JP2007270751A - Steam turbine nozzle box and steam turbine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a steam turbine nozzle box capable of easily removing intermixture adhered and accumulated on inside of the steam turbine nozzle box to reduce troubles caused by the intermixture such as boiler oxidized scale included in a main stream. <P>SOLUTION: Inside the steam turbine nozzle box 2, a closable through-hole 12 for operation communicated with a steam inflow space of the steam turbine nozzle box 2 is formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a steam turbine nozzle box and a steam turbine including the nozzle box.

  FIG. 12 is a diagram showing an example of a cross-sectional assembly diagram of a large steam turbine. In such a large steam turbine, high-pressure and high-temperature steam supplied from a boiler passes through a main steam pipe 1 to a ring-shaped nozzle box 2. After being guided, it flows through the speed-control stage stationary blade 3 and the speed-control blade 4 arranged in the circumferential direction integrally with the nozzle box 2 and flows to a plurality of blade rows arranged downstream thereof, pressure, Turbine power is generated while lowering the temperature.

  In the steam turbine having such a structure, the oxide scale or the like generated on the inner wall of the boiler is peeled and dropped and is carried into the nozzle box 2 together with the main steam, and a part of this is accumulated in the nozzle box 2 and the rest is the nozzle box. 2 to the speed-control stage stationary blade 3, the speed-control blade 4, and a plurality of subsequent paragraph groups, eroding the blade surface and progressing the deterioration of the blade surface roughness, leading to a rapid decrease in turbine performance. FIG. 13 schematically shows the deposit 5 on the high-pressure blade tip shroud side observed during the periodic inspection. This deposit is mainly composed of oxide scale that originates from the boiler or peels off the upstream blade surface, and the oxide scale, etc. flying from the upstream side during steam turbine operation is trapped in the corner on the blade tip shroud side by centrifugal force. It has been done.

  FIG. 14 is an explanatory view schematically showing the state of contaminants accumulated in the steam turbine nozzle box 2, wherein (a) is a sectional view of the nozzle box 2 as viewed from the front, and (b) is the nozzle box 2. Is a cross-sectional view as seen from the side, and contaminants such as oxide scales generated and peeled off on the boiler inner wall flow into the nozzle box 2 of the steam turbine together with the main steam. The main steam reversely turns inside the nozzle box 2 and flows out from the governing stage stationary vane 3, but the contaminants 5 that form large particles that cannot follow this mainstream flow are caused by the inertial force on the inner peripheral wall of the nozzle box 2. It is carried to the side, adheres to the inner wall of the nozzle box 2, and accumulates at the corner inside the nozzle box 2, particularly at the bottom corner located below in the vertical section as the main steam flows. Therefore, if these deposits 5 are not removed at any time during periodic inspections, a large amount of these deposits 5 are mixed and flown into the main steam when the operation is resumed, and the blade cascade located in the subsequent stage is eroded and the turbine performance is deteriorated. It will be accelerated. However, as described above, since the contaminants are often accumulated at the corners in the nozzle box 2, it is difficult to access from the main steam pipe 1 side, and a sufficient removal operation cannot be performed.

  Conventionally, it has been proposed to provide a bell mouth at the inlet of the governing stage stationary blade so as to reduce the pressure loss of the flow in the steam turbine nozzle box (see Patent Document 1). For the purpose of reducing the flow pressure, it has also been proposed to form the inlet wall on the outer peripheral side of the speed-control stage stationary blade and the inner peripheral side of the speed-control stage stationary blade in a curved shape, and use the throttle stage stationary blade inlet as a throttle channel (Patent Document 2). reference). Further, in the steam turbine in which a plurality of steam chambers are defined by a plurality of partition plates extending radially in the casing, a small hole is provided in the partition plate so that the steam chambers communicate with each other. It has also been proposed to blow off solid particles accumulated near the nozzle upstream by steam ejected from the nozzle (see Patent Document 3).

However, those described in the above patent documents are not designed to remove the accumulated matter accumulated in the nozzle box to prevent the deterioration of the turbine performance, and the accumulated matter flows out of the nozzle box. It has not taken any measures to prevent this.
JP-A-8-14003 JP 10-14003 A Japanese Utility Model Publication No. 61-23601

  In view of these points, the present invention is capable of easily removing contaminants deposited and deposited inside the steam turbine nozzle box in order to reduce harmful effects caused by contaminants such as boiler oxide scale contained in the main steam. In order to reduce the harmful effects of these contaminants during operation, the outflow of these contaminants was prevented in the steam turbine nozzle box. The object is to obtain a steam turbine nozzle box.

