Brief Analysis On Dynamics And Numerical Simulation On Thermodynamics Of A New Type Of High-efficiency VCR Hybrid Engine With Large Expansion Ratio

The internal combustion engine(ICE)has been the main power supply of passenger cars for a long period.It not only brings great convenience,but also causes damages to the environment and accelerates the consumption of oil and gas on the earth.As far as the current situation,the most essential issue is to develop the modern ICE with low energy consumption and pollutants emissions in accordance with the regulations.Therefore the goal of energy saving and emission reduction can be achieved.There have been many difficulties of mass production of VCR engines since it was proposed.Facing the current regulations,VCR will be also impacted by new energies.In order to improve its competitiveness,on the one hand,we should explore its other characteristics under heavy load conditions deeply.On the other hand,it is necessary to take the advantages of flexible compression ratio over coupling with other engine technologies.Only in this way,VCR engines will win a place in ICE power sources or hybrid systems.This paper will analyze double shaft controlled variable compression ratio(DSGC-VCR)from the following aspects.At first,the kinematic and dynamic characteristics of DSGC-VCR are introduced.The piston movement law of DSGC-VCR is similar to that of conventional crank connecting rod mechanism.Meanwhile,it has several advantages,such as wide range of adjustable compression ratio,variable stroke length,and large expansion ratio.The balance effect of4-cylinder DSGC-VCR engine is nearly the similar to that of base engine.The strength of its main parts has been checked by engineering algorithm.The theoretical thermal efficiency of DSGC-VCR is deduced,which has essential guiding significance for improving the thermal efficiency of engines.The performance prediction analysis of a 1.5T 4-cylinder gasoline engine with DSGC-VCR is carried out to show the fuel saving effect under heavy load conditions.The combustion system of the engine has been further optimized,based on which we have explored the lean combustion limit.Under our calculation conditions,under the condition of BMEP of 12 bar,17bar and 22 bar,the brake efficiency is above 46%,44% and 42% in order.For the lean burn with EGR,lean burn with EGR and air,and HCCI combusiton,the brake efficiency is 46.32%,48.8% and 50.15% in order.According to our estimation,when combing with HEV system,the advantages of DSGC-VCR would make HEV operating in the area with higher efficiency.In this paper,the research of DSGC-VCR has presented the advantages over traditional VCR mechanism.As the only power source,it may cope with the increasingly stringent emission law.With the combination of high tumble intake system,high pressure in cylinder direct injection,lean combustion with EGR and other technologies,the engine can achieve higher thermal efficiency,which shows that DSGC-VCR may follow the trend of the times hopefully after verifying by machine manufacturing and bench test.