have analyzed. Based on the engine performance and emissions characteristics the fuel injection pressure and the fuel system temperature have optimized to produce a suitable fuel premixed ratio and the perfect fuel/air mixture homogeneity at different engine operating conditions. The optimal injection pressure ranges between 150 - 200 bars, while the fuel system temperature lies within 175℃ - 200℃. Loops of exhaust gas recirculation (EGR) are used to extend the engine load by controlling the combustion phasing.
