JP4413732B2 - Steam turbine plant - Google Patents

Description

The present invention relates to a steam turbine plant, in particular concerning the part of the turbine components in a steam turbine plant which is to be cooled by the cooling steam.

In recent steam turbine plants, as part of a review of measures for enhancing and improving plant thermal efficiency, higher temperatures of steam are being considered. The steam turbine plant has a Rankine cycle characteristic, and it is said that the higher the steam temperature, the more the plant thermal efficiency can be improved.
For this reason, the steam turbine plant is becoming almost established from the relatively low temperature and low pressure steam conditions to the single-stage reheating of the steam temperature of 538 ° C / 566 ° C or 538 ° C / 538 ° C.

  However, in recent years when global warming and environmental destruction have been highlighted on a global scale, research and development to reduce the fuel consumption and increase the unit capacity in the steam turbine plant field are also underway. For example, it has been proposed to set the reheat steam temperature to 700 ° C. or higher and supply the ultrahigh temperature reheat steam to the intermediate pressure turbine.

As for the technology for introducing high-temperature steam of about 600 ° C. into the intermediate pressure turbine, the invention in which the main steam inlet pipe of the intermediate pressure turbine has a double structure to suppress the temperature rise of the passenger compartment is disclosed in Patent Document 1 below. It is published in
JP 11-350911 A

Since Patent Document 1 is not an invention for cooling a diaphragm outer ring and a turbine casing, which are turbine components, with cooling steam, there is no description of introducing cooling steam into the turbine casing. Therefore, the turbine casing and the diaphragm outer ring are not provided. It is unclear how to cool, but in the case of a high-temperature and high-temperature steam turbine exceeding 650 ° C., as shown in FIG. 12, the fitting and fixing portion between the turbine casing 32 and the diaphragm outer rings 39 _U and 39 _D communicates with each other. Since the groove 52 is formed and there is a gap G between the diaphragm outer rings 39 _U and 39 _D , the cooling steam is mixed into the high temperature main steam for driving through the communication groove 52 and the gap G as shown by arrows. There has been a problem of reducing the thermal efficiency of the steam turbine.

  Many problems remain to be solved when the reheat steam temperature exceeds 650 ° C. and is raised to 700 ° C. or higher. In particular, there is a current search for how to ensure the strength of turbine components. It is in. Conventionally, in thermal power plants, improved heat-resistant steel is used for turbine components such as turbine rotors, turbine nozzles, turbine blades, nozzle boxes (steam chambers), and steam supply pipes used in steam turbines. When the reheat steam temperature is 700 ° C. or higher, it is difficult to maintain high strength assurance of the turbine component.

For this reason, even in a steam turbine plant of 700 ° C. or higher, it is desired to realize a new cooling technology that can maintain a high strength guarantee even if the conventional improved heat-resistant steel is used as it is for a turbine component, Steam cooling has been studied as a means to meet this demand.
However, steam cooling technology is still under development for the field of steam turbines, and is in a state of repeated trial and error.

The present invention has been made in view of the above-mentioned problems of the prior art, and in a steam turbine plant adapted to cope with the increase in temperature of reheated steam by cooling a part of turbine components with low temperature steam, low temperature steam and an object thereof is to provide a steam turbine plant provided with the sealing device to prevent reducing the thermal efficiency by mixing the high-temperature main steam for driving.

In order to achieve the above object, the invention of the steam turbine plant according to claim 1 is directed to a plurality of stages of turbine blades and inner peripheral portions that are implanted in the turbine rotor, and the outer peripheral portion is supported by the diaphragm outer ring. And a nozzle box for supplying driving steam to the first stage of the turbine stage is housed in a double-structure turbine casing comprising an inner casing and an outer casing, and the turbine casing is A ground seal portion is provided in a portion penetrated by the turbine rotor, and further includes a cooling steam introduction portion for flowing cooling steam between the inner casing and the outer casing, between the inner casing and the diaphragm outer ring, and the ground seal portion. In a steam turbine plant
The outer peripheral surface of the outer periphery of the turbine outer blade of the diaphragm outer ring is formed in a cone-like shape whose diameter decreases in the direction of the driving steam flow, and the downstream diaphragm outer ring has the inner peripheral surface diameter of the driving steam. A cone-shaped gap is formed between the cone-shaped convex portion and the cone-shaped concave portion by projecting upstream so as to form a cone-shaped concave shape that decreases in the flow direction and surrounding the cone-shaped outer peripheral portion through a gap. In addition, a cooling steam seal portion is provided in the cone-shaped gap .

