Structure Analysis And Simulation Of Diesel Engine Piston Based On Thermal And Mechanical Loads

The piston is one of the central accessories of the internal-combustion engine. The stabilityof the piston has directly affected on series of important performance of the internal-combustionengine, such as reliability, durability, economical efficiency etc. The piston has a complexstructure and usually works under poor conditions. When in use, it will endure not only theperiodical action of the high temperature and high pressure gas, but also the alternant action ofthe multiple loads of inertia-pressure, side direction pressure and friction force caused by its highspeed reciprocating motion. These affections will cause thermal invalidation and mechanicaldamage of the piston when it is in work. Especially, thermal stress and thermal deformation willappear in the piston because of the high temperature at the top of the piston, and even the wholepiston, caused by the high temperature gas produced in the burning, as well as the asymmetrytemperature distribution along the axis and radical directions. When the mechanical load coupledwith the thermal load, it will cause crack in the top of the piston and in the piston bore, pistonring glued and even scuffing of cylinder bore in severe occasions. It is important for improvingthe piston structure and its reliability and durability that acquiring the temperature distributionand coupling stress distribution situation in the piston. So measuring and analyzing the pistontemperature field, finite element analysis on the temperature field, stress field and coupling stressfield caused by thermal and mechanical loads is essential.In this paper, the temperature of the key points on the surface of pistons with differentstructures in6125model diesel engine under different working conditions was determined byusing rigidity-plug temperature measurement method. The relationship between the workingtemperature of the piston with its structure characteristic and the rotate speed of the diesel enginehas been analyzed. The thermal boundary condition of the6125diesel engine under the declared working condition were determined more accurately by comparing the experimental temperaturewith that obtained by temperature field calculation using the piston surface heat transfercoefficient estimated by an empirical equation. The finite element analysis results of temperaturefield, stress field and deformation, coupling stress field and deformation under the joint action ofmechanical and thermal loads of the piston with different structures of6125diesel engine underdeclared working condition by using a MSC.Marc finite element analysis software wereanalyzed and compared. The characteristic of the temperature field, stress field and deformationof the piston and the relationship between them and the piston structure were obtained. This willlay a theoretical fundamental for the structure optimization design of the piston.