JPH0315605A - Steam turbine - Google Patents

Abstract

PURPOSE:To enlarge a clearance in the inoperative state of a steam turbine having a movable blade disposed in a rotor and a stationary blade disposed in a blade ring while reduce the clearance in the operative state thereof so as to enhance efficiency by making the blade ring of a material having a thermal expansion coefficient lower than those of other component parts. CONSTITUTION:In a steam turbine with a movable blade 2 embedded in a rotor 1 serving as a rotary unit while a stationary blade 4 embedded in a blade ring 3 serving as a stationary unit, the rotor 1, movable blade 2 and stationary blade 4 are made of a material having a high thermal expansion coefficient such as austenite and refractive alloy, while the blade ring 3 is made of a material having a relatively low thermal expansion coefficient such as chrome steel 12. Therefore, using a difference in thermal expansion due to a change in temperature, a clearance can be enlarged in the inoperative state of the steam turbine while the clearance can be reduced in the operative state thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a steam turbine, and particularly to adjusting the play between a rotating part such as a rotor and a stationary part such as a blade ring.

However, the invention is not limited to this and can also be applied to gas turbines.

BACKGROUND OF THE INVENTION A clearance is formed between a rotor of a steam turbine and a rotating part consisting of a rotor and a large number of moving blades provided on the rotor, and a stationary part consisting of a blade ring and a large number of stationary blades provided on the blade ring. .

Naturally, in order to maintain high efficiency of the steam turbine, it is desirable that this clearance be as small as possible to prevent leakage of high-temperature, high-pressure steam, which is the working fluid.

However, as shown in FIG. 4, when a conventional steam turbine is stopped, the upper and lower casings 1' are combined into one.
There is a temperature difference between the upper and lower compartments 1' and 2', specifically, the temperature of the upper compartment 1' becomes higher than the temperature of the lower compartment 2', and the center of each compartment 1' and 2' moves upward due to the bimetallic effect. Deforms by δ. This phenomenon is called ``cabin cat sledding'' because of its shape.

On the other hand, during driving, the temperature difference between the upper and lower compartments decreases, and the temperature difference between the upper and lower compartments decreases.
2' cat sledding will almost disappear.

In this way, when stopped and when driving, especially in the passenger compartments 1' and 2.
Since the central part of ' is displaced in the vertical direction, it is currently impossible to make the play between the rotating part and the stationary part smaller than this amount of displacement.

Furthermore, even if the play between the rotating part and the stationary part is smaller than this amount of displacement, the casing l'. Due to the displacement of 2', the rotor and the stationary part come into contact when stopped or in operation, and the seal fins used in the play area wear out, resulting in an increase in play.

The amount of displacement of the compartments 1', 2' between when the vehicle is stopped and when the vehicle is in operation can reach approximately 10 degrees, and the reduction in efficiency due to the inability to reduce the play cannot be ignored.

In order to improve these points, the fifth known technique
The clearance control type seal structure illustrated in the figure has been devised and is used in some cases.

That is, in the figure, 01 is the clearance, 02 is the rotor blade, 03 is the blade ring,
04 is a movable seal ring, 05 is a bellows, and 06 is a steam pressure application hole.In order to reduce the clearance 01 between the tip of the rotor blade 02 and the blade ring 03, the movable seal ring 04 is replaced with a bellows 05. This is a sole mechanism inserted into a blade ring 03 having a perforated hole on the inner circumferential surface so as to be movable in the radial direction via the sole mechanism.

During operation, a portion of steam adjusted to an appropriate pressure is introduced into the bellows 05 through the steam pressure application hole 06, thereby expanding and contracting the bellows 05, that is, moving the movable seal ring 04 radially outward or inward. to automatically control the clearance of the clearance O1 portion.

In the figure, numeral 07 indicates a stationary blade, and 08 indicates a seal fin.

Further, as shown in FIG.
In order to allow thermal deformation of the seal ring (201), a spring (203) is used to hold down the seal ring (201), as in the conventional example. , (204), (205) to be movable in the radial direction.
l) Seal mechanisms retained within have already been devised.

Problems to be Solved by the Invention The conventional steam turbine described above, however, has the following problems.

That is, in a clearance control type seal mechanism such as the former shown in FIG. 5, the structure is complicated, and the number of manufacturing steps, steps, and costs increase.

Moreover, there are also dimensional constraints within the vehicle interior, and there is a problem in that the number of stages that can be disposed in the same space between the blade ring 03 and the movable seal ring 04 is limited.

