On-cam operating characteristics of draft tube of tubular turbine based on vortex field analysis

In order to improve the efficiency of water turbine and the stability of the unit, numerical simulation is carried out for the draft tube of tubular turbine, The evolution characteristics of the vortex belt under different working conditions and the variation rule of the enstrophy and pressure pulsation are obtained. The results show that the kinetic energy of the fluid is affected by the enstrophy, and the rotation vortex belt is related to the flow energy in the tail water flow path, so the rotation vortex belt is closely related to the enstrophy. With the increase of the draft tube guide vane opening, the vortex belt with obvious changes, when the guide vane opening is large, that is close to the on-cam operating condition, in the center of the tail water flow path shows a whole vortex runner, at that time the tail water energy recovery is the best. The efficiency of water turbine is the best. The trend of vortex energy and pressure pulsations shows the opposite variation, so there is a certain correlation between the enstrophy and the pressure pulsation.