Investigation of unsteady flow in the unscalloped radial turbine cavity

Abstract This paper presents an unsteady numerical study of the unsteady flow in the unscalloped radial turbine cavity considering the effect of computational sector size and sealing flow rate. A simplified U-shaped cavity with vanes and blades was simulated and the sealing efficiency was obtained using additional variables method. Unsteady low-pressure structures exist under a certain sealing flow rate, which is similar with axial turbine cavity, while the impact area is much larger. A comparison of computational domains sizes for 60° and 360° shows that whether the sector model can accurately predict the flow field depends highly on the number of low-pressure structures. As the sealing flow rate increases, the number and the speed of low-pressure structures at high radius decrease, and the corresponding low-frequency amplitude increases initially but decreases subsequently. The speed of low-pressure structure is positively correlated with its number, which seems contrary to the phenomenon observed in the axial turbine cavity.