JPS5968501A - Method and device for cooling steam turbine rotor - Google Patents

Abstract

PURPOSE:To prevent the steam, which leaks out of the first stage blade head, from flowing toward an intermediate packing, by providing a labyrinth packing between the outer periphery of a steam outlet part of a nozzle box and the inner periphery of a wheel chamber. CONSTITUTION:A labyrinth packing 36 is provided between the outer periphery of a steam outlet part of a nozzle box 6 and the inner periphery of a wheel chamber 20. In such a structure, a flow passage 25b through which a steam leaked out of a radial fin 29 of the first stage blade part is flowed to an intermediate packing 13 is cut off, then a large part of a cooling steam 35 flowed through the intermediate packing 13 is composed of a leak steam 33 of a steam 23a after finishing its work. Thereby, the enthalpy of the cooling steam 35 is reduced and the cooling effect is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method and apparatus for cooling a steam turbine rotor.

[Prior Art] 1 FIG. 1 is an explanatory diagram of a schematic structure of a steam turbine equipped with a turbine rotor having a high-pressure/medium-pressure one-piece structure. Main steam 1 supplied from a boiler (not shown) is supplied to main steam stop valve 2.
and the main steam control valve 3 into the nozzle box 6. The high/medium pressure port 10 is made up of a high pressure section 4 and a medium pressure section 5 arranged concentrically, and a front barragin section 12. Intermediate packing part 13. A rear paragin part 14 is provided. The rotor is supported by a front bearing 7 and a rear bearing 8, and the axial force is supported by a thrust bearing 9. 11 is a low pressure rotor (not shown)
It is a coupling that transmits power to.

The exhaust gas from the high pressure section 4 is reheated by a reheater 15 and passed through a reheat steam stop valve 16 and an intercept valve 17 to the intermediate pressure section 5.
The exhaust from the intermediate pressure section 5 is supplied to the crossover vibe 1.
8 to a low pressure section (not shown).

In the steam turbine equipped with the above-mentioned high-pressure/medium-pressure single-piece turbine rotor, one
FIG. 2 shows an enlarged cross-sectional view of the vicinity of the intermediate packing portion 13 in the example.

The high-pressure section 4 is composed of a high-pressure first stage 4a, a high-pressure second stage 4b..., and the intermediate-pressure section 5 is composed of an intermediate-pressure first stage 5a, a middle-pressure second stage 5b, etc.
It is composed of...

The single compartment is a double compartment consisting of an external compartment 19 and an internal compartment 20. The main steam is guided by an expansion joint 21 to a nozzle box 6 provided within the internal compartment 20. The steam 23 accelerated by the nozzle rotates the high-pressure first stage 4a. Steam 25 leaking from the gap between the pressure first stage 4a (rotating body) and the internal casing 20 (stationary body) cools the rotor while flowing through the intermediate backing 13 to the intermediate pressure first stage 5a side. A part of the leaked steam 25 is taken out from the extraction port 26 and discharged through the external conduit 27 through the discharge port 29 provided in the diaphragm of the medium pressure second stage 5b, and is discharged from the front and back of the disk portion of the medium pressure first stage 5a. Cooling. The external conduit 27 is provided with an orifice 28 for controlling the flow rate.

FIG. 3 shows details of the conventionally commonly used structure of the disk cooling device described above.

The steam 23 is accelerated by the nozzle 32 of the nozzle box 6 to generate rotational force in the high-pressure first stage 4a, and its exhaust gas 23a flows to the second stage side. A radial fin 29 is provided between the blade head of the high-pressure first stage 4a and the nozzle box 6 to regulate leak steam 25. A portion of the leaked steam 25b is removed from the bleed port 26.
It is taken out to the outside and enters the external cooling line. The remaining leak steam 25a flows to the intermediate packing portion 13 side.

On the other hand, leak steam 31 leaks from the root fin 30 of the high-pressure first stage 4a. Also, part of the backflow steam 33 of the exhaust gas 23a passes through the balance hole of the high-pressure first stage blade root and collects at the lower part of the nozzle box. 22 is a balance weight mounting groove.

The leak vapors 33 and 31 merge to form a leak vapor flow 34. Furthermore, these merge with the steam 25a to form a steam flow 35, and the intermediate packing portion 13a.

13b and flows to the intermediate pressure first stage side.

