The internal flow of the draft tube is very complicated. There are various problems with the inside of the draft tube and the turbine because of the asymmetrical pressure distribution of its internal cross-section. A rectifying cylinder having openings at both ends of the front and rear ends is arranged in the channel of the draft tube. The CFD technique is used to simulate the typical working conditions, and the influence of the rectifier on the internal flow of the draft tube is discussed. The results show that under normal operating conditions, the pressure distribution of the outlet section of the draft tube is relatively uniform, and when the diameter of the rectifier cylinder is 1.05D1, the increase of the pressure is most obvious. Under different conditions, the hydrostatic distribution of the center of the inlet cross-section of the draft tube and the pressure distribution of the central axis cross-section are calcula-ted, and the pressure fluctuation of the recording point on the wall surface of the inlet pipe at the inlet is monitored. It is concluded that the rectifier has a positive effect on improving the distribution of the pressure field of the draft tube and inhibiting the effect of cavitation when the diameter of the rectifier cylinder is 1.05D1. The pressure gradient of the axial center is reduced in the draft tube with recti-fier. At the inlet cross-section of the draft tube, the vortex is dispersed and the number is reduced, and the pressure difference between the axial center and the wall surface of draft tube is reduced, and the stability of the flow field of the draft pipe increases.
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