JP4673743B2 - Steam turbine connecting pipe - Google Patents

Description

  The present invention relates to a steam turbine connecting pipe that guides steam flowing out from a final stage outlet of a high pressure turbine or an intermediate pressure turbine to a plurality of low pressure turbines.

  Some steam turbines have a steam turbine connecting pipe that guides the steam flowing out from the final stage outlet of the high-pressure turbine or the intermediate-pressure turbine to a plurality of low-pressure turbines (see Patent Document 1, etc.).

Japanese Patent Laid-Open No. 11-229818

  In this type of steam turbine connecting pipe, the turbines are often connected coaxially. In this case, the steam that has flowed upward from the exhaust chamber of the high-pressure or medium-pressure steam turbine passes through the main steam pipe to the rotating shaft. It is configured such that a part of the steam flowing through the main steam pipe is guided to another low-pressure turbine by a branch pipe branched downward in the middle of the main steam pipe. It is common.

  However, the steam that is diverted from the main steam pipe to the branch pipe that branches downward is changed in the flow path direction and is accompanied by pressure loss. This pressure loss increases as the turning angle when the steam flowing through the main steam pipe flows into the branch pipe increases. Therefore, it is desirable that the branch angle of the branch pipe with respect to the main steam pipe is small.

  However, since the branch pipe is usually branched from a straight pipe portion where the diameter of the main steam pipe is constant, the end face shape of the inlet portion (connection portion with the main steam pipe) becomes longer as the branch angle is reduced. The elliptical shape has a large deviation between the radius and the short radius, and the bending moment generated in this part becomes large. In order to suppress the stress generated at the pipe inlet when the branch angle of the branch pipe relative to the main steam pipe is reduced, it is normal to increase the wall thickness of the branch pipe inlet or to provide a reinforcing member. This was a factor in increasing the thermal stress due to the increase in the weight and thickness of the connecting pipe.

  The present invention has been made in view of the above, and it is possible to improve the turbine performance by reducing the branching angle of the branch pipe relative to the main steam pipe while minimizing the increase in the thickness of the branch pipe and the increase in thermal stress. An object of the present invention is to provide a steam turbine connecting pipe that can be used.

(1) In order to achieve the above object, the present invention provides a steam turbine connecting pipe that guides steam flowing out from the final stage outlet of a high-pressure turbine or intermediate-pressure turbine to a plurality of low-pressure turbines. Connecting the final stage outlet and the inlet of the one low-pressure turbine to guide the steam flowing out from the final-stage outlet to the one low-pressure turbine, in the middle of the straight pipe portion arranged almost horizontally A main steam pipe having a constricted portion that reduces the pipe diameter toward the downstream side of the steam flow direction, and one of the steam flowing through the main steam pipe that branches downward from the main steam pipe and is connected to another low-pressure turbine. part a intended to lead to the other low-pressure turbine, an upstream end, the respect to the center line on the inclined portion with respect to a center line of the main steam pipe of the diaphragm portion of the main steam pipe How steam flows in the main steam pipe Characterized in that a partial branch pipes that are connected by inclined on the downstream side of the.

  (2) In the above (1), preferably, in the main steam pipe, the pipe center line of the portion of the straight pipe portion on the downstream side of the throttle portion is more than the pipe center line of the portion on the upstream side of the throttle portion. It is characterized by being eccentric upward.

  According to the present invention, the branching angle of the branch pipe with respect to the main steam pipe can be reduced while minimizing the increase in the thickness of the branch pipe and the increase in thermal stress, so that the pressure loss of the steam can be reduced. Turbine performance can be improved.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view illustrating a schematic configuration of a steam turbine connecting pipe according to an embodiment of the present invention, and FIG. 2 is an external view illustrating an extracted main part of the steam turbine connecting pipe according to an embodiment of the present invention. 3 is a cross-sectional view taken along the line II-II in FIG.
The present invention relates to a steam turbine connecting pipe that distributes steam from an outlet of a high-pressure or intermediate-pressure turbine to inlets of a plurality of low-pressure turbines. In the present embodiment, as shown in FIG. A case where the steam flowing out from the final stage outlet of the intermediate pressure turbine is led to two low pressure turbines will be described as a representative example.

  In FIG. 1, the steam turbine connecting pipe 1 includes a main steam pipe 10 that connects the final stage outlet of the intermediate pressure turbine 50 and the inlet of the first low pressure turbine 60, and a second branch branched downward from the main steam pipe 10. And a branch pipe 20 connected to the low-pressure turbine 70.

  The main steam pipe 10 guides the steam S <b> 1 emitted from the final stage moving blade 51 of the intermediate pressure turbine 50 to the first low pressure turbine 60, and the inlet portion 11 rises upward from the exhaust chamber 52 of the intermediate pressure turbine 50. , A turning portion 12 that continues to the inlet portion 11 and turns the flow direction substantially horizontally, and a straight pipe portion 13 that continues to the turning portion 12 and extends substantially parallel to the shafts of the intermediate pressure turbine 50 and the low pressure turbines 60, 70, A turning portion 14 that continues to the straight pipe portion 13 and turns downward in the flow path direction, and an outlet portion 15 that continues to the turning portion 14 and connects to the inlet of the first low-pressure turbine 60 are provided.

