Pump turbine plant

Abstract

There is provided a method of operating a pump turbine plant including a turbine with a turbine impeller and a turbine spiral casing having a first pressure pipe, and a pump with a pump impeller and a pump spiral casing having a second pressure pipe; an electrical machine dynamically in a drive connection with a shaft, the pump turbine plant further including a hydraulic short-circuit that can be created between the turbine and the pump, wherein the turbine has a greater rated power than the pump, and wherein the turbine and the pump operate under partial load at least temporarily in the hydraulic short-circuit. The method further includes operating the turbine or the pump in the hydraulic short-circuit when a degree of efficiency of the pump and of the turbine in the hydraulic short-circuit is greater than a degree of efficiency of the turbine on its own.

Claims

1. A method of operating a pump turbine plant including a turbine with a turbine impeller and a turbine spiral casing having a first pressure pipe, and a pump with a pump impeller and a pump spiral casing having a second pressure pipe, an electrical machine dynamically in a drive connection with a shaft, the pump turbine plant further including a hydraulic short-circuit that can be created between the turbine and the pump, wherein the turbine has a greater rated power than the pump, and wherein the turbine and the pump operate under partial load at least temporarily in the hydraulic short-circuit, the method comprising: operating the turbine or the pump in the hydraulic short-circuit when a degree of efficiency of the pump and of the turbine in the hydraulic short-circuit is greater than a degree of efficiency of the turbine on its own.

2. The method according to claim 1, wherein: at least one of the turbine and the pump has an adjustable guide apparatus; a rated power N.sub.T of the turbine is up to five times larger than a rated power Np of the pump; the turbine spiral casing and the pump spiral casing are supported against one another; and the first pressure pipe and the second pressure pipe emerge in a common pressure line.

3. The method according to claim 2, wherein the electrical machine is situated in an intermediate space between the turbine spiral casing and the pump spiral casing.

4. The method according to claim 2, wherein the electrical machine is situated outside of an intermediate space between the turbine spiral casing and the pump spiral casing.

5. The method according to claim 2, wherein the turbine spiral casing and the pump spiral casing are supported directly by a supporting element, wherein the supporting element comprises a cylindrical supporting ring or a supporting cone.

6. The method according to claim 3, wherein the turbine spiral casing and the pump spiral casing are supported directly by a supporting element, a cylindrical supporting ring or a supporting cone.

7. The method according to claim 4, wherein the turbine spiral casing and the pump spiral casing are supported directly by a supporting element, wherein the supporting element comprises a cylindrical supporting ring or a supporting cone.

Description

(1) Both hydraulic machines can have respectively a single impeller, but also several impellers. The impellers can be arranged on a common shaft or on different shafts. The invention is described below with reference to the drawing. The following details are shown:

(2) FIG. 1 shows two Francis-type hydraulic machines, the one as a turbine and the other as a pump, in an axial section.

(3) FIG. 2 shows in diagrammatical illustration of a pump turbine plant according to a first embodiment with a shaft rotating in vertical direction.

(4) FIG. 3 shows a diagrammatic illustration of a further embodiment of the pump turbine plant with a shaft arranged in horizontal direction.

(5) FIG. 4 shows a diagrammatic illustration of a third embodiment, in which an electrical machine is situated between both spiral housings.

(6) FIG. 5 shows a schematic diagram of the degree of efficiency of the turbine as well as of the turbine and of the pump in hydraulic short-circuit over the rated power of the turbine.

(7) The pump turbine plant shown in FIG. 1 is constructed as follows: The turbine 1 comprises a turbine impeller 1.1, comprising a plurality of guide vanes. The turbine impeller 1.1 is fitted with a shaft 3 in a torque-proof manner and its rotary axis 7 is mounted rotatably. The turbine impeller 1.1 is surrounded by a turbine spiral housing 1.2. Moreover, a crown of guide vanes is connected upstream of the turbine impeller 1.1.

(8) The turbine 1 has a turbine suction pipe 1.5. Said suction pipe is connected downstream of the guide vanes and generates an inlet diffuser with a manifold connected thereto and a pipework also connected thereto, which can widen the flow cross-section in flow direction of the water.