On the other hand, the latter sealing mechanism shown in FIG. 6 has the following problems.

The seal ring (201) has a presser spring (
204), (205) and (203).

If it is pressed down by the pressing springs from both sides like this,
The relationship between the radial position of the seal ring (201) in the groove of the dummy ring (5l) and the spring force is as shown in the figure, that is, the force acting on the seal ring (201) from the presser spring at a certain radial position A. becomes 0.

Furthermore, when the seal ring (201) is displaced inward, it is pushed outward by the respective presser springs (204) and (205).

Here, as shown in Fig. 7, the resultant force of the presser springs (204) and (205) shown on the upper side of the figure is in the direction (sixth direction) in which the seal ring (201) approaches the dummy ring (5l).
P in the diagram. indicates the absolute value of the force in the direction of (this is called the outer direction).

In addition, the pressing force of the pressing spring (203) that crosses it is oppositely applied in the direction in which the seal ring (201) separates from the gummy ring (5l) (in the direction of Pi, which is opposite to the direction of P in Fig. 6). indicates the absolute value of the force (called).

Therefore, considering the direction, the resultant force of these three springs is the resultant force of presser springs (204) and (205) and presser spring (203).
), and if the value of this difference is positive (+), it indicates that the seal ring (201) as a whole is pushed outward (in the direction of P in the figure), and the value of this difference is A negative (-) value indicates that the seal ring (201) as a whole is pushed inward (in the direction of Pi in the figure).

This difference is shown in the upper part of FIG. 7 when the distance a1 between the two crossing lines, that is, the resultant force of the presser springs (204) and (205) is larger than the presser force of the other presser springs (203).
Alternatively, the distance Mb with a negative sign (-), that is, the resultant force of the presser springs (204) and (205) or the presser spring (2
03) is smaller than the pressing force.

When the seal ring (201) is near position A in the radial direction, the force applied to the seal ring (201) from the entire presser spring becomes almost 0, and the seal ring (201) loses orientation.

Therefore, the seal ring (201) generates vibrations, which adversely affects the reliability of the steam turbine.

Preferably, when the body is hot, the sealing ring (201) should be displaced to the innermost side with respect to the gummy ring (5l) due to the difference in thermal expansion. At this time, the seal ring (201) receives an outward force from the entire presser spring.

However, in general, the seal ring (201) is as shown in Fig. 8(a) (
As shown in b), since it is divided into several parts in the circumferential direction, the individual seal rings (201) do not come into close contact with each other in the circumferential direction, and steam leaks from the gap S, reducing the sealing effect. It happens.

Therefore, in order to prevent this inconvenience, the presser spring (204) located on the inside in FIG. If (205) is not used, the seal ring (201) can be in close contact with the gummy ring (51) in the innermost part when the body is hot, but when the body is cold, the outer pressing spring (203) is strong. The seal ring (201) must be displaced to an intermediate position while receiving a spring force, and if there is any disturbance between the cold body state and the hot body state as shown in FIG. b occurs, which reduces the sealing effect.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides four constituent members: a rotor, a moving blade provided on the rotor, a blade ring, and a stationary blade provided in the blade ring. In the steam turbine equipped with the steam turbine, the blade ring is made of a material having a smaller coefficient of thermal expansion than the other constituent members.

Effect According to this method, materials with a large coefficient of thermal expansion, such as austenite or refract alloy, are used for the rotor and moving blades, which are the rotating parts, and the stationary blades, which are the stationary parts. By using a material with a small coefficient of thermal expansion, such as l2 chrome steel, for the partition plate (or partition plate), the difference in thermal expansion due to temperature changes can be used to increase the play when stopped and reduce the play during operation. I can do it.

EXAMPLES Below, examples of the present invention will be described in detail with reference to FIGS. 1 to 3. In addition, in FIG. 1, for the sake of simplicity, only the rotor and stationary blades of the first stage and the last stage are shown, and the rotor and stationary blades of intermediate stages are omitted.

According to the present invention, in a steam turbine in which moving blades 2 are installed in a rotor l that is a rotating part, and stationary blades 4 are installed in a blade ring 3 that is a stationary part, these Of the constituent materials, rotor l1 rotor blade 2 and stationary blade 4
The blade ring 3 is manufactured using a material with a large coefficient of thermal expansion, such as saiichi stenite or refracted alloy, whereas the blade ring 3 is manufactured using a material with a relatively small coefficient of thermal expansion, such as 12 chrome steel. Note that each shape may be of a conventional type.

