EP1611315A1

EP1611315A1 - Turbomachine

Info

Publication number: EP1611315A1
Application number: EP04725711A
Authority: EP
Inventors: Armin Busekros; Darran Norman; Matthias Rothbrust
Original assignee: Alstom Technology AG
Current assignee: General Electric Technology GmbH
Priority date: 2003-04-07
Filing date: 2004-04-05
Publication date: 2006-01-04
Anticipated expiration: 2024-04-05
Also published as: EP1611315B1; WO2004090291A1; US7766610B2; CN1802489A; US20060073010A1; CN100516469C

Abstract

Ring-shaped or ring segment-shaped cavities (2, 7), which are configured particularly in multi-shell (11; 12, 13) housings of turbomachines, are preferred along appropriate with means for compensating temperature stratifications that build up. According to the invention, an overlfow channel (14) connects two sites located in different peripheral positions of the cavity. An ejector (17) is arranged in the overflow channel (14), which can be operated with a drive fluid and which serves to drive a flow through the overflow channel from one end (15) upstrem of the flow to another end (16) downstream of the flow.

Description

turbomachinery

Technical field

The present invention relates to a turbomachine according to the preamble of claim 1. It also relates to a method for operating such a turbomachine.

State of the art

The phenomenon of the so-called "hump" of the rotor as well as the housing of turbo machines such as gas turbines and steam turbines is well known. It is caused by the fact that the large and massive structures of such machines have stored large amounts of heat after prolonged operation comparatively large flow channels a pronounced vertical temperature stratification, which leads to uneven temperature distributions in the static as well as the rotating components, which results in a distortion of the housing and rotor and deviations from the rotationally symmetrical target geometry due to the different thermal expansions In turbomachinery, the rotor is blocked in the housing, which impairs start availability and can also jeopardize the mechanical integrity for example from US 3,793,905 or US 4,854,120 systems for shaft rotation or also for so-called shaft switching. The rotor of a turbomachine is rotated further at a certain speed after it has been switched off. As in the case of known shaft switching, low speeds in the range of 1 / miπ or less are preferred. On the one hand, this is sufficient to uniform the cooling of the rotor in the circumferential direction; on the other hand, the speed is low enough so as not to provoke a pronounced axial flow, for example of the hot gas path of a gas turbine, with the associated cold air entry and thermal shocks. 0

Modern gas turbines are often designed with double-shell housings in the part exposed to high temperatures. In this case, an annular space is formed between an inner housing and an outer housing, which is frequently subjected to cooling air or other coolant during operation. After the gas turbine has been switched off, no more is formed in the 5 annular space

Measures also vertical temperature stratification, which leads to a distortion of the housing.

DE 507 129 as well as WO 00/11324 propose to provide means in the case of a double-shell casing of a turbine in order to disrupt the stable temperature stratification by a forced flow within the intermediate space. It is essentially proposed to convey fluid outside the annular space from one point in the annular space to another point in the annular space, whereby a compensating flow 5 is induced within the annular space. The documents state that an overflow channel is preferably arranged outside the machine housing, which connects two points located at different circumferential positions of the housing, and a circulation fan is arranged within this overflow channel to drive the compensating flow. In practice, the drive of the circulating fan proves to be problematic. A drive shaft of the fan, which from a motor arranged outside the overflow channel to the inside arranged fan wheel must be reliably sealed under operating conditions. Due to the prevailing high pressures, which can reach values of around 30 bar and above in modern gas turbines, and which can be even higher with steam turbines, and the temperatures, which can already reach up to 500 ° C in the cooling air, this task is only to solve with great effort, and there is a latent risk of failure over a long period of operation.

Presentation of the invention

The object of the invention is to provide a turbomachine of the type mentioned at the outset which avoids the disadvantages of the prior art.

According to the invention, this is achieved by the entirety of the features of claim 1.

