Optimization And Matching Of A Small Multi-cylinder Diesel Engine’s Swirl Chamber Combustor

With the advancement of agricultural supply-side structural reform,Chinese agricultural machinery,which has entered the era of "CHINA III",has entered a period of deep adjustment.For diesel engines in the main supporting areas on agricultural machinery,technical upgrading and structural optimization are still in progress.Because there is more demand for 10~37kW multi-cylinder diesel engine at home and abroad,it has become an urgent task to develop a domestic low-power multi-cylinder diesel engine with high cost performance,good power and better emission performance.Some non-road type three-cylinder diesel engine has the problem of lack of power,in order to meet the requirements of the engine,the following research is carried out:(1)Firstly,the combustion chamber 3D model is imported into Hypermesh for geometric cleaning and surface mesh division,then the dynamic mesh division is carried out by using FIRE software,and then the boundary conditions and initial conditions are defined for combustion simulation analysis.Using cylinder pressure curve to verify the correctness of the model;(2)By analyzing the simulation results of the main combustion chamber and swirl chamber combustion of the original engine,to find out the causes of poor combustion and insufficient power performance of the engine,and put forward the optimization scheme of changing the installation angle of the original engine nozzle,the spray cone angle,the connecting channel angle and the chamfering angle of the piston top diversion groove;(3)Changing the original engine nozzle installation angle,angle of spray,angle of connecting channel and the shape of the top diversion groove of the piston in the main combustion chamber,using FIRE software to simulate and analyze the influence of various factors on the combustion;(4)Taking the average pressure and pressure rise rate in cylinder as the evaluation index and adopting the response surface optimization technique,the factors of the swirl chamber are fitted by multi-element quadratic nonlinear fitting,and the optimum scheme of engine combustion is obtained by synthesizing the analysis results of the main combustion chamber.The optimal scheme is verified by simulation;(5)The results of the bench test show that the engine power and torque are improved obviously,the engine power and torque reach the rated value,and the fuel consumption rate is reduced.The emission reached the requirement of the third stage of the limit valueand measurement method for exhaust pollutants of diesel engines for non-road mobile machinery in China.