This paper presents an analysis of the performance of the unstable flow detection system based on pressure derivatives. The control algorithm was proven to work on different machines and with different unstable flow phenomena.

Compressors are known to be affected by unstable flow conditions appearing at low mass flow rate conditions. The most known and dangerous phenomenon is the surge which is known as a global instability affecting the whole impeller and regions upstream and downstream of it. List of identified local phenomena includes among others: impeller rotating stall, diffuser rotating stall and inlet recirculation. All of them have a specific pressure signature that is used for early identification.

The method presented in this paper is based on a control parameter named as the rate of derivative fluctuation (RDF). This approach allows having a simple measure of flow instability that is universal and reacts to the flow disturbances in general. RDF has been already confirmed to identify the inlet recirculation and the surge in experiments conducted on a low-speed centrifugal blower DP1.12. The aim of this study is to conduct tests on other impellers in order to see the RDF sensitivity to different instabilities observed in the different impeller geometries.

Results have shown that the RDF is indeed sensitive to different types of flow instabilities regardless of the machine geometry. For each compressor, there are certain spots, where RDF monitoring is most effective. Positions of these points are discussed in the paper. At nominal working conditions with a minimum amount of flow instability, its value is normalized to 1. Each RDF increment is resulting from higher local flow instability and indicates possible losses. The parameter reacted to the inlet recirculation, the rotating stall, the surge. The algorithm also reacted to the tip leakage vortices for the transducers located in the blade tip region. This shows the potential of using this relatively simple method for both anti-surge systems and losses monitoring.


Experimental Analysis of Surge-Detection System Based on Pressure Derivatives at Part-Speed Operation

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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