Research Of Injector Spray Measurement System Of Constant Volume For Gasoline Direct Injection Engine

With the global car inventory's increasing, the car industry is going to face a series problems, for example, the energy dry up, the petroleum price rises unceasingly, the emissions laws and regulations are strictly day by day, global warming and so on. Every country's automobile production manufacturer starts to put in the massive manpower and resources to seek for the new clean energy, or makes the technical change to the existing engine. In order to enhance the fuel oil efficiency, lower automobile's emission level and face the future challenge. Direct injection gasoline engine technology is a way to improve fuel efficiency and reduce fuel consumption.According to different conditions the direct injection gasoline engine uses different control strategies. At part load, the throttle full open, uses the late compression stroke injection control strategy, to be formed stratified combustible mixture gas near the spark plug, which can effectively reduce pumping loss and reduce the amount of fuel injection to improve fuel economy; at high load, uses the early intake stoke injection control strategy, to be formed the uniform combustible in the cylinder to meet the power requirements; in the two-stage transition condition uses two pates injection control strategy, in order to achieve a smooth transition of torque. This control strategy is proposed a higher requirement for fuel injection system. In the post-injection of the compression stroke, due to higher cylinder pressure, in order to quickly form the necessary cylinder combustible mixture gas, require a higher fuel injection pressure to make a high degree of atomization, spray in the intake process, the cylinder pressure is low, in order to prevent the fuel inject to the wall, worsen the emission, require the injection pressure is not to high. This strategy determines the fuel injection pressure located between the 5-12MPa.The spray characteristic impact upon the formation and combustion of the fuel mixture in cylinder directly. Constant volume spray testing system provides one of the main meanings to research the characteristic. The main content in this thesis based on the enterprise project"The development of the Constant volume spray testing system"sponsered by the Chinese FAW Technology Center.According to the project reqirment we developed the testing system, which includes constant volume body, intake system, exhaust system, fuel injection system, system controller and the real time monitor and calibrating software.The system can achive the ajustment of fuel pressure and the environmental temperature so that it can provides the most real environment in engine cylinder in which we conduct the spray character experiment.During the experiment it can instantly display the state of the temprature and pressure in the constant volume body. We can ajust the injection parameters such as injection pressure, injection pulse width and the current that powered injector. All the control and state parameters can be recorded instantly by carlibration software for the analysis later.Morover we developed the spray image processing software, which can provides means to analysis the picture taken during the experiment. From the images we can achive the measurement, analysis, averaing and the data storage of the injector spray cone angle and penetration. In addition we can find the average from the images of spray in multi-cycles, process unbiased variance of the variation of spray and the images.In the third chapter of this paper, analyze the structure of gasoline direct injection porous injector, and build the simplified mathematical model and the simulation model of solenoid valve, then the model was validated by the simulation analysis. The results show that the control amount of solenoid valve - voltage on the solenoid valve open and close impact is: With the increase of excitation voltage, the speed of the solenoid valve opening response improve, but the requirements of the power supply and injector performance will be higher, so the choice of voltage should be weighed. Furthermore, it should notice that due to the characteristics of the simplified model, the simulation results only to provide general trends reference for designing.The fourth chapter of this paper analyzes the characteristics of various fuel injection driver circuit to fulfill the requirement of the direct injection gasoline injector response characteristics, the dual voltage peak - holde current mode drive circuit is designed. The fuel injector driver circuit in order to achieve the rapid open, early in the injector open, provide a very high voltage to the injector, then the injector coil will generate a current of about 10A to make the injector Increase rapidly, when the injector is on, supply it with 12V car voltage to the fuel injector to provide and then, form a smaller current in the injector coil to maintain injector open by the current feedback control of PWM. The driver circuit can effectively reduce the power consumption of fuel injectors, and fuel injector can achieve fast response, so is the more advanced fuel injector drive circuit now. The difficulty lies in the drive circuit is to achieve high voltage, high-end switches drive and the loop control of current in the injector coil.In the fifth chapter of this paper experimental validation of the driver circuit, and test on the side of the spray injection image obtained from data analysis bases on the design of the spray in the constant volume testing system.