| In recent years,the thermal efficiency and lift power of diesel engines have gradually increased,and the thermal and mechanical loads that the pistons need to bear are also increasing,which places higher demands on the reliability of the pistons.As an important component in an engine,the piston works in an extremely harsh environment,so it must be effectively cooled to improve its service life.Most of the current research on piston internal cooled oil gallery focuses on the analysis of temperature field and thermal stress field under single operating conditions.In this paper,the influence law of changing the position of internal cooled oil gallery on the coupled stress field of piston is studied.This paper takes a type of diesel engine piston as the research object,the specific contents and conclusions are as follows: Firstly,establish the piston model,study the flow pattern and circumferential flow pattern of oil in the internal cooling oil gallery,and compare and analyze the heat transfer characteristics of the internal cooling oil gallery under different injection flow rate and rotational speed,and derive the change law of the average heat transfer coefficient of the wall surface with the crankshaft rotation angle,the results show that: the change trend of the average heat transfer coefficient of the wall surface with the crankshaft rotation angle under different injection flow rate or rotational speed is the same,and the average heat transfer coefficient of the wall surface of the internal cooling oil gallery is increasing with the increase of injection flow rate and rotational speed,but the growth rate is decreasing.Then,the piston was loaded with thermal load,mechanical load and thermo-mechanical coupling load respectively,and the distribution laws of temperature field,thermal stress,mechanical stress and coupling stress of the piston before and after the oil gallery cooling were compared and analyzed.The results showed that the temperature,thermal stress and coupling stress of each region of the piston decreased to different degrees after the piston was oscillation cooled,and the coupling stress value obtained by the piston subjected to thermal load and mechanical load at the same time was smaller than the sum of the two acting separately,which indicated that it was the result of the combined action of the two loads.Finally,the highest temperature field and mechanical stress field are mapped to the wall of the solid oil gallery of the piston,and the changes of temperature field,thermal stress field,mechanical stress field and thermo-mechanical coupling stress field when the axial and radial positions of the internal cooled oil gallery are changed respectively,the results show that the change of axial position has a more obvious effect on the temperature field,and the highest position of the internal cooled oil gallery is its center is level with the position of the first ring groove,and the distance between the outer edge of the internal cooled oil gallery and the ring groove should not be too small,generally greater than 5 mm.In this paper,the influence law of the change of the position of the internal cooling oil gallery on the coupling stress field of the piston is investigated,and the results of the study help to improve the cooling effect of the piston,and provide a certain theoretical basis for the optimal design of the internal cooling oil gallery of the piston. |
