Research On Prediction Model Of Fuel Injection Law In Common Rail Based On Riemann Wave Theory

With the stringent requirements of emission regulations,in order to achieve high efficiency and low emission of diesel engines,more accurate control of in-cylinder combustion is needed.Therefore,the pressure fluctuation of fuel system can be used as an important parameter to be measured in the working process of diesel engine,and can be used to predict the fuel injection rule and in-cylinder combustion.However,the real-time prediction model of fuel injection law is poor,so it cannot be used in the development of control system.In this paper,the concept of Riemann wave is introduced,and a prediction model of fuel injection law based on the Riemann wave theory is established based on the Riemann invariant of pressure and velocity on the characteristic line.Firstly,this paper explores the characteristics of pressure fluctuation in the fuel injection system.For this purpose,a joint measurement platform and a one-dimensional simulation model are built to explore the generation mechanism,transmission process and pressure fluctuation law of the pressure wave in the fuel system.At the same time,the discrete model of high pressure tubing is built,the synthesis of pressure wave in the transmission process is explored,and the law of injector inlet pressure fluctuation is explored.Then the mathematical model and one-dimensional simulation model of fuel injection law prediction model based on Riemann wave theory are built.And prediction model parameters have done many work,including the condition of jet,determine whether they for short pulse width injection of different jet under the condition of sound velocity correction,correction of needle valve open before the interference wave,segmenting the long pulse width prediction model of computing time node calculation,the nozzle pressure prediction,and finally using Simulink to build the fuel injection law based on the theory of the Riemann wave forecasting model.Finally,the accuracy,stability,sensitivity and adaptability of the model are tested.The results show that the maximum error between the calculated model and the measured model is less than 3%,and the goodness of fit is above 0.93.At the same time,this paper analyzes the adaptability of the prediction model under different conditions,proposes a linear interpolation correction method to solve the accuracy problem of the prediction model under low sampling,analyzes the accuracy of the multi-injection prediction model,and analyzes the influence of the prediction model on the structural change of different fuel systems.