Abstract: The effects of return water temperature on the piston erosion, in-cylinder pressure and heat release rate are studied to solve the ablation problem of piston in a diesel engine in low temperature environment. Typical characteristics of in-cylinder combustion process for ablation of piston are determined through the experiment. Results show that the average maximum pressure rise rate reaches 25- 40 MPa/ms under the condition of 70% load at 1 500 rpm at the return water temperatures of 15 ℃, 25 ℃ and 40 ℃, which exceed the limit of pressure oscillation in a common diesel engine. Under this condition, the average maximum combustion pressure reaches the allowable pressure of 13 MPa during 120 cycles. The results indicate that the strong combustion pressure oscillation exists at this operating point. Especially in the case of return water temperatures of 15 ℃ and 25 ℃, the number of cycles is up to 33% when the maximum cylinder pressure is over 13 MPa. Moreover, the maximum pressure rise rate in a single cycle is over 100 MPa/ms in these two cases. Above all, with the decrease in return water temperature, the number of cycles exceeding the limits of maximum pressure and pressure rise rate increases sharply. This is the main reason of piston ablation for this series of diesel engines under the condition of low temperature. Key

Key words: dieselengine, pistonablation, detonation, returnwatertemperature