Structural Optimization Design Of High-pressure Common Rail Electronically Controlled Fuel Injection System For Diesel Engine

For the social status of energy shortage and environmental pollution,it is imminent to develop a resources-economy and environment-friendly internal combustion engine.Diesel high-pressure common rail electronically controlled fuel injection system is used in many fields because of its high control accuracy,fast response and flexible control.However,the issue of emissions limits its development.The domestic research in this field has started relatively late,it was mainly for the system of key components.For the complete system development,production is still long duration of time.How to further improve combustion efficiency is the mainstream direction of diesel engine technology development.However,the injection characteristics and atomization characteristics of injection system affect the combustion efficiency of the diesel engine directly.For the above key issues,the structure of diesel high-pressure common rail electrically fuel injection system is optimized based on the Key Development Projects of Zhejiang Province and the National Natural Science Foundation of China,and the influence of system structural parameters on injection characteristics and atomization characteristics was analyzed.The main research work is as follows.(1)The composition,function and working principle of injection system are analyzed in detail.Then the mathematical model of the coupling between mechanical and fluid was established in order to provides a theoretical basis for the simulation analysis of fuel injection system based on the theory of mechanical dynamics and engineering fluid mechanics.(2)The fuel injection system simulation model was establish based on the mathematical model by using hydsim simulation platform,calculating the injection rate and the cumulative fuel injection under 150 MPa of the common rail pressure,and comparing with standard value and test result.Compared with the standard value,the maximum error of fuel injection rate and cumulative fuel injection were 6% and 3.5%,compared with the test result,the maximum error of fuel injection rate and cumulative fuel injection were 6.5% and 2.5%,the effective and accuracy of the simulation model was verified.The influence of structural parameters on injection characteristics is analyzed by changing the structural parameters of the inlet,outlet throttle and control piston.(3)For the existing fuel injection system hydraulic delay phenomenon,on the basis of the original system,the structural of the electronically controlled injector is optimized by cancelling the high-pressure oil passage leading to the control chamber.The optimized simulation model of fuel injection system was establish.By comparing with the former system's needle movement,injection pressure and fuel injection rate,verifying the optimized fuel injection system can eliminate hydraulic delay phenomenon,reduce injection pressure fluctuations and shorten the fuel injection duration.(4)In order to analyze the effect of structure parameters on nozzle atomization characteristics,the model of diesel engine nozzle is set up,the grid is divided,the parameters are set up and the calculation is calculated.Analyzing the influence of nozzle diameter,Jet hole entrance chamfer and back pressure to atomization characteristics.Therefore,the results of this paper provides theoretical and practical guidance for the optimization design of the fuel injection system,further improves the combustion efficiency of the system,and contributes to solving the problems of energy shortage and environmental pollution.