  The main steam pipe 10 has a throttle part 13a for reducing the pipe diameter in the middle of the straight pipe part 13 arranged substantially horizontally, and a large diameter part 13b upstream of the throttle part 13a and the throttle part. It is further divided into a small diameter portion 13c on the downstream side of the portion 13a. The small-diameter portion 13c has its tube center line eccentrically above the tube center line of the large-diameter portion 13b. In the present embodiment, the large-diameter portion 13b and the small-diameter portion 13c have a substantially straight tube wall on the upper side. It is connected via the throttle part 13a so that it may become. The narrowed portion 13a has a pipe wall portion on the lower side whose diameter is reduced downstream with an angle α (0 ° <α <90 °) with respect to a line parallel to the center line of the straight tube portion 13. It is formed to do.

On the other hand, the branch pipe 20 divides a part of the steam S2 flowing through the straight pipe portion 13 of the main steam pipe 10 and leads it to the second low-pressure turbine 70, and its upstream end is the main steam pipe 10. An inlet portion 21 connected to the throttle portion 13 a provided in the straight pipe portion 13, and an outlet portion 22 connected to the second low-pressure turbine 70 at the downstream end portion continuous to the inlet portion 21. The inlet portion 21 is inclined at an angle θ (0 ° < θ <90 °) with respect to a line parallel to the center line of the straight pipe portion 13 and is guided to the lower second low-pressure turbine 70 inside thereof. The steam S3 to be burned is formed so as to have a flow direction component of S2 flowing through the straight pipe portion 13. The branch pipe 20 is more preferable when the angle of attachment of the throttle portion 13a to the pipe wall surface is closer to a right angle (that is, more preferably α + θ = 90 °).

  In the steam turbine connecting pipe 1 configured as described above, the steam that has worked in the intermediate pressure turbine 50 and has flowed out of the intermediate pressure final stage moving blade 51 flows into the intermediate pressure exhaust chamber 52, It is introduced into the inlet 11. The steam S <b> 1 is turned almost horizontally at the turning portion 12 and flows into the straight pipe portion 13. A part of the steam S2 flowing through the large diameter part 13b of the straight pipe part 13 is throttled by the throttle part 13a, flows into the small diameter part 13c and flows in the horizontal direction as it is, and the other part is shunted downward to branch the pipe 20. Flows into the inlet portion 21. The steam S3 that has flowed into the inlet portion 21 of the branch pipe 20 is guided to the second low-pressure turbine 70 via the outlet portion 22, and the steam S4 that has flowed into the small diameter portion 13c of the straight pipe portion 13 is lowered at the turning portion 14. To the first low-pressure turbine 60 through the outlet 15 (steam S5).

Here, FIG. 4 is a sectional view showing a schematic configuration of a general steam turbine connecting pipe. However, in FIG. 4, the same reference numerals are given to the same parts as those in FIG.
In the steam turbine communication pipe 1 ′ shown in FIG. 4, the branch pipe 20 ′ is branched from the large diameter part 13 b in the straight pipe part 13 of the main steam pipe 10. The branch pipe 20 ′ is connected substantially perpendicularly to the lower part of the pipe wall surface of the large-diameter portion 13 b (angle θ is about 90 °), and extends vertically downward to connect to the second low-pressure turbine 70.

  In such a configuration, since the branch pipe 20 ′ is connected to the main steam pipe 10 at a substantially right angle, a large pressure loss is generated in the steam that changes the flow direction in the portion where the steam is diverted. In order to reduce the pressure loss, as shown in the steam turbine connecting pipe 1 ″ shown in FIG. 5, the inlet portion 21 ′ of the branch pipe 20 ′ is connected so that the branch angle θ becomes smaller with respect to the large diameter portion 13b. However, when the branch pipe 20 ′ is inclined and connected to the straight pipe portion 13 in this manner, the cross-sectional shape of the connection portion with respect to the large diameter portion 13b of the inlet portion 21 ′ of the branch pipe 20 ′ is as shown in FIG. (Fig. 6 is a cross-sectional view taken along line VI-VI in Fig. 5) An elliptical shape having a large deviation between the major radius a2 and the minor radius b2 is obtained. The stress distribution on the tube wall becomes non-uniform and the bending moment generated in this part becomes large.In this case, measures such as increasing the size of the reinforcing member that reinforces the tube and increasing the wall thickness of the connecting tube are required. This increases the weight of the steam turbine connecting pipe or Increase due to has been a factor causing an increase in heat stress.

  On the other hand, according to the present embodiment, in the steam turbine connecting pipe that leads the steam flowing out from the final stage outlet of the intermediate pressure turbine to the low pressure turbine of at least two compartments, the branch position of the branch pipe 20 is set to the main steam pipe. The branch pipe 20 is connected to the pipe wall of the throttle part 13a of the main steam pipe 10 so as to coincide with the throttle position of 10, thereby reducing the branch angle θ.

