Prediction of optimum guide vane angle based on runner inflow

Bulb turbine has adjustable guide vanes and runner vanes. The combinations of guide vane setting angle αG and runner vane setting angle φR is innumerable. The purpose of this paper was to predict optimum combination of αG and φR (i. e. on-cam angle) during the design stage by means of CFD (Computational Fluid Dynamics), so as to furthest improve the hydraulic performance and characteristics. In the paper, the flow pattern in the guide vanes, runner vanes and the draft tube was discussed by using the distributions of velocity vectors, Euler energy factor, pressure energy factor and total energy factor to illustrate the effect of runner vane angle φRcam on the optimum guide vane angle αGcam and to propose the mechanism and method of using runner relative inflow angle to predict the optimum guide vane setting angle under the on-cam conditions. The predictive equation deduced in the paper can be used not only in CFD analytical results but also in the early design stage. The research results can provide reliable technical support for the runner optimized design.