Effect of Runner Solidity on Performance of Elbow Draft Tube

Abstract

AbstractThe significant amount of kinetic energy comes out of runner in reaction turbines and the draft tube is used to recover this kinetic energy into useful pressure energy. The energy recovery in draft tube depends on its design and magnitude of velocity components at runner exit. Further the amount of kinetic energy coming out of runner depends on the solidity of runner as well as its rotational speed. Hence draft tube is important component of turbine next to runner. In this paper, 3D viscous turbulent flow simulation has been done in the complete flow passage of Francis turbine using commercial Computational Fluid Dynamics (CFD) code for three runner solidities at different rotational speeds. The draft tube performance parameters in non-dimensional form are computed from simulation results and the effects of runner solidity and operating speed on draft tube performance are discussed. The simulation results are also compared with the experimental results for validation and are found to be within reasonable accuracy