The essence of the invention is therefore to arrange an ejector within the overflow channel, through which, if necessary, a propellant flow can be conducted to drive the flow through the overflow channel. It is therefore not necessary to seal a passage of a movable component through the wall of the overflow channel. Because on the one hand the mass flow of the propellant which is passed through the ejector is significantly lower than the design mass flow of the overflow channel, and on the other hand the flow velocity through the ejector should be high anyway, much smaller flow cross sections are advantageously used for the supply to the ejector than for the overflow channel , The design mass flow of the ejector is typically around 8% to 15%, in particular 10%, of the design mass flow of the overflow channel. The ejector inflow line can thus isolate from the volume of the cavity in a much simpler manner by means of a check valve and / or a shut-off device to let. Furthermore, since the ejector flow essentially serves as a propellant and an external auxiliary medium can be used, there is great freedom in the choice of the suitable drive source. For example, the ejector flow does not necessarily have to be driven by a blower, but it is also possible, for example, to use air from a compressed air system or steam from a boiler. Because the system is operated when the turbo machine is at a standstill, the ambient pressure prevails when the ejector is operated in the cavity. This does not even impose high requirements on the form of the blowing agent used for the ejector flow. In the case of air as the propellant of the ejector and the atmospheric pressure in the cavity, critical states are already reached in the ejector with a pre-pressure of the propellant of around 1.7 bar. In a preferred embodiment of the invention, the propellant source for the ejector is selected so that the admission pressure of the propellant is 1.3 to 3 times, preferably 1.5 to 2 times, the pressure in the cavity. It is further preferred if the volume of the cavity is circulated around 4 to 8 times, preferably about 6 times, per minute by the flow in the overflow line. In a very particularly preferred embodiment of the invention, the volume of the cavity is circulated once in around 11 seconds. It has been shown that this circulation rate leads to a particularly good homogenization of the temperature distribution in the cavity.

The device according to the invention is preferably operated such that, when the turbomachine is at a standstill, in particular in a cooling phase of the turbomachine following decommissioning, a fluid as a propellant is passed through the ejector into the overflow channel and drives a flow through which the gas content of the cavity is circulated becomes. A fluid mass flow is thus supplied to the cavity through the ejector, which in preferred embodiments of the invention is in the range from 0.5% to 2% and very particularly preferably around 1% of the content of the cavity per second, in such a way that the contents of the cavity are exchanged once in the range from 50 to 200 seconds. In contrast to the prior art, there is therefore no completely closed system. Ambient air or air from an auxiliary air system, for example instrument air, can in particular be used as the blowing agent. This can be used to advantage to help even out the temperature distribution and to shorten the cooling phase. If fluid is removed from the housing cavity at a lower point and mixed with cold ambient air by the ejector inflow, and this mixed overflow is reintroduced into the upper part of the cavity, this contributes to an additional, absolutely desirable cooling in the upper housing segments. This additional cooling effect due to the propellant flow supplied from the outside results in additional cooling, with a corresponding design, precisely where it is desired, namely in the upper part, which tends to be too hot. In another embodiment of the invention, the propellant of the ejector is preheated, for example it can be passed over or through other heated components of the turbomachine. Medium must of course also flow out of the cavity to compensate; this is preferably done through the coolant path of the turbomachine.

The cavity is in particular formed between an inner and an outer housing of the turbomachine, for example between a wide space wall and an outer housing of a gas turbine. In this case, the cavity is designed with an essentially annular cross section, in particular as a To, or with a cross section in the form of a ring segment. The overflow channel is advantageously arranged outside the housing of the turbomachine. This ensures outstanding accessibility and makes it easier to retrofit existing installations. The overflow channel advantageously connects two points which are arranged essentially at diagonally opposite circumferential positions of the cavity. The mouths of the overflow channel are also included Advantageously arranged at different geodetic heights of the cavity, the downstream end of the overflow channel, to which the ejector drives the flow, advantageously being arranged at the higher point. This arrangement uses the differences in density of the fluid within the cavity. In a very particularly preferred embodiment of the invention, the mouths of the overflow channel are arranged at a geodetically highest and a geodetically lowest circumferential position of the cavity, the flow in the overflow line from bottom to top, so to speak, from the "bottom" of the cavity to its " Roof ". In this way, when the device is operating, comparatively cool fluid is conveyed from the lower part of the cavity into the overflow channel, where it is mixed with the propellant of the ejector, which is generally even cooler. At the location of the outflow into the cavity, in the upper part thereof, the fluid is warmer and therefore has a lower density. As a result, the cooler fluid introduced drops, and thus induces a compensating flow in the cavity. This equalizing flow is even self-regulating to a certain extent: the greater the temperature difference between the upper part and the lower part of the cavity and the turbomachine housing, the greater the difference in density that drives the flow. This means that the more uneven the temperature distribution in the cavity, the stronger the driving forces which induce a compensating flow to equalize the temperature.

