A draft tube using regular hexagonal guide grid as vortex suppression device

Abstract

The invention discloses a draft tube connected to the outlet of a water turbine runner and using a regular hexagonal diversion grid as a vortex suppression device. , the lower end is the large tapered end, the small tapered end is the inlet, and the large tapered end is the outlet. There is a diversion grid inside the straight cone, and the outer wall of the diversion grid is surrounded by a cross-section. The outer contour is a regular hexagon. In the cylindrical structure, each vertex of the regular hexagon and the center of the straight cone are connected with a horizontal internal bracket, and each internal bracket is a vertically arranged plate structure, and each internal The radial length of the bracket is equal to the side length of the regular hexagon. The six internal brackets divide the interior of the cylindrical structure into six identical equilateral triangular channels, which increases the control of the dead water area in the center of the draft tube and inhibits the circulation movement. Reduce the eccentricity of the vortex to reduce the strength of the vortex and weaken the pressure pulsation caused by the vortex.

Description

technical field [0001] The invention relates to the field of a low specific speed Francis water turbine, in particular to a draft tube structure connected with a runner outlet of the water turbine. Background technique [0002] A water turbine is a power machine that can convert the potential energy of water flow into mechanical energy. It uses water flow as the power to drive other machines to work, and belongs to the turbine machinery in fluid machinery. All hydraulic turbines are provided with a draft pipe at the outlet of the runner, which collects the water flowing out of the runner and sends it to the downstream river channel and recycles the remaining energy of the water flow at the outlet of the runner. When the turbine operates away from the design working conditions, the velocity at the outlet of the runner may produce a circumferential component, causing the central pressure inside the draft tube to be low and the surrounding pressure to be high. The central area ...

AI Technical Summary

Problems solved by technology

Supplementary air can also cause some adverse phenomena, for example, under normal operating conditions, the output of the turbine will decrease, and the pressure pulsation behind the runner will increase instead

[0005] 3) Improve the outlet structure of the runner to weaken the pressure pulsation, but this method is not applicable to all working conditions and has a great impact on the overall operation of the turbine

However, the problem of this kind of draft tube is: due to the structure and layout of the splitter, the cross-sectional area of ​​the flow is small, the local fluid velocity in the main flow area becomes low, and backflow is easy to occur

In addition, when the shunt plate and shunt cylinder are damaged, it is not easy to disassemble and replace

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