Abstract: Internal cooling gallery can strengthen the heat transfer of piston greatly, but also affect the strength of piston head. In order to systemically study the effects of the structural and positional parameters on the heat transfer and structural strength of piston, and optimize the type of cooling gallery and its position in piston, the piston of a high pressure common rail diesel engine is taken as the object of study, a liquid-solid coupled heat-transfer finite element model of piston is built based on its temperature field measurement, and the heat transfer and structural strength of piston are analyzed. On this basis, the orthogonal design of experiment is adopted to analyze the effects of three factors, i.e. the type, the distance from its geometric center to the top plane of piston and the surficial area of cooling gallery, on the heat transfer and structural strength of piston. The results show that the effects of three factors have no significant difference, but in which the surficial area has the most influence, the distance from its geometric center to the top plane of piston has slightly less influence and its type has the least effect. Appropriately reducing the surficial area of cooling gallery can improve the thermal load of piston head and the stress concentration in cooling gallery, oil return hole and pin boss, and reduce deformations

Key words: diesel engine, piston, internal cooling gallery, heat transfer, strength