  That is, when the branching angle θ of the branch pipe 20 is reduced by connecting to the lower wall surface of the throttle part 13a inclined at an angle α with the large diameter part 13b or the small diameter part 13c of the main steam pipe 10, The attachment angle (α + θ) of the branch pipe 20 with respect to the pipe wall can be closer to 90 ° than in the configuration example of FIG. As a result, the cross-sectional shape of the connecting portion (for example, a welded portion) of the branch pipe inlet portion 21 can also be a shape close to a circle having a small deviation between the major radius a1 and the minor radius b2, as shown in FIG.

  Thereby, the stress which generate | occur | produces in the branch pipe entrance part 21 can be equalize | homogenized, and sufficient intensity | strength can be ensured, suppressing the increase in a plate pressure to the minimum and suppressing the increase in a thermal stress. Therefore, the branching angle θ of the branch pipe 20 with respect to the main steam pipe 10 can be made smaller without any special reinforcement and without increasing the weight, and the pressure loss due to the branching of the steam flow is reduced. The turbine performance can be improved.

  Further, in the present embodiment, the narrowed portion 13a is formed so that the small-diameter portion 13c of the straight pipe portion 13 is decentered upward from the large-diameter portion 13b. Since the flow path is narrowed by inclining the tube wall, the narrowing angle α of the narrowed portion 13a can be made larger than when the narrowed portion 13a is formed in a substantially conical shape. Therefore, it is advantageous in reducing the branching angle θ, and when the branching angle θ is reduced, the cross section of the branch pipe inlet portion 21 can be brought closer to a circle having a smaller deviation between the major radius a1 and the minor radius b1. Therefore, there is a great merit by reducing the pressure loss and making the generated stress uniform.

  In the present embodiment, as described above, the straight pipe portion 13 is configured such that the center line of the small diameter portion 13c is decentered upward from the center line of the large diameter portion 13b with the throttle portion 13a interposed therebetween. As shown in FIG. 7, even when the throttle portion 13a is formed in a substantially conical shape so that the center lines of the large diameter portion 13b, the throttle portion 13a, and the small diameter portion 13c coincide, By connecting the inlet 21 of the branch pipe 20, the cross section of the branch pipe inlet can be made closer to a circle than when the branch pipe inlet is connected to the pipe wall of the large diameter portion 13b with an inclination angle, for example. The effect close to the embodiment shown in FIGS. 1 to 3 can be obtained.

  Further, as shown in FIG. 7, a further reduction in pressure loss can be expected by connecting the inlet portion 21 and the outlet portion 22 of the branch pipe 20 with a smooth curved pipe having no corners. The same applies to both ends of the throttle 13a.

  Further, in the above description, the case where the present invention is applied to the steam turbine connecting pipe that diverts the steam emitted from the intermediate pressure turbine to the two low pressure turbines is described as an example. Steam turbine connecting pipe that leads steam from a high-pressure turbine to multiple medium-pressure turbines or low-pressure turbines, and steam turbine connecting pipe that guides steam from an intermediate-pressure or high-pressure turbine to three or more medium-pressure or low-pressure turbines The present invention is also applicable, and the same effect can be obtained.

It is sectional drawing showing schematic structure of the steam turbine connecting pipe which concerns on one embodiment of this invention. It is an external view which extracts and represents the principal part of the steam turbine connecting pipe which concerns on one embodiment of this invention. It is sectional drawing by the II-II cross section in FIG. It is sectional drawing showing schematic structure of a general steam turbine connecting pipe. It is an external view which extracts and represents the principal part of a general steam turbine connecting pipe. It is sectional drawing by the VI-VI cross section in FIG. It is an external view which extracts and represents the principal part of the steam turbine connecting pipe which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steam turbine connecting pipe 10 Main steam pipe 13 Straight pipe part 13a Restriction part 13b Large diameter part 13c Small diameter part 20 Branch pipe 50 Medium pressure turbine 51 Final stage moving blade 60 1st low pressure turbine 70 2nd low pressure turbine S1-5 Steam

Claims (2)

In the steam turbine connecting pipe that leads the steam flowing out from the final stage outlet of the high pressure turbine or the intermediate pressure turbine to a plurality of low pressure turbines,
The final stage outlet of the high-pressure turbine or intermediate-pressure turbine is connected to the inlet of one low-pressure turbine, and the steam flowing out from the final-stage outlet is led to the one low-pressure turbine, and is disposed substantially horizontally. A main steam pipe having a throttle part that reduces the pipe diameter toward the downstream side in the steam flow direction in the middle of the straight pipe part;
The main steam pipe is branched downward from the main steam pipe and connected to another low-pressure turbine to guide a part of the steam flowing through the main steam pipe to the other low-pressure turbine, and its upstream end is the main steam. and the main steam pipe the main steam pipe that is connected to be inclined to the downstream side of the flow direction of the steam partial branch pipes with respect to the center line on the inclined portion with respect to the center line of the aperture of the tube A steam turbine connecting pipe characterized by comprising.   2. The steam turbine connecting pipe according to claim 1, wherein the main steam pipe has a pipe center line of a portion downstream of the throttle portion of the straight pipe portion above a pipe center line of a portion upstream of the throttle portion. A steam turbine connecting pipe characterized by being eccentric.

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