According to the steam turbine plant of the present invention, it is possible to prevent from being mixed into high-temperature steam through the diaphragm outer ring gaps between the low-temperature cooling steam adjacent, it is possible to prevent a decrease in thermal efficiency of the steam turbine.

  The steam turbine plant according to the present invention to be described below will be described for an intermediate pressure turbine. However, the present invention is not limited to an intermediate pressure turbine, and can be applied to a high pressure turbine and a low pressure turbine.

FIG. 1 is a steam system diagram of a steam turbine plant according to the present invention.
In FIG. 1, a steam turbine plant 1 includes a steam turbine 3 including a boiler 2, a high-pressure turbine 3-1, an intermediate-pressure turbine 3-2, and a low-pressure turbine 3-3, a generator 4, a condensate system 5, and a feed water system 6. Has been. Among them, the high-pressure turbine 3-1 introduces high-temperature high-pressure steam from the steam generator 2-1 of the boiler 2, and the intermediate-pressure turbine 3-2 is reheated by the reheater 19 to a temperature of 700 ° C. or higher. Steam is introduced through an intermediate-pressure turbine bleed system 20, and the low-pressure turbine 3-3 introduces exhaust from the intermediate-pressure turbine 3-2, and a generator is generated by rotational torque generated when each steam turbine performs expansion work. 4 is driven to rotate.

  Exhaust gas from the low-pressure turbine 3-3 is guided to a condenser 7 constituting the condensate system 5 where it is condensed to condensate. The condensate pump 8 of the condensate system 5 and the low-pressure feed water heaters 9 to 9 are condensed. 12 is supplied to the water supply system 6. The feed water system 6 is a steam generator through a deaerator 13 for removing oxygen in the steam sent from the low pressure feed water heater 12, a feed water pump 14 for boosting feed water, high pressure feed water heaters 15 to 17, and a superheater 18. 2 to reflux.

  In FIG. 1, reference numeral 21 denotes a high-pressure turbine bleed system for supplying high-pressure turbine bleed air to the final-stage high-pressure feed water heater 17, and a path 22 indicated by a broken line branches the bleed of the high-pressure turbine bleed system 21. The steam cooling system for steam-cooling the intermediate pressure turbine 3-2 is shown.

  FIG. 2 is a partially cutaway longitudinal sectional view of an intermediate pressure turbine 3-2 that causes reheat steam from the reheater 19 of the boiler 2 shown in FIG. 1 to perform expansion work.

  Reference numeral 30 denotes a casing of the intermediate pressure turbine 3-2, which has a double-structure axial flow type including an outer casing 31 and an inner casing 32. The inner casing 32 accommodates a nozzle box (steam chamber) 33 and a plurality of turbine stages 34. The turbine stage 34 is constituted by a combination of a turbine rotor blade 37 implanted in a turbine disk 36 formed on the turbine rotor 35 and a turbine nozzle 40 supported by a diaphragm inner ring 38 and a diaphragm outer ring 39 by welding or the like. .

  The diaphragm inner ring 38 is provided with a packing and a labyrinth seal 41 that closes the gap with the turbine rotor 35 at the inner periphery thereof, and the outer periphery of the diaphragm outer ring 39 is fitted and fixed to the inner casing 32.

  In addition, regarding the outer casing 31 and the inner casing 32, an outer casing gland portion 42 and an inner casing grant portion 43 for preventing steam leakage are respectively provided in portions that are penetrated by the turbine rotor 35.

