JPH066162Y2 - Mounting structure for the interior of the steam turbine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a mounting structure for an inner casing of a steam turbine applied to a steam turbine.

2. Description of the Related Art A conventional mounting structure for a vehicle interior of a steam turbine will be described with reference to FIG. 3, which shows a high-pressure turbine portion of a steam turbine.

A nozzle chamber 4 ', a blade ring 5', a dummy ring 6 ', and the like are supported and fixed inside the inner casing 1', and these members 4'-6 'are provided.
A rotor 7'is disposed inside the.

In this case, the inner casing 1'is usually divided into upper and lower parts by a horizontal joint surface (not shown), and after these are combined, they are fastened with a tightening bolt (not shown). In addition,
Reference numeral 8'denotes a radial pin for axial positioning.

On the other hand, it is often practiced to increase the steam condition at the turbine inlet in order to improve the thermal efficiency of the steam turbine. However, if the steam temperature is raised to 649 ° C (1200 ° F), for example, ferrite materials such as 12 chrome steel, which are generally used as the material for the inner casing 1 ', lack high temperature strength and have high heat resistance. It is necessary to switch to other austenitic steels.

It is known that the former 12-chromium steel has a smaller coefficient of thermal expansion α than the latter SUSF316H.

The problem to be solved by the invention is that austenitic steel has excellent high-temperature strength such as creep strength, but its yield stress is low. Cause

As a result, if the tightening bolts on the horizontal joint surface are loosened at the time of release, the inner casing 1'may be deformed, which interferes with play management during reassembly. In addition, the tightening of the horizontal joint surface in the cold state before and after the operation may be insufficient, and steam may leak when starting.

As one of such measures, in order to prevent the above nonconformity, a thermal shield (not shown) is separately provided on the inner and outer surfaces of the inner casing 1'to reduce the temperature difference between the inner and outer casings 1 '. Although it is considered that the thermal shield on the inner surface is not practical in terms of strength and structure, and the thermal shield on the outer surface is also structurally complicated, there is a problem in that it takes time to install and remove.

Means for Solving the Problems In order to solve such a conventional problem, the present invention is made of a material having a relatively large thermal expansion coefficient in a mounting structure of a steam turbine inner casing and is divided by a joint surface or the like. The inner cylinder is placed in an outer cylinder made of a material having a thermal expansion coefficient smaller than that of the above material with a proper gap, and the inner cylinder is fastened by the outer cylinder due to the difference in thermal expansion amount due to the temperature difference before and after the operation. It is a thing.

According to such means, the inner cylinder of the inner casing is made of a material having a large thermal expansion coefficient to have a further divided structure, and the outer cylinder is made to be an integral structure using a material having a small thermal expansion coefficient. Therefore, during operation, the outer cylinder and the inner cylinder are in a tightly tightened state due to thermal expansion, so that the outer cylinder and the inner cylinder can always be brought into close contact with each other without external tightening such as a tightening bolt.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS.

Then, as shown in FIG.
Is made of a heat-resistant material having a large coefficient of thermal expansion, such as SUSF316H steel, and can be divided into two or more parts, for example, a horizontal joint surface 9 or the like, and has one shape, for example, a substantially cylindrical inner shape. The cylinder 2 and the outer cylinder 3 which is made of a material such as the above-mentioned 12 chrome steel having a relatively smaller thermal expansion coefficient than the above-mentioned materials and which is integrally formed in a substantially cylindrical shape corresponding to the outer peripheral surface of the inner cylinder 2. It has a double structure that combines and.

Then, the inner cylinder 2 is arranged in the outer cylinder 3 and assembled, and the thermal expansion amount of each inner cylinder 2 and the outer cylinder 3 due to the temperature difference before and after the operation, that is, the difference between the gaps δi and δo described later is used. The outer peripheral surface of the inner cylinder 2 is fastened to the outer peripheral surface of the inner cylinder 2 without using external fastening means such as a fastening bolt.

In this case, as shown in FIG. 2, the nozzle chamber 4, the blade ring 5, and the dummy ring 6 supported on the inner cylinder 2 side may adopt the same assembly method as a conventional ordinary turbine.

That is, in the assembly, the lower half side of each of the nozzle chamber 4, the blade ring 5, and the dummy ring 6 is assembled in the lower half part of the inner cylinder 2,
The rotor 7 is received there.

