机械类外文翻译.docx

The application of Acoustic Emission for detecting incipient cavitation and the best efficiency point of a 60KW centrifugal pump; case study L. Alfayez, D. Mba, G. Dyson July 2005 Abstract Pumps play a significant role in Industrial plants and need continuous monitoring to minimize loss of production. To date, there is limited published information on the application of Acoustic Emission (AE)to incipient pump cavitation. This paper presents a case study where AE has been applied for detecting incipient cavitation and determining the best efficiency point (BEP)of a 60KW centrifugal pump. Results presented are based on NPSH (Net Positive Suction Head)and performance tests. In conclusion the AE technique was shown to offer early detection of incipient cavitation, furthermore, the technique has demonstrated the ability to determine the BEP of a pump 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 comparing 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 xx 大学机械工程学院毕业设计（论文） Application of the high frequency Acoustic Emission (AE)technique in condition monitoring of rotating machinery has been growing over recent years[1-9].Typical frequencies associated with AE activity range from 20 KHz to 1MHz.The most commonly 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 applicatio