Abstract: The loss characteristics and its ability to match with the downstream impeller of the volute are affected by its geometric parameters. For the circular section volute of a He-Xe radial turbine, the flow performance is compared between three different sizes and outlet width volutes under the different section angle, which is based on the similarity criterion of the same flow boundary conditions and isentropic expansion capacity of the working fluid. The impeller inlet Mach number increases with an appropriately reduced volute outlet width, which will benefit the turbine output power. The development of the throat trailing edge loss at different positions in the contraction section is analysed. The momentum exchange between throat wake and circumferential flow reduces the angle deviation and velocity loss gradually. The volute capacity to match with the impeller is defined by the variation range of the outlet angle in the case that the section angle ranged from 30° to 90°. The results showed the outlet angle is sensitive to the variation of the outlet width and section angle. By changing the outlet width and adjusting the section angle, the outlet angle of the volute can be more easily matched with the impeller inlet.

Key words: radial turbine volute, He-Xe fluid, section angle, geometrical characteristics, throat wake