JPH04203395A - Turbo pump - Google Patents

Abstract

PURPOSE:Not to reduce a performance of a pump but to reduce an occurrence of cavity even in the case that an actual flow rate is out of a design flow rate point by a method wherein a flow regulating vane is provided with an injection flow hole passing through a front edge and a rear edge of a vane, an inlet port of the hole is provided with a water guiding part and an outlet port is provided with an enlarged part having an increased sectional area of flow passage. CONSTITUTION:A shroud side plate 3 and flow regulating vanes 5 fixed to a hub wall 4 are disposed at an upstream side of a vane front edge 2 of a vane wheel 1. Each of the flow regulating vanes is provided with an injection flow hole 8 passing through a front edge 6 and a rear edge 7 of it. An inlet of the injection flow hole is applied as a water guiding part set in consideration of a variation of a flow direction and a shape of outlet of the injection flow hole is a tapered enlarged part in which a flowing-out direction of the injection flow is along a pressure surface of the vane, i.e., a negative pressure surface. With such an arrangement a flow at a non-designed flow rate point having a certain angle of incidence is also supplied only at a vane surface where a peeling may easily be attained from the vane inlet, so that it is possible to prevent any occurrence of cavity without reducing performance of the pump.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pump impeller shape for reducing cavitation in a pump.

[Prior Art J] Pumps are operated in a wide flow range from large flow rates to small flow rates. Therefore, the large flow rate deviated from the design flow point.

In the operating state of small flow rate, the flow flowing into the impeller is ``1''.
The angle of attack increases without following the shape, and the flow separates from the blade surface, creating a cavity.

For this reason, the flow path between the blades is narrowed, leading to a decrease in pump performance, and the cavity disappears as it is carried downstream, resulting in unstable flow, which can damage the blade surface and cause vibration and noise. becomes.

In order to avoid such adverse effects, for example, conventional devices have a continuous communication with the gap formed by the disk and the casing on the front or back of the blade jlL, as described in Japanese Patent Application No. 72152/1983. Feather hole 01j
It was provided at the edge of the blade to eject pressure water from the gap from the blade surface to prevent cavities from forming due to separation from the blade when the blade is at an angle of attack.

In this method, pressurized water is always ejected from both i/+i of the blade, regardless of the angle of attack (pressure side or suction side) due to changes in flow bk. For this reason, the jet flow from the surface where separation does not occur will instead disturb the flow, causing a decrease in the performance of the pump. Further, providing a communication hole inside the blade increases manufacturing cost.

[Problems to be Solved by the Invention] The purpose of the present invention is to increase the angle of inclination without degrading the performance of the pump in both cases of large flow rate and small flow rate that are outside the design flow point. The purpose is to reduce the occurrence of cavities caused by peeling.

[Means to solve the problem]

In order to achieve the objective 1-1, the present invention
A straightening blade that follows the blade inlet shape is arranged upstream of the blade nf edge, and the straightening blade is provided with a jet hole that penetrates the if edge and trailing edge of the blade. The outlet shape is such that it has a tapered enlarged part that increases the cross-sectional area of the flow path.

[Made in November] The jet holes installed in the rectifier blade have an inlet as a water guide part and an outlet as an enlarged part. Further, the cross-sectional shape of the passage in the enlarged part of the jet hole is tapered along the pressure surface and negative pressure surface of the blade located at the rear.

As a result, when a large flow rate at a non-design flow point and a flow having a different angle of attack at a small flow point 11 flow into the blade, the flow that flows into the water guide section and flows out through the tapered expanded section has an angle of attack of The state of the pressure field of the rear wing man 11 changes depending on how it is attached. Therefore, if the Coanda effect acts under the influence of the pressure difference in the pressure field and an angle of attack is created on the pressure side of the blade, an angle of attack is created on the pressure side of the blade (individual 1-1) and on the negative pressure side of the blade. In this case, since it is supplied in the form of a jet to the negative pressure side of the vane insert [1], it is possible to prevent the formation of cavities due to peeling.

In addition, the flow path cross-sectional shape of the water guide section 11 can smoothly guide a tapered flow by taking into account changes in the flow direction due to changes in flow rate, and the jet flow from the enlarged part of the jet hole originates. The energy becomes larger, which is more effective in preventing the formation of layer cavities.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

Vane +l (blade 1 of l; j edge 2Q)] - A straightening vane 5 fixed to the shroud side plate 3 and boss wall 4 is arranged in the flow, and the straightening vane has a leading edge 6 of the straightening vane and The trailing edge 7 is ('
1 to 1
is a water guide part that takes into account changes in the flow direction, and the shape of the jet hole is a tapered enlarged part so that the outflow direction of the jet flow follows the pressure surface and negative pressure surface of the blade. .

As a result, when a flow flows into the blade with an angle of attack at one non-design flow point, the flow passing through the water guide part 9 of the jet hole and flowing out of the enlarged part 10 of the jet hole depends on the angle of attack. Under the influence of the change in the pressure field of the rear blade 6 [l, the Coanda effect acts, and in the case of a flow where the angle of attack is on the + side, the blade pressure side 11 is In the case of a flow where the angle of attack is on the suction side 12 of the blade, how many people on the suction side of the blade IJ
Since the flow is supplied as a 117'χ flow, even at a non-design flow point where the angle of attack occurs, the jet flow is supplied only to the blade surface side where it is easy to separate A from the blade man j1, reducing the performance of the pump. The occurrence of cavities can be prevented by one step without causing any damage.

FIG. 3 shows another embodiment 5. The difference from the embodiment shown in FIG. 2 is that the shape of the water guide section 9 provided on the straightening blade 5 is made into a tapered contracted flow shape, so that the flow whose angle of attack changes depending on the change in the operating flow rate is directed to the water guide section. =4- This is the case where it is possible to flow into the moose. Compared to the case shown in Fig. 2, the flow with an angle of attack can be guided smoothly to the water guide section, so the energy of the jet supplied to the separation impeller [1] increases, which has the effect of preventing the occurrence of cavity johns. becomes larger.

〔Effect of the invention〕

According to the present invention, the rectifier vane having the jet hole provided in the first stream at the leading edge of the vane can prevent the formation of cavities without degrading the performance of the pump, thereby preventing damage to the vanes and vibration of the pump. , noise can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of an embodiment of the present invention. Figure 3 is an A-A confidential IJIJ diagram of Figure 1.

Claims (1)

[Claims] 1. A straightening vane fixed to the shroud side plate and the boss wall is arranged upstream of the leading edge of the blade of the impeller of the pump, and the straightening vane is provided with a jet hole penetrating the leading edge and the trailing edge of the blade, A turbo pump characterized in that the inlet of the jet hole is provided with a water guiding part, and the outlet thereof is provided with an enlarged part in which the cross-sectional area of the flow passage becomes large.