JPS6040705A - Steam turbine draining device - Google Patents

Abstract

PURPOSE:To prevent deterioration in durability due to remaining water by forming a water draining port in a tenon caulking part for fixing a shroud, and draining water in a gap space formed between said tenon and a tenon fitting hole of said shroud. CONSTITUTION:On an annular belt-like shroud 12, holes 12a are provided and tenons 13 are fitted into the holes 12a. Each end part of the tenons 13 is formed into a caulking part 14, whereby the shroud 12 connects more than one blade 11 in an annular state. A water draining port 15, which extends in the radial direction of a turbine shaft, is provided in the caulked part 14 of the tenon 13. And, the both end openings of the water draining port 15 are opened to a gap space 16 formed between a tenon 13 and the hole 12a of the shroud 12, and to a space 17 outside the tenon respectively, mutually connecting the both spaces 16, 17. Thereby, water drops which are deposited on the blade 11 and enter the gap space 16, are drained to the tenon-outside space 17 through a water draining port 15.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a drain recovery device for a steam turbine, and in particular, improves durability and improves durability by forming a water discharge path for discharging water droplets accumulated in a shroud fixed portion to the outside. The present invention relates to a steam turbine drain recovery device that can improve safety.

[Technical background of the invention]

Generally, as shown in FIG. 1, tenons 2, 2 are integrally formed at the tip of a blade 1 of a steam turbine so as to protrude outward. 7 Yuroud 8 is fitted. And the above Tenon 2,
The tips of the blades 2 are caulked, thereby fixing the shroud 8 to connect the plurality of blades 1 in an annular manner.

Note that Figure 1 shows the blades in the low-pressure part near the saturated region, and the blade 1 and shroud 8 are expanded toward the steam downstream side (right side in Figure 1), and the diameter is expanded on the downstream side. is set to .

[Problems with background technology]

However, near the saturation region of the steam turbine.

Due to the expansion of the steam, fine water droplets adhere to the steam turbine components such as the blades 1. And this water drop.

The shroud 8 enters into the gap 4 created by being pushed outward by rotational centrifugal force, and further flows into the gap space 5 formed between the tenon 2 and the tenon insertion hole provided in the shroud 8. and stay there.

Since the steam contains corrosive factors such as chlorine, the retained water also contains corrosive factors.

This retained water causes pitting.

The nuclear force endurance limit decreases early (for example.

Mo Muller”Theoret, 1cal 0on
Cideration on Corrosion Fa
tigue crade engineering n1ti-ation”.

MetallurgiQal Transaction
American Society for Met
als and the Meta'llurgical
of AIMP, Vow 18 A, April
(See 1982-649°).

In addition, since steam turbine blades and shrouds are constantly subjected to stress due to centrifugal force per rotation and stress due to minute vibrations, the unloading force progresses quickly, and as mentioned above, when the nuclear force durability limit decreases, blades 1 and shrouds In some cases, cracks occurred in the 8, and they were scattered during operation. In addition, stress corrosion cracking (SaC) may occur in particularly stressed parts such as blades in a resonant state (for example.

RlJ, Lindinger ana R,M, 0ur
ran, “Bxperience with 0oss
ion Oraking in Large Syst
emTurbine”, Material Parf
ormance, NationalAvociat
ion of Corrosion Hinginee
rs.

February 1982, PP 22-
26).

[Purpose of the invention]

The present invention overcomes the drawbacks of conventional steam turbines.

Prevents water droplets from accumulating between the blades and shroud, and prevents early cracks in the blades and shroud.'11
An object of the present invention is to provide a drain recovery device for a steam turbine that can be stopped.

[Summary of the invention]

In order to achieve the above objects, the present invention provides a drain recovery device for a steam turbine, in which a water discharge path is formed in the tenon caulking portion, and a gap is formed between the tenon and the tenon insertion hole of the shroud by the water discharge path. It is characterized in that the space is communicated with the Tenon outer space, so that water that tends to accumulate between one blade and the shroud is guided to the outside by a water discharge path.

[Embodiments of the invention]

EMBODIMENT OF THE INVENTION Below, one embodiment of the present invention will be described in detail based on the drawings.

The blades 11 shown in FIGS. 2 and 3 are for low pressure near the saturated temperature region, and the diameter of each blade 11 and shroud 12 increases toward the steam downstream side (right side in FIG. 2). It looks like this.

Tenons ia and ta are integrally formed at the tip of the blade 11 so as to protrude outward. Also.

Ring-shaped shroud 121Cij Tenon insertion hole 12a,
12a is opened, and the tenon 13.13 is fitted into this tenon insertion hole 512a. moreover.

Each tip portion of the tenons 13, 13 is formed into a peeling portion 14, by which the shroud 12 is fixed so as to connect the plurality of blades 11 in an annular shape.

Further, a water discharge hole 15.15 extending in the radial direction of the turbine shaft is formed through the caulked portion 14.14 of the tenon 13.13. Both ends of this water discharge hole 150 are opened into a gap space 16 formed between the tenon 13 and the tenon insertion hole 12a of the shroud 12, and a tenon outer space 17, respectively. 15 allows the above-mentioned spaces 16 and 17 to communicate with each other.

Further, the gap space 16Fi forms an annular space.

