基于声发射和小波分析的活塞环-缸套系统的摩擦润滑状态研究

利用声发射(AE)技术对摩擦润滑状态进行在线监测。采用小波多分辨率分析技术抑制由阀门开关和燃烧震荡引起的大幅值声发射AE信号,并采用阈值降噪的方法提取出由粘滞摩擦力引起的声发射信号。然后运用小波包络分析计算冲程中部的声发射信号幅值的平均值作为评价活塞环-缸套系统润滑状态的指标。试验结果显示:冲程中部的声发射信号能够有效地表征活塞环-缸套的摩擦润滑状态,并能够通过声发射指示标准区分不同类型的油品对系统润滑状态的影响。其中,声发射信号的幅值随着载荷的增大而小幅增大,且随着转速的增大而明显增大。研究结果充分证明了声发射监测技术在活塞环-缸套摩擦润滑状态在线监测的有效性。

Study on Friction and Lubrication Condition between Piston Rings and Cylinder Liner Based on Acoustic Emission and Wavelet Analysis

The acoustic emission technology was used to on-line monitor friction and lubrication state. The wavelet multi-resolution analysis was adopted to inhibit high amplitude signals of oscillatory acoustic emission caused by valve switch and combustion, and the threshold de-noising method was used to extract the acoustic emission signals caused by viscous friction. Then the wavelet envelope analysis was applied to calculate the average amplitude of the acoustic emission signals in the middle of a stroke as criteria for evaluating the lubrication state of a system of piston rings and cylinder liner. The results show that the acoustic emission signals in the middle of a stroke can effectively characterize the friction and lubrication condition between a system of piston rings and cylinder liner, and can distinguish the effect of different types of oil product on the lubrication state of a system of piston rings and cylinder liner through the standard acoustic emission signals. It is also shown that the amplitudes of acoustic emission signals increase slightly with load and significantly with engine speed. The acoustic emission monitoring technique is fully demonstrated to be effective for online monitoring of the friction and lubrication state of a system of piston rings and cylinder liner.