When performing variable pressure operation with a turbine whose high-pressure first stage is a regulating stage type, the main steam pressure is changed with three of the four regulator valves 2 fully open and the remaining one closed. method results in optimal thermal efficiency.

FIG. 4 shows a state in which steam flows out from the nozzle box 6. For convenience of reading, this figure omits illustration of the high-pressure first stage 4a, and only depicts the nozzle box 6 and the flow of steam. The nozzle groups that make up the nozzle box 6 are 6a, 6b, ic,
It is divided into 4 parts of 6d. This figure shows nozzle groups 5a, 6b,
5c is fully opened and the nozzle group 6d is fully closed. In this state, leak steam 25 is generated from the blade head in the fully open nozzle group, and exhaust gas 23a flows backward and leaks from around the fully closed nozzle group.

FIG. 5 shows these state quantities on a vapor diagram (enthalpy entropy S diagram). The expansion line L1 is the high pressure part,
L2 indicates a medium pressure-low pressure section, respectively. The enthalpy of leak steam 25 and leak steam 31 is the same as that of the main steam (H) because they are not heated at the high pressure first stage. The enthalpy of leak steam 33 is H3. The enthalpy of steam 35 when these are combined is H3. , leak steam 31+25 is large in quantity, resulting in H3!;Hl. When the steam 35 passes through the intermediate packing section 13 and reaches the intermediate pressure first stage section, the temperature becomes T2, and the intermediate pressure section main steam 24 The disk portion of the intermediate pressure first stage 5a is cooled by ΔT1, which is lower than the outlet temperature T of the intermediate pressure first stage 5a. The rotor is cooled by cooling steam as described above.
In a variable pressure turbine, the steam power decreases as the turbine becomes partially loaded, so the enthalpy increases even if the temperature is kept constant. In other words, the enthalpy H8 of the leak steam 35 approaches the enthalpy H4 of the main steam after the intermediate pressure first stage, resulting in a decrease in the cooling amount ΔT1. An example of this state is shown in FIG. In this figure, the horizontal axis represents the load factor (%) of the steam turbine, and the vertical axis represents the steam temperature T.

In this example, the total pressure (2
46Kq/c! l-g) constant pressure operation with a load factor of 9.
In the VP section from 0% to 30%, variable pressure operation is performed with 311 vA of the four control valves fully open. Furthermore, in the LP section where the load factor is 30% or less, the boiler is operated at a low pressure of about 869/cr/l-g to stabilize the operation. The main steam temperature T4 (53sc) and the reheat steam temperature Ta (566C) are kept constant up to about 25% load and gradually decrease below that. In this operating system, the temperature T2 of the leak steam 35 approaches the intermediate pressure first stage blade outlet temperature TI as the load becomes lower, and ΔT becomes the minimum at about 25% load. In this example, ΔT1(MIN)'
-113C.

As explained above, the conventional method for cooling a turbine rotor has a problem in that the enthalpy of the cooling steam increases during partial load, and the cooling effect decreases.

If the rotor is made of high-grade heat-resistant steel, it can withstand the lack of cooling effect and maintain high-temperature strength, but it is uneconomical as it significantly increases manufacturing costs.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and provides a method for cooling a steam turbine rotor that can suppress the increase in enthalpy of cooling steam and exhibit a good cooling effect even during partial load, and a method for easily using the above-mentioned method. An object of the present invention is to provide a cooling device that can fully exhibit its effects.

[Summary of the invention]

In order to achieve the above object, the cooling method of the present invention uses steam downstream of the high-pressure first-stage blades and leakage steam from the high-pressure first-stage blades in a turbine rotor having a high-pressure/medium-pressure single unit structure having a single-flow nozzle box. It is characterized by cooling the pressure first stage disk and making the enthalpy of the cooling steam separated from the rear of the high pressure first stage approach the enthalpy of the steam at the outlet of the high pressure first stage blade, thereby making the cooling effect uniform.

In addition, the cooling device of the present invention is a turbine rotor having a high-pressure/medium-pressure single unit structure having a single-flow type nozzle box, in which a labyrinth backing is provided between the outer periphery of the steam outlet part of the nozzle box and the single chamber, and a high-pressure first stage is provided. The present invention is characterized in that the flow path through which steam leaks from the radial fins of the wing head passes through the intermediate backing and flows to the medium pressure first stage disk is completely blocked, thereby making it possible to easily apply the above method of the invention.

