Simulation Optimization And Experimental Study On The Combustion System Of Atkinson Cycle Gasoline Engine

Atkinson cycle engine adjust the load by controlling the intake valve closing time,result in keeping the throttle fully open,which can largely reducing the pumping losses.Additionally,its compression ratio is higher than Otto cycle engine,which can result in the expansion ratio greater than the efficient compression ratio and then improvesbrake efficiency and fuel consumption is reduced too.So the Atkinson cycle engine is widely used in hybrid vehicles.The one-dimensional simulation model of the engine was established by GT-Power,and the knocking boundary criterion was detected and walidated.Studied the economic and dynamic performance of a 1.5L Atkinson cycle engine,by changing intake duration,maximum valve lift,intake manifold forms.After that,we selected the intake duration of 240 ° CA,the maximum lift of the valve 8mm,intake manifold length of 300mm（case₁）and an intermediate form of the intake manifold（case₃）as a final test study.The AVL-Fire（3-D）computational model was built and calibrated with experimental data to analyze the intake process and combustion process.The results demonstrate that the new chamber improves the turbulent kinetic energy at ignition time,and accelerates the flame propagation speed,and shorten the combustion duration.The case₁ and case₃ have a similar influnence in cylinder combustion.Base on the simulation results,the engine test bench was set up to verify the simulation results and study the fuel saving effect of the engine.The results show that: case₁ has a reduce in the minimum average specific fuel consumption about 8 g /（kW· h）,and case₃ is 9 g /（kW · h）,comparing with the original engine.Definitely,the coverage of the fuel economy area is significantly expanded about the two cases compared to the initial.After that,the combustion characteristics in cylinder was studied,and the results show the ignition delay and combustion duration is shorter than the initial which effectively improve the combustion containment.The brake efficiency of case₁ and case₃ is 34.5% and 34.7% respectively,which is bigger than initial（33.3%）.In conclusion,case₁ and case₃ are all can meet the need of the engine.