利用机体表面振动信号诊断活塞环失效的研究

建立了活塞环失效时活塞－缸套撞击的力学模型，通过理论计算证明活塞环失效后活塞组的撞击参数将会改变。分析了活塞环振动和悬浮的条件。给出了活塞环径向振动固有频率范围的计算式。通过两种机型对活塞环失效故障诊断进行了模拟试验。得到了利用机体表面振动信号诊断活塞环失效的方法；当从机身外表面监测到的振动参数在低频段出现了与单环径向振动固有频率相近的特征频率，该特征频率处谱值显著增大，含该特征频率的窄带内功率也显著增大，可认为有活塞环（通常是第一道环）失效了。

Diagnosis of Compressing Rings Fault from the Vibration Signal of the Engines Block Surface

An impact mechanics model of thepiston cylinder is proposed,and it is verified by computations that the impact parameters of the piston set increase when the compressing rings are in fault conditions, such as gumming,wore out ,etc.The factors which influence the vibration and drifting process of the rings are analyzed .The formula for calculating the natural frequency of ring in the cylinder is obtained.The method to diagnose the fault rings through the vibration signals of the block surface is got by the simulation tests of diesel engines. One can believe that there exist some faults in compress rings,if in the low frequency range the characteristic frequency measured at the block surface is close to the radial vibration natural frequency of the single ring ,if the PSD value of the characteristic frequency grows,and if the power value in the narrow frequency band including the characteristic frequency is growing obviously.