Simulation Of High Pressure Common Rail Fuel Injection System And Test Of Diesel Engine Performances

Using diesel fuel has been a trend of modern automobile engine,The 21st century is the century of diesel vehicles,and it has been reached a consensus in international automotive field. Diesel engine's owns many advantages such as high thermal efficiency, easy to using with turbo-charge, low fuel consumption, high torque, high reliability and long life-span.Relative petrol, the energy density of diesel is high,and its prices is low and maintains stability.Awareness of the energy crisis and environmental problems,people not only seek after more economy of diesel engine,but pay more attention to the emission .To meet requirements of the increasing engine performances and emission control , electronic control has become an inevitable trend. And the core of electronic control to diesel engine is electronic control of fuel injection system.The high pressure common rail fuel injection system has come true the high pressure injection which improves the mixture formation and the combustion process. The generation of high pressure is independent of the injection process. So there is no influence on engine speed, the load and the fuel injection quantity on it in a certain range. The high pressure common rail fuel injection system strengthens to the flexible controlling of the injection system parameters, specially the injection quantity, injection timing, injection rate, injection pressure and so on, in order to get the ideal regularity of fuel injection.Put into practical application, has been widely received and promoted since the end of the 20th century. High Pressure Common Rail Injection is a reasonable way to improve the efficiency, emissions and economy of the diesel engine.Electronic fuel injector finally obtains the signal of the fuel injection characteristics, and its major structural parameters and the working performance directly affect the fuel injection characteristics and the performance of the entire high pressure common rail system. Furthermore, it has an impact on the performance of the diesel engine.This paper analyzes structure components of the high pressure common rail system and its work process. in view of featuresof a typical high-pressure common rail fuel injection system, applying the software of GT-FUEL established a high pressure common rail system simulation model ,which is used to analyze injection characteristics. First, the high-pressure pump is simplified to source of oil, which can offer a regulating pressure.And the common-rail line is simplified into a volume model; Furthermore, in accordance with the principle of the injector, the injector will be divided into sub-module ,such as control signal module, anchor module, pin module, the needle module, control volume module . and establish the injector module. Against characteristics of GW2.5TC diesel engine, the engine is divided into diesel engine intake and exhaust system modules, fuel injection module and cylinder crankshaft module. Applying GT-POWER software establishs GW2.5TC Diesel Engine Simulation Model.GT-FLOW software which works as simulation platform couples the High Pressure Common Rail system simulation model and engine simulation model, and establishs the coupled simulation model.First, against the main structure parameters of the injector ,this paper using the coupled simulation model studys the injection characteristics and analyzes the economy and dynamic performances of diesel engine.Reducing the diameter and increase the number of fuel injector nozzle, can improve fuel spray atomization capabilities, and improved combustion thermal efficiency and the economy ,dynamic performances of diesel engine.Excessive control volume slows the response of fuel injection, so minimize control volume as soon as possible.When diameters of inlet and outlet hole becomes little , volume control room pressure unloads relatively quickly. Once the electromagnetic valve is opened, the needle quickly opens; When the electromagnetic valve is shut down, volume control room pressure rises slowly, resulting in fuel injection pulse width increased, Oil slowly breaked down.When diameters of inlet becomes larger,needle opens slowly,and the response of injector becomes worse. Diameters of inlet and outlet hole designed to ensure the needle rapidly open, and no secondary injection. Preload of the pin and impact on the initial injection rate is larger by electromagnetic force. And the injection characteristics can achieve certain injection trend which injects fuel slowly in the beginning and quickly later, Therefore,need to select a suitable preload and the appropriate electromagnetic materials.Secondly, using GT-POWER completely established diesel engine model, And studyed impact of the injection pressure, injection timing and injection characteristics on engine performance, then summarized a brief analysis of the emission characteristics .The impact of injection timing on the engine performance is complex, and suitable injection timing can improve the engine power and economy.To pursuit of low fuel consumption rate, injection timing should be advanced with higher speed, but NOx emissions increaseHigher common rail pressure can improve the engine power and economy ,but NOx emissions increase remarkably.Injection characteristics have great impact on the engine performance.Through comparing the boot-shaped, triangular and multiple times injection , the results are: Compared to other fuel injection characteristics, multiple times injection not only to enhance the economy of engine power, but also marked improves in nitrogen oxides emissions. Therefore, multiple times injection is the development trend in the future.Through simulation, analyze impact of the structure parameters of the system on the injection and adjust parameters on the performance of diesel engine.And offer some important conclutions , which have great guide signification. And some data are provided for system parameter design,Which providing the parameters for experimention.