  The first invention is characterized in that the steam turbine nozzle box is formed with a work through-hole that can be closed and communicated with a steam inflow space of the steam turbine nozzle box.

  The second invention is characterized in that a dustproof plate is further provided in the steam inflow space of the steam turbine nozzle box.

  According to a third aspect of the present invention, in the steam turbine, the steam turbine nozzle box according to any one of the first and second aspects is provided.

  For example, a suction machine is used to easily remove deposits in which main steam collides directly and deposits of many contaminants such as oxide scales from the work through-holes during periodic inspections. When the operation is resumed, a large amount of these deposits 5 are mixed and flown into the main steam, eroding the blade cascade located in the subsequent stage, and preventing the turbine performance from being deteriorated. Can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  FIG. 1 is a cross-sectional view of the nozzle box according to the first embodiment of the present invention as viewed from the front, and a steam turbine nozzle box in which main steam is supplied from four main steam pipes (two at the top and two down). 2 shows the upper half casing side. The arch type nozzle box has a configuration in which each main steam pipe is partitioned at about 90 degrees inside.

  In the present embodiment, in the steam turbine nozzle box, the joint surface 11 of the upper half casing and the lower half casing of each of the first chamber 10a and the second chamber 10b of the nozzle box with which the steam main steam pipe 1 communicates is provided. A work through hole 12 is provided for effectively removing the accumulated deposit 5 such as the boiler oxide scale from the nozzle box. The working through-hole 12 can be closed using a closing member such as a closing screw 13 so that unnecessary steam does not leak during operation.

  Since the working through hole 12 is provided on the joining surface 11 of the upper half casing and the lower half casing of the nozzle box as described above, even if a malfunction occurs in the closing portion during operation of the steam turbine, the joining surface is provided. Therefore, it is possible to prevent a risk that high-pressure steam leaks, and to maintain high sealing performance even during operation of the steam turbine.

  On the other hand, from the casing joint surface 11 side where the main steam collides directly and deposits a large amount of contaminants such as oxide scale, the above-described operation is performed using, for example, a suction machine through the working through-hole 12 during periodic inspection. The deposit 5 can be easily removed. Therefore, a large amount of these deposits 5 are mixed and flown into the main steam when the operation is resumed, and the blade row located in the subsequent stage can be eroded to prevent the turbine performance from deteriorating, realizing a long-term healthy operation of the steam turbine. can do.

  FIG. 2 is a diagram showing a second embodiment of the present invention, and shows a case where the present invention is applied to a type of nozzle box having four rooms only on the upper half casing side. The arch type nozzle box is partitioned at about 45 degrees, and a first chamber 10a, a second chamber 10b, a third chamber 10c, and a fourth chamber 10d are formed. The first chamber 10a, the second chamber 10b, the third chamber 10c, and the fourth chamber 10d are provided with working through holes 12 that can be closed using a closing member such as a closing screw 13 on the inner peripheral wall 14 side. It has been.

  Thus, the inner wall of the casing joint surface where the main steam that easily deposits contaminants such as oxide scale directly collides and the deposit 5 at the corner of the nozzle box are used from the work through-hole 12 using, for example, a suction device. And can be easily removed. Therefore, a large amount of these deposits 5 are mixed and flown into the main steam when the operation is resumed, and the blade row located in the subsequent stage can be eroded to prevent the turbine performance from deteriorating, realizing a long-term healthy operation of the steam turbine. can do. In addition, even when a malfunction occurs in the closing portion during operation of the steam turbine, the sealing performance is maintained with the rotor seal packing (not shown), so that it is possible to prevent a danger that high-pressure steam leaks.

  FIG. 3 is a view showing a third embodiment of the present invention, in which the lower half casing side of the nozzle box 2 has a work penetration that can be closed by using a closing member such as a closing screw on the outer peripheral wall 15 side. A hole 12 is provided. Thus, the deposit 5 at the corner of the nozzle box where contaminants such as oxide scale easily accumulate in the lower half casing can be easily removed from the working through-hole 12 using, for example, a suction machine. . Therefore, the same effects as those of the first embodiment are obtained.

  FIG. 4 is a view showing a fourth embodiment of the present invention, in which a closing member such as a closing screw 13 is used on the joint surface 11 and outer peripheral wall 15 side of the upper half casing and the lower half casing of the nozzle box 2. A work through hole 12 that can be closed is provided. Further, in FIG. 5, work through-holes 12 are respectively provided on the joint surface 11 and the inner peripheral wall 14 side of the upper half casing and the lower half casing of the nozzle box 2. Therefore, in these cases, by providing at least two or more working through holes 12 in one steam inflow space of the nozzle box, the nozzle box in which main steam that easily deposits contaminants such as oxide scale directly collides. The deposits 5 at the corners of the inner wall and the nozzle box can be more easily removed from the working through hole 12 using, for example, a suction machine.

