Research On Working Characteristics Of Small Displacement Atkinson Cycle Gasoline Engine

The huge market demand and severe energy situation pose great challenges to the development of China's automobile industry,oil price stability,oil safety and emission control.The Otto cycle engine limits the increase of the compression ratio due to its large-load knocking combustion.Under partial load conditions,the gasoline engine controls the load through the throttle valve,the intake throttle is severe,and the negative pressure is formed in the intake manifold when the throttle portion is opened.,causing resistance to the downward stroke of the intake stroke piston.The Atkinson cycle gasoline engine has a higher expansion ratio,using the intake valve to close the load for load regulation,with higher thermal efficiency and lower fuel consumption.At the same time,the combination of Atkinson cycle gasoline engine and external EGR technology can further improve thermal efficiency and reduce NO_X emissions.Therefore,it is of practical significance to study the cooperative application conditions of the engine Atkinson cycle combined with EGR technology.Based on the numerical simulation model,this paper realizes the improved design of small displacement Otto cycle,so that it can obtain the cam profile of Atkinson cycle gasoline engine.Based on the GT-POWER to construct the engine one-dimensional simulation model,it is improved to Atkinson cycle gasoline engine.Research and simulation optimization are required for the influence of key parameters.The key parameters are preferably matched by simulation.It is concluded that at the 2 bar average effective pressure operating point of the Atkinson cycle of 2000r/min,the pumping loss is reduced by 19.9%;the indicated thermal efficiency is increased from 27%of the original machine to 30.47%,and the effective fuel consumption rate is reduced by 10.8%.While the engine's external characteristics ensure the power,the effective fuel consumption rate of all working points is significantly reduced,and the fuel consumption improvement rate is up to 5.9%.By establishing the combustion numerical simulation model of Atkinson cycle gasoline engine,the simulation analysis of the flow field of Atkinson cycle gasoline engine under partial load condition is carried out by CONVERGE.It is found that the gas flow in the initial stage of the intake air is stronger than that of the original machine.At the bottom dead center,the gas flow in the cylinder begins to weaken compared to the original machine.The gas flow rate in the cylinder is significantly weaker than that of the original machine,and the turbulent energy is 25%lower than the original machine.Based on the one-dimensional simulation model of Atkinson cycle gasoline engine,combined with external cooling EGR technology,the pumping loss of gasoline engine is further reduced by 23%,the thermal efficiency is increased by 3%,the effective fuel consumption rate is reduced by 0.6%,and the NO_X emission is reduced by 3.7%.The microscopic analysis of the temperature field in the cylinder was carried out by CONVERGE to further verify the macroscopic simulation results.This paper lays a theoretical foundation for the application research of Atkinson cycle combined with EGR technology for small displacement gasoline engine.