Development Of EVVTL System Performance Based On Benchmarking Test And Numeric Simulation

In recent years,with the rapid economic and social development,the number of cars has been increasing,while environmental pollution and energy consumption have been accelerated,and environmental and energy problems have become increasingly serious.Variable valve lift(VVL)technology and variable valve timing(Variable Valve Timing,VVT)technology have attracted the attention of major automobile manufacturers due to their effect on reducing gasoline engine fuel consumption,and they have invested a lot of manpower and material resources to carry out the study.This article is based on a patent applied by the team—Variable Valve Timing and Lift(VVTL)mechanism.Based on this patent,the research team designed a new type of VVTL with the goal of testing the original machine.This mechanism uses an electric motor to realize the synchronous control of valve lift and timing,and uses a camshaft to realize the control of valve action,referred to as EVVTL(Electrical Variable Valve Timing and Lift).The author of this article has participated in the development of the EVVTL system.The main research work and conclusions are as follows:(1)For a general naturally aspirated four-stroke gasoline engine,the factors that affect its operating economy are studied theoretically,and the relevant factors are decomposed,and the factor that directly affects its fuel economy—in-cylinder is selected.High pressure cycle indicates thermal efficiency;pumping loss;friction loss.In terms of the way of influence: the ratio of PMEP and FMEP to IMEP is more important than PMEP and FMEP itself.(2)Taking the factors that affect gasoline engine fuel economy as a starting point,this paper analyzes several common technologies on the market to improve gasoline engine fuel economy—VVT technology,exhaust gas recirculation(EGR)technology,and VVL technology’s effect on improving fuel economy.The influence of VVT and VVL on pumping loss is comparatively analyzed,and the analysis of energy-saving mechanism of VVL is carried out.The analysis results show that: VVT and EGR technology rely on adjusting intake pressure to control,and the potential to reduce pumping loss under medium and small loads is very limited;while VVL technology is realized by adjusting the effective displacement of the engine,and there is no need to reduce intake pressure under medium and small loads..So theoretically,there is the potential to greatly reduce the pumping loss.(3)A brief introduction to the EVVTL mechanism was made,and a GT-power one-dimensional performance simulation model was built for the original test machine and the gasoline engine equipped with the EVVTL system(the principle prototype for short).And set up an experimental platform to conduct a series of tests on the original test machine and the principle prototype,such as a running-in test,a mechanical loss power cold machine reverse drag test,and a universal characteristic test.(4)According to the experimental data,through comparative analysis,the reliability of the one-dimensional simulation model of the EVVTL principle prototype is verified;by comparing the experimental results of the original machine and the EVVTL principle prototype,the pumping loss,combustion process,and mechanical loss of the gasoline engine are analyzed..The results show that the built performance simulation model has high accuracy;EVVTL has significant energy-saving potential under medium and small loads(common working conditions of vehicle engines).Through the analysis and research of the influence of EVVTL system on gasoline engine performance,the simulation model,test method and analysis results built in this paper have reference for future VVTL research.