| High pressure common rail fuel system is one of the core systems for modern diesel engines to achieve efficient combustion and ultra-low emissions,while common rail fuel injector is the key component of high-pressure common rail system,the reliability of common rail system design depends on the common rail fuel injector.At present,during using commercial software is used to study the theory of common rail injector,the simplified method is usually used in the electromagnetic valve model.For example,the curve of electromagnetic force changing with time is used to approximate the work of electromagnetic valve,or the threedimensional electromagnetic software is used to calculate the relationship of electromagnetic force changing with gap and driving current,and then the three relationships are loaded into the commercial form of map The work of common rail injector is carried out in the software.The above "simplified" treatment mode leads to the split of the electric field,magnetic field,mechanical field and hydraulic field involved in the working process of the common rail injector,which makes the mathematical model of the common rail injector unable to realize the multi physical coupling.Therefore,it is very important to develop a mathematical model of high-pressure common rail injector with high prediction accuracy and multi physical field transient coupling.As the core control part of the common rail injector,the dynamic response of the highspeed solenoid valve is very important for the injection timing,cycle injection quantity and injection stability of the common rail injector.In this paper,the model of the solenoid valve is established by using the method of Cauer type equivalent external circuit,which includes the detailed driving circuit,electromagnetic field of the solenoid valve and the transient hydrodynamic coupling inside the solenoid valve.The model can accurately predict the dynamic response of the solenoid valve and calculate the eddy current loss,hysteresis loss,wire loss and mechanical energy during the working process of the solenoid valve.Taking Bosch common rail injector as an example,the fuel flow model,mechanical motion model,fuel leakage model in the gap considering the transient gap of the couple,and the hydraulic mechanism model of the common rail injector considering the transient fuel physical are established.By coupling the detailed model of the high-speed solenoid valve and the hydraulic mechanism model of the injector,the electric mechanism of the common rail injector is established.Based on the comparison of the experimental data and calculation results of the injection law under different rail pressure and injection duration,the prediction accuracy of the multi physical field coupled mathematical model of the common rail injector established in this paper is proved.Driving parameters such as peak voltage,holding current and structural parameters such as inlet orifice(OZ orifice),drain orifice(OA orifice),control plunger diameter,maximum lift of needle valve and orifice area have different effects on dynamic response and cyclic injection quantity of common rail injector.Taking the Bosch high-pressure common rail injector as the object,the multi physical field coupling model of the common rail injector is established by coupling the detailed model of high-speed solenoid valve and the hydraulic mechanism model of the injector.The model is checked by comparing the experimental value and the calculated value of the cycle injection quantity.Then the dynamic response of the driving parameter and the structural parameter to the common rail injector is compared The influence of cycle injection quantity is studied,and the influence degree of different factors is analyzed by means of quantitative analysis.Referring to the above analysis results,on the premise of both improving the dynamic response and energy conversion efficiency,the optimization design scheme of structural parameters and driving parameters of common rail injector is proposed and realized by MATLAB.The optimization results can effectively improve the mechanical energy conversion efficiency and the promotion rate on the premise of meeting the requirements of opening,closing response and circulating injection quantity of common rail injector Above 60%,it is beneficial to the reasonable design of the structure and the effective improvement of the service life of the common rail injector. |