In a further preferred embodiment of the invention, the overflow line opens into the cavity with a defined outflow section. The outflow section is in particular designed such that the outflowing medium is oriented at least with one speed component in the circumferential direction of the cavity. This has the advantage that the flow in the cavity is more defined. Advantageously, the outflow section, which acts as an outlet guiding device, opens essentially in the circumferential direction, or in such a way that it outflow direction by an angle of less than 30 °, preferably less than 10 °, in the axial direction against the circumference of the cavity is inclined. In a very particularly preferred embodiment, the outflow section is designed as a nozzle, so that it acts as an ejector and also drives the fluid within the cavity. In particular in connection with an axially defined defined outflow direction and in the case of an axially extended cavity, the mouths of the overflow channel are arranged at different axial positions in a preferred embodiment of the invention. The resulting helical flow through the cavity then causes the temperature distribution in the axial and in the circumferential direction to be evened out.

In one embodiment of the invention, the cavity has openings for draining off fluid, through which fluid can flow out of the cavity. This is particularly advantageous if fluid is brought in from the outside. The openings are preferably arranged symmetrically on the circumference, for example in the form of an annular gap, annular segment-shaped gaps, or bores distributed around the circumference. The openings are, for example, in fluid communication with the hot gas path of a gas turbine, so that fluid in the cavity, which is displaced by newly introduced fluid, can flow out into the hot gas path. In this context, the hot gas path is the entire flow path from the entry into the first

Understand turbine guide line up to the exhaust gas diffuser. In particular, the fluid can be discharged into the hot gas path via the cooling air path and the cooling openings, for example the first turbine guide row.

Brief description of the drawing

The invention will be explained in more detail below with reference to the drawing. In detail, FIG. 1 shows a part of the thermal block of a gas turbine;

Figure 2 shows a first example of the embodiment of the invention

Cross section of the gas turbine from FIG. 1; Figure 3 shows a second example of the inventive execution of

Cross section of the gas turbine from FIG. 1; and

Figure 4 shows another preferred embodiment of the invention.

Of course, the following figures are only illustrative examples and are far from being able to present all the embodiments of the invention disclosed to the person skilled in the art, as characterized in the claims.

Way of carrying out the invention

The invention is to be explained in the context of a turbomachine. The thermal block of a gas turbine is therefore shown in FIG. 1, only the part located above the machine axis 10 being shown. The machine shown in FIG. 1 is a gas turbine with so-called sequential combustion, as is known for example from EP 620362. Although their mode of operation is of no primary importance for the invention, it is explained in broad outline for the sake of completeness. A compressor 1 draws in an air mass flow and compresses it to a working pressure. The compressed air flows through a plenum 2 into a first combustion chamber 3. A quantity of fuel is introduced there and burned in the air. The resulting hot gas is partially expanded in a first turbine 4 and flows into a second combustion chamber 5, a so-called SEV combustion chamber. Fuel supplied there ignites due to the still high temperature of the partially released hot gas. The π-heated hot gas is expanded further in a second turbine 6, with mechanical power being transferred to the shaft 9. In operation, temperatures of several hundred already prevail in the last compressor stages, especially in the area of the combustion chambers 3, 5 and in the turbines 4, 6 ° C. After such a machine has been switched off, the large masses - for example a mass of the rotor 9 of 80 tons - store a large amount of heat over a longer period of time. A pronounced vertical temperature stratification occurs in the flow cross-sections of the machine, at least in the usual installation of a gas turbine with a horizontal machine axis, during cooling at a standstill. This leads to the fact that the lower and upper parts of the housing and the rotor cool down at unequal speeds, which leads to a distortion of the components, which is referred to as "bucking".

