Research On Improving Gasoline Engine Performance By Application Of Electromagnetic Valve Train

Electromagnetic valvetrain is a typical camless variable valve technology,with the characteristics of fully independent,continuous and real-time adjusting parameters of valve motion;it is considered one of the key technologies to improve the engine power and fuel economy.As a new kind of fully variable valve train,while the application of electromagnetic valvetrain to engine,it will improve the charging efficiency at full load conditions and the pumping loss at part load conditions can be decreased widely,as a result,the engine power and fuel economy are improved significantly.However,when the electromagnetic valvetrain installed in engine(with the application to intake system in this work),it is not only needed to consider the power consumption for electromagnetic valvetrain(EMVT)itself,but also needed to change the valve working mode flexibility according to the actual operating conditions of the engine,so the engine can obtain good performance.But the working conditions of the engine are complex and the performance is affected by so many factors which influence each other,how to develop a series of EMVT working modes which can switch flexibly according to engine operating conditions is a huge challenge for EMVT application on engine.Based on a moving coil EMVT,with theoretical analysis,simulating calculation and experimental verification,research on the application of EMVT on intake system is carried out in the thesis.In order to impro,ve the power and economy performance of engine,it is important to re-plan the valve operation strategies with engine working condition.The research conclusion has important research significance and application value,which gets great values both on theory and practice.The main contents and results of this thesis are summarized as following:(1)The opening performance and the power consumption were analyzed by testing under different EMVT operating parameters,it shows that this EMVT can meet the needs of this research for the characteristics of fast response,low energy consumption,stable operation.Compared with the cam driven variable valve mechanism,there are more valve operation strategies can be obtained,which provides a basis for the optimization of the intake valve working mode.(2)When application of electromagnetic valvetrain engine intake system,due to the characterizes that the motion strength of gas in cylinder changes sensitively with the valve operation mode,during process of the engine modeling,it is needed to modify combustion model,so the turbulent kinetic energy was introduced in Fractal combustion,which can more accurately predict the operating condition of the engine with electromagnetic valvetrain.For analysis of cylinder flow field in the process of engine charging and compressing process,a CFD model is established based on prototype machine parameter,by definition of dynamic grid,define the initial boundary,which can predict air motion evolution process in charging and compression strokes with changing valve operation parameters.(3)With characteries of transition time for valve opening and closing is independent from engine speed,and the valve operation parameters can be regulated flexibly for this EMVT,such discipline is proved that the main barriers are not always improve flow capacity of the intake valve,in the lower engine speed,the charging efficiency has reached the limit value by EMVT,other factors such as pumping loss and EMVT power cumsuption can be taken into account when improving the charging efficiency,to further improve the power performance of the engine;at high engine speed conditions,with continuous improvement of EMVT,the charging efficiency has increased significantly by faster response time.(4)To the demand and contradiction of reducing pumping loss and enhancing charge motion when improve fuel economy at part load engine working condition,valve working modes were redesigned.The advantages of the EMVT in improving the fuel economy are proved at engine partial load conditions,and the improvement range can more than 12.2%compared with the prototype.In addition through tradeoff single/double valve mode,with adjusting valve lift and transition time,proved the optimal valve operation mode for engine different working conditions,the valve operation MAP is identified,which lays the foundation for the EMVT aplication on engine.(5)In order to improve the motion strength of gas movement under low engine speed and lower load,a new intake valve working strategy is put forward to improve engine economic performance based on EMVT,which is carried out by allowing the most requirement air charged into cylinder at the early stage of intake to prevent the pumping loss increasing,and movement intensity of gas is ensured by late intake valve opened and charged the remain air with lower opened lift.Take the typical valve strategies of engine load adjusting technology as a comparison,it can be obtained a good balance between reducing pumping loss and enhancing movement intensity of gas in cylinder by the new intake valve working strategy,The researches shows that,the improvement of engine fuel economy and emissions performance can achieve optimal at low engine speed and small load.