Research On The Influence Of The Three-cylinder Engine Piston Asymmetric Design On Friction Wear And Knocking Energy

Due to the advantages of small displacement and small size,the three-cylinder engine has become the current mainstream model for energy saving and emission reduction.However,the noise problem has always been a key issue that limits the quality of the three-cylinder engine.As a key component of the internal combustion engine for energy conversion,the piston's structural design plays an important role in the overall performance of the internal combustion engine,especially the engine reliability noise and friction and wear performance.Therefore,this paper takes a threecylinder gasoline engine as the object,and adopts the method of simulation calculation combined with test verification.By carrying out the asymmetric design of the piston assembly,the second-order movement process of the piston is simulated,the influence of the asymmetric design of the piston of the three-cylinder gasoline engine on the friction and wear and knock energy is studied and the design parameters are optimized.First,a multi-body dynamic model of the piston considering the effects of roughness,elasticity and thermal deformation is established,and the accuracy of the model is verified by the piston temperature field test and skirt wear test.Then,through the design of the asymmetric skirt profile and the simulation of the second-order motion process of the piston,the effects of the asymmetric reduction design and the doublebump design on the main thrust side on the knocking energy,the friction loss and the wear load of the skirt are studied,and the design parameters are optimized.Furthermore,the results show that an asymmetric design with a relatively small reduction on the secondary thrust side and an appropriate increase in the radial reduction of the top and bottom of the main thrust side skirt of the piston,which can reduce the tilt of the piston during commutation and improve the friction of the piston skirt loss;After adopting the design scheme of the double thrust points on the main thrust side,it was found that with the increase of the height of the cavity,the friction loss of the skirt showed a trend of decreasing first and then increasing,and the knocking energy peak first increased and then decreased.As the depth of the cavity increases,the friction loss of the skirt decreases first and then increases,and the knocking energy peak gradually increases.As the width of the cavity expands,the skirt frictional loss increases,the knocking energy peak decreases,and the wear area of the skirt expands.After the asymmetric design of the skirt profile,the overall friction and wear performance is improved.Then,through the asymmetric structural design of the piston assembly,the effects of the center of the piston pin hole,the center of gravity of the piston and the center of the crankshaft on the knocking energy,the skirt friction loss and the wear load are studied,and the parameters are optimized.The results show that the proper design of the negative bias of the piston pin can reduce the overall friction loss and the knocking energy peak.The negative displacement of the piston's center of gravity in the X direction increases the knocking energy peak,while the positive displacement can reduce the knocking energy peak near the top dead center effectively,and the skirt friction loss decreases first and then increases,and the center of gravity shift along the Y direction has a small effect on performance.The positive bias of the crankshaft can delay the moment of the second-order movement speed peak of the piston,and the knocking energy peak and friction loss decrease,while the negative bias design of the crankshaft can lead to the peak time advance,which exacerbates the knocking and friction loss.Furthermore,multi-objective optimization through range analysis is carried out,and the optimal level combination is determined.