Thermo-mechanical Coupling Researched For Diesel Piston Based On FEA Calculation

As the single-cylinder agricultural diesel engine was restricted by its using object and purpose, the cost of diesel engine couldn’t overspend. On this premise, the overall performance improvement should give preference to the optimizing measures. This project proposed a new integrated combustor, which combined the advantages of direct-injected and separation type combustion chamber. However, the surface to volume ratio of the new type combustion chamber was much larger. And there was a big heat loss, while the piston at the top of the shape mutation sites increased. The piston stood periodic loads, such as high gas-pressure, frictional force, high speed reciprocating inertia force inertia-pressure, and side direction pressure, which may lead to produce crackling, piston ring glued and scuffing of cylinder bore. Great harm would come to the work of piston assembly reliability and durability.Under the different crank shaft angle, this paper obtained the temperature and heat transfer coefficient distribution of the new type combustion chamber piston with CFD numerical analysis by Changing the traditional empirical formula of the third kind boundary condition. The proper solution with piston pin auxiliary constraint was used to changed the previous way for function of load, and contact condition for the piston and piston pin was much authentic. The feasibility of new method was verified by contrast analysis for piston with the new method for the coupling of the CFD and FEA, and by experience or half experience formula in traditional research method. The results proved that, the integrated stress, strain and deformation of the piston in the new type combustion chamber were within the range allowed of the piston material, while the temperature for the region under the throat and mouth of the piston in the new type was not well distributed, which would lead to stress concentration easily. And the average temperature for the first ring groove of the piston was exceeded that glue temperature of lubrication oil, which might glue the piston ring, destroyed the normal fit clearance, broke ring shore under this working condition for a long time. By processing the drainage channel, the highest temperature of the piston, the temperature of the first ring groove and the piston chamber at the top of the central had a certain reduce the ease of utility, as the cooling was effectively. The thermal deformation under thermo-mechanical coupling effect played a leading role in the piston crown deformations, while for the effect of piston thermal deformation, the stress concentration in piston pin hole under thermo-mechanical coupling effect was significantly lower than that only in the condition of mechanical stress. In addition, the paper discussed the influence of the piston with different combustion chamber shapes, and with or no drainage channels under the low frequency thermal fatigue, so as to offer certain theoretical foundation and reference for improvement and development of the series diesel engines piston, reduce blindness and experimental cost and improve the design efficiency at the same time.