Research On Electronic Controlled Injector Design And Performance For Middle-high Speed Diesel Engine

The deterioration of environment and the deficiency of petroleum resource have already become global issues. As one of the main pollution sources, diesel engines receive much concern in recent years. How to reduce the emissions of harmful substances became the first issue of restricting the development of diesel engines. As the heart of diesel engines, the fuel injection system has great effects on reducing harmful emissions, improving fuel economy and power performance of diesel engine. Advanced high-pressure common rail fuel injection system can not only realize flexible control, but also have the ability of multiple split injection and closed-loop control on rail pressure. According to the wide speed range, fast dynamic response and large cycle fuel injection quantity of middle-high speed diesel engine, more strict requirements are put forward for the design of electronically controlled injector in high pressure common rail system, study on the design and fuel injection performance of electronic control injector provides important theory basis for the improvement and perfection of the high pressure common rail system.First,a high-pressure common rail electronic-controlled injector which has an accumulator chamber and dual inlet for control chamber is designed , and a three-dimensional structure model is built in Pro/e. Simulation analysis is taken after establishing one-dimensional models with AMESim, and the result shows that the dual-inlet injector not only requires less time for needle valve seating but also has a shorter delay for closing, and thus a better response.Then, this paper researches on primary influence parameters of the electronic-injector dynamic characteristics, further on the influence law of structural parameters of accumulator cavity,flow-limiting valve,high speed solenoid valve and nozzle on the needle valve response delay time, fuel injection rate and the pressure in control chamber. And come to the conclusion that the structure parameters of flow-limiting valve only has a great influence on the response speed of the metering valves, while almost has no influence on response speed of needle valve, parameters such as electromagnetic valve throttle aperture, needle valve lift,apertures of inlet and outlet throttle orifice of control chamber, the diameter of the needle valve are important factors affect the fuel system response. Through analyzing the influence of different parameters on the response characteristics, the optimal design values of parameters are obtained.Under the premise of satisfying the injection response requirements, to meet the requirements on cycle fuel injection quantity control ,it studies the influence mechanism of the characteristic parameters, such as the electromagnetic valve throttle diameter , the inlet orifice diameter, the outlet orifice diameter and the needle valve spring pretightening force, on the pilot and main injection quantity during double injection process, and also the post injection and cycle fuel quantity injection during multiple injections. The controlling strategy for small oil quantity is realized, and effects of characteristics parameters on small oil quantity fluctuation under different rail pressure are explored. Finally, the stability of split injection quantity under different pressures during the multi-cycle injection process is studied.