JP2596910B2 - Steam turbine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam turbine having a double inner casing and an outer casing, and more particularly to an improvement in a structure for preventing deformation and damage of the inner casing.

FIG. 1 is a longitudinal sectional view of a high-pressure section of a steam turbine. Referring to FIG. 1, the structure of an inner and outer casing of a conventional steam turbine will be described first.

In FIG. 1, reference numeral 11 denotes an outer casing, and a high-pressure steam inlet 12 for taking in high-pressure steam 70 is provided. twenty one
Is an inner casing located in the outer casing 11 and has a high-pressure steam inlet section.
A nozzle chamber 31 connected to the nozzle 12 is provided. The nozzle chamber 31 is formed by welding or insertion into the inner casing 21. A nozzle block 32 is provided at the tip end side of the nozzle chamber 31 along the axial direction of the rotor 41, and a speed-controlling rotor blade 42 fixed to the rotor 41 is opposed to the steam outlet of the nozzle block 32. Is located.

A high-pressure dummy ring 51 and a high-pressure blade ring 61 are located in the inner casing 21 along the rotor 41 with the nozzle chamber 31 interposed therebetween.
Accordingly, a steam passage 101 is formed in the inner casing 21 around the outer wall of the nozzle chamber 31. Reference numeral 43 denotes a high-pressure stage moving blade implanted in the rotor 41, and reference numeral 62 denotes a high-pressure stage stationary blade implanted in the high-pressure blade ring 61.

In the conventional steam turbine having such a configuration, the high-pressure steam 70 is supplied to the high-pressure steam inlet of the outer casing 11 as shown by an arrow.
The nozzle chamber 31 of the inner casing 21 is introduced into the turbine from
Through the nozzle block 32 at high speed. Since the governing blade 42 is located in front of the nozzle block 32, the steam ejected from the nozzle block 32 impinges on the governing blade 42 to apply a rotational force to the rotor 41.

Further, the spouted steam 70 is guided at high speed in a steam passage 101 formed inside the inner casing 21, and the high-pressure stage stationary blade 62 and the high-pressure stage blade 43 located on the opposite side of the governing stage moving blade 42. During this time, the temperature and pressure are gradually reduced while applying a rotational force to the rotor 41.

By the way, when a cross section orthogonal to the axial direction of the inner casing 21 is shown, as shown by a solid line in FIG. 2, the ordinary inner casing 21 has flanges 21f on both sides, and bolt holes formed in the flange 21f are formed. It is made of a member having a semicircular cross-section and integrally fixed to 21h through a bolt (not shown). However, due to long-term use, the inner casing 21 whose inner surface is in direct contact with high-temperature and high-pressure steam may be deformed as shown by a broken line in FIG. If the opening deformation 2D of the flange 21f shown in FIG. 2 exceeds 4 mm, it becomes difficult to adjust the clearance of each part, and the performance of the turbine may be reduced due to steam leak from the flange surface. Also,
Due to such deformation of the inner casing 21, the bolts passing through the bolt holes 21h cannot be removed, making maintenance and the like difficult, and furthermore, the inner casing 21 is difficult to insert into the dummy ring 51 and the wing ring 61. Sometimes occurred.

It is considered that the cause of the deformation generated in the inner casing 21 is a large temperature difference between the inner wall surface and the outer wall surface of the inner casing 21. That is, as shown in FIG. 3, when the inner steam temperature of the inner casing 21 is 500 ° C. and the outer steam temperature is 340 ° C., in the conventional turbine, the inner temperature of the inner casing 21 is 493 ° C. and the outer temperature is 387
° C, and the temperature difference reaches 106 ° C. As described above, since the temperature difference between the inner and outer surfaces of the inner casing 21 is large, the plasticity and creep during the start-up and steady operation of the turbine cause the fourth
A large residual stress is generated as shown by the broken line in the figure. Due to this residual stress, the bolt shown in FIG. 2 is deformed by releasing the bolt holding the flange 21f of the inner casing 21. Is what happens.

The present invention has been made for the purpose of preventing the deformation of the inner casing 21 as described above.

Therefore, the present invention comprises a double casing of an outer casing and an inner casing, in which high-pressure steam is introduced and jetted at high speed from a nozzle block in the inner casing to a governing stage moving blade. In a steam turbine having a moving blade arranged in front of the governing stage moving blade, a high-pressure blade ring on which the high-pressure stage stationary blade is implanted extends to an upper portion of the governing stage moving blade and to a nozzle block, and further has a high pressure. A dummy ring is also placed close to the nozzle chamber,
The steam turbine is characterized in that the entire inner surface of the inner casing is covered.

Hereinafter, an embodiment of the steam turbine according to the present invention will be described in detail with reference to FIG. FIG. 5 is a longitudinal sectional view of the high-pressure section of the steam turbine similar to FIG. 1, and the same parts as those in FIG. 1 are denoted by the same reference numerals and will not be described.

The steam turbine of the present invention is characterized in that high-pressure steam introduced into the inner casing and ejected from the nozzle block does not directly hit the inner surface of the inner casing, and is guided to the high-pressure stage stationary blades and the moving blade side.

