Experimental and Numerical Investigation of Deep Surge in a Centrifugal Compressor With Vaned Diffuser and Piping System

Deep surge is a violent flow instability that affects the flow field throughout the entire compression system, potentially leading to performance deterioration and mechanical failures in compressors. A deeper understanding of this system instability is crucial for advancing design theory and developing effective flow control strategies. In this article, both experimental and numerical investigations are conducted to uncover the flow mechanism of deep surge. Transient velocity and static pressure measurements are performed to capture the surge limit cycles and the developing characteristics of the diffuser rotating stall under various throttling conditions. A three-dimensional numerical model of the compression system is developed to predict the system instability of deep surge. The numerical results demonstrate very good quantitative agreement with the experimental data in terms of the system characteristics and the development of diffuser rotating stall. The predicted internal flow field is analyzed to reveal the three-dimensional flow structure, with particular emphasis on the development of diffuser rotating stall during the deep surge cycle. Both experimental and numerical results demonstrate that the stall cells appear and disappear as the transient operating point periodically shifts between the stall and nonstall regions within the operating range. Furthermore, flow reversal during the deep-surge cycle suppresses the circumferential propagation of the stall cells.