JPS61126375A - Water turbine - Google Patents

Abstract

PURPOSE:To improve the water turbine efficiency by setting the radius of curvature of the camber line of a guide vane to 0.5-1 times of the diameter of the pitch circle of the guide vane and allowing said camber line to be curved for the formation of runner. CONSTITUTION:A Francis-type water turbine has twelve guide vanes, and the radius of curvature R of the camber line is set R=(0.5-1.0)Dg or so for the diameter Dg of the pitch circle of the guide vane 1. Therefore, the speed triangle of the flow flowing from the guide vane coincides with at the max. efficiency point to the speed triangle of the flow at the inlet of a runner vane 2, and the max. efficiency of the water turbine can be improved.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a guide vane for a water turbine.

(Problem that the invention attempts to solve) A conventional water turbine will be explained based on FIGS. 3 to 5.

The guide vanes of a water turbine are used to direct the appropriate amount of flow into the runner vane at an appropriate angle, and are closely related to the performance of the water turbine. Generally, the casing of a water turbine is often manufactured in parts, so the guide vanes are usually 16,
There are about 20 and 24 pieces. On the other hand, due to manufacturing cost constraints, a small number of guide vanes is required.

Figure 3 is a plan view of a conventional Francis type water turbine with a total of 16 guide vanes, Figure 4 is a plan view of a guide vane with 12 guide vanes, and Figure 5 is a plan view of the guide vane with 12 guide vanes. In the diagram, the runner vanes 01 are open, and regardless of the number of id vanes 01, both must be the same. However, when the port area is the same, the smaller the number of guide vanes 701, the greater the angle θ that the camber line of the guide vane 0 design forms with the center line of the runner, so the flow that exits the guide vane 01 is directed to the runner bay 702. It becomes difficult to flow in at an appropriate angle (in other words, to reduce manufacturing costs, the guide bay 701 is
If the number is reduced to two, the velocity triangle of the flow coming out of guide vane 01 and the velocity triangle of the flow at the inlet of the runner vane do not have to match even at the highest efficiency point, resulting in a decrease in turbine efficiency. have.

(Means for Solving the Problems) The water turbine according to the present invention is equipped with 12 guide vanes in order to solve the above problems and maintain performance even when the number of guide vanes is reduced to 12. The camber line of the guide vane has a radius of curvature of 0.5 to 1.0 times the pitch diameter of the guide vane, and is curved toward the runner.

(Function) In other words, the camber line of the guide vane does not have a conventional straight line shape, but instead maintains a circular arc with a single radius of curvature and is curved toward the runner. The angle between the two sides is made smaller. If the radius of curvature is made too small, the hydraulic loss of the guide vanes increases, but when there are 12 guide vanes, the radius of curvature R of the camber line is R = (0.5 to 1. 0) The degree of Dg is excellent overall, and the velocity triangle of the flow exiting from the knobid vane and the velocity triangle of the flow at the runner vane inlet match at the maximum efficiency point, improving the maximum efficiency of the water turbine.

In this case, the opening degree of the guide vane from fully closed to fully open is about 10 times narrower than when the camber line is straight, so the velocity triangle of the flow from the guide vane and the runner vane population The range in which the velocity triangles of the flow coincide with each other is expanded, the overall efficiency of the water turbine is improved, and the operating mechanism of the guide vane can also be made smaller. Generally, the no-load opening exists when the guide vane is slightly opened from the fully closed state, but when the guide vane is slightly opened from the fully closed state, the flow exiting the guide vane is directed to the outside of the runner. Since the camber line is directed inward, the no-load rotation speed can be obtained with less flow than when the camber line is straight.
It's true. Further, since the camber line of the guide vane is formed by one circular arc, manufacturing is not particularly complicated compared to a case where the camber line is a straight line.

(Example) The structure and operation of the present invention will be specifically explained based on an example shown in FIGS. 1 and 2. Figure 1 is a plan view of a guide vane in a Francis type water turbine according to the present invention in which there are 12 guide vanes in total, and Figure 2 is an explanatory diagram of the flow exiting the guide vanes. Guide vane 1
The camber line has been changed from the conventional straight line to a circular arc with a single radius of curvature and combed toward the runner. If the radius of curvature R is made too small, the hydraulic loss of the guide vane 1 will increase, but if the radius of curvature R is made too small, the hydraulic loss of the guide vane 1 will increase.
The degree of Dg is excellent overall, and as shown in Figure 2, the velocity triangle of the flow exiting from guide vane 1 and the velocity triangle of the flow in the runner vane population match at the highest efficiency point, and the highest efficiency point of the water turbine is achieved. Increased efficiency.

In this case, the opening degree of the guide vane 1 from fully closed to fully open is about 10% narrower than when the camber line is straight, so the velocity triangle of the flow from the guide vane 1 and the runner vane 2 population The range in which the velocity triangles of the flow coincide with each other is expanded, the overall efficiency of the water turbine is improved, and the operating mechanism 3 of the guide vane can also be made smaller.

In general, there is a no-load opening at which the guide vane 1 is slightly opened from the fully closed state.
When the runner is slightly opened from the fully open state, the flow exiting the guide page/1 is directed from the outside of the runner to the inside, so the no-load rotation speed is reduced with less flow than when the camber line is straight. can get. In addition, since the camber line of the guide vane 1 is formed by one circular arc,
Manufacturing is not particularly complicated compared to the case where the camber line is straight.

(Effects of the Invention) Due to this configuration and operation, even if the number of guide vanes is reduced to 12, the flow exiting the guide vanes will flow into the runner vanes at an appropriate angle, just as in the case of 16 or more guide vanes. Therefore, the performance of the water turbine is maintained and manufacturing costs are reduced.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a guide vane in a Francis type water turbine according to the present invention in which there are 12 guide vanes in total;
Figure 2 is an explanatory diagram of the flow exiting the guide vane, Figure 3 shows the flow of guide vanes in a conventional Francis type turbine with 16 guide vanes in total, and Figure 4 shows the flow of guide vanes in a conventional Francis type turbine with 12 guide vanes. The plan view and FIG. 5 are explanatory views of the flow exiting the guide vanes in the case of 12 guide vanes. 1... Guide vane, 2... Runner vane. +! J'J'i::)

Claims (1)

[Claims] A water turbine comprising 12 guide vanes, the radius of curvature of the camber line of the guide vanes being 0.5 to 1 times the pitch circle diameter of the guide vanes, and curved toward the runner side.