Experimental Investigation on the Surge Behaviors in the Centrifugal Compressor With Volute

The surge phenomenon seriously restricts the stable operating range of centrifugal compressors, and how to delay the occurrence of surge has always been a hot topic in centrifugal compressor research. For centrifugal compressors with volutes, the asymmetric structure of the volute can cause circumferential flow field distortion; however, its impact on the surge evolution behaviors has not been thoroughly studied. Based on the unsteady static pressure measurement and the wavelets analysis, the various time–frequency characteristics of disturbance signals during the surge evolution have been obtained, and the volute influence on the surge evolution behaviors at the different rotational speeds has been investigated. The wavelet analysis successfully resolves the complete time–frequency evolution throughout the deep surge cycle. At low speeds, the impact of the volute on the surge flow field in the centrifugal compressor is relatively small. The triggering instant of a deep surge can be accurately determined at certain speeds (80 krpm), whereas not at other speeds (50 krpm). At medium speeds, the strong volute-induced distortion leads to the significant circumferential nonuniformity in the surging flow field at the diffuser. At a certain circumferential position, the deep surge frequency disappears, while the stall and mild surge coexist at this circumferential position. At high speeds, the key component determining the compressor stability shifts from the impeller to the diffuser, leading to significant differences in the nonuniform surge behaviors at the diffuser compared to medium speeds. The research outcomes provide significant value for surge margin enhancement and surge simulation validation.