The Research Of Structural Parameters On Hydraulic Response Of Injector

The fuel efficiency and exhaust emissions of diesel engine is more advantaged than gasoline. High-pressure Common-rail Fuel Injection System is a developing trend of fuel injection technology in vehicle diesel engine, which is acknowledged as an optimal fuel injection system at present. It can supply high-pressure and small injection, to actualize ideal combustion and to improve diesel's fuel efficiency and reduce exhaust emissions.One of the key technologies of the high-pressure common-rail fuel injection system is the dynamic response of the injector. To achieve an ideal fuel injection rate, the dynamic response of the injector must be improved. Although the piezo injector can efficiently overcome the problem of electromagnetic injector's response time because of solenoid valve, it also needs to improve hydraulic response of control cavity, thus improving response of injector.This paper, the mathematical model of hydraulic control of high-pressure common-rail injector is built up, based on structure characteristic analysis of injector, including the common-rail tube model, the drive component model, the injector control cavity and the needle component model. Taking into account the high-pressure conditions, the leakage is increased rapidly, it's necessary to establish the models of leakage at control cavity and at needle component. Using AMESim software calculates those mathematical models and analyzes the effects of the hydraulic response that are caused by all parameters of common-rail and injector, identifying the key structural parameters:diameter of inlet and outlet orifice, diameter of control chamber, diameter of needle and flow coefficient of the nozzle.Using nondimensional parameters research further analysis and research on the hydraulic response and their relationship between the matching, then find out the best range of parameters. By orthogonal test, an integrated score is obtained for quantitative analysis that the factor of key structural parameters is ordered in decreasing:diameter of control chamber dc, diameter of needle dn, flow coefficient of the nozzleμ, diameter of outlet orifice dout, diameter of inlet orifice din. When dc is 4.6mm, dn is 3.69mm,μis 0.85, dout is 3.06mm, din is 0.185mm, the hydraulic response is best. Compared with original injector, the optimized injector's hydraulic response is improved 29.5%, to achieve a small pulse width and stable supply of fuel injection, in order to meet the high-pressure common-rail fuel injection system.