中文摘要：

气门是柴油机的关键部件之一，故障率较高，如果出现故障将严重影响柴油机的性能．文中介绍了时频分析理论，利用时频分析方法对柴油机正常和排气门漏气故障状态下的缸盖和机体表面振动响应信号进行了分析，2种状态下结果区别明显，说明时频分析方法能够应用于柴油机的故障诊断和状态监测．

英文摘要：

The exhaust valve is a key part of diesel engine and it has high failure rate. If it were invalid, the performance of diesel would become worse. The theory of time frequency analysis is described in the paper and surface vibration signals of diesel are analyzed with it. The results show that the time frequency spectrums of normal and leakage condition are distinct, so it can be used for fault diagnosis of exhaust valve leakage of diesel engine.