Research On The Influence Of Standing Vortex-channelization Piston Shape On Ignition And Combustion Of Gasoline Engine

As the emissions regulations are increasingly stringent,they make higher demands on the various aspects performance of the engines,the organization of air-fuel mixture and the combustion mode of fuel is the key factor that affects the engine performance,and the shape of the combustion chamber plays an important role in the organization and combustion of the fuel.It has the advantages of low technology,low cost and convenient implementation by improving the shape of the piston and increase compression ratio.Based on the modified manifold electric injection WH125-6 engine test data,one-dimensional and three-dimensional modeling simulation and numerical simulation were conducted through GT-Power and CONVERGE to contrast and correct with the test cylinder pressure to get reasonable boundary conditions.The V-type combustion chamber was obtained by building the standing vortex-channelization piston crown shape of a compression ratio?=12 gasoline engine.Standing vortex pit diameter ₁x,standing vortex pit depth ₂x and channelized groove ₃x of the piston crown as variables,40 groups of three dimensional numerical model samples of V-type combustion chambers were generated which variables interval were uniformly sampled by using optimal Latin hypercube test design method?Opt LHD?,and the numerical simulation work were carried out respectively.Kriging unbiased estimation prediction model in discourse domain was established based on sample simulation results.The maximum of power P and the minimum of emissions NOx,HC,CO as optimization targets,₁x,₂x,₃x variable interval as constraint,the optimal shape scheme of standing vortex-channelization piston crown was got through multi-objective variable optimization by applying non dominated sorting genetic algorithm?NSGA-II?to the kriging model in discourse domain.The combustion simulation results based on V-type combustion chamber of the optimal standing vortex-channelization piston crown and L-type combustion chamber of the flat piston crown show that,at the ignition time,the standing vortex pit of V-type combustion chambers can forms obviously standing vortex effect,V-type combustion chamber has lower gas flow velocity and lower turbulent kinetic energy near the spark plug electrode,2m/s and 2.6m²/s²,and has a higher fuel air equivalence ratio of 1.12which is easy to achieve stable ignition.According to the analysis of flame propagation process,it is found that the design of piston crown standing vortex-channelization shape can effectively reduce the flame propagation speed during piston upward,and simultaneously accelerate the expansion speed after flame enters the channel groove division during piston downward at the initial stage.The combustion of V-type combustion chamber is basically completed at ATDC 15°CA,and the heat release rate was concentrated in the range of ATDC 0°¹5°CA,which has more stronger constant volume combustion characteristics.Therefore,it is an effective way to effectively organize the in-cylinder flow field,enhance the ignition combustion quality,and improve the compression ratio at a low cost that reasonably design of the standing vortex-channelization piston crown shape.