Study On Sealing And Friction Characteristics And Optimization Of Structural Parameters Of Piston Assembly Of High Power Diesel Engine

With the rapid development of engine industry,high speed,high density and low energy consumption have become its important development direction,and the working environment of piston components has become increasingly harsh.The increase of the explosion pressure puts forward requirements and challenges to the sealing components of the engine.The friction loss work of the engine piston group is relatively high,resulting in the reduction of the working efficiency of the engine.In this paper,the force and motion state of piston and piston ring were analyzed theoretically.Considering the surface morphology and elastic deformation of cylinder liner ring group,a single-cylinder analysis model was established with AVL-Piston&Rings software to analyze the influence of structural parameters of piston and piston ring on the average gas flow of single cylinder and the friction work loss of ring group.The stiffness matrix of the piston was calculated,and the piston and cylinder liner were divided according to the different heat transfer conditions.The combustion temperature and heat transfer coefficient of the cylinder were obtained by AVL Boost,and the temperature field and thermal deformation of the piston and cylinder liner were calculated,and the profile lines of the piston and cylinder liner were revised.The influences of crankshaft bias,pin bias,cylinder clearance and bump height of piston on gas channeling and friction loss were evaluated.The optimization scheme of piston body was obtained used orthogonal test and range analysis,and the primary and secondary order of the affect by piston body parameters on sealing effect and friction loss were obtained.Taking the piston ring group as the research object,a full-factor test was conducted on the opening Angle of the ring group.It was found that when the opening Angle of the first ring was 150° and the opening Angle of the third ring was 270°,the blow-by was low and the friction loss was small..Taking the surface morphology of piston ring and cylinder liner as the research object,the effects of texture direction and roughness on sealing characteristics and friction loss were studied,and the optimal motion surface profile of piston ring was obtained.The open clearance,back clearance and side clearance of different ring groups were simulated and analyzed,and the influence rules on seal and friction characteristics were studied.An 8-factor factorial test was designed to get the primary and secondary order of the influences of piston ring structural parameters on blow-by and friction work loss.By using BP neural network and genetic algorithm to lateral clearance of ring group,the abutment as design variables,gas channeling and friction loss function as the optimization goal to establish the nonlinear model,obtained the pareto optimal objective solution and corresponding optimal parameters of piston ring group,it was close to the simulation value,verified the reliability of forecasting model,to improve the sealing characteristics reduces the friction loss,It provides a reference for the Piston rings design.