JPS6155368A - Water turbine - Google Patents

Abstract

PURPOSE:To increase an relative inlet angle with a runner vane and to improve cavitation performance, by a method wherein water a flow guide vanes is installed between a guide vane and a runner, the plural guide vanes are situated on the periphery of the runner, and are supported on a stator side. CONSTITUTION:A water flow guide vane 4 is installed to an inner wall 3 on the forward end of a flowing water part between a guide vane 1 and a runner 2. The plural guide vanes 4 are located in the periphery direction of the runner, and are adapted to be operated in linkage with function of the guide vane 1 through a driving mechanism 5. This enables increasing of a peripheral speed on the forward end side of a runner vane 2A, and permits increasing of a relative inlet angle of the tip side at an runner inlet. This enables reduction of the loss of a water turbine, and permits prevention of the occurrence of cavitation.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention particularly relates to improvements in water turbines with high specific speeds.

[Background of the invention]

FIG. 7 shows the results of measuring the flow at position A in FIG. 6 using a pitot tube. In the figure, the horizontal axis represents the measurement position as a dimensionless quantity. is the length from the root of the runner vane 2A to the tip, and t is the length from the root of the runner vane 2A to the measurement position. The vertical axis indicates the flow velocity, Vu is the circumferential component toward the rotation direction of runner 2, and VZ
is a velocity component directed toward the rotation center axis of the runner 2, and is called an axial component. Moreover, the absolute values of these speeds are calculated by converting them to a test head of 1 m. As shown in FIG. 7, it can be seen that the difference in VU between the root side and the tip side is larger than that in Vz, and the difference in VU is also larger on the root side. In this way, Vu is large on the root side because the flow coming out of the guide vane l flows close to the free strip 1. Figure 8 shows the velocity triangle near the tip of the runner vane. U is the circumferential speed of the runner, Vl″ll: absolute speed of IR,
W indicates the relative velocity at which the flow enters the runner. The tip side of the runner vane has a larger rotation radius R (Fig. 6) than the root side, so the runner circumferential speed U is large, and as shown in Fig. 7, the circumferential component of the absolute speed Vt+ is small, so it goes to launch. The inflow angle β is small. FIG. 9 is an expanded view of the cylindrical surface with the approximate radius shown in FIG. 6, where r is the angle between the chord of the runner vane and the circumferential direction and is called the blade angle. Normally, the blade angle r shown in FIG. 9 is made approximately equal to the relative inflow angle β shown in FIG. 8, so if β is small, it is necessary to reduce the blade angle interval γ. When the blade angle r is decreased, the shortest distance between the blades becomes smaller, and the loss caused by the blades increases.
Since the static pressure on the blade surface also decreases, cavitation is more likely to occur. Taking these into consideration, a technique for controlling the flow at the runner inlet is disclosed in Japanese Patent Application Laid-Open No. 51-72846. This technology improves hydraulic performance by changing the circulation distribution at the runner inlet by changing the shape of the guide vane, but since the circulation changes by the change in flow angle α due to the change in the radial position of the guide vane exit, The required circulation may not be obtained. Furthermore, Japanese Patent Application Laid-open No. 57-108468 discloses a technology in which a cantilevered water flow guide vane is provided on the inner wall of the water flow section on the tip side of the runner vane, but this technology provides a water flow guide vane on the downstream side of the launch. However, Vu at the runner inlet cannot be changed.

[Purpose of the invention]

An object of the present invention is to reduce loss in the runner vane and improve cavitation performance by increasing the relative inflow angle to the runner vane.

[Summary of the invention]

That is, the feature of the present invention resides in a water turbine in which a water flow guide vane is provided in the water flow section between the guide vane and the water turbine launch, and a plurality of water flow guide vanes are arranged in the circumferential direction of the launch and supported on the stationary body side.

[Embodiments of the invention]

An embodiment of the present invention will be explained below with reference to FIG. A water flow guide vane 4 is provided on the inner wall 3 on the tip side of the water flow section between the guide vane 1 and the runner 2. A plurality of water flow guide vanes 4 are arranged in the circumferential direction, and are guided through a drive mechanism 5. It is installed so as to be interlocked with vane 1. FIG. 2 is an expanded view of a cylindrical surface with a radius R', and shows the relationship between the runner vane 2A and the water flow guide vane 4.

According to the present invention, the velocity component of the runner vane tip side of the flow exiting the guide vane 1 in the circumferential direction is increased by the water flow guide vane 4 immediately before it flows into the two-nona vane 2A. FIG. 3 shows the measurement results at the lunch entrance section A when the present invention was implemented. As shown in FIG. 3, according to the present invention, the circumferential velocity V6 of the runner vane tip side at the υ runner inlet is
can be made larger. As a result, as shown in Fig. 4, the relative inflow angle β' on the tip side at the runner inlet becomes sharper. The blade angle can be made larger than r, and the shortest distance L' between two runner vanes can be made larger than the conventional distance @L. In this way, by increasing the shortest pressure ILL' between the runner vanes 2A, it is possible to reduce the maximum speed between the runner vanes 2 and reduce the loss between the runner vanes 28. Further, by reducing the pupil large-velocity reaction between the runner bays 728, the minimum value of static pressure can be increased, and cavitation can be made less likely to occur.

〔Effect of the invention〕

As described above, according to the present invention, since the blade angle r on the tip side of the runner vane can be increased, the shortest distance L' between the runner vanes can be increased, thereby reducing loss and preventing cavitation due to an extreme decrease in static pressure. It is effective in preventing occurrence.

[Brief explanation of the drawing]

Is Figure 1 an embodiment of the present invention? Fig. 2 is a developed view of the cylindrical surface of radius R' of No. 1 (2), Fig. 3 is a velocity line diagram at the inlet of the 2-inner according to the present invention, and Fig. 4 is a longitudinal cross-sectional view of the Kaburan turbine shown in Fig. 4. 5 is a cylindrical sectional view at the runner vane tip side of the present invention, FIG. 6 is a vertical sectional view of a conventional Kablan turbine, and FIG. 7 is a conventional runner. FIG. 8 is an explanatory diagram showing a velocity triangle at the tip side of the runner vane of the conventional example, and FIG. 9 is a cylindrical cross-sectional view at the tip side of the runner vane of the conventional example. DESCRIPTION OF SYMBOLS 1... Guide vane, 2... Runner, 28... Runner vane, 3... Water flow part tip side inner wall, 4...
Water flow guide vane, 5...l @ moving @ structure.

Claims (1)

[Claims] 1. A water flow guide vane is provided in the water flow section between the guide vane and the water turbine runner, and a plurality of water flow guide vanes are arranged in the circumferential direction of the runner and are supported on the stationary body side. A water wheel. 2. The water turbine according to claim 1, characterized in that the water flow guide vanes are mounted in multiple stages in the water flow direction. 3. The water turbine according to claim 1, characterized in that the water flow guide vanes are rotatably mounted. 4. The water turbine according to claim 3, characterized in that the rotation of the water flow guide vanes is provided so as to be interlocked with the rotation of the guide vanes.