JPS61279777A - Cavitation control method for double current water wheel - Google Patents

Abstract

PURPOSE:To prevent the occurrence of cavitation in a double current water wheel having a runner part with a plurality of runner vanes right and left on the periphery of a runner crown by providing an air blow nozzle near the connection of the aforesaid runner and the crown. CONSTITUTION:A double current water wheel has a runner part 1 wherein a runner crown 1a surrounds a water wheel shaft 2, a plurality of runner vanes 1b is fitted right and left to the outer surface of said runner crown 1b and a runner band 1c of ring plate shape connects each tip of the right and left runner vanes 1b, and a plurality of guide vanes 3 is provided at the entrance of a driving channel. In this constitution, a plurality of nozzles 5 is provided near the connection of the runner vanes 1b and the runner crown 1a or, for example, on the runner crown 1a in a radial direction from the inner diameter to the outer diameter thereof. And these nozzles 5 are made continuous to an air feed hole 6 on the water wheel shaft 2 and the air is made to flow in an arrow direction of broken line, thereby enabling an air blow from the nozzles 5.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention relates to: Cavitation in return flow water turbines 1
Regarding suppression methods, prevent cavitation from occurring:
□
related.

Conventionally reduced vibration and suppressed cavitation:
Oh, yeah. ,. Ka2. - Yoe 1.1. Wow, 1j□ The method of paying attention is adopted. The place where air is supplied is
(1) It is best to do this near the area where running water is likely to separate.
"・Usually. The parts where flowing water is most likely to separate are shown in Figure 3 and 4Ef41C. In other words, in Figure 3, when viewed from the cross section of y, y, ・:・- A whirlpool is generated and the water is separated from the surface of runner vane lb. This is seen from the side of runner vane lb as shown in Figure 4. la is the runner crown, lb is the runner vane, IC is the runner band, and the water flow is separated from the surface of the runner vane lb. A vortex A flows relative to P in the direction shown.

The occurrence of this separation phenomenon of flowing water is shown by the curve in FIG. If the horizontal axis is the head H and the vertical axis is the flow rate Q, then song 111
The shaded area 't is the area where cavitation and n-shaped vortices are generated from the separation of flowing water, the solid line curve 115 is an equal output line, and the broken line curve 'r is a line where the guide vane opening degree is constant. In order to prevent such cavitation, a nozzle is provided on the cover near the lunch inlet, and air is blown out from the nozzle to suppress separation of flowing water on the surface of the guide vane 1b. However, in the case of the double-flow type water turbine proposed this time, unlike the single-flow type runner described above, there was a problem in that the areas where flowing water was likely to separate were too far away from the cover that conventionally supplied air. In view of the above-mentioned problems, the invention aims to suppress the separation of running water by providing a nozzle near the joint between the runner vane and the runner crown where running water is likely to separate, and blowing air from this nozzle. [Summary of the Invention] In order to achieve the above object, the present invention places the nozzle in the vicinity of the joint between the runner vane and the launch crown. First, a plurality of nozzles are provided radially from the inner diameter of the runner crown toward the outer diameter, and the nozzles are communicated with an air supply hole provided in the water wheel shaft to blow out air. Secondly, at least one of the plurality of guide vanes
More than one guide vane is provided with a nozzle, the air is blown out in the direction of air centered around the crown, and the air is communicated with an air supply hole provided in the guide vane shaft.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the present invention, which is constructed with double-flow water 1C, and shows a runner crown 1a attached to a water wheel shaft 2. A plurality of guide vanes 3 provided at the water turbine inlet are attached to a cover 4 by guide vane shafts 3a. The water flow flows in the direction of solid arrow P. A plurality of nozzles 5 according to the present invention are provided radially from the inner diameter side to the outer diameter side of the runner crown la. Then, the air is communicated with the air supply hole 6 provided in the water wheel shaft 2, and the air is caused to flow in the direction shown by the broken line arrow, and is blown out from the nozzle 5. The members having the same structure as those in FIG. In this case, the installation position of the nozzle 15 is the guide vane 3, and is 21I! At least one of the several guide vanes 3 is provided with the blowing direction set at the center of the runner crown (the base of the runner vane 1b). The guide vane shaft 3a is connected to an air supply hole 16 provided in the guide vane shaft 3a, and air is caused to flow in the direction indicated by the broken line arrow and blown out from the nozzle 15.

〔Effect of the invention〕

In this invention, a nozzle is provided on the runner crown or guide vane, and air is supplied through the nozzle from near the joint between the runner vane and the launch crown, where the water flow tends to separate. opening)
This has the effect of suppressing cavitation that occurs due to flow separation on the runner crown side during operation, reducing noise, and making it possible to expand the operating range.

[Brief explanation of the drawing]

Figure 1 shows a double flow turbine showing an embodiment of this invention.
A side sectional view, FIG. 2 shows another embodiment of the invention.
□A cross-sectional side view of a double-flow turbine; Figure 3 is a cross-sectional view of the runner vane showing areas where water flow separation is likely to occur;
f Figure 4 is a side view of Figure 3, and Figure 5 is a side view of Figure 3.
, 1″ The Q-Hrm line shows the condition where biting is likely to occur.
1゛:1 is shown.
;(, -1 1: Runner part, 1a: Runner crown, 1b leek
′,: 1c: u7su/<7)' 2: Water wheel shaft; : 3 guide vane, 3a guide vane shaft, :'□5.15: Nozzle, 6,1
6: Air supply hole 0 Figure 1

Claims (1)

[Claims] 1) A runner crown surrounding the water turbine shaft, a plurality of runner vanes attached to the left and right sides of the outer circumference of the runner crown, and an annular plate-shaped runner that connects the tips of the left and right runner vanes, respectively. In a double-flow water turbine in which a runner part is constituted by a band and a plurality of guide vanes are provided at the entrance of a waterway; a nozzle is provided near the joint between the runner vane and the runner crown, and air is blown out from the nozzle. A method for suppressing cavitation in a double flow turbine, characterized by: 2) In the method for suppressing cavitation in a double flow water turbine as set forth in claim 1; a plurality of nozzles are provided radially from the inner diameter to the outer diameter of the runner crown, and are communicated with an air supply hole provided on the water turbine shaft to supply air. A method for suppressing cavitation in a double flow water turbine, characterized by blowing out. 3) In the method for suppressing cavitation in a double flow water turbine according to claim 1, the nozzle is provided on at least one of the plurality of guide vanes, and the blowing direction is set at the center of the runner crown (the center of the runner vane). A method for suppressing cavitation in a double-flow water turbine, characterized in that the guide vane is connected to an air supply hole provided in a guide vane shaft to blow out air.