【正文】 . O. Derakhshan, Houghton, R. Keith Jones(1989).Cavitation Monitoring of Hydro turbines with RMS Acoustic Emission Measurements. World Meeting on Acoustic Emission,p305315,March 1989. 11. G D Neill, R L Reuben, P M Sandford (1997).Detection of Incipient cavitation in Pumps Using Acoustic Emission. Journal of Process Mechanical Engineering, ImechE,211(4),267. 12. G D Neil, et al.(1996)Detection of Incipient cavitation in Pumps Using Acoustic Emission. In proceedings of COMADEM University, July 1618,391401. 13. . McNulty(1981)Measurement Techniques and Analysis of FluidBorne Noise in Pumps. National Engineering Laboratory. NEL Report Noxx 大學(xué)機械工程學(xué)院畢業(yè)設(shè)計（論文） 第 52 頁 共 57 頁 聲發(fā)射檢測初生空化及其應(yīng)用 60KW 離心泵最佳效率點案例研究 ， ， 2020年 7 月 摘要 泵在工業(yè)領(lǐng)域發(fā)揮著顯著的作用，需要持續(xù)監(jiān)控，以盡量減少生產(chǎn)損失。 on the casing in the vicinity of the impeller discharge tip。 Pump performance 1. Introduction Typically the pump manufacturer will undertake performance and NPSH(Net Positive Suction Head)tests on supplied pumps, the significance of the latter is to determine the 3%drop in head at which serious cavitations will occur. The NPSH can be expressed as the difference between the suction head and the liquids vapour head. The concept of NPSH was developed for the purpose of paring inlet condition of the system with the inlet requirement of the pump. Cavitation causes a loss of pump efficiency and degradation of the mechanical integrity of the pump. It must be noted that cavitation starts to develop before the 3%drop in head. It is generally accepted that the critical pressure for inception of cavitation is not constant and varies with operation fluid physical properties and the surface roughness xx 大學(xué)機械工程學(xué)院畢業(yè)設(shè)計（論文） 第 46 頁 共 57 頁 of the hydraulic equipment. Application of the high frequency Acoustic Emission (AE)technique in condition monitoring of rotating machinery has been growing over recent years[19].Typical frequencies associated with AE activity range from 20 KHz to most monly used method for identifying the presence of cavitation is based on observations of the drop in head. Whilst other techniques such as vibration analysis and hydrophone observations for pump fault diagnosis are well established, the application of AE to this field is still in its infancy. In addition, there are a limited number of publications on the application of AE to pump health and cavitation monitoring. Derakhshan et al [10]investigated the cavitation bubble collapse as a source of acoustic emission and mented that the high amplitude pressure pulse associated with bubble collapse generated AE. With the AE sensor was placed on the actual specimen experiencing cavitation Derkhshan observed increasing AE levels with increased pressure of flow and cavitation. However, with the AE sensor mounted on the tank wall the reverse was observed, decreasing AE levels with increasing pressure and cavitation. This was attributed to a visible bubble cloud that increased with pressure. It was mented that this cloud attenuated the AE signature prior to reaching the transducer on the wall casing. Neill et al[11,12]assessed the possibility of early cavitation detection with AE and also noted that the collapse of cavitation bubbles was an impulsive event of the type that could generate AE. It was observed that when the pump was under cavitation the AE operational background levels dropped in parison to noncavitating conditions. In conclusion Neill stated that loss in NPSH before the 3%dropoff criterion was detectable with AE and evidence of incipient cavitation was detectable in the higher