In the gas turbine shown as an example, the invention is implemented in the region of the cavities 2, 7 surrounding the combustion chambers 3, 5. The cross-sectional illustration in FIG. 2 is highly schematic and could represent a section in the area of the first combustion chamber 3 as well as in the area of the second combustion chamber 5. An annular cavity 2, 7 is formed between an outer casing 11 of the gas turbine and a combustion chamber wall 12, 13, which can also be understood as an inner casing. After the machine has been switched off, heat that is stored in the structures 9, 12, 13 is largely dissipated via the outer housing 11. Due to density differences, fluid in the cavities 2, 7 tends to build up the mentioned stable temperature stratification, which is the object of the invention to avoid. In the example shown for the embodiment of the invention, the outer housing is provided with an extraction point 15 which is connected to a first, upstream end of an overflow line 14. The second, downstream end 16 of the overflow line again opens into the cavity at a point substantially diagonally opposite the tapping stalls 15. To drive a flow through the overflow line, a jet pump arrangement 17 with an ejector is arranged in the overflow line. A propellant mass flow 18 is led from an arbitrary source for a medium under pressure to the ejector and flows out there at a comparatively high speed, whereby further in fluid located in the overflow line is entrained, and thus flow through the overflow line is induced. Due to the design of a jet pump, the mass flow of the entrained fluid is a multiple of the propellant mass flow; typically the mass flow of the driven flow in a preferred embodiment of the invention is around 10 times the propellant mass flow. The orientation of the flow from an upstream end 15 to a downstream end 16 is predetermined by the orientation of the ejector. In the exemplary embodiment, the mouth of the upstream end is arranged at a geodetically lowest point and the mouth of the downstream end 16 at a geodetically lowest point. The coolest fluid in the cavity is thus sucked into the overflow line 14. This is mixed with the propellant mass flow 18, which is often colder again; for example, it can be a conveyor fan or a

Act compressor 20 brought ambient air. However, this means that the fluid emerging at the downstream end of the overflow line has a greater density than the fluid at a location geodetically at the top of the cavity. As a result, a sinking movement begins in the cavity, which further intensifies a compensating flow 19. This intensification is greater, the greater the density differences in the cavity, that is, the more pronounced the temperature stratification. The system is thus self-regulating in a way, and the equalizing flow 19 is more intense the more pronounced the temperature stratification is. The fluid in the cavity is preferably circulated once in about 8 to 15 seconds. With the propellant mass flow indicated above, the fluid content in the cavity is exchanged once every 80 to 150 seconds for fresh fluid flowing in via the ejector 17. Under certain circumstances this results in an undesirably rapid cooling of the machine structures. It is then of course also possible to preheat the propellant of the ejector in order to reduce this cooling. The device according to the invention is advantageously not operated during operation of the gas turbine group. Lie in the cavity then temperatures typically range from around 350 ° C to over 500 ° C, and the pressure is typically from 12 bar to over 30 bar. These conditions essentially also prevail in the overflow duct 14. It is therefore an essential advantage of the invention that, in contrast to the prior art, no moving parts are arranged in the part which is highly loaded with regard to temperature and pressure, and no relatively moving parts such as a drive shaft for a circulating fan are sealed Need to become. For example, a blowing agent blower 20 can be arranged at a point which is slightly loaded with regard to pressure and temperature, which on the one hand increases the reliability of the overall system and on the other hand reduces effort and costs. Alternatively, the blowing agent can of course also come from a compressed air system. To isolate the propellant supply from the high pressures and temperatures during operation of the gas turbine group, a non-return element 23 and a shut-off element 24 are arranged.

The embodiment according to FIG. 3 differs from the previous example in that a flow-guiding device 21 is arranged at the downstream end of the overflow line 14, which in the present case is designed as a nozzle, in such a way that the emerging flow 22 also acts as a propellant in the manner of an ejector a circulation flow 19 acts in the cavity 2, 7. This enables a directional flow to be generated in the cavity.

This is particularly advantageous when there is a configuration as shown in FIG. 4. FIG. 4 shows a perspective illustration of an annular cavity. The inner boundary 12, 13 is only shown schematically as a solid cylinder. A cavity 2, 7 is formed between this inner boundary and an outer jacket 11. Distributed in the axial direction, three ejectors 21 which are guided through the outer casing 11 and are not visible in the illustration are passed through, which are indicated schematically by dashed lines. The ejectors are arranged in such a way that the orientation of the blowing direction of the blowing agent 22 in the axial direction by an angle α with respect to that by a dash-dotted line U indicated circumferential direction is inclined. In order to particularly stimulate the primarily desired circumferential flow, this angle of attack α can be restricted to values below 30 °, in particular to values less than 10 °. As a result, there is a helical flow through the cavity, not shown, which further helps to avoid an axial temperature gradient that may occur. This is further supported if the downstream end and the upstream end of an overflow line are arranged at different axial positions.