  The reheat steam having a temperature of 700 ° C. or more supplied from the reheater 19 shown in FIG. 1 is configured to be introduced into the nozzle box 33 through a reheat steam pipe 44. The reheat steam pipe 44 adopts a double pipe structure, and is configured so that a space 47 between the outer pipe 45 and the inner pipe 46 arranged concentrically functions as a cooling steam passage. Yes. An outer casing sealing device 49 is mounted between the outer tube 45 and the flange portion 48 of the outer casing 31.

  By the way, a part of the steam extracted from the high-pressure turbine 3-1 is introduced from the cooling steam system 22 into the cooling steam introduction part 50 formed between the nozzle box 33 and the inner casing gland part 43. As the cooling steam 51 flows from the introduction part 50, it flows to the stationary part of the intermediate pressure turbine 3-2. That is, a part of the cooling steam 51 cools the outer casing 31 and the inner casing 32 through the space between the outer casing 31 and the inner casing 32 constituting the double casing through the inner casing gland 43. The other portion passes through a communication groove 52 (details of the communication groove 52 are shown in FIG. 3) formed in a fitting and fixing portion between the inner casing 32 and the diaphragm outer ring 39, and the inner casing 32 and the diaphragm outer ring. The cooling steam 39 flows while cooling, and finally, the cooling steam joins with the turbine exhaust which has finished the expansion work and is exhausted from the exhaust port 53. The remainder of the cooling steam 51 leaks out of the intermediate pressure turbine through the outer casing gland 42.

  The present invention prevents the cooling steam 51 passing through the communication groove 52 formed in the fitting and fixing portion between the inner casing 32 and the diaphragm outer ring 39 from being mixed with the reheat steam for driving the intermediate pressure turbine 3-2. In the following, each embodiment of the cooling steam sealing device shown in FIGS. 3 to 11 will be described.

Example 1
FIG. 3 is an enlarged cross-sectional view illustrating the configuration of the cooling steam seal device according to the first embodiment of the present invention.
In the case of the first embodiment, as shown in FIG. 3, the outer appearance of the diaphragm outer ring 39 itself is not particularly different from the conventional example shown in FIG. 12, but the fundamental difference from the conventional example is an adjacent diaphragm. the outer ring 39 in that a cooling steam sealing device 54 ₁ by the so-called "high-low-type" labyrinth therebetween.

Hereinafter, an explanation will be mainly cooled vapor seal device 54 _1. Incidentally, description in the present invention for convenience, the subscript on the sign of the diaphragm outer-ring positioned on the upstream side of the reheat steam turbine driving a _(U), the subscript _(D) on the sign of the diaphragm outer-ring positioned downstream I will display it. Incidentally, the sign of the upstream diaphragm outer ring 39 _U, the sign of the downstream diaphragm outer ring is 39 _D.

Now, the diaphragm outer ring 39 _U located upstream of the reheat steam, the portion surrounding the outer peripheral portion of the turbine blade 37 through a labyrinth 37 _L (hereinafter, for convenience of explanation, simply referred to as blades surrounding portion) Two seal rings R are provided concentrically on the end face of 39 _U E. On the other hand, the seal fins F for forming the labyrinth of the opposing end surface of the diaphragm outer ring 39 _D downstream in cooperation with the seal ring R so-called "high-low-type" adjacent to the diaphragm outer ring 39 _U of the upstream _A plurality of _Ds are provided concentrically (in FIG. 3, one each at a position facing two seal rings R and three on both sides, a total of five). That is, by forming a labyrinth seal adjacent the diaphragm outer ring 39 _U, 39 _D high and low type therebetween, is provided with a cooling steam sealing portion 54 ₁ having a sealing gap axially.

According to the first embodiment. Thus a gap is provided cooling steam sealing device 54 ₁ between the diaphragm outer ring mutually adjacent, communicating groove formed on the fit fixing part between the inner casing 32 and the diaphragm outer ring 39 Since it is possible to prevent the cooling steam 50 flowing through 52 from entering the high-temperature reheat steam through the gap G between the diaphragm outer rings, it is possible to improve the thermal efficiency of the steam turbine plant and for sealing device 54 ₁ which has a structure having a sealing gap in the axial direction, it is possible to differential expansion of the diaphragm outer ring that occurs when the turbine start or stop to provide a highly effective sealing device is larger in the radial direction .

