Effect of the gap between the diffuser blade and impeller blade on the internal complex flow and aerodynamic performance of a centrifugal compressor

In this paper, the impact of the ratio (Rd= R2/R1) between the diffuser inlet radius (R2) and the impeller outlet radius (R1) on internal complex flow and the aerodynamic performance of a centrifugal compressor is deeply studied through numerical simulations. The study investigates how variations in Rd affect the efficiency, differential pressure and minimum allowable mass flow rate of the compressor. The difference in pressure, velocity and turbulent kinetic energy of the centrifugal compressor is demonstrated at three different values of Rd. Additionally, the spatiotemporal evolution of the complex internal flow of the centrifugal compressor is captured under an unsteady operational state. The characteristics of pressure and velocity fluctuations in the centrifugal compressor are deeply analyzed by fast Fourier transform (FFT) spectral analysis, which reveals that with increasing Rd, the intake conditions are significantly improved at the diffuser inlet. The findings offer physical insights into enhancing the efficiency and lowest allowable mass flow rate of the centrifugal compressor by minimizing energy loss from airflow impacting the diffuser blades.