The invention is in no way limited to being used in the outermost cavities 2, 7. The invention can also be implemented very simply for the combustion chambers 3, 5 or and the space formed between the housing elements 12, 13 and the shaft 9.

Those skilled in the art will readily recognize that the application of the invention is in no way limited to gas turbines, but that the invention can be used in a large number of other applications. Of course, the application of the invention is not limited to a gas turbine with sequential combustion shown in FIG. 1, but it can also be used in gas turbines with only one or more than two combustion chambers. In particular, the invention can also be implemented in steam turbines.

LIST OF REFERENCE NUMBERS

1 compressor 2 cavity, plenum

3 combustion chamber

4 first turbine 5 combustion chamber

6 second turbine

7 cavity 9 shaft 10 machine axis

11 outer housing, outer jacket, outer wall

12 inner housing, inner wall, combustion chamber wall

13 inner housing, inner wall, combustion chamber wall

14 Overflow line 15 Tapping point, upstream end of the overflow line

16 downstream end of the overflow line

17 ejector arrangement

18 propellant flow

19 Balancing flow

20 fuel blower

21 flow control device, ejector

22 outlet flow

23 kickback device

24 shut-off device U circumferential direction α angle of attack against the circumferential direction

Claims

claims

1. turbomachine which has at least one cavity (2, 7) with an annular or ring-segment-shaped cross section, an overflow channel (14) being arranged which connects two locations of the cavity located at different circumferential positions, characterized in that an ejector is located within the overflow channel (17) for driving a flow through the overflow channel (14) from an upstream end (15) to a downstream end (16) of the overflow channel.

2. Turbomachine according to claim 1, characterized in that the overflow channel is arranged outside the housing (11) of the turbomachine.

3. Turbo machine according to one of the preceding claims, characterized in that the overflow channel opens into the cavity at two substantially diagonally opposite points of the cavity.

4. Turbo machine according to one of the preceding claims, characterized in that the overflow channel opens into the cavity at two positions arranged at different geodetic heights.

5. Turbo machine according to claim 4, characterized in that the overflow channel opens at a highest and a lowest point of the cavity.

6. Turbo machine according to one of claims 4 or 5, characterized in that the downstream end of the overflow channel is arranged at the higher point.

7. Turbo machine according to one of the preceding claims, characterized in that an outlet guide device (21) is arranged at the downstream mouth (16) of the overflow channel (14), through which the overflow channel opens into the cavity, and which of the emerging flow ( 22) impresses a defined flow direction.

8. Turbo machine according to claim 7, characterized in that the outflow direction of the outlet guide device is oriented substantially in the circumferential direction (U) of the cavity, and / or at an angle

() of less than 30 °, preferably less than 10 °, is inclined in the axial direction against the circumferential direction of the cavity.

9. Turbo machine according to one of claims 7 or 8, characterized in that the outlet guide device (21) is a nozzle.

10. Turbo machine according to one of the preceding claims, characterized in that the mouths of the overflow channel are arranged at different axial positions of the overflow channel.

11.Turbomachine according to one of the preceding claims, characterized in that openings for removing fluid from the cavity are arranged in the cavity.

12. A method for operating a turbomachine according to one of the preceding claims, characterized in that when the turbomachine is at a standstill, in particular in a cooling phase following a decommissioning, a fluid flows through the ejector into the overflow channel and thus drives a flow in the overflow channel.

13Nerfahren according to claim 12, characterized in that the mass flow through the overflow channel is dimensioned such that the Volume of the cavity is circulated between 4 times and 8 times, preferably 6 times, per minute.

Nerfahr according to one of claims 12 or 13, characterized in that the mass flow through the ejector between 8% and 15%, preferably

10% of the mass flow through the overflow channel.

Driving according to one of the preceding claims, characterized in that fluid flows out of the cavity through the coolant path of the turbomachine.

Nerfahreπ according to any one of the preceding claims, characterized in that the fluid is heated before the inflow to the ejector.