The upper half parts of these constituent members 4 to 6 are assembled to this, and further the upper half part of the inner cylinder 2 is assembled.

The steps up to this point are almost the same as the conventional one.

In the next step, the positioning bolts and nuts 10 are used to axially position the inner cylinder 2 that has been divided into two parts.

However, in this case, fastening the upper and lower halves of the inner cylinder 2 with the bolts and nuts 10 is not the main purpose, but is merely used as a positioning means.

Therefore, the outer cylinder 3 is fitted in the outer peripheral surface of the integrated inner cylinder 2 along the axial direction.

The inner cylinder 2 and the outer cylinder 3 are axially positioned by, for example, a radial pin 8. However, in this case as well, the purpose of fastening the inner cylinder 2 and the outer cylinder 3 with the radial pin 8 is not the purpose, but the procedure of positioning is still provided.

After that, the rotor 7 and the inner casing 2 that have been assembled are assembled in the outer casing (not shown).

In FIG. 1, reference numeral 11 denotes an insertion hole for the radial pin 8 and 12
Indicates a through hole of the bolt / nut 10, and 13 indicates a steam inlet opening.

According to the present invention, a gap δ having an appropriate gap width is provided between the inner cylinder 2 and the outer cylinder 3 assembled in this way by design.

Hereinafter, the relationship between the clearance δ and the clearances δi and δo between the inner cylinder 2 and the outer cylinder 3, which are generated by thermal expansion, will be determined, and its operation will be described. The relationship between the inner cylinder 2 and the outer cylinder 3 will be described. The gap (diameter gap) δ between them is set to a value that allows easy assembly in the cold state before and after the operation.

Now, the outer diameter of the inner cylinder 2 is di, the inner diameter of the outer cylinder 3 is do, the temperature rise during operation is ΔTi for the inner cylinder 2, ΔTo for the outer cylinder 3, and the thermal expansion coefficient of the material is αi for the inner cylinder 2 and the outer The cylinder 3 is αo (where αi> α
o), the relative gap δ ′ between them during operation is δ ′ = δ + αoΔTodo−αiΔTidi (1).

As a specific example, when the inner cylinder 2 is made of SUSF316H steel and the outer cylinder 3 is made of 12 chrome steel, αi = 1.8 × 10 ⁻⁵ 1 / ° C., αo = 1.2 × 10
^-5 1 / ° C. Further, if ΔTi = 550 ° C, ΔTo = 500 ° C,
And substituting each value set as di = do = 1,500 mm into the equation (1), δ ′ ＝ δ ＋ 1.2 × 10 ^-5 × 500 × 1,500−1.8 × 10 ^-5 × 550 ×
1,500 = δ + 9.0-14.85 = δ-5.85 mm That is, the operating clearance δ'is smaller by 5.85 mm than the cold clearance δ.

At this time, in principle, if the gap δ in the cold state is smaller than 5.85 mm, the gap δ'in operation will be a negative value, that is, the inner cylinder 2 and the outer cylinder 3 will be an interference fit during operation.

Focusing on this point, if the clearance δ in the cold state before operation is set to an appropriate value smaller than 5.85 mm, the pressure p _s of the interference fit between the inner cylinder 2 and the outer cylinder 3 during operation becomes Can overcome internal pressure p _i .

For simplicity, both the inner cylinder 2 and the outer cylinder 3 are calculated as thin cylinders. If the thickness of the inner cylinder 2 is t _i , the elastic coefficient of the material is E _i , the thickness of the outer cylinder 3 is t _o , the elastic coefficient of the material is E _o , and the external pressure of the outer cylinder 3 is p _o , then each inner cylinder 2, the strain of the outer cylinder 3 From the balance of the inner cylinder 2 (per unit length in the axial direction) From the balance of the outer cylinder 3 (per unit length in the axial direction) Here, δi and δo are the amount of contraction of the diameter of the inner cylinder 2 and the amount of expansion of the outer cylinder 3 due to the interference fit, and the clearance δ ′ during operation can be obtained from the sum thereof.