(Example 2)
FIG. 4 is an enlarged cross-sectional view illustrating the configuration of the cooling steam seal device according to the second embodiment of the present invention.
This second embodiment is a modification of the first embodiment of FIG. 3, but the point that a cooling steam seal ₅₄₂ having a sealing gap in the axial direction is the same as in Example 1, whose sealing structure Slightly different.

In other words, in the case of the second embodiment, a so-called “comb shape” is applied to the high / low type, and the end surface of the rotor blade surrounding portion 39 _U E of the upstream diaphragm outer ring 39 _U and this end surface opposite the downstream side of the diaphragm outer ring 39 _D sealing fins F _U, respectively so as to face each other between the end surfaces concentric of _the, by forming the cooling steam seal ₅₄₂ having a sealing gap axially provided F _D Yes.

According to the second embodiment, it is possible to obtain the same effect as in Example 1, the cooling steam seal 54 _2, radial diaphragm outer ring 39 than the cooling steam sealing device 54 ₁ of Example 1 If expansion difference greater to the opposing seal fins F _U, has a structure in which F _D together do not contact.

(Example 3)
FIG. 5 is an enlarged cross-sectional view illustrating the configuration of the cooling steam seal device according to the third embodiment of the present invention.
The third embodiment is a modification of the first embodiment, in which seal fins F _U , respectively, are disposed between the end surface of the moving blade surrounding portion 39 _U E of the upstream diaphragm outer ring 39 _U and the opposite end surface of the downstream diaphragm outer ring 39 _D. a high-low-type opposed to F _D is obtained by forming a cooling steam seal ₅₄₃ according to the so-called "staggered type".
In the case of the third embodiment, the same operational effects as those of the first embodiment can be obtained.

Example 4
FIG. 6 is an enlarged cross-sectional view illustrating the configuration of the cooling steam seal device according to the fourth embodiment of the present invention.
The fourth embodiment, is provided with a cooling steam sealing device 54 ₄ having a radial sealing gap between the adjacent diaphragm outer ring 39 to each other.

That is, both between by surrounding the further outside of the upstream diaphragm outer ring 39 _U of the blade surrounding portion 39 U _E, a cylindrical portion 39 D _C provided protrudes from the end surface of the downstream-side diaphragm outer ring 39 _D on the upstream side to form a cylindrical shape void, moreover, provided two sealing rings R on the outer peripheral surface of the blade surrounding portion 39 U _E on the upstream side diaphragm outer ring 39 _U, whereas the cylindrical portion which projects from the downstream side diaphragm outer ring 39 _D 39 D mounted a plurality of seal fins F _D on the inner peripheral surface and _C, these seal rings R and the seal fins F _D high-low type having a sealing gap radially by facing the cooling steam seal device 54 ₄ Is configured.

According to the fourth embodiment, there is an effect of preventing the low-temperature cooling steam from being mixed into the high-temperature driving steam from the outside in the radial direction to the inside, and the start-up of the turbine by having a structure having the seal gap in the radial direction. This structure is effective when the difference in the expansion of the diaphragm outer ring that occurs during stoppage is large in the axial direction.

(Example 5)
FIG. 7 is an enlarged cross-sectional view illustrating the configuration of the cooling steam seal device according to the fifth embodiment of the present invention.
Example 5 is a modification of the fourth embodiment shown in FIG. 6, which has a cooling steam sealing device 54 ₅ having a radial sealing gap between the diaphragm outer ring mutually adjacent in the same manner as in Example 4 some, but it is different from slightly shape of the cooling steam sealing device 54 _5.

That is, the outer peripheral surface of the upstream-side diaphragm outer ring 39 _U of the blade surrounding portion 39 U _E provided two annular seal fins F _U, of the cylindrical portion 39 D _C for further surrounding the periphery of the seal fins F _U by providing to face the seal fins F _D on the peripheral surface, which is constituted of the cooling steam sealing device 54 ₅ according to the so-called comb type high-low type.
In the case of the fifth embodiment, the same effects as those of the fourth embodiment can be obtained.

