Key Technology Research On The Application Of Electromagnetic Valve Train In Engine Exhaust System

Variable valve train is one of the key technologies to improve engine thermal efficiency.As a new kind of fully variable valve train,electromagnetic valve train(EMVT)can regulate the motion of the valves independently,continuous variably and real-time according to engine working conditions.With the application to intake system,the charging efficiency at full load conditions can be enhanced and the pumping loss at part load conditions can be decreased widely.As a result,the engine power and fuel economy are improved significantly.While the application of EMVT to exhaust system can further explore the potential of variable valve train,it will improve the charging expansion ratio and reduce the exhaust loss and emissions.However,subjected to the high pressure and temperature of gas in cylinder,there are still some difficulties and limited factors for its application.Based on moving coil electromagnetic valve train,with theoretical analysis,simulating calculation and experimental verification,further research on the application of EMVT to engine exhaust system is carried out in the thesis,and the new strategies based on fully variable valve train are explored to improve engine thermal efficiency,which gets great values both on theory and practice.The main contents and results of this thesis are summarized as following:(1)The electromagnetic linear actuator is optimized based on the requirement of electromagnetic exhaust valve train,and the working performance is tested.The prototype engine is reprocessed to adapt the variable valve train,and then puts forward the experimental scheme of camless engine.Also the engine thermal simulation model is carried out and validated by the experimental data,which provides theoretical basis for the later research.(2)The thesis studies the opening performance of electromagnetic exhaust valve train under different gas force and analyses the variation of valve train’s power loss.Multi-physics coupling model between electromagnetic exhaust valve and engine gas exchange is established.Experimental system is carried out based on the electrical linear load simulator,in the case the load simulator is used to simulate the engine combustion pressure on the test bench.The opening performance of exhaust valve is verified by simulation and experiment,the effect of gas pressure on valve opening is also analyzed.The researches indicate EMVT has meet the requirement of exhaust system,and also reveal the relationship among valve motion,gas pressure and power loss.(3)The thesis analysis the heat-generating characteristic of EMVT.While according to the argument of variable cooling solutions,a novel scheme based on pumping effect of moving coil is proposed to enhance the heat dissipation,which does not need the extra power and also has little influence on the structure of EMVT.The feasibility of this scheme is verified by the CFD simulation and the temperature tests under long-time operation,results show that the scheme has achieved a better efficiency to suppress the temperature of EMVT.(4)The effect of different exhaust valve motion on engine performance is analyzed,and confirmed the optimal valve strategies under variable engine conditions.Based on the effect of different exhaust valve motion on engine power and valve’s power loss,a new approach to define the optimal exhaust valve motion is proposed innovatively,with the optimization of valve motion under full load and variable speeds,it makes a good compromise between exhaust valves’ power loss and engine power.At the condition of part load,the valve motion strategies is optimizaed with the target of fuel economy,finally the operational MAP diagram of electromagnetic exhaust valve at full operating regions is carried out.Results show that the torque of camless engine has an improved of 8.9%,the fuel consumption has a decrease about 5%～15%.(5)Based on the application of variable intake and exhaust valves,the high compression ratio technology is discussed in the thesis.The variable valve technology can be used to avoid the interference phenomenon of scavenging and decrease the initial temperature in cylinder.While with the integrated optimization of intake valve strategy and AF,the engine compression ratio is promoted to 13.5 with no knock combustion,and the engine thermal efficiency has a further improvement.