That is, in a steam turbine in which the governing stage moving blades 42, the high-pressure stage stationary blades 62, the high-pressure stage moving blades 43, etc. are arranged on the steam ejection side of the nozzle block 32, the steam passage 101 conventionally formed around the nozzle chamber 31 is formed. In order to prevent the formation, the high-pressure blade ring 161 in which the high-pressure stage stationary blades 62 are implanted is extended to extend over the upper part of the governing stage moving blades 42 and the nozzle block 32 so as to cover the inner surface of the inner casing 21 of this portion. I have to. Further, a high-pressure dummy ring 151 is also arranged close to the nozzle chamber 31 so as to cover the inner surface of the inner casing 21 as well.
A structure in which the entire inner surface of the inside 21 is covered with the high-pressure blade ring 161 and the high-pressure dummy ring 151 is provided.

Therefore, until the steam ejected from the nozzle block 32 hits the governing blade 42 and applies a rotational force to the rotor 41, the same as the conventional one, but in the above-described structure of the present invention, the subsequent steam immediately It flows to the high-pressure stage stationary blade 62 and the high-pressure stage blade 43 side to perform work.

And, although the gap 103 is formed inside the inner casing 21, the steam does not directly flow into the gap 103, and the gap 103 is simply a stagnation state without steam flow. I have. Accordingly, since the entire inner surface of the inner casing 21 is in a state of thermal insulation, high-temperature and high-pressure steam does not directly contact the inner wall surface, and the heat transfer coefficient is greatly reduced. As a result, FIG. As shown by the solid line, even if the steam temperature is the same, the inner surface temperature of the inner casing 21 is reduced to 435 ° C, the outer surface temperature is reduced to 369 ° C, and the temperature difference is greatly reduced to 66 ° C as compared with the conventional case. . Therefore, the residual stress distribution after turbine operation also decreases as shown by the solid line in FIG. 4, and the estimated value of the amount of deformation of the inner casing at this time is, as shown in FIG. It drops significantly.

As described in detail above, according to the present invention, since the temperature difference between the inner and outer surfaces of the inner casing 21 can be kept low, deformation can be prevented, and fatigue and creep damage can be reduced. Also, fine adjustment of the clearance is possible, which can contribute to improvement of the performance of the turbine. Further, it is possible to prevent troubles such as the bolts for fixing the inner casing 21 and the dummy ring 51, the wing ring 61 and the like from coming off, thereby facilitating maintenance work and contributing to improvement of reliability.

It is needless to say that the present invention is not limited to the above-described embodiment and can be implemented with various modifications without departing from the scope of the invention. For example, the present invention may be applied not only to the inner compartment but also to the outer compartment. As shown in FIG. 7, the nozzle chamber 131 is separated from the inner casing 21 and horizontally supported, and the tip of the high-pressure blade ring 161 projects over the governing blade 42 so as to protrude. It may be made to extend to. In this type, the high-pressure blade ring 161 is moved to the inner casing 21 before the nozzle chamber 131.
Can be incorporated into Other configurations are the same as those in FIG. 5, and the same parts as those in FIG. 5 are denoted by the same reference numerals and description thereof will be omitted.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a high-pressure section of a conventional steam turbine,
FIG. 2 is a cross-sectional view in a direction orthogonal to the axis of the inner casing in FIG. 1, FIG. 3 is an explanatory diagram showing the temperature of the inner and outer surfaces of the inner casing,
FIG. 4 is an explanatory view showing the residual stress in the inner casing, FIG. 5 is a longitudinal sectional view of a high-pressure section showing one embodiment of the steam turbine according to the present invention, and FIG. 6 explains the effect of the present invention. FIG. 7 is a longitudinal sectional view of a high-pressure section showing another embodiment of the present invention. 11 …… Outer cabin, 21 …… Inner cabin, 31 …… Nozzle car, 32 ……
Nozzle block, 41 …… Rotor, 42 …… Governor stage blade, 43
... high-pressure stage rotor blade, 62 ... high-pressure stage stationary blade, 151 ... high-pressure dummy ring, 161 ... high-pressure blade ring.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yoshiyuki Hamakami 1-1, Akunouracho, Nagasaki-shi Mitsubishi Heavy Industries, Ltd. Nagasaki Research Laboratories (72) Inventor Hiroshi Yokota 1-1-1, Akunouracho, Nagasaki-shi Mitsubishi Heavy Industries, Ltd. (72) Inventor Akio Hizume 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Heavy Industries, Ltd. (56) References JP-A-54-163205 (JP, A) JP-A-46-30414 (JP, B1)

Claims (1)

(57) [Claims] 1. A high-pressure steam is introduced from a nozzle block in the inner cabin and jetted at high speed from a nozzle block in the inner cabin to a governing stage moving blade. In a steam turbine having blades disposed in front of the governing stage rotor blades, a high-pressure blade ring on which the high-pressure stage stationary blades are implanted is extended to the upper part of the governing stage rotor blades and the nozzle block, and further extended. A steam turbine wherein a ring is also arranged close to the nozzle chamber so as to cover the entire inner surface of the inner casing.