(Example 6)
FIG. 8 is an enlarged cross-sectional view showing the configuration of the cooling steam seal device according to Embodiment 6 of the present invention.
This Example 6 is also a modification of Example 4, to a structure having a radial sealing gap between the diaphragm outer ring mutually adjacent in the same manner as in Example 4, the diaphragm outer ring 39 _U of the blade surrounding portion 39 a plurality of seal fins F _U provided on the outer peripheral surface of the _{U E,} high in the seal fins F _D provided on the inner peripheral surface of the cylindrical portion 39 D _C for further surrounding the outer peripheral surface of the seal fins F _U from the outside low type is obtained by constituting the cooling steam sealing device 54 ₆ having a sealing gap in the axial direction according to the discrepancy type.
Also in the case of the sixth embodiment, the same operational effects as those of the fourth embodiment can be obtained.

(Example 7)
FIG. 9 is an enlarged cross-sectional view illustrating the configuration of the cooling steam seal device according to the seventh embodiment of the present invention.
In the seventh embodiment, the end surface of the rotor blade surrounding portion 39 _U E of the upstream diaphragm outer ring 39 _U is tapered so that the end surfaces facing each other of the adjacent diaphragm outer rings are inclined surfaces while maintaining a certain distance. that is, formed as a cone-shaped convex portion, whereas to form the inner peripheral surface of the facing cylindrical portion 39 is provided to protrude from the downstream side diaphragm outer ring 39 _D on the upstream side of D _C as conical recess, further upstream one end of the leaf spring-like seal ring PS is fixed to the cone-shaped convex portion of the diaphragm outer ring 39 _U, the cooling steam sealing device 54 ₇ so as to contact the free end cone shaped recess on the downstream side diaphragm outer ring end face 39 _D It is composed.

According to the seventh embodiment, there is an effect of preventing the low temperature cooling steam from being mixed into the high temperature driving steam from the fitting fixing portion of the inner casing 32 and the diaphragm outer ring 39, that is, from the radially outer side to the inner side. When the difference in elongation of the diaphragm outer ring 39 that occurs when the turbine is started or stopped occurs in the axial direction or in the radial direction, the leaf spring-like seal ring PS can be expanded and contracted to always minimize the seal gap. Incidentally, a leaf spring-like seal ring PS may be attached to the end surface of the downstream-side diaphragm outer ring 39 _D. The same effect can be obtained by applying a so-called brush seal instead of the leaf spring seal ring PS.

(Example 8)
FIG. 10 is an enlarged cross-sectional view illustrating the configuration of the cooling steam seal device according to the eighth embodiment of the present invention.
In the eighth embodiment, an annular groove SL is provided on the side surface of one of the adjacent diaphragm outer rings 39 (in the illustrated example, the rotor blade surrounding portion 39 _U E of the diaphragm outer ring 39 _U on the upstream side of the reheated steam). the cross section matches the retractable seal ring SR annular in which the C-shaped, so as to separate a slight axial clearance to the side of the diaphragm outer ring 39 _D of the reheat steam downstream side opening of the seal ring SR it is obtained by constituting the sealing device 54 ₈ Te.

  In this way, by adopting a structure in which the expandable seal ring SR is sandwiched between the diaphragm outer rings, this seal ring can be used even when a difference in elongation that occurs at the start and stop of the turbine occurs in the axial direction or the radial direction. The expansion and contraction of the seal can always minimize the seal gap.

  The seal ring SR need not be limited to the C-shaped cross section shown in FIG. 10, but the cross section is an inverted C-shaped as shown in FIG. 11A, and the W-shaped cross section is shown in FIG. 11B. As shown in FIG. 11 (c), the cross section may be a 2W type, and even when these seal rings are employed, the same operational effects as in FIG. 10 can be obtained.