In this way, by giving different coefficients of thermal expansion to each constituent material, the difference in the amount of thermal expansion caused by temperature changes can be used to increase the play when the steam turbine is stopped, and then increase the play when the steam turbine is in operation. It becomes possible to make it smaller.

The above actions and functions will be explained below using mathematical formulas.

That is, the thermal expansion coefficient of the material of the rotor 1 is α1, that of the rotor blade 2 is α, that of the blade ring 3 is α, and that of the stationary blade 4 is α4.
Also, the rotor radius of the rotor blade 2 embedded part of the rotor 1 is rl
q Let the radius of the blade ring of the stationary blade 4 implanted portion be rt, and the height of the rotor blade 2 be h. However, the height h' of the stationary blade 4 is approximately the height h of the moving blade 2.
is equal to (h#h').

Therefore, due to the mutual dimensional relationship, rx=r+ + h ・ ・ ・ ・ ・ ・
(1) Now, the temperature rise of the rotor l, rotor blade 2, blade ring 3, and stationary blade 4 from room temperature to during operation is calculated by ΔT1. ΔT,. ΔT
3 and ΔT4, the amount of change in play between the rotating part and the stationary part is as follows.

a) Clearance between the tip of the rotor blade 2 and the blade ring 3: Let the clearance at room temperature be CI, and the clearance at high temperature be /, then Ct=c. -a. ΔTart-α! ΔT. h+a,
ΔTsrt=c, − a, ΔT+r+ atΔT
th+ a sΔTsr++α3ΔT. h ・ ・ ・ ・ ・ ・ ・ (2) b) Clearance between the inner circumference side tip of stationary blade 4 and rotor l: Let the clearance at room temperature be C, and the clearance at high temperature be c,′ Then, ct=c, −αtΔTart 10(X, ΔT, r.−
a. ΔT. h=C, -ff, Δ7, r, +α, ΔTsr
l+ α3ΔT, h−α4ΔT+h ・ ・ ・ ・ ・ ・ ・ (3) For simplicity, assume that the temperature rise of all members from room temperature is the same, that is, ΔT. =ΔTt=ΔTs=ΔT. =ΔT---(4), then each (2). Equation (3) is C%=C+ (ff r (l s)ΔTr+
Cat - αs) ΔTh・ ・ ・ ・ ・ ・ ・(
5) C*'=Ct (ff + (X s)ΔTr+
(αa as)ΔTh・ ・ ・ ・ ・ ・
(6) These equations (5) and (6) and α, . α,. α4〉α,
In the relationship, that is, the coefficient of thermal expansion α of the material of the blade ring 3
, is the thermal expansion loss α of the other rotor l1 rotor blade 2 and stationary blade 4
1. α,. α. By selecting a material that makes each gap relatively smaller, C. , C, and the size relationship of each gap CI'+ Cm at high temperature is c+'< C
I C-゜α1-α3〉0,α,-α3〉0)・・
・ ・ ・ ・ ・(7) Ct'< Ct ('.'α1−α,〉O,α4−
α3〉O) ・ ・ ・ ・ ・ ・ ・ (8) Therefore, this means that the gap automatically becomes smaller at high temperatures, that is, when the steam turbine is operating, and that it becomes larger at normal temperatures, that is, when the steam turbine is stopped. .

The above (7) is now a combination of materials that can actually be used. (8
) Calculate the amount of change in play as shown in the equation.

For example, the material of the rotor l is austenitic A2.
86, αl = 1.8X to-' 1/
'C. When refract alloy R26 is used as the material for the rotor blades 2 and stationary blades 4, α, = α, = 1.5x
1G-'1/'C.

When 12 chromium cast steel is used as the material for the blade ring 3, α3=
1.2X 10-'l/"C.

In addition, the temperature rise from room temperature is ΔT = 500℃, the radius of the rotor blade 2 embedded part of the rotor l is rl-400jIJff, the radius of the stationary blade 4 embedded part of the blade ring 3 is r, = 500xx, each rotor blade Assuming that the height of stator blade 2 and stationary blade 4 is approximately h=100im, C. ' = CI - (1.11! - 1.2)X
10-'X 500X 400 (1.5-1.2)
x 10-'x 500x 1001C. -1.2-0
．． 15 = C+ − 1.35xm ・ ● ・ ・
● ●(9) Cx'=Ct (1.8 1.2)
x10-'x500x400(1.5-1.2)x
10-'x 500x 100=CI- 1.2- 0
．． 15 = Ct-1.35+u ・ ・ ・ ・ ・ ・
(10) Therefore, the free play Cl'+ Cl' during operation at high temperature
to an appropriate value within a range of about 1xm or less, for example 0.
It can be set to 75zz. That is, each (9),
(10) is modified to obtain Ct=C%+1.35=0.75+1.35=2.
You can set it to 1xm. In other words, each play gap C. ，
C, in advance 2. By adopting the size of IJFI, a clearance of 0.75 gm can be obtained at high temperatures.