[Embodiments of the invention]

FIG. 7 shows an embodiment of the apparatus of the present invention configured to carry out the method of the present invention, and corresponds to FIG. 3 of the conventional apparatus. High pressure section first stage 4a, nozzle box 6, intermediate packing M with the same drawing reference numbers as in Fig. 3
13 a + 13 b, 'Balance weight installation $22. Bleed air 26. Radial fin29. Root fin 30. And the nozzle 32 is a cooling device (
It is necessary to use the same structural members as in Fig. 3). A labyrinth packing 36 is provided between the outer periphery of the steam outlet portion of the nozzle box 6 and the inner periphery of the casing 20. As a result, a flow path (indicated by an imaginary line arrow 25b) through which steam leaks from the radial fin 29 of the high-pressure first stage blade head toward the intermediate packing 13 is blocked.

In this embodiment, the above-mentioned labyrinth snowboard 36
is provided upstream of the air bleed port 26.

In addition, the labyrinth grip 36 of this embodiment has a structure in which its comb teeth (not shown) are urged by a spring (not shown) and brought into close contact with the outer circumferential surface of the nozzle box 6.

In the cooling device configured as described above, the steam 23 accelerated by the nozzle 32 of the nozzle box 6 drives the high-pressure first stage blade 4a. The steam 23a that has completed its work is further expanded in the high-pressure second and subsequent stages. Since the high-pressure first-stage blade 4a is a rotating body, the connection part with the nozzle box 6, which is a stationary body, is sealed by the fins 29 on the outer circumference and the blade root fins 30. Most of the main steam 230 drives the high-pressure first stage blade 4a, but the steam 25 and 31 leaking through the fins 29 and 30 do no work, so their enthalpy and temperature are kept high. On the other hand, the leak steam 33 flowing through the gap at the base of the high-pressure first stage blade 4a is low temperature because it is part of the steam 23a that has finished its work, and this low-temperature steam cools the intermediate pressure section as if it were missing. serves as a cooling source.

The above-mentioned low-temperature leak steam 33 flows backward through the high-pressure first stage blade 4a, and then merges with a small amount of high-temperature leak steam 31 to form a mixed leak steam 34, intermediate packing parts 13a, 13b, etc.
- resulting in cooling steam 35 flowing through.

As in this embodiment, when the comb teeth of the labyrinth gasket 36 are biased by a spring and brought into contact with the outer circumferential surface of the nozzle box 6, this area is completely sealed, and the tar leak flow is shown by the imaginary line 2.5b. can be considered to be a practical zero.

Furthermore, as in this embodiment, if the labyrinth pipe 736 is provided upstream of the cooling steam extraction port 26 of the cooling line including the external conduit (27 in FIG. 2), the supplementary cooling steam will be the mixed leak steam. Branching off from part of 34,
Since it is supplied to the external cooling line as low-temperature cooling steam 34a, the cooling effect is large.

FIG. 8 shows the flow state of leaked steam in the cooling device constructed as described above. This figure corresponds to FIG. 4, which shows the flow state in the cooling device for Yone Cedar. The high-temperature leak steam 25, which mixes with the cooling steam and causes its temperature to rise, is removed from the labyrinth packing 3 as described above.
6, the high pressure 2 is cut off as shown in this figure.
In this example, high temperature Leak steam 25 does not flow toward the intermediate pressure section.

Low-temperature steam 23a, which has been injected from other nozzles and has been subjected to work by the high-pressure first-stage blades 4a, flows back into the nozzle group 6d where steam is injected.

If the above-mentioned state is expressed in a thermal expansion diagram, as shown in FIG. Because of this, the temperature of the main steam is equal to that of the main steam. However, the enthalpy of the leaked steam 33 that flows in a large amount is H! after it has been worked by the high-pressure first stage blade 4a. and low temperature. The enthalpy H8 of the cooling steam 35 in which these leaked steams are mixed is
It remains at a low temperature, almost the same as the enthalpy H2 of 3.

This cooling steam 35 is isenthalpically expanded through the intermediate packing portion 13, and its pressure drops to the intermediate pressure after the first stage. The cooling steam after the pressure has been reduced is slightly heated while passing through the intermediate backing part, but becomes a low temperature steam of Tta.

Therefore, the steam temperature T after the intermediate pressure first stage and the cooling steam temperature T2
Difference ΔT from a! is the cooling effect.

The above action is shown in FIG. 10 in terms of the relationship between steam turbine load and steam temperature. This figure corresponds to FIG. 6 explaining the prior art.

