Finite Element Analysis And Structural Optimization Of A Certain Aviation Kerosene Engine Piston

The aviation kerosene piston engine has the advantages of excellent power,fuel safety,simple maintenance and low cost,which is more and more popular in the military / civil field.The aviation kerosene piston engine is in the condition of large load and high speed for a long time.The harsh working environment is easy to cause cracking and deformation of the piston.The development of high-performance pistons with high strength and light weight will help promote the rapid development of aviation kerosene piston engine technology.The 3-D finite element model of a certain type of aviation kerosene engine piston was established in this paper,to meet the high strengthen and lightweight work,analyzed the rule of piston temperature,stress,deformation and fatigue at different cycle times under full load cruise condition,and studied the influence of piston pin hole profile and transition fillet between piston pin seat and inner cavity on piston strength.Improvement project was obtained through lightweight research,based on the thickness of piston pin hole side and secondary thrust side skirt.The main conclusion are as following:(1)The variation of piston temperature,stress,deformation and fatigue at different cycle times was studied in this paper.The maximum temperature of the piston was located at the center of the piston top,and the temperature gradually decreased along the axis.The transient maximum temperature was 287.3 °C at 59 °CA,and the maximum difference of the maximum temperature of the piston top was 6.6 °C.The coupling stress distribution of the piston was periodic.The maximum stress was 99.34 MPa at 28 °CA,showed at the upper edge of the inner side of the piston pin hole.At same time,the maximum stress of the transition fillet between the piston pin seat and the inner cavity was 93.64 MPa,within the material yield limit and strength meets the requirements.The minimum fatigue safety factor of the piston at the maximum stress moment was 1.34.At the time of the compression top dead center,the maximum stress of the piston was43.49 MPa,located in the top center of the inner cavity.The maximum comprehensive deformation of the piston has always been located at the edge of the piston top surface,and the maximum deformation was not exceed the tolerance value between the piston and the cylinder wall.(2)Modified piston pin hole and the transition fillet between the piston pin seat and the inner cavity,and studied the influence of the starting point of the profile pin hole,the angle of the pin seat,the radius of the transition fillet between the pin seat and the inner cavity on the piston strength.With the outward movement of the starting point of the special-shaped pin hole profile,the maximum stress of the round corner of the piston pin seat decreased,the maximum stress of the pin hole decreased first and then increased.The maximum stress of the round corner of the pin seat decreased with the increase of the drawing angle or the transition fillet radius.The maximum stress of the special-shaped pin was all located at the starting point of the upper power function profile.When the starting point of the profile was 0.45 times the contact length between the piston pin and the pin hole,the stress reached the minimum,was 59.97 MPa,at the same time,stress of the transition fillet between the piston pin seat and the inner cavity was reduced from 93.64 MPa to 78.33 MPa.When the angle of the pin seat was 1.5° and the fillet radius of the pin seat was 6 mm,the stress reached 71.72 MPa lowest,located at the fillet between the piston pin seat and the inner cavity on the main thrust side.Taking the starting point of the contact length profile of 0.45 times the piston pin and the pin hole,the pin seat drawing angle of 1.5° and the pin seat fillet radius of 6mm as improvement scheme,the maximum stress of the piston cycle was reduced from 99.34 MPa to 71.72 MPa,decreased 27.80%.The position was transferred from the upper edge of the pin hole inner side to the fillet of the pin seat.The maximum stress of the pin hole was reduced from 99.34 MPa to 59.97 MPa,decreased 39.63%.The maximum stress of the pin seat was reduced from 93.64 MPa to 71.72 MPa,decreased 23.41%.(3)The lightweight of the wall thickness of the secondary thrust side skirt and the pin hole side skirt was studied,analyzed the effects of the reducing wall thickness of the secondary thrust side skirt and the upward movement of the pin hole side skirt profile on the quality and strength of the piston.With the decrease of the wall thickness of the secondary thrust side of the piston skirt,the maximum stress on the outer side and inner side of the secondary thrust side skirt increased slightly,same as skirt deformation;when the secondary thrust side wall thickness of the piston skirt reduced from 3.25 mm to 2.65 mm,the piston mass reduced by 4.44 g,1.38%lower than the non-lightweight piston;the maximum stress on the outer side of the secondary thrust side skirt increased from 27.27 MPa to 33.47 MPa,and the maximum stress on the inner side increased from 34.20 MPa to 42.72 MPa,which was far lower than the yield limit of the material.As the first center of the piston pin hole side skirt profile moved up,the maximum stress of the pin hole side skirt surface and the maximum stress of the pin seat bottom surface did not increase significantly,when the center of the circle was moved up to 30 mm,the mass of the piston was reduced by 9.32 g,which was 2.90% lower than non-lightweight piston;the maximum stress of the skirt on the side of the pin hole increased from 36.07 MPa to 44.95 MPa;the bottom of the pin seat stress increased from 34.06 MPa to 44.35 MPa,which were far lower than the yield limit of the material.(4)Proposed the lightweight improvement scheme of piston.The wall thickness of the secondary thrust side skirt was 2.85 mm,and the center of the first section of the pin hole side skirt profile was moved up by 20 mm.After improved,the mass of the piston reduced by 7.56 g,which was 2.35% lower than before.The maximum stress on the inner and outer sides of the secondary thrust side skirt and the maximum stress on the pin hole side skirt and the bottom surface of the pin seat we’re slightly increased,far lower than the maximum stress of the overall piston cycle and the material yield limit.