In the above-mentioned first embodiment, an example was shown in which refract alloy R26, which has a large coefficient of thermal expansion, was used as the material for the rotor blades 2 and stationary blades 4. Next, in the second embodiment, refract alloy R26, which has a large coefficient of thermal expansion, was used as the material for the rotor blades 2 and stationary blades 4.
, from the mutual dimensional relationship between the blade ring 3, the rotor blades 2, and the stator blades 4, even if the coefficient of thermal expansion of the materials of the rotor blades 2 and stator blades 4 is the same as the coefficient of thermal expansion of the blade ring 3, The blade ring 3 (= rotor blade 2
, if the stator blade 4) is smaller than the thermal expansion coefficient of the rotor 1, then
The invention still stands.

That is, if the moving blades 2 and stationary blades 4 are made of the same l2 chromium steel as the blade ring 3, and the rotor l is made of austenitic A286, then (, + = Cl'+ 1. 35 = 0.' ys+
1.35=2. 1xxα,=α3=α,=1.
2X 10-' 1/℃a. = 1.8x 10
−' 1/”C. These values are expressed in (5) above,
Substituting into equation (6), C. '=CI- (1.8- 1.2)X 10-'X
500X 400=C,=1.2u・●・・・・(1
l) C%=Ct (1.81.2)x10-'x50
0x400=C*-12zm ・ ● ・ ・
- (10) Here, as in the first embodiment, the gap C. , C, by transforming equations (11) and (12) and substituting an appropriate value of 0.75zm. However, in this case, the coefficient of thermal expansion of the rotor l and the blade ring 3 is α
Let 1=α.

Further, the height h of the rotor blade 3 and the height h' of the stationary blade 4 are set to h=h'.

Now, let us calculate the temperature rise of each component 1 to 4 from room temperature by ΔT (:
-Tt=T*=Ts=T4), the amount of change in the play between the rotating part and the stationary part is as follows.

a) Clearance between the tip of the rotor blade 2 and the blade ring 3: From equation (5), c. '=c,-o-ΔTrt (fft (Is)
ΔTh=ct (α, −α,) ΔTh ... (
5)′. '． C+=C%+1.2==0.75+
1.2=1.95xm.゜． Ct=Ct'+1.
2=0.75+1.2=1.95xi.

Furthermore, as a third embodiment, the present invention can also be achieved by using materials with large coefficients of thermal expansion for the rotor blades 2 and stationary blades 4, and materials with small coefficients of thermal expansion for the rotor l and blade ring 3. do.

b) Play between the inner tip of the stationary blade 4 and the rotor 1: (6)
From the formula, C*'=Ct O"ΔTrr-Cab-as)ΔTh
=Ct-(α4-α,)ΔTh... (6)'
These equations (5)', (6)' and α,,α4〉α
3 (=α1), that is, the coefficients of thermal expansion α3, α1 of the materials of the blade ring 3 and the rotor l are the coefficients of thermal expansion α, . α. By selecting a material that is relatively smaller, the size relationship between each gap CI+Ct at room temperature and each gap 01', C, / at high temperature is c. '<c. ('.' α, −α, 〉0)・・
・(7)′C. '<Ct ('.゜ α4−α3
〉0)...(8)' Here, the amount of change in play is estimated in the same way as described above.

When l2 chromium forged steel is used as the material for the rotor l and l2 chrome cast steel is used as the material for the blade ring 3, α, = α, = 1.2X
10-51/'C.

Refract alloy R26 is used as the material for the rotor blades 2 and stationary blades 4.
Using α, = α, = 1.5x to-' l/
℃.

Here, assuming that the temperature rise from room temperature is ΔT=500°C and the height of each rotor blade 2 and stationary blade is approximately h(#h')=200xg, C,'=C. - (1.5- 1.2)X 10-'X
500X 200-Ct-0.3xm ・
・ ・ ・ ・ ・(9)'Ct'=C+'=Ct
-0.3mm” ” ” ” ” (10)'
In order to set the clearance c+', ct' to an appropriate value, for example, 0.75xm during operation at high temperature, each (9)', (10)
'Changing the formula, Ct = Ct' + 0.3 = 0.75 + 0.3
= 1 05xx'Ct-C*' + 0
．． 3=0.75+0.3=1.05xx.