  By the way, by using the working through hole 12 as described above, it is possible to effectively remove deposits such as oxide scale accumulated in the nozzle box at the time of periodic inspection. However, if the amount of outflow to the downstream side of such boiler-derived oxide scale or the like can always be reduced during operation, it is possible to suppress erosion of the blade row group located subsequent thereto.

  FIG. 6 and FIG. 7 are views showing a fifth embodiment invented to meet such a demand, and deposits such as oxide scale accumulated in the nozzle box 2 inside the nozzle box 2. A dustproof plate 16 is provided to prevent 5 from flowing out of the nozzle box 2, and the work through hole 12 is provided in the inner peripheral wall portion 14 of the nozzle box 2. The dust-proof plate 16 has a substantially arc shape in cross section, and as shown in FIG. 7, is attached to the inner peripheral side of the speed-control stage stationary blade inlet so as to cover the entire area of the speed-control stage stationary blade inlet. In the nozzle box 2, the main steam flows toward the inner peripheral wall of the nozzle box 2 so as to wind up the accumulated material 5, and the accumulated material 5 is moved to the destination by the dustproof plate 16. The amount of sediment 5 flowing out of the nozzle box 2 is reduced, the erosion of the downstream blade row group can be suppressed, and the nozzle box can be used by using the work through-hole 12 at the time of periodic inspection. 2 can be effectively removed, so that erosion of the downstream blade row group can be suppressed during operation and when operation is resumed, and long-term sound operation of the steam turbine is possible. Become. Further, as shown in FIGS. 80 and 9, at least two working through holes 12 can be provided in one steam inflow space of the nozzle box 2, and in this case as well, the fourth embodiment and the sixth embodiment are provided. The same effect as the embodiment is achieved.

Sectional drawing which looked at the nozzle box in the 1st Embodiment of this invention from the front. The longitudinal cross-sectional view which shows the 2nd Embodiment of this invention. The figure which shows Embodiment 3 of this invention. The figure which shows the example which provided the through-hole for work of this invention in the joint surface of a casing, and the outer peripheral wall side of a nozzle box. The figure which shows the example which provided the through-hole for work of this invention in the joint surface of a casing, and the inner peripheral wall side of a nozzle box. Sectional drawing of the nozzle box which shows other embodiment of this invention. Sectional drawing of the nozzle box shown in FIG. Sectional drawing of the nozzle box which shows other embodiment of this invention. Sectional drawing of the nozzle box shown in FIG. Sectional assembly drawing of a large steam turbine. The figure which showed typically the deposit by the side of the high voltage | pressure stage blade tip shroud observed at the time of a periodic inspection. It is a figure which shows typically the mode of the contaminant accumulate | stored in the conventional nozzle box, (a) is sectional drawing which looked at the nozzle box from the front side, (b) looked at the nozzle box from the side. Sectional drawing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main steam piping 2 Nozzle box 3 Adjusting stage stationary blade 4 Adjusting stage moving blade 5 Deposit 10a, 10b, 10c10d The 1st chamber of the nozzle box, the 2nd chamber, the 3rd chamber, the 4th chamber 11 Upper half casing and lower half Casing surface 12 Working through-hole 13 Closing member 14 Inner wall side 15 Outer wall side 16 Dustproof plate

Claims (8)

  A steam turbine nozzle box, wherein the steam turbine nozzle box is connected to a steam inflow space of the steam turbine nozzle box and has a work through hole that can be closed.   2. The steam turbine nozzle box according to claim 1, wherein the working through hole is provided in a joint surface between an upper half side and a lower half side of the casing of the nozzle box.   The steam turbine nozzle box according to claim 1, wherein the working through hole is provided on an inner peripheral wall side of the nozzle box.   The steam turbine nozzle box according to claim 1, wherein the working through hole is provided on an outer peripheral wall side of the nozzle box.   5. The steam turbine nozzle box according to claim 1, wherein at least two working through holes communicating with the steam inflow space of the steam turbine nozzle box are formed.   The steam turbine nozzle box according to any one of claims 1 to 5, wherein a dustproof plate is provided in a steam inflow space of the steam turbine nozzle box.   The steam turbine nozzle box according to claim 6, wherein the dust-proof plate is provided on the inner peripheral side of the speed-control stage stationary blade inlet.   A steam turbine comprising the steam turbine nozzle box according to claim 1.

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