(9) In this case, a pump 2 is facing the turbine 1 directly. The latter means that both hydraulic machines are arranged axially close to one another and there is no motor-generator between them. The pump 2 is here mounted below the turbine 1. Their configuration can also be in the reverse order, pump above and turbine below.

(10) The pump 2 comprises a similar assembly to the turbine 1: The pump impeller 2.1 is also fitted with the shaft 3 in a torque-proof manner and includes a plurality of guide vanes. The pump 2 comprises a separate pump spiral housing 2.2, hydraulically separated from the turbine spiral housing 1.2, which surrounds the pump impeller 2.1. A crown of guide vanes 2.2.1 is preferably connected upstream of the pump impeller.

(11) The pump 2 also presents a pump suction pipe 2.5 which can be designed as that of the turbine 1.

(12) The turbine 1 is configured in such a way that its rated power N.sub.T is larger than the rated power N.sub.P of the pump 2. In the present case, the difference is 2.5. It means that the rated power of the turbine corresponds to 2.5 that of the pump. Larger differences can also be envisioned, for example 3 or 4. In practice, any value can be contemplated between 1 and . . . 4 or 5.

(13) From the construction viewpoint, the differences in rated powers are induced by the sizing of the pump and of the turbine, and admittedly as regards the dimensions or the selected resistance values. The figures only represent schematically the relationships without taking into account the differences in rated power.

(14) In the present case, both spiral housings 1.2 and 2.2 lie at a mutual distance directly on top of one another. The intermediate space 5 they formed is here free from any

(15) electrical machine. The intermediate space 5 is in this instance delineated from the spiral housings 1.2 and 2.2 facing each another. Both spiral housings 1.2 and 2.2 can be supported against one another via a supporting element.

(16) The supporting element can be of different form. In the present case, it is designed as a cone mantle 10.1; The cone mantle is supported on the one hand against the traverse ring 1.2.2 of the turbine and on the other hand against the traverse ring 2.2.2 of the pump. A further support 10.2, likewise in a ring shape, is situated between the spiral housings 1.2 and 2.2. Supports could also be envisioned between the spiral housing of the one machine and the traverse ring of the other machine.

(17) A further support 10.3 in the form of a cylinder is situated between the turbine lid and the pump lid. The support 10.3 advantageously generates a force compensation between both machines. A support can also be contemplated between the traverse ring of the one machine and the lid of the other machine.

(18) As can be seen, the shaft 3 is mounted in a bearing 9. The bearing 9 can be integrated into one of the supports 10.1 or 10.3.

(19) The following components can form a single construction unit: the turbine spiral housing 1.2, the pump spiral housing 2.2, the supporting elements 10.1, 10.2, 10.3, possibly as well the traverse rings 1.2.2 and 2.2.2 as well as the bearing 9. The three of the supporting elements aforementioned 10.1,10.2,10.3 can be present, or only one of the supporting elements or two of the supporting elements.

(20) FIG. 2 shows a first embodiment of the pump turbine plant according to the invention. As can be seen, a pressure line 1.3 is connected to the turbine spiral housing 1.2 whereas a pressure line 2.3 is connected to the pump spiral housing 2.2. Both pressure lines 1.3, 2.3 emerge in a common pressure line 6, in which a common shut-off device 6.1 is situated.

(21) The common shut-off device 6.1 in the pressure line 6 remains preferably open permanently and is closed only in case of an emergency shutdown or for maintenance purposes. This has the advantage that both spiral housings 1.1 and 2.2 are always acted upon with the same pressure, i.e. the upstream water pressure available at the upstream water and are hence not exposed to any frequent load changes.

(22) Corresponding suction lines 1.4 and 2.4 are then respectively connected to both suction pipes 1.5 and 2.5. A separate shut-off device 1.6 and 2.6 is respectively arranged in both suction lines 1.4 and 2.4. Both suction lines 1.4 and 2.4 emerge in a common suction line 8.

