JPS584192B2 - Water thrust reduction device for hydraulic machinery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates in particular to a water thrust reduction device for hydraulic machines such as Francis turbines or pump turbines.

In general, water in a runner back pressure chamber surrounded by the back surface of the runner's crown and the inner surface of the upper cover opposite thereto is dragged by the rotation of the runner and swirls at a flow velocity of about half the circumferential speed of the runner.

This also applies to water in the runner-side pressure chamber surrounded by the side surface of the runner band and the inner surface of the lower cover opposite thereto.

In fact, since the leakage flow through the runner seal is superimposed on this swirling flow, the swirling speed of water in the back pressure chamber and the side pressure chamber increases, and corresponding back pressure and side pressure are generated.

Therefore, for example, if the seal gap on the runner band side increases, the leakage flow through the side pressure chamber increases and the swirl flow velocity increases, resulting in a decrease in side pressure and an increase in water thrust.

Generally, thrust bearings must be designed for this increased water thrust, making them large and expensive.

The invention was invented in view of this problem, and includes a back pressure chamber in at least one of the back pressure chamber between the runner crown and the upper cover and the side pressure chamber between the runner band and the lower cover. If installed in the side pressure chamber in the same direction as the rotational direction of the runner, a jet pump is installed in the opposite direction to the rotational direction of the runner to accelerate the swirling flow in the backpressure chamber or to rotate the side pressure chamber. It is characterized by reducing the water thrust acting on the runner by decelerating the flow, and according to the invention, water is injected into at least one of the back pressure chamber and the side pressure chamber to reduce the swirling flow there. Water thrust can be reduced simply by accelerating in the former case and decelerating in the latter case,
Furthermore, since water thrust can be controlled by adjusting the amount of water injected, it is possible to reduce changes in water thrust over time and improve operational reliability.

Hereinafter, the invention will be described in detail based on the embodiment shown in the drawings. It is composed of runner vanes 4.

5 is an upper cover, 6 is a lower cover, 7 is a back pressure chamber surrounded by the upper cover 5 and the runner crown 2, and 8 is a side pressure chamber surrounded by the lower cover 6 and the runner band 3.

A jet pump 9 is provided in the runner back pressure chamber γ, preferably on its outer diameter side and axially symmetrically, oriented in the same direction as the rotational direction of the runner according to the invention.

From this jet pump 9, as a working medium, for example, pressurized water in a penstock (not shown) is jetted into the back pressure chamber 7 in the direction of rotation of the runner.

Therefore, the water in the back pressure chamber 7 is accelerated by this jetted water,
Water thrust is reduced because the back pressure is reduced.

Further, in the case of this embodiment, a jet pump 10 is also provided in the runner side pressure chamber 8.

However, this jet pump 10 is installed facing in the opposite direction to the rotational direction of the runner 1.

Therefore, the pressurized water jetted from the jet pump 10 in the direction opposite to the rotational direction of the runner 1 decelerates the swirling flow in the side pressure chamber and increases the side pressure, so that the water thrust can be similarly reduced.

Further, since the water thrust can be easily controlled by adjusting the amount of injection from the jet pumps 9 to 10, it is possible to eliminate secular changes in the water thrust due to wear of the runner seal.

As described above, according to the invention, the water thrust of a hydraulic machine can be reduced in a very simple manner, and the thrust bearing can be made smaller and less expensive.

In addition, the water thrust can be controlled as necessary, reducing aging of the water thrust and improving operational reliability.

In the case of the embodiment, the jet pump is provided in both the back pressure chamber and the side pressure chamber, but the jet pump may be provided only in the back pressure chamber or only in the side pressure chamber, if necessary.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a Francis type hydraulic machine according to the present invention, and FIG. 2 is a bottom view of an upper cover showing the arrangement structure of a jet pump in a back pressure chamber. 1: Runner, 2: Runner crown, 3: Runner band,
5: Upper cover, 6: Lower cover, 7: Back pressure chamber, 8: Side pressure chamber, 9, 10: Jet pump.

Claims (1)

[Claims] 1. If the back pressure chamber is provided in at least one of the back pressure chamber between the runner crown and the upper cover and the lateral pressure chamber between the runner band and the lower cover, the lateral pressure chamber is provided in the same direction as the rotational direction of the runner. Water thrust of a hydraulic machine characterized by a jet pump being provided in the opposite direction to the rotational direction of the runner to accelerate the swirling flow in the back pressure chamber or decelerating the swirling flow in the side pressure chamber. Reduction device.