The steam system figure of the steam turbine plant concerning this invention. Sectional drawing which shows the intermediate pressure turbine concerning this invention. The expanded sectional view which shows the structure of the cooling steam seal apparatus concerning Example 1 of this invention. The expanded sectional view which shows the structure of the cooling steam seal apparatus concerning Example 2 of this invention. The expanded sectional view which shows the structure of the cooling steam seal apparatus concerning Example 3 of this invention. The expanded sectional view which shows the structure of the cooling steam seal apparatus concerning Example 4 of this invention. The expanded sectional view which shows the structure of the cooling steam seal apparatus concerning Example 5 of this invention. The expanded sectional view which shows the structure of the cooling steam seal apparatus concerning Example 6 of this invention. The expanded sectional view which shows the structure of the cooling steam seal apparatus concerning Example 7 of this invention. The expanded sectional view which shows the structure of the cooling steam seal apparatus concerning Example 8 of this invention. (A), (b), (c) is a figure which shows the cooling steam seal ring concerning Example 8 of this invention. The expanded sectional view of the conventional diaphragm inner and outer ring part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Steam turbine plant, 2 ... Boiler, 3 ... Turbine, 3-1 ... High pressure turbine, 3-2 ... Medium pressure turbine, 3-3 ... Low pressure turbine, 4 ... Generator, 5 ... Condensate system, 6 ... Feed water system DESCRIPTION OF SYMBOLS 4 ... Steam cooling system, 5 ... High pressure turbine extraction system, 6 ... Superheater, 7 ... Condenser, 8 ... Condensate pump, 9-12 ... Low pressure feed water heater, 13 ... Deaerator, 14 ... Feed water pump DESCRIPTION OF SYMBOLS 15-17 ... High pressure feed water heater, 18 ... Superheater, 19 ... Reheater, 20 ... Medium pressure turbine extraction system, 21 ... High pressure turbine extraction system, 22 ... Steam cooling system, 30 ... Casing, 31 ... Outer casing , 32 ... inner casing, 33 ... nozzle box, 34 ... turbine stage, 35 ... turbine rotor, 36 ... turbine disk, 37 ... turbine blade, 38 ... diaphragm inner ring, 39 ... diaphragm outer ring, 39 _U E ... turbine blade Perimeter Enclosed part (moving blade surrounding part), 40 ... turbine nozzle, 41 ... seal, 42 ... gland part for outer casing, 43 ... gland part for inner casing, 44 ... reheat steam pipe, 45 ... outer pipe, 46 ... inside Pipe, 47 ... Cooling steam passage, 48 ... Flange, 49 ... Sealing device for outer casing, 50 ... Cooling steam introduction part, 51 ... Cooling steam, 52 ... Communication groove, 53 ... Exhaust port, 54 ... Sealing device for cooling steam, F _U ... seal fin, F _D ... seal fin, R ... seal ring, SR ... seal ring, PS ... leaf spring-like seal ring, SL ... annular groove.

Claims (3)

A turbine stage composed of a turbine nozzle having a plurality of stages of turbine rotor blades and an inner periphery supported by a diaphragm inner ring, and an outer periphery supported by a diaphragm outer ring, and a first stage of the turbine stage. A nozzle box for supplying steam is housed in a double-structure turbine casing composed of an inner casing and an outer casing, and a gland seal portion is provided in a portion where the turbine casing is penetrated by the turbine rotor, and the inner casing and the outer casing are further provided. Between the inner casing and the diaphragm outer ring, in the steam turbine plant provided with a cooling steam introduction part for flowing cooling steam to the ground seal part,
The outer peripheral surface of the outer periphery of the turbine outer blade of the diaphragm outer ring is formed in a cone-like shape whose diameter decreases in the direction of the driving steam flow, and the downstream diaphragm outer ring has the inner peripheral surface diameter of the driving steam. A cone-shaped gap is formed between the cone-shaped convex portion and the cone-shaped concave portion by projecting upstream so as to form a cone-shaped concave shape that decreases in the flow direction and surrounding the cone-shaped outer peripheral portion through a gap. A steam turbine plant characterized in that a cooling steam seal portion is provided in the cone-shaped gap . The cooled using a seal fins steam seal parts high-low type, comb or steam turbine plant according to claim 1 Symbol mounting characterized by being constituted by any discrepancies type labyrinth. The steam turbine plant according to claim 2, wherein the seal fin is formed in a leaf spring shape or a brush shape.

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