In conventional technology, the main steam pressure changes with the load and the cooling effect decreases as the main steam pressure changes with the load and the main steam enthalpy increases and the cooling effect decreases in the present example. The temperature T2a is kept approximately 22 C lower than in the prior art at full load. - As described with reference to FIG. 6, the temperature difference ΔT1 of the cooling steam in the prior art example was the minimum at 25% load and decreased to about 13r, but in the present example, the temperature difference ΔT1 of the cooling steam was reduced to about 13r.
ΔT1 at % load is approximately 35C.

In this way, keeping the cooling steam temperature as low as 35C-120=22C means that the high-temperature strength of the rotor is approximately 2
This corresponds to a strength increase of 0'%.

[Effects of the Invention] As explained above, the turbine rotor cooling method of the present invention reduces steam downstream of high-pressure first-stage blades and leakage steam from high-pressure first-stage blades in a turbine rotor having a single-piece high-pressure/medium-pressure structure having a single-flow nozzle box. The intermediate pressure first stage disk is cooled using the high pressure first stage, and the enthalpy of the cooling steam separated from the high pressure first stage is made to approach the enthalpy of the high pressure first stage blade outlet steam, thereby making the cooling effect uniform, even during partial load. A good cooling effect can be obtained.

Further, the turbine rotor cooling device of the present invention provides a labyrinth/ The cooling method described above can be easily carried out and its effects can be fully achieved by blocking the flow path through which steam leaks from the radial fin at the top of the high-pressure first stage blade through the intermediate backing and reaching the medium-pressure first stage disk. can be demonstrated.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the general structure of a steam turbine equipped with a turbine rotor having a single high-pressure/medium-pressure structure, and Fig. 2 is an intermediate packing section of an example of a steam turbine equipped with a disk cooling device. It is a sectional view of the vicinity. 3 to 6 show rotor disk cooling devices in the prior art.
The figure is a sectional view, FIG. 4 is an explanatory diagram of steam flow conditions, FIG. 5 is an IS diagram, and FIG. 6 is a load factor-steam temperature chart. 7th
Figures to Figures 10 show the turbine rotor cooling device of the present invention, Figure 7 is a sectional view, Figure 8 is an explanatory diagram of steam flow state,
FIG. 9 is an i-s diagram, and FIG. 10 is a load factor-steam temperature chart. 1... Main steam, 4... High pressure section, 4a... High pressure section first stage, 4b... High pressure section second stage, 5... Intermediate pressure section, 5a.
... intermediate pressure section first stage, 5b... intermediate pressure section second stage, 6... nozzle box, 6 a to 6 d- nozzle group, 13,
13a, 13b - intermediate packing part, 20.
... Vehicle interior, 26... Air bleed port, 29... Radial fin, 30... Root fin, 32... Nozzle, 36
... Labyrinth snow. Agent Patent Attorney Masami Akimoto Condolences 1

Claims (1)

[Scope of Claims] 1. In a turbine rotor having a single-piece high-pressure/medium-pressure structure having a single-flow nozzle box, an intermediate-pressure first-stage disk is cooled using steam downstream of the high-pressure first-stage blade and leakage steam from the high-pressure first-stage blade; A method for cooling a steam turbine row rig, characterized in that the enthalpy of cooling steam diverted from after the high-pressure first stage approaches the enthalpy of the high-pressure first stage leaking steam to achieve a uniform cooling effect. 2. In a high-pressure/medium-pressure one-piece turbine rotor with a single-flow nozzle box, a labyrinth backing is provided between the outer periphery of the steam outlet of the nozzle box and the single chamber, and a labyrinth backing is provided between the radial fin downstream of the high-pressure first stage blade. The flow path through which the leaked steam flows to the intermediate pressure first stage disk through the intermediate backing is blocked, and the intermediate pressure first stage disk is cooled using the steam downstream of the high pressure first stage blade and the high pressure first stage leaked steam. Features: Steam turbine rotor cooling system. 3. The steam turbine rotor cooling device according to claim 2, wherein the nolabyrin packing is provided upstream of a cooling steam outlet of a cooling line provided with an external conduit. . 4. According to claim 2 or 3, the labyrinth backing has comb teeth urged toward the outer peripheral surface of the nozzle box by a spring so as to be brought into close contact with the outer circumferential surface of the nozzle box. A cooling device for a steam turbine rotor as described.