柴油机活塞开裂故障分析及改进

马燕燕^1,2，崔凯^1,2，张金芳^1,2，刘蒙^1,2，黄鹏^1,2

1.内燃机可靠性国家重点实验室，山东 潍坊  261061；2.潍柴动力股份有限公司，山东 潍坊  261061

摘要：针对某高功率国六轻型柴油机耐久试验中铝活塞开裂故障，分别从试验工况、活塞热负荷、机械负荷、活塞材料、活塞冷却能力等方面分析故障原因，采用有限元分析软件ABAQUS建立活塞仿真模型，分析活塞温度场与疲劳强度。结果表明：活塞燃烧室与排气门避阀坑相交处存在尖角，导致应力集中，形成开裂源；高温燃气及活塞冷却喷嘴流量小导致活塞顶面热负荷增大，可靠性降低。通过改进燃烧室结构、优化活塞热处理工艺、增大活塞冷却喷嘴流量等措施优化活塞，对优化后的柴油机进行耐久试验，未发现活塞开裂问题，且活塞内腔变色情况改善，改进措施有效。

关键词：轻型柴油机；铝活塞；开裂故障；有限元分析

Failure analysis of diesel engine piston and its improvement

MA Yanyan^1,2, CUI Kai^1,2, ZHANG Jinfang^1,2, LIU Meng^1,2, HUANG Peng^1,2

1.State Key Laboratory of Internal Combustion Engine Reliability, Weifang 261061,China；2.Weichai Power Co., Ltd., Weifang 261061,China

Abstract：The aluminum piston crack failure for a high power density CHINA Ⅵ light diesel engine is analysed, and the piston thermal load, mechanical load, piston cooling capacity, etc, are investigated. Piston simulation model is established by using finite element analysis software ABAQUS, the piston temperature field and high cycle fatigue strength are analysed. The results show that there is a sharp angle at the intersection of the combustion chamber and the vent avoidance pit, which leads to stress concentration and becomes the cracking source. High temperature gas and piston cooling nozzle flow is small, resulting in large heat load on the top surface of the piston and reduced reliability. The piston is optimized by improving the combustion chamber structure, optimizing the piston heat treatment process and increasing the flow rate of the piston cooling nozzle. The durability test of the optimized piston is carried out, and no cracking problem is found. The discoloration of the piston cavity is improved, indicating that the improvement measures are effective.

Keywords:light diesel engine；aluminum piston；crack failure；finite element analysis