柴油机回水温度对燃烧过程影响试验研究

针对某柴油机在低温环境下工作频繁出现活塞烧蚀的问题，开展了回水温度对燃烧过程影响的试验研究。通过分析不同回水温度下燃烧压力变化特点，确定产生活塞烧蚀时缸内燃烧过程典型特征，初步建立了活塞烧蚀与燃烧过程的对应规律。试验结果表明：在1 500 r/min、70%负荷工况点，当回水温度分别为15 ℃、25 ℃和40 ℃时，燃烧压力剧烈振荡，循环平均的最大压升率达到25~40 MPa/ms，且最高燃烧压力已达到或超过许用爆压限值13 MPa，说明该工况点燃烧粗暴。循环分析结果表明：在回水温度为15 ℃和25 ℃时最高燃烧压力超过爆压限值13 MPa的循环数约占总循环数的33%，最大压升率最高值超100 MPa/ms. 回水温度的降低引起的燃烧粗暴是导致柴油机在低温环境下发生烧蚀故障的重要因素。

Experimental Research on Effect of Return Water Temperature on the Combustion Progress in a Diesel Engine

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