Measurement for the Internal Flow Field in a Francis Turbine's Draft Tube by Two-dimensional PIV

Due to lack of experimental data in the research of Internal-flow,the forecast of accuracy evaluation is restricted in the Internal-flow numerical CFD analysis.The present paper introduced the method and scheme in the internal-flow testing of 4H Draft tube by 2D-PIV,associated with the experiment of Francis turbine model.4H Draft tube was manufactured for tests in different positions,e.g.the outlet of taper pipe and elbow pipe as well as the inlet and outlet of diffuser.Transient velocity data in the positions were obtained in optimum operation conditions.By time averaged data process,the Internal-flow distribution results in the operating mode in different positions could be obtained.The Internal-flow velocity,vorticity and distribution of streamlines are given,which supply the experimental results for the Draft tube CFD optimum analysis.The result indicate that the PIV testing method can distinctly obtain the flow feature at different positions of the Draft tube.The method is effective for the Internal-flow stability research of hydraulic machinery.