δi + δo = −δ ′ (4)

From these equations (2) to (4), the shrinkage amount δ of the diameter of the inner cylinder 2
i is In order to keep the horizontal joint surface of the inner cylinder 2 airtight, the inner cylinder 2
It is necessary that the shrinkage amount δi of is equal to or more than the limit shrinkage amount δi _min . That is, Transforming equation (6) Here, for example, E _i = E _o = 1.8 × 10 ⁴ kg / mm ² , t _i = t _o = 50 m
m, di = do = 1,500 mm, p _i = 70 kg / cm ² = 0.7 kg / mm ² , p _o = 3
Substituting the respective values assuming 0 kg / cm ² = 0.3 kg / mm ² and δi _min = 0.2 mm into the equation (7), Therefore, the gap δ in the cold state at the design stage is 5.85−0.9 = 4.95m
It turns out that it is better to take m or less.

From the above, at the time of starting the turbine, the temperature of the inner cylinder 2 first rises, the expanded inner cylinder 2 comes into close contact with the outer cylinder 2 and then the temperature of the outer cylinder 3 rises, while the internal pressure and the external pressure are not applied. Occurs.

Further, when the turbine is stopped, the temperature of the inner cylinder 2 is reduced after the internal pressure and the external pressure are eliminated.

Therefore, when the inner pressure is applied to the inner cylinder 2, a shrink fitting pressure is always generated due to the thermal expansion difference with the outer cylinder 3, so that the joint surface 8 of the inner cylinder 2 does not open.

This is because when the inner cylinder 2 itself or between the inner cylinder 2 and the outer cylinder 3 is assembled, the hermetically sealed state can be achieved by a diametric fit, so that the tightening bolt or the like from the outside can be used.
Moreover, it means that it is not necessary to receive a local tightening force.

Further, since the inner casing 1 has the double structure of the inner cylinder 2 and the outer cylinder 3 as described above, the thermal resistance at the boundary portion between the inner and outer cylinders can be increased. The outer cylinder 3 functions as a thermal shield against the outer surface of the inner cylinder 2, while the strength of the pressure container against the internal pressure can be taken up by the outer cylinder 3 in close contact with the outer cylinder 3. The thickness will be small in terms of work.

By combining these actions, the temperature difference between the inner and outer surfaces of the inner cylinder 2 can be reduced, and since the inner cylinder 2 also serves as a thermal shield against the inner surface of the outer cylinder 3, the temperature of the outer cylinder 3 is low. It is possible to maintain the state.

Effect of the Invention As described in detail above, according to the present invention, a double structure of an inner cylinder into which the inner casing is divided and an integrated outer cylinder is provided, and a gap between them is appropriately maintained. As a result, the effect of an interference fit can be obtained, so that the following effects are achieved.

(1) Since the outer cylinder is integrally formed, for example, in a cylindrical shape, it is difficult to deform due to its structure, and tightening bolts are not required.Therefore, local tightening is required in the inner compartment when the vehicle is cold before and after operation. Since no load is applied, that is, the load can be lightened in terms of strength, it is possible to prevent deformation at various places.

(2) For example, even if the inner cylinder is made thin, the temperature difference between the inner and outer temperatures of the inner cylinder is reduced by the effect of the thermal shield.
No deformation occurs.

(3) Since the temperature of the outer cylinder is also reduced, the strength margin is increased even if a ferrite-based material that lacks high-temperature strength is used as the material.

Furthermore, by using a material with a relatively large coefficient of thermal expansion for the inner cylinder and a material with a relatively small coefficient of thermal expansion for the outer cylinder, due to the difference in thermal expansion due to the temperature difference between before and after operation (at assembly) and during operation, As described above, automatic tightening (drawing fit) is possible, so the number of parts for tightening can be reduced, and therefore, the assembly / release work can be performed easily and reliably, and the manufacturing process and Manufacturing costs and maintenance costs can also be reduced.

[Brief description of drawings]

FIG. 1 is a schematic structural composition perspective view showing an example of a mounting structure of a steam turbine inner casing according to the present invention, FIG. 2 is a schematic sectional view showing an assembled state of the inner casing, and FIG. 3 is a conventional steam turbine. It is a schematic sectional drawing which shows the assembled state of an inner vehicle compartment. 1 ... inner compartment, 2 ... inner cylinder, 3 ... outer cylinder, 9 ... joint surface, δ ... gap.

Claims (1)

[Scope of utility model registration request] 1. An inner cylinder made of a material having a relatively large thermal expansion coefficient and divided by a joint surface or the like is arranged with an appropriate gap in an outer cylinder made of a material having a smaller thermal expansion coefficient than the material, A structure for mounting an inner casing of a steam turbine, wherein an inner cylinder is fastened by an outer cylinder due to a difference in thermal expansion amount due to a temperature difference before and after operation.