Research Of An Electronically Controlled Injection Device For Gas Fuel Heavy-duty Engine

Gas engine has advantages of less harmful pollutants and CO2emissions. It can play an important role not only in high efficient and clean energy utilization, but also in effective utilization of combustible gas. Energy saving and environment protection can promote the gas engine technology process and application. The adoption of gas fuel electronically controlled injection device realizes multi-point sequential and intermittent supply mode so that it supplies gas fuel to engine inlets sequentially and intermittently. It can effectively solve the problems of backfire in engine inlets and gas fuel loss during scavenging phase, and as a result improve the engine performance. Gas engine is applicable to many types of gas fuel. The gas fuel pressure required is relatively low, especially suitable for large flow rate and low pressure gas supply. In order to achieve the advanced level of engine economy, power and emission index in international, and adapt all kinds of different ingredients and heat value combustible gas perfectly, further study on gas fuel electronically controlled injection device which is the core technology is necessary. This thesis puts forward a kind of adopting moving-coil electromagnetic linear actuator and bacterium type valve gas fuel electronically controlled injection device. The structural design, control strategy, performance and flow characteristics of this device are systematic and deeply studied through the methods of theoretical analysis, simulation calculation and experiment. This thesis lays a good foundation for the further research and application of the heavy-duty gas fuel engine.(1) The development of gas fuel injection device is analyzed in this study, and an innovation gas fuel injection device using the moving-coil electromagnetic linear actuator and mushrooms type valve structure is proposed. Then, the structure, main design parameters and controller design are deeply researched. Finally the prototype of the injection device is developed and the performance test is completed. The results show that the transition time of the injection device is controlled in5ms, and the maximum valve lift can be reached4mm. The device works stable and reliably, and the technical solution can meet the requirements of high flow rate and response of the engine.(2) The numerical simulation models are established in this paper. The static and transient flow characteristics of the gas fuel injection device are calculated, and the experimental validation was also completed. The variation law between injection device and the main design and control parameters such as maximum valve lift, valve diameters, pressure differences, and valve open durations is determined. The mapping relationship of the injection quantity of gas fuel and the total opening time of the valve is established, which lays a good foundation for the gas fuel electronically controlled injection device’s engineering application.(3) The layout scheme of gas fuel injection device is determined, and the technology way to improve engine performance after the application of injection device is discussed. Engine controller is developed and control scheme is designed with engine speed as the control target. Analog signal input port and PWM signal output port multiplexing technology is adopted. Moreover, the entire function of engine controller which should realize during integrated design in advanced research is put forward and close-loop control of air fuel ratio is implemented. In the end, the improved engine controller scheme is presented.(4) The transient CFD numerical simulation model of a gas engine cylinder based on an electronically controlled gas fuel injection device is built, and influences to gas fuel intake and mixing process caused by control parameters and installation parameters of the gas fuel injection device are investigated. The gas fuel intake process is analyzed when the installation of gas fuel injection device is different, and the advantage of higher gas fuel intake sufficient degree is determined when the installation is close to combustion chamber. The injection pulse width regulation range of the electronically controlled gas fuel injection device is determined, and a method of increasing gas injection through increasing the pressure difference between gas fuel and air is discussed.(5) The real machine confirmatory test of a heavy-duty engine applied with gas fuel injection device is completed. Experiments including engine starting, idle speed stability, uniformity adjustment of each cylinder and load increasing and decreasing under given speed are conducted. The developed gas fuel injection device has the advantages of good control characteristics, high response speed and low seating speed, and can inject the gas fuel into intake manifold close to inlet port of each cylinder at fixed time with fixed quantity. Also it is capable of multi-point sequential intermittent supply method and regulating air-fuel ratio of each cylinder real-time, accurately and independently, which verifies the feasibility of the technology.