Cavitation Characterization of Fluid Machinery Based on Cyclostationary Analysis: Part 2—Cavity Development Evaluation by Modulation Intensity

Abstract

In the previous paper, the high potential of the spectral correlation to identify cavity type has been demonstrated. This paper dedicates its efforts to cavity development evaluation and shows how the proposed modulation intensity indicators can achieve this goal. First, the signal model of cavitating impeller is established, and detailed cyclostationary analysis is implemented. Then, modulation intensity indicators—absolute carrier power level (AP), relative carrier power level (RP), and characteristic modulation components ratio (CMCR), are designed to evaluate cavitation degree. The AP proves to be useful in measuring the early developing cavitation, the CMCR is capable of detecting the key turning point from the early developing cavitation to the fully developed cavitation, and the RP can reflect cavitation degree from the view of signal-to-noise ratio (SNR). In summary, these indicators solidly complement each other, thus their combination provides an efficient solution to cavitation characterization. Lastly, the diagnosis strategies of qualitative detection by carrier distribution in Part 1 and quantitative characterization by modulation intensity in Part 2 are promising to be generalized to more scenarios.