Experimental study on the effects of compressor rotational speed on surge characteristics: Spatial and temporal frequencies

Surge is a significant concern in compression systems utilizing turbo-compressors as the core component, as it induces violent fluctuations in pressure and flow rate, which can potentially damage the mechanical structure. Surge characteristics can be categorized into temporal and spatial frequencies. This paper presents an experimental study of surge's temporal and spatial frequencies in both a subsonic axial compressor and a subsonic centrifugal compressor setup. A key finding of the study is the distinction between surge's spatial and temporal frequencies. The surge spatial frequency is defined as the number of surge cycles per rotor rotation (1 rad), rather than per unit time (1 s). The experimental results yield two novel conclusions: (1) surge spatial frequency is insensitive to compressor rotational speed in the experimental setups used, whereas surge temporal frequency is sensitive; (2) the surge temporal frequency exhibits a quasi-linear relationship with the compressor rotational speed across both compressor setups. The repeated observations in the two rigs suggest that this quasi-linear relationship is not an isolated occurrence. A supplementary experiment, however, disproves the universality of the quasi-linear relationship across all compressor setups. To the authors' knowledge, this is the first study to analyze surge spatial frequency, report the quasi-linear relationship, and confirm its existence in this class of compression systems.