PUMP FOR A HYDROELECTRIC POWER PLANT

Description

[0001] The invention relates to a pump for a hydroelectric power plant. The pump may also be a pump turbine.

[0002] Such a pump comprises an impeller, a volute casing and a suction pipe.

[0003] DE 10 2010 050 001 A1 discloses such a pump or pump turbine. It comprises a counter-swirl generator, which can be activated in the pumping direction during start-up. The counter-swirl generator comprises a plurality of guide elements or swirl-generating nozzles. These are arranged at the outlet section of the suction pipe and around the rotational axis of the impeller.

[0004] JP S63 88278 A also discloses such a pump. The disclosed pump comprises a connecting line connecting the high-pressure side water path with the low-pressure side water path, and a swirl generator that is not arranged in the connecting line.

[0005] Furthermore, pumps with connecting lines between the volute casing and the suction pipe are known from the prior art. For example, JPS5 181974 A discloses such a connecting line. The connecting line disclosed in the cited document serves to drain the volute casing.

[0006] The object of the invention is to provide an arrangement which is capable of generating a counter-twist and is simpler in design than the arrangement known from the prior art.

[0007] The object is achieved according to the invention by an embodiment according to the independent claim. Further advantageous embodiments of the present invention can be found in the subclaims.

[0008] The invention is explained below with reference to the figures. The figures show in detail: Fig.1 Pump according to the invention Fig.2 Swirl generator in a first embodiment Fig.3 Swirl generator in a second embodiment

[0009] Figure 1 shows a pump according to the invention in a highly simplified representation. The pump comprises a high-pressure side waterway, a low-pressure side waterway and an impeller, which is designated by 1. The high-pressure side waterway comprises a spiral casing, which is designated by 2, and a pressure pipe, which is designated by 4. The pressure pipe 4 is connected to the spiral casing 2. The low-pressure side waterway comprises a suction pipe, which is designated by 3. The axis of rotation of the impeller 1 is in Figure 1 indicated by the vertical dashed line. In the representation of Figure 1 The impeller is a Francis impeller. However, the impeller can also be designed differently, for example, as a Kaplan impeller or a propeller impeller.

[0010] The pump includes a closure member, designated 8, which can prevent the flow of water through the pump. The closure member 8 is located in the high-pressure waterway. In the illustration of Figure 1The closure element is a guide vane with closable guide vanes. However, it could just as well be a spherical valve or another type of valve in the pressure pipe 4. A closure element 8 designed in this way is referred to as a "main inlet valve." The closure element 8 is closed before the pump starts up and only opens when the pump has reached its operating speed. Pumps according to the invention can also comprise more than one closure element 8, e.g., a spherical valve and a guide vane. In this case, the guide vane is usually closed when the pump starts up. If the pump is a pump turbine, it generally comprises a guide vane with movable guide vanes.

[0011] The pump further comprises a connecting line, designated 5, which connects the high-pressure side waterway with the low-pressure side waterway. This is a bypass line, as it allows water to flow from the pressure pipe 4 into the suction pipe 3 without the water passing through the impeller 1. For this purpose, the connecting line 5 can be connected to the pressure pipe 4, as shown in Figure 1 shown, or branch off from the spiral casing 2, the connecting line 5 in each case branching off in the pump flow direction behind the closure member 8. If the pump comprises more than one closure member 8, the connecting line 5 branches off in the pump flow direction behind the closure member 8 which is closed before the pump is started.

[0012] In the connecting line 5 there is a valve, which is designated 6 and which can regulate the water flow through the connecting line 5.

[0013] A swirl generator, designated 7, is arranged in the connecting line 5. The swirl generator 7 is designed such that water passing through the swirl generator 7 in the connecting line 5 is imparted with a swirl as it passes through the swirl generator. Swirl means that the water moving in the direction of the connecting line in addition to this movement rotates around the centerline of the connecting line. In other words, any partial volume of water away from the centerline of the connecting line follows a helical trajectory after the swirl generator.

[0014] When the swirling water jet from the connecting line 5 enters the suction pipe 3, the swirl of the water jet creates a rotating flow within the suction pipe. This means that the swirl of the water jet entering the suction pipe sets the water in the suction pipe into a rotating motion. This creates a counter-swirl in the water at the inlet side of the impeller, which facilitates pump start-up and reduces vibrations during start-up.

[0015] In order to reliably create the above-mentioned favorable conditions, it is advantageous if the connecting line 5 opens into the suction pipe 3 in the region in which the axis of rotation of the impeller intersects the wall of the suction pipe 3. Furthermore, it is advantageous if the connecting line 5 opens into the suction pipe 3 in such a way that the connecting line 5 is aligned at the opening point so that it points in the direction of the impeller 1. In this way, a rotating water cone can form in the suction pipe 3, which in Figure 1 is indicated by the inclined dashed lines. In other words, it is advantageous if the connecting line 5 opens into the suction pipe 3 in such a way that a rotating water cone can form in the suction pipe 3, which extends in the suction pipe 3 between the opening of the connecting line 5 and the impeller 1 when water flows through the connecting line 5 into the suction pipe 3.

[0016] In Figure 1A particularly advantageous arrangement is shown, since the opening of the connecting line 5 is located exactly at the point where the axis of rotation of the impeller 1 intersects the wall of the suction pipe 3. Furthermore, the connecting line 5 is aligned exactly coaxially with the axis of rotation at the opening. Minor deviations from this arrangement lead to only a negligible impairment of the described advantageous effect.

