Simulation of volute tongue of small-size centrifugal compressor

A high speed and small mass-flow-rate centrifugal compressor with original and modified volute tongue shape was simulated by 3D viscous Navier-Stokes equations. A sharp and a round tongue of volute were modeled to compare their pressure ratios and efficiency characteristics. The flow fields around volute tongues were investigated; the velocity and pressure distributions of volute inlet were studied by unsteady simulation. Static pressure fluctuation near volute tongue was monitored and transformed into amplitude spectrum to identify blade passing frequency influence. The results show that the tongue simplification can cause certain difference on pressure ratio and efficiency. The pressure and velocity distribution of volute inlet indicate obvious circumferential distortion due to volute tongue especially at low mass flow rate. In addition, the static pressure pulsation of volute inlet and the noise level in diffuser and volute increase significantly under low mass flow operating condition.