Experimental Investigation On Centrifugal Compressor Blade Crack Detection

Centrifugal compressor which can produce high pressure gas, is the core equipment for petrochemical industrial. With the increasing of productivity, more and more compressors are needed, what’s more the work environment for compressors is becoming more and more complex. However, the compressor blade fracture accident happens usually. In order to reduce the number of blade failure accident and reduce the economic lose, early warning for the blade crack is needed.This paper focus on the compressor blade crack detection, a large number of studies have been performed on the blade strain test, pulsation test, blade modal test and tip timing test. In this research the method for early warning and detection for the blade crack is studied, meanwhile a data gathering system for blade tip timing based on Labview is also developed.(1)At first, an artificial crack is manufactured on a compressor blade. A strain test is carried out on both the crack blade and normal blade. After the analysis for the strain data, the frequency of blade crack is obtained.(2)The pressure pulsation test is carried on the compressor with a crack blade. Due to there is a strong noise in pressure pulsation data, the frequency of blade crack is overwhelmed by noise. The empirical mode decomposition (EMD) method and squared envelop spectrum (SES) method are investigated in the analysis of the pressure pulsation data. The frequency for blade crack which is same with the strain data is obtained in the end.(3)The modal experiment is carried out on the impeller with crack blade. Based on modal analysis, it is found that the amplitude for crack blade vibration is bigger than normal one.(4)The tip timing test is also carried out on the compressor. Due to the change of the speed location, there will be some error in tip timing data. So in this research the rotation speed signal is modified. Though data analysis, the amplitude of asynchronous vibration is acquired. The result of the tip timing test is same with the modal experiment.(5)The blade vibration data gathering system based on tip timing technology is developed by using the Labview software. As well experimental test are carried out to verify the effectiveness of the system.