【正文】 無損 檢測 E 國際， 37（ 7）， 507516 頁 [7]. 爾 ， ， （ 2020） 聲發(fā)射檢測大型機組 連續(xù)轉子 定子摩擦故障 41，（ 9）， 765773 頁 [8]. ，（ 2020），轉子定子摩擦聲發(fā)射診斷，機械系統(tǒng)和信號處理， 18（ 4）， 849868 頁 [9]. D. 姆巴， N，伽瑪魯丁，監(jiān)控極緩慢的滾動元件軸承：第一部分和第二部分，無損檢測和 E國際， 35（ 60）， 349366頁， 2020 [10]. O. Derakhshan，理查德 AE 也被發(fā)現在確定泵的最佳效率點上具有巨大的潛力，雖然這一潛力尚需進一步的研究。據推測，在 NPSH 試驗開始時 AE 有效值增加是因為氣蝕。隨著壓力的進一步降低 ， 這些 漩渦在 液體 中形成氣泡 。/h，汽蝕余量為 至 11m 時， AE 有效值增加了 223%。尼爾也觀察到了這種和空化有關的AE 有效值的變化，泵吸入口和排出口處的 AE 有效值變化也印證了這種現象。 汽蝕余量測試 實驗分別測試了流量分別為 10 14 180m179。相比于其他流量下流體在泵和管道內產生的聲發(fā)射，在 179。所有測試的采樣率均為 100 毫秒，計算聲發(fā)射有效值的時間也是 100 毫秒。布朗的 60KW離心泵（型號 DB22），最大流量為 204m179。尼爾等人評估了利用 AE 檢測早期氣蝕的可能性，并且指出，空化氣泡的破裂所產生的脈沖可以產生聲發(fā)射。最常用的用于識別汽蝕存在的方法是觀測泵揚程的下降。 通常情況下，泵制造商將對泵進行性能和 NPSH（汽蝕余量）測試，后者 的意義在于確定揚程下降 3％時將發(fā)生嚴重的氣穴現象。該案例的結果是基于 NPSH（汽蝕余量）和性能測試得到的。 on the pump casing in the vicinity of impeller suction eye。 E International, 2020, 38(5): 354358 The application of Acoustic Emission for detecting incipient cavitation and the best efficiency point of a 60KW centrifugal pump。 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 大學機械工程學院畢業(yè)設計（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 s