Mixed-flow turbine draft tube improvement method based on energy gradient theory
An energy gradient, draft tube technology, applied in the fields of hydropower, mechanical equipment, engine components, etc., can solve the problem of lack of clear research to explain the performance of the isolation pier draft tube
Inactive Publication Date: 2014-04-16
ZHEJIANG SCI-TECH UNIV
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Problems solved by technology
Most of the existing draft tubes are equipped with one or two partitions (isolation piers) in the diffusion section, but there is no clear research on the influence of the location and number of isolation piers on the performance of the draft tube
Especially at present, my country's hydropower units are often under non-design working conditions, and their stability problems are becoming more and more prominent, and it is urgent to optimize the draft tube design
Method used
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[0069] The present invention will be further described below in conjunction with the accompanying drawings.
[0070] Such as figure 1 , figure 2 , image 3 , Figure 4(a), Figure 4(b), and Figure 4(c), an improved method for draft tube isolation pier based on energy gradient theory, specifically includes the following steps:
[0071] Step (1). Simulate the flow physical parameters in the draft tube
[0072] 1-1. Use CFD technology to simulate the flow in the draft tube of the Francis turbine to obtain the physical parameters of the entire flow field.
[0073] The physical parameters include water flow velocity, pressure, and turbulent viscosity, which are specifically obtained as follows:
[0074] For turbines under some working conditions, CFD technology is used to numerically simulate the unsteady flow in the draft tube of Francis turbines. During the simulation process, the unsteady three-dimensional incompressible Reynolds-averaged Navier-Stokes equation ( RANS) and c...
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The invention provides a mixed-flow turbine draft tube improvement method based on the energy gradient theory. The method includes the following steps that first, flowing physical parameters in a draft tube are simulated; second, an energy gradient function K of a whole flow field is calculated; third, the flowing unstable position in the draft tube is found; fourth, the number of partition piers is changed, and the optimum number of the partition piers is found; fifth, the positions of the partition piers are changed, and the optimum positions of the partition piers are found. According to the method, the CFD technology and the energy gradient theory are utilized, by comparing values of the energy gradient function K under different arranging conditions of the partition piers, the optimum arranging of the partition piers is determined. According to the obtained mixed-flow turbine draft tube, the size of a vortex strip in the turbine draft tube under part of work conditions can be reduced through the arrangement of the partition piers, and therefore pressure pulsation is reduced, and the stability of a turbine is improved.
Description
technical field [0001] The invention belongs to the technical field of water conservancy and hydropower, and in particular relates to an improvement method for a draft tube of a Francis water turbine based on the energy gradient theory. Background technique [0002] During the operation of the turbine, complex flow phenomena such as friction, impact, eddy current, and shedding will occur when the water flows through the volute, water guide mechanism, runner, and draft tube. The unstable flow in the draft tube will affect the performance of the turbine. impact is very large. When the turbine runs away from the optimal flow rate, an eccentric vortex will appear in the draft tube, which will cause water flow turbulence and increase the internal hydraulic loss rapidly. Due to the instability of the vortex belt, it can cause the unit to vibrate. On the other hand, the center pressure of the vortex belt is very low, and cavitation erosion, which is extremely harmful to the turbi...
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IPC IPC(8): F03B11/00F03B11/04
CPCY02E10/226Y02E10/20
Inventor 窦华书牛琳蒋威贲安庆马晓阳郑路路
Owner ZHEJIANG SCI-TECH UNIV