Coupled Design and Optimization for Runner Blades of a Tubular Turbine Based on the Boundary Vorticity Dynamics Theory

In this paper the Boundary Vorticity Dynamics Theory is applied to optimize the runner blade shape of a bulb tubular turbine, based on a three-dimensional coupled design model. The initial spatial runner blades and guide vanes are designed together with the simultaneous equations solved in the flow domain involving them. Since the wake flow behavior of guide vanes influencing the inflow condition of runner blades is taken account of, compared with that on separate design method, the static pressure distribution obtained on coupled model is improved near the inlet of the blades. Thus the effective head becomes higher and the runner’s efficiency rises. To improve the performance on the design point, the boundary vorticity flux (BVF) on the runner blade surfaces is simulated to analyze its effect to the unit output emphatically. The runner blade shape is modified by changing the prescribed distribution of swirl according to the diagnosed position where the flow behavior is defective. The static pressure on optimized runner blades varies indistinctly, which is difficult to estimate the flow behavior. Nevertheless the BVF distribution indicates that near the hub of the pressure surface the negative effect on the output becomes weak, and negative region near the leading edge reduces obviously in area, which results in the further rise of runner’s efficiency. The result shows that the BVF distribution on blade surfaces can more potently reflect the performance of tubular turbines and provide reliable solution for shape optimization.