Simulation And Optimization Of The Common Rail Fuel Injection System

In recent years, the emission law with diesel engine becomes severe. Meanwhile, tosatisfy the call of “Energy saving and emission reduction”, the advantages of electronic highpressure common-rail injection system have highlighted. The advantages of CR system aresuch as independently flexibly adjusting injection pressure, injection timing, fuel charge andfuel injection rate curve, which make the CR system to be the inevitable trend of diesel enginetechnology development at present stage.In this paper, an overall simulation model of electronic common-rail injection system on6-cylinder diesel engine has been established with AVL-HYDSIM software. The effects ofpump structure parameters, common-rail pipe structure parameters and CR system operationparameters on common-rail pressure oscillation have been compared and analyzed. To restrainthe pressure oscillation in common-rail and to raise the fuel charging uniformity between eachcylinder, some structure parameters have been optimized according to the analysis results.Meanwhile, some key structure parameters of electronic injector, of which are buffer chambervolume, control piston, inlet and outlet orifice diameter, have been separately analyzed tosearch the influences on injector needle response and spray characteristics. And finally theoptimization scheme is determined to boost the needle response speed.Due to the solenoid valve is one of the most important components in electronic-controlfuel injection system, the operating principles and mathematic models of the solenoid valveshould be detailed on. The simulation research on solenoid valve dynamic characteristics hasbeen done with SIMULINK model. The influences of operation and structure parameter asdriving voltage, initial air gap, spring preload and turn ratio on valve dynamic characteristicare analyzed. The results show that properly raising the driving voltage can cut down theresponse time of solenoid valve. To ensure the solenoid valve can be on and off regularly,spring preload might chose as smallest as possible. The initial air gap is in inverse proportionto electromagnetic force, and the turn ratio is in proportion to electromagnetic force.At the final part, a new idea has came up, which is that adding a pressure buffer on therail. The variable volume of the common-rail could reduce pressure fluctuations.