The water discharge hole 15 is arranged so as to open to the downstream side (right side in FIG. 2) of the annular gap space 16 in the steam flow direction. Furthermore, the water discharge hole 1 of this gap space 16
A portion of the inner wall of the tenon insertion hole 12a is cut away at the opening 5 to enlarge the gap space 16, so that the water discharge hole 15 and the gap space 16 can be sufficiently communicated with each other.

In a steam turbine having such a configuration, when water droplets adhere to one blade 11, the water droplets are deposited in the gap space 1 between the tenon 13 and the tenon insertion hole 12a of the shroud 12.
6, and by the steam flow, it moves to the downstream part of the gap 116 in the steam flow direction and tends to accumulate there. However, since the water discharge hole 15 is opened in this space,
The S accumulated water is discharged to the outside of the Tenon caulked portion 14 through the water discharge hole 15 by the centrifugal force of one rotation and is recovered. Therefore, no water traps Nb in the gap space 16, no pitting occurs due to accumulated water, and the early occurrence of one crack is prevented.

Note that the water discharge hole 15 can also be formed from a groove-shaped or pipe-shaped water discharge path.

In addition, Schride 12 in this embodiment, 6A1-4
It is made of titanium alloy such as V. In this way, the following effects can be obtained.

First, since titanium alloy has extremely excellent corrosion resistance, it is possible to completely eliminate corrosion of the shroud 12.
There is almost no decrease in fatigue endurance limit.

For example, in the case of 12Or steel, 42F4/
The rotational bending fatigue endurance limit of tJ was 0.81
In steam containing H2S, the fatigue endurance limit decreases to 11 kg/-. On the other hand, the titanium alloy of 6Ax-4V.

It has a fatigue endurance limit of 49Kg/+eF in the atmosphere and 0.8
It has a fatigue durability limit of 46 kg/- even in steam containing %H2S.

Further, since titanium alloy has a very small specific weight, which is less than 60 inches of 12Cr steel, the stress generated in the shroud 12 can be kept very small. Therefore, the progression of the ailment phenomenon can be reliably prevented.

Furthermore, if cracks occur in the tenon 13 or shroud 12, the shoulder of one blade 11 may be ground down and the blade 11'1 may be reused. in this case.

By replacing the original 120r steel of the shroud 12 with one of titanium alloy, the longitudinal elastic modulus of the shroud 12 is approximately halved, and the natural frequency of each blade 1 can be significantly changed. Therefore, cracks in the tenon 13 and shroud 12 are caused by synchronous excitation forces resulting from turbulence in the steam flow (e.g., Mechanical Engineering Handbook, 4th Edition).

(Refer to Part 13, 8, 7, 8) or due to resonance with rotational excitation force.

Prevents the recurrence of resonance phenomena and eliminates cracks, especially stress corrosion cracks (se
The early occurrence of a) can be prevented.

FIG. 4 shows how the natural frequency of the blade changes when the rigidity of the shroud 12 is reduced as described above.

In Figure 4, the horizontal axis shows the stiffness of the shroud in the axial direction (steam turbine axial direction), and the vertical axis F shows the primary natural vibration k of one blade.
It shows h. For example, the rigidity θ of the shroud was originally G point vr-ant.

It is assumed that the natural frequency is at the FiJI point. And by adopting a titanium alloy shroud.

The rigidity of the shroud makes it the H point, and the natural frequency F is 5.
It turns into a point. On the other hand, the resonance occurrence region is indicated by the shaded area E,
It can be seen that the shroud, which originally had six resonance generating regions FIC, deviates from the resonance generating region E with the adoption of titanium alloy.

〔Effect of the invention〕

As described above, in the steam turbine drain recovery device according to the present invention, a water discharge path is formed in the tenon caulking portion, and the gap space formed between the tenon and the tenon insertion hole of the shroud is filled by this water discharge path. Since the rain space is communicated so that water can be discharged to the outer space of the tenon, water will not accumulate in the shroud fixing area, and there will be no pitting of the blades or shroud caused by water accumulation. It is possible to prevent the fatigue durability limit from decreasing and prevent the early occurrence of single cracks.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the tip of a blade of a conventional steam turbine, FIG. 2 is a sectional view corresponding to FIG. 1 showing the tip of a steam turbine blade in an embodiment of the present invention, and FIG.
FIG. 3 is a partial plan view of the vane shown in the figure. FIG. 4 is a diagram showing the natural vibration characteristics of the blade. 1]...Blade, 12 River shroud, 13...Tenon, 14...Caulking part, 15...Water discharge hole, 16
...Gap space, 17...Tenon outer space. Applicant's representative: Inomata, 14th, 2nd eye, 3rd eye, 4th eye, 1 louder, 4th eye, 1st student Is

Claims (1)

[Scope of Claims] l) In a drain recovery device for a steam turbine, the shroud is fixed by fitting an annular shroud into a tenon provided at the blade tip and caulking the tenon; A water discharge path is formed in the tenon caulking part so as to penetrate in the radial direction of the turbine shaft, thereby converting the gap space formed between the tenon insertion hole provided in the shroud and the tenon into the outer space of the tenon. A steam turbine characterized in that the steam turbine is connected to each other. 2) Drain recovery for a steam turbine according to claim 1, wherein the water discharge passage is opened in the downstream side in the steam flow direction of the gap space between the tenon insertion hole of the shroud and the tenon. Device. 8) The steam turbine drain recovery device according to claim 1, wherein the shroud is made of a titanium alloy.