Research On Robustness Optimization Of Electronically Controlled Fuel For Medium And Low Speed Diesel Engines

As the final injection end of the electronic fuel injection system,the electronic fuel injector determines the fuel injection quality.At present,its core technology is mainly mastered by foreign developed countries.Although many scholars and scientific research institutions have carried out relevant research and achieved good results in the design,analysis and optimization of electronic fuel injectors in China,there is still a certain gap compared with foreign enterprises,and the research on the reliability and robustness of the overall performance of electronic fuel injectors is not deeply involved,In particular,it is necessary to conduct in-depth research and analysis on robustness.This paper takes the electronically controlled fuel injector of a domestic low-speed diesel engine as the research object,and uses the method of combining theory with simulation modeling to calibrate the simulation model,analyze the structural parameters,optimize the robustness and verify the internal flow field of the electronically controlled fuel injector.The specific research work and conclusions are as follows:(1)According to the structure and working principle of the electronically controlled fuel injector,a simulation model was built based on AMESim software.Seven parameters that are difficult to measure in the experiment are defined as adjustment variables,and the Optimal Latin Hypercube(OLH)sampling method is used to complete the calibration of the simulation model.The results show that the maximum error between the simulated and experimental values of the cycle fuel injection quantity q,the fuel injector opening response process ac,and the fuel injector closing response process df under different operating conditions is within 10%,which proves the accuracy of the model calibration.(2)In order to analyze the influence characteristics of fuel injector parameters,single factor and partial factor test methods were used to explore the level of parameter values and the significance of influencing performance indicators.The results show that the change of ball valve diameter Dball has the greatest impact on the opening delay time ab and closing delay time de of the needle valve,and it is a competitive relationship;The change of needle valve lift L has the greatest influence on the opening time bc,closing time ef and circulating injection quantity q of the needle valve,and the influence is identical;The interaction between the valve port diameter Dvalve,solenoid valve spring stiffness Rsolv,needle valve spring stiffness Rspring,and parameters between the needle valve and the nozzle lower chamber did not have a significant effect on each performance index;The other 10 parameters play an important role in different performance indicators.(3)Based on the joint simulation of AMESim and Isight software,the mean reliability sampling method and genetic algorithm were used to optimize the certainty and 6 σrobustness of the significance parameters of electronically controlled fuel injectors.The optimal optimization scheme for minimizing the opening time bc and closing time ef of the needle valve was obtained through deterministic optimization.However,the robustness of the constraint conditions such as needle valve opening delay time ab,needle valve closing delay time de,and cycle fuel injection quantity q under this scheme is relatively low.Considering the influence of random variables,a robust scheme with constraint quality levels above 3 σ is obtained through 6 σ optimization and tolerance adjustment.(4)In order to verify the feasibility of the robust optimization results,the closing motion of the needle valve was simulated by using the dynamic grid technology in FLUENT software,and the influence of pressure change and cavitation phenomenon during the movement of the needle valve was analyzed.The results show that the fuel pressure in the lower chamber of the nozzle will increase briefly and then decrease rapidly with the pressure of the needle valve.With the decrease of the fuel injection opening and closing valve port,the fuel pressure in the lower chamber of the nozzle will gradually increase to the same as the fuel inlet pressure.The cavitation phenomenon of the optimized injector mainly occurs at the nozzle position,especially near the wall of the nozzle.