A novel, fast, physics-based, and efficient design method for radial turbine rotors

Abstract

Wide range of radial turbine applications with often severe constrained working conditions necessitates an efficient design tool. With a novel method of this research, radial turbine rotor is designed based on relating multi-directional flow accelerations and rotor geometrical features. In rotor meridian plane, flow accelerations in streamwise and spanwise directions are determined by variations of the passage width and hub and shroud radii of curvatures, respectively. Three functions of these geometrical features are defined and a weighted summation of them is selected to obtain exact coordinates of two 2D curves for meridian passage hub and shroud. Next, circumferential coordinates are specified for meridian passage 2D contours which gives blade hub and shroud 3D curves. The ratio of circumferential deviation to radius change is adjusted for controlling two different work transfer mechanisms of the blade. By this simple and fast design method, flow acceleration and work transfer mechanisms of the rotor are governed by only four design parameters. The design procedure is employed for upgrading performance of GT-4082 turbocharger turbine rotor. The best case, within ten new design iterations, shows 1.5 % improvement of total to static efficiency at design point and all off-design conditions with U/C_s < 0.7. The detailed flow field investigations show mildly accelerating flow throughout the rotor passage at design point which reduces entropy generation of boundary layer and tip leakage, by 26.8 %, 8.5 %, respectively; along with 11.9 % lower exit kinetic energy. The same trend of blade loading and entropy generation is observed at off-design conditions. These achievements are considerable and valuable.