On the other hand, in the first to third embodiments described above, an example of a reaction turbine mainly having a three-ring structure was shown, but as a modification thereof, an impulse turbine having a partition plate structure as shown in FIG. It can also be applied to Note that calculations are omitted.

That is, l is the rotor, 2 is the rotor blade, 3' is the partition plate ring, 4 is the stationary blade, and 4' is the partition plate. In the case of an impulse turbine, the tip of the rotor blade 2 and the blade ring 3 of the reaction turbine Corresponding partition plate ring 3
Regarding the play between ', the same applies to the reaction turbine in FIG.

Furthermore, the play between the partition plate 4' and the rotor 1 is determined by the inner diameter r,' of the seal ring 5 attached to the inner peripheral surface of the partition plate 4'.
If considered in the same way as the inner tip of the stationary blade 4 of a reaction turbine, it can be applied when the coefficient of thermal expansion of the partition plate 4' is smaller than that of the rotor 1 as in the first and second embodiments, and the same as in each embodiment. Effects and functions can be obtained.

However, this does not apply if the coefficient of thermal expansion of the partition plate 4' is not smaller than the rotor l.

It goes without saying that the present invention can also be applied to gas turbines in principle in substantially the same manner as the above-mentioned steam turbines.

In addition, in the following Table 1, the relative magnitude relationship of the thermal expansion coefficient α of each component in the first to third embodiments described above is summarized and shown.

Table l Also, in addition to the selection and construction of the relative magnitude relationship of the thermal expansion coefficients of each component, although it is not the main topic, as shown in Figure 3, conventional seal structures such as play control type ( 5 and 6)
In particular, as an improvement to the seal structure shown in FIG. 51) is a presser spring (204) placed inside. (
205) is abolished, and the outer presser spring (203) is biased to keep it in close contact in the inner direction Pi at all times.

Therefore, by taking this measure, in addition to the action and function of the constituent materials, the gap S between the abutting surfaces of the splittable seal ring (201X, see Figure 8) [seal ring (201) and gummy ring (51) This phenomenon occurs when there is a difference in the coefficient of thermal expansion of the materials of
5l) will no longer occur.

Effects of the Invention As detailed above, according to the present invention, by using a material with a coefficient of thermal expansion always smaller than that of other structural members in the blade ring, the structure and structure of the blade ring or other structural members can be improved. Without making any particular improvements to the shape, it is possible to maintain a large play between the rotating part and the stationary part when the bottle is stopped, so it is possible to prevent contact between the rotating part and the stationary part due to the reduction in play caused by cat sledding in the passenger compartment. It is possible to reliably prevent seal fin wear caused by

In addition, since the play between the rotating part and the stationary part during turbine operation can be kept small to an appropriate value of approximately 111z or less, the increase in the gap and misalignment at the split plane of the seal ring are suppressed, and the seal part steam leakage can be reduced, thereby increasing the efficiency and reliability of the turbine.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the main part structure showing an embodiment of the steam turbine according to the present invention, Fig. 2 is a sectional view of the main part structure showing other modifications, and Fig. 3 is a clearance control type seal mechanism around the seal ring. Fig. 4 is a schematic diagram showing the conventional cat sledding phenomenon in the turbine casing, and Fig. 5 is an Ichiro cross section showing a conventional clearance control type seal mechanism for preventing cat sledding in the casing. 6 is a sectional view of Ichiro showing another seal mechanism, FIG. 7 is a diagram showing the relationship between the magnitude of the resultant force of the presser spring and the displacement of the seal ring in the seal mechanism of FIG. 6, and FIG. Invention and conventional split seal rings are shown, (a) is a schematic front view thereof, (b)
is a schematic diagram showing a gap S generated on the dividing surface (abutting surface) of the seal ring, and FIG. ■ - Rotor, 2 - Moving blade, 3 - Blade ring, 4 - Stationary blade.

Claims (1)

[Claims] In a steam turbine comprising four components: a rotor, a moving blade provided on the rotor, a blade ring, and a stationary blade provided in the blade ring, the blade ring is made of a material having a smaller coefficient of thermal expansion than the other components. A steam turbine characterized by: