Numerical study on the effects of different total temperature inlet distortions on the aerodynamic performance and stability of the centrifugal compressor

This study investigates the detrimental effects of total temperature inlet distortion on the aerodynamic performance and stability of centrifugal compressors through full-annulus unsteady numerical simulations. The research comprises two parts: baseline analysis under uniform inflow condition and systematic investigation of different total temperature inlet distortion conditions. First, the flow characteristic of uniform inflow is studied as a reference for the inlet distortion cases. The results reveal that entropy evolution along the flow direction is inapparent under uniform inflow conditions. The instability signal of blade tip region is identified by Hilbert-Huang transform and frequency slice wavelet transform. Then, aiming at near stall condition, different inlet distortion parameters are set to explore the effects on aerodynamic performance and instability characteristics. The study indicate that total temperature inlet distortion causes the aerodynamic performance deterioration, the distortion intensity has the greatest impact on it, the maximum stall margin loss reaches 62.02 %, followed by the distortion angle, the maximum stall margin loss is 45.69 %. The reason is that unstable flow characteristics such as leading edge overflow and trailing edge backflow appear in advance. The impact of the distortion intensity on the distortion transmission is more drastic than that of the distortion angle. The intrinsic mode function components obtained by the empirical mode decomposition of the pulsation pressure signal at the blade tip of the impeller are used to extract the main characteristic frequencies of the signal. The high-energy frequency band annihilates with time evolution in frequency slice wavelet transform results, which represents instability flow characteristics.