(23) An electrical machine 4, which is designed as a motor-generator, is in this instance in driving connection with the shaft 3. The latter is arranged above the turbine 1 and hence outside the intermediate space 5 axially close to the turbine. It is hence possible to insert a bearing 9 in the intermediate space 5, which is delineated by both spiral housings 1.2 and 2.2 as well as the supporting element 19, a bearing which serves for example as guide bearing or a combined thrust and guide bearing for supporting the shaft 3. To do so, the smoothness of the shaft 3 will improved further.

(24) FIG. 3 shows a further embodiment of the pump turbine plant according to the invention with reference to FIG. 2, whose arrangement has been rotated only by 90 degrees to the left, so that the rotary axis 3 runs in horizontal direction and the electrical machine 4 is arranged laterally close to both hydraulic machines 1 and 2. To do so, the substantially same structural elements are designated with the same reference signs as represented in FIG. 2.

(25) FIG. 4 shows a further embodiment in which the electrical machine 4 is arranged between both said spiral housings 1.2 and 2.2. The arrangement of both spiral housings 1.2 and 2.2 as well as of the electrical machine 4 can be a strongly symmetrical one.

(26) Preferably, both spiral housings 1.2 and 2.2 could be completed cemented in place independently of the position of the shaft 3, while remaining free-standing. The intermediate space 5 can be large enough to achieve a revision opening for maintenance or assembly and disassembly of both hydraulic machines without any problems.

(27) The invention can be used among other things with the following construction types of plants: Single-stage turbine with single-stage pump.Single-stage turbine with multistage pump.Multistage turbine with single-stage pump.Multistage turbine with multistage pump.

(28) An operating method for the pump turbine plant should be described below. Said operating method hence relates to the operation of the turbine of the pump turbine plant and is described more in detail with reference to the diagram in FIG. 5. The diagram of FIG. 5 shows in full line the degree of efficiency .sub.1 of the turbine 1 over the rated power N.sub.T of the turbine 1 plotted on the X-axis. The degree of efficiency .sub.2 of the turbine 1 and of the pump 2 is indicated with a dotted line in the diagram, when said elements are operated in the hydraulic short-circuit. Said degree of efficiency .sub.2 is in the partial load range much higher than the degree of efficiency .sub.1 of the turbine 1 on its own.

(29) An optimised operation of the pump turbine plant thus sets forth that in the partial load range, and indeed in particular as long as the degree of efficiency .sub.2 of the pump 2 and turbine 1 in operation with hydraulic short-circuit is greater than the degree of efficiency of the turbine on its own, the operation of the pump turbine plant takes place during the operation of the turbine with the turbine 1 and pump 2 in hydraulic short-circuit. The system switches from the range designated as N.sub.Ti on the diagram, in which the degree of efficiency .sub.1 of the turbine on its own and the degree of efficiency .sub.2 of the turbine 1 and of the pump 2 in hydraulic short-circuit are more or less the same, to the sole operation of the turbine 1. This enables to achieve a very good degree of efficiency over the whole power range available of the turbine 1 during the operation of the turbine and to obtain an optimal operational behaviour in terms of stability and cavitation.

(30) The exact range N.sub.Ti, in which the system switches from the partial load range with the pump 2 and the turbine 1 in hydraulic short-circuit to the sole operation of the turbine 1, hence depends among other things on the relation of the rated power N.sub.T of the turbine 1 to the rated power N.sub.P of the pump 2, similarly to other different boundary conditions. It is typically smaller than approx. 30%-60% of the rated power N.sub.T of the turbine 1.

LIST OF REFERENCE NUMERALS

(31) 1 Turbine 1.1 Turbine impeller 1.2 Turbine spiral housing 1.2.1 Guide vane 1.2.2 Traverse ring 1.3 Pressure line 1.4 Suction line 1.5 Turbine suction pipe 1.6 Shut-off device 2 Pump 2.1 Pump impeller 2.2 Pump spiral housing 2.2.2 Traverse ring 2.2.1 Guide vane 2.3 Pressure line 2.4 Suction line 2.5 Pump suction pipe 2.6 Shut-off device 3 Shaft 4 Electrical machine 6 Pressure line 6.1 Shut-off device 7 Rotational axis 8 Suction line 9 Bearing 10.1 Supporting element 10.2 Supporting element 10.3 Supporting element