Vortex Evolution and Energy Production in the Blade ‎Channel of a Francis Turbine Operating at Deep Part ‎Load Conditions

Abstract

The blade vortex evaluation in Francis Turbine under deep part load conditions generates severe pressure ‎fluctuations in the runner. The complex flow in a model turbine is numerically investigated based on a ‎modified Partially Averaged Navier-Stokes method. The main emphasis is focused on revealing the ‎correlation mechanism of blade vortex evolution and energy production. The results indicate that the ‎modified PANS method shows significant advantages in hydro turbine’s simulation than the traditional ‎RANS method. At deep part load conditions, the vorticity formed at the leading edge of the suction ‎surface and the trailing edge of the pressure surface in the blade channels. The stretching term provides ‎the most vorticity increments while the dilation term inhibiting part which only provides a decrement of ‎the vorticity evolution. Based on the entropy production theory, the total entropy production distribution ‎is consisting with the distribution of vorticity. At deep part load condition, direct dissipation and turbulent ‎dissipation provide the most entropy, while at part load condition the proportion of these two-part ‎decreased‎.

Keywords

• francis turbine; vortex evolution; energy production; vorticity transport equation; entropy production ‎theory.