Numerical Investigation of Rotating Stall Characteristics in a Full-Annulus Transonic Centrifugal Compressor

The present paper numerically investigates the rotating stall mechanism in the NASA CC3 transonic centrifugal compressor with wedge-type vaned diffuser. The three-dimensional compressible, unsteady Navier-Stokes equations have been applied to a full-annulus high-speed centrifugal compressor comprising an inlet duct, impeller, and vaned diffuser. The scale-adaptive simulation model is selected as the turbulent closure model. The aim of this paper is to predict and capture the key features of rotating stall in a transonic high-pressure centrifugal compressor based on the scale-adaptive simulation approach. First, the steady numerical model was validated by the experiment for the aerodynamic compressor performance at different operating conditions from choke to surge. Then, unsteady simulations were conducted near the surge point to propose a detailed analysis of stall characteristics within the compressor diffuser passages. Comparison of the unsteady pressure signals with those of the measurement data revealed that the numerical results matched well with the experimental data to capture the rotating speed of the stall cells. Time/space analysis of transient entropy production distribution was performed within the diffuser passages to show the stall behavior and to confirm the existence and development of rotating stall cells during the impeller revolutions. Evaluation of the spectral analysis of the computed pressure fluctuation by the current numerical approach showed reasonable agreement with the experimental data for blade passing and rotating stall frequencies. The present paper demonstrates that the current numerical model is a beneficial engineering approach to provide accurate solutions compared to experimental data for prediction of the rotating stall as well as to resolve the unsteady turbulence structures.