Phase space reconstruction and fractal characteristic of rotating stall in impeller of centrifugal compressor

Based on phase space reconstruction and fractal theory in nonlinear dynamics, a method was proposed to analyze the dynamics characteristic of rotating stall in the impeller of centrifugal compressor. The rotating stall of impeller in low speed centrifugal compressor (LSCC) was numerically simulated, and the time series of pressure at rotating stall was obtained at various locations at impeller outlet. The technique of phase space reconstruction was applied to these pressure time series, and a low-dimensional dynamical system, which the dynamic properties were included in, was reconstructed. In order to determine the time delay and the embedding dimension in the reconstructed phase space, C-C method was introduced to deal with the pressure time series. The fractal characteristics of the reconstructed dynamic system phase diagrams were analyzed, and the corresponding fractal dimensions were given. The results show that the pressure signal of the impeller after rotating stall is in chaotic state, and some fractal structures are found in the reconstructed phase space. These fractal structures reveal the intrinsic dynamics of rotating stall flow. When the data collection points in the same radius, they have the similar fractal dimension, nearly 3.39. The fractal dimension decreases with the radius of collection points increasing.