[0017] An almost equivalent arrangement is obtained if the opening of the connecting line 5 deviates significantly from the point where the axis of rotation of the impeller 1 intersects the wall of the suction pipe 3, but the connecting line 5 is aligned there so that it points towards the center of the impeller 1. Even minor deviations from this arrangement are tolerable. It can even be advantageous if the connecting line 5 is not aligned exactly with the center of the impeller 1 at the opening in order to account for the asymmetry caused by the shape of the suction pipe 3. The person skilled in the art, instructed by the technical teaching of the present invention, can find such an advantageous deviation from the described arrangement with the aid of a flow simulation without engaging in inventive activity.

[0018] Since the swirl in the water flow through the connecting line 5 after the swirl generator 7 decreases with increasing distance due to friction effects, it is advantageous if the swirl generator is arranged as close as possible to the opening of the connecting line 5 into the suction pipe 3. However, since the swirl generator 7 is always located outside the suction pipe 3, the water flow through the suction pipe 3 is not disturbed by the swirl generator 7 during normal operation of the pump.

[0019] Furthermore, it may be advantageous if the connecting line 5 is designed as a nozzle at the outlet, i.e., if the cross-section of the connecting line 5 narrows before the outlet. This increases the speed at which the swirling water flows from the connecting line 5 into the suction pipe 3. This can increase the effective range of the resulting rotating water cone in the suction pipe.

[0020] Figure 2shows a possible embodiment of a swirl generator 7 with a fixed arrangement of the swirl-generating elements. The figure shows a view along the axis of the connecting line 5, whereby the hatching is merely intended to clarify the illustration. This means that the hatched areas are not sectional areas. The swirl generator 7 arranged in the connecting line 5 comprises four swirl-generating elements, one of which is designated 7.1. The swirl-generating elements 7.1 comprise an outer side, with which they are fastened to the wall of the connecting line 5. For further stabilization, the swirl-generating elements can be fastened internally to one another or to a hub. Figure 2The swirl-generating elements 7.1 are attached to a small hub, which is designated 7.2. In order for the swirl-generating elements 7.1 to fulfill their purpose, they must have an appropriate inclination, especially on the outside. They can also have a curvature. The number of swirl-generating elements 7.1 is arbitrary. In principle, a screw-like bent sheet metal, which is attached externally to the inner wall of the connecting line (i.e. similar to an Archimedes screw), is sufficient. In the embodiments with immobile swirl-generating elements 7.1, the range of the generated rotating water cone in the suction pipe 3 can be adjusted by the amount of water flowing through the connecting pipe 5, i.e. with the aid of the valve 6.

[0021] Figure 3shows an embodiment of a swirl generator 7 with movable swirl-generating elements 7.1. The swirl-generating elements 7.1 comprise axes that are rotatably mounted and guided through the wall of the connecting line 5. In the embodiments with movable elements 7.1, the number of these should be at least two. The swirl imparted to the water flowing through the connecting line 5 can be adjusted by rotating the elements 7.1 about their axes. List of reference symbols

[0022] 1Impeller 2Volt casing 3Suction pipe 4Discharge pipe 5Connecting pipe 6Valve 7Swirl generator 7.1Swirl-generating element 7.2Hub 8Closing element

Claims

1. Pump comprising a high-pressure-side water path, a low-pressure-side water path and an impeller (1), wherein the high-pressure-side water path comprises a volute casing (2) and a discharge pipe (4), and wherein the discharge pipe (4) is connected to the volute casing (2), and wherein the low-pressure-side water path comprises a suction pipe (3), and wherein the pump comprises a closure member (8), which can prevent the flow of water through the pump and which is arranged in the high-pressure-side water path, and a connecting line (5), which connects the high-pressure-side water path to the low-pressure-side water path and is designed in such a way that water can pass through the connecting line (5) from the pressure pipe (4) into the suction pipe (3) without the water passing through the impeller (1), and wherein the connecting line (5) branches off from the high-pressure-side water path in the pump flow direction downstream of the closing element (8), and wherein the pump comprises a valve (6), which is arranged in the connecting line (5), wherein the pump comprises a swirl generator (7) which is arranged in the connecting line (5) and is designed in such a way that water which passes the swirl generator (7) in the connecting line (5) can be provided with a swirl as it passes through it.

2. Pump according to claim 1, wherein the connecting line (5) opens into the suction pipe (3) in such a way that a rotating water cone can form in the suction pipe, which cone extends in the suction pipe (3) between an opening of the connecting line (5) and the impeller (1) when water flows through the connecting line (5) into the suction pipe (3).

3. Pump according to claim 1 or 2, wherein the connecting line (5) is designed as a nozzle at an opening into the suction pipe (3).

4. Pump according to one of the preceding claims, wherein the connecting pipe (5) branches off from the pressure pipe (4)5. Pump according to one of claims 1 to 3, wherein the connecting line (5) branches off from the volute casing (2).

6. Pump according to one of the preceding claims, wherein the connecting pipe (5) comprises a wall, and wherein the swirl generator (7) comprises at least one swirl-generating element (7.1), and wherein each swirl-generating element (7.1) comprises an outer side with which the same is fixed to the wall of the connecting pipe (5).

7. Pump according to claim 6, wherein the swirl-generating elements (7.1) are fastened internally to each other or to a hub (7.2).

8. Pump according to one of claims 1 to 5, wherein the connecting line (5) comprises a wall, and wherein the swirl generator (7) comprises at least two swirl-generating elements (7.1), and wherein the swirl-generating elements (7.1) comprise axles which are rotatably mounted and guided through the wall of the connecting line (5).