JP4627217B2 - Turbine exhaust system - Google Patents

Description

  The present invention relates to a turbine exhaust device that guides a steam flow that has passed through the final stage of a steam turbine to a condenser that is provided below.

  As described in Patent Document 1 and the like, in a steam turbine facility having a condenser, generally, steam (exhaust gas) that has worked inside the turbine is guided to a turbine exhaust device, and the final stage outlet ring zone of the turbine rotor. After passing through an annular diffuser formed by a bearing cone and a steam guide respectively extending from the inner peripheral portion and the outer peripheral portion, it diffuses downward and is led downward into the condenser and returned to the water. Steam recovers pressure in the exhaust chamber, but the internal pressure of the condenser is generally defined by the temperature and flow rate of the cooling water. Therefore, the larger the pressure recovery width in the exhaust chamber, the lower the turbine outlet pressure. The workload is increased and the turbine efficiency is improved. Therefore, the pressure recovery performance of the exhaust chamber greatly affects the turbine plant performance.

JP-A-8-260904

  In the turbine exhaust system configured as described above, it is necessary to secure the axial length of the rotor along with the expansion of the appropriate area in order to make the annular diffuser work efficiently. In practice, however, the axial length of the entire turbine equipment is shortened. For this reason, the axial length of the exhaust chamber cannot be made long, and the steam flow leaving the final stage of the low-pressure turbine is turned from the axial direction to the radial direction at a short distance.

  The steam flow leaving the last stage of the low-pressure turbine can be broadly divided into an upward flow that flows to the upper half casing side of the exhaust chamber, a lateral flow that flows in the width direction of the exhaust chamber, and a downward flow that flows toward the condenser located below. . The upper flow exits the steam guide and reverses toward the turbine inlet side, and then merges with the lower flow along the exhaust chamber outer casing. The side flow also spreads in the exhaust chamber width direction, joins the lower flow, and is guided to the condenser. In this way, the lower opening of the exhaust chamber outer casing is a flow field in which the upper flow and the side flow are mixed except for the flow region of the lower flow that goes out of the steam guide and goes directly to the condenser. Pressure loss is likely to occur due to stagnation and interference in the merge area.

  An object of the present invention is to provide a turbine exhaust device that can suppress the stagnation and interference of the exhaust flow in the exhaust chamber and improve the turbine efficiency.

(1) In order to achieve the above object, the present invention provides a turbine exhaust device for guiding a steam flow that has passed through a final stage of a steam turbine to a condenser provided below the steam turbine, wherein the turbine rotor of the steam turbine is provided. An exhaust chamber outer casing composed of an upper half casing surrounding the upper half of the upper half casing and a lower half casing connected to the lower side of the upper half casing. The lower half casing is connected via a connecting cylinder that expands downward. The width of the condenser connected to the condenser and taken in a direction perpendicular to the axis of the turbine rotor is Wc, and the diameter of the circle drawn by the blade length direction center of the last stage rotor blade of the steam turbine Is the PCD, the exhaust chamber width W of the lower half casing taken in the same direction is configured to satisfy the conditions of W <Wc, W / PCD ≧ 3 To do.

(2) In the above (1), preferably, based on an exhaust chamber outer casing in which a ratio W / PCD of the exhaust chamber width W and the turbine final stage blade height central diameter PCD is set to less than 3, The upper half casing is formed so that a height dimension is substantially the same as the reference, and a radius of curvature of a cross section along a plane orthogonal to the axis of the turbine rotor is larger than the reference. Features.

(3) In the above (1), preferably, an exhaust chamber outer casing in which a ratio W / PCD of the exhaust chamber width W to the turbine final stage blade height central diameter PCD is set to less than 3 is used as a reference. The upper half casing has a width direction dimension larger than the reference while maintaining a height dimension at the reference level by providing a flat end portion in the center of the width direction of the ceiling surface. Features.

  (4) In the above (1), and preferably, a line extending radially from the center of rotation of the turbine rotor is provided continuously to the inner peripheral portion of the outlet of the casing inside the exhaust chamber containing the turbine rotor. A steam guide formed so that an outermost peripheral portion is positioned closer to the turbine rotor than a bisection position of a line segment connecting two points intersecting the outer peripheral portion of the outlet ring zone and the inner wall surface of the outer casing. It is characterized by.

  According to the present invention, it is possible to reduce the pressure loss by suppressing the flow interference and the like, suppress the stagnation and interference of the exhaust flow in the exhaust chamber, and improve the turbine efficiency.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a side sectional view of a turbine exhaust system according to an embodiment of the present invention. FIG. 2 is a front view showing a part of the appearance viewed from the right side in FIG. The vessel is also shown.
The illustrated turbine exhaust device is configured to drive the turbine rotor 1 and guide the steam flow that has passed through the final stage of the steam turbine to a condenser 20 provided below the steam turbine. The turbine exhaust device is connected to a condenser together with an exhaust chamber casing 2 containing the turbine rotor 1, a bearing cone 3 covering a bearing (not shown) of the turbine rotor 1, and the exhaust chamber casing 2 and the bearing cone 3. An exhaust chamber outer casing 5 that forms the exhaust chamber 4 and a steam guide 6 that forms an annular diffuser channel with the bearing cone 3 are provided.

  The exhaust chamber inner casing 2 includes a stationary blade (only the final stage stationary blade 7 is shown) supported by a diaphragm outer ring and an inner ring on the inner peripheral side thereof, and a moving blade (final stage moving blade 8) installed in the turbine rotor 1. Only the turbine stage is formed. In general, a diaphragm (not shown), which is a mounting portion of a stationary blade, is provided in an annular shape on the inner peripheral side of the exhaust chamber inner casing 2. The stationary diaphragm arranged in a ring and the turbine rotor 1 on the rotating side are opposed to each other with an appropriate gap.

  The exhaust chamber outer casing 5 covers the exhaust chamber inner casing 2 and the bearing cone 3, and surrounds the upper portion of the turbine rotor 1 and the lower half casing 11 connected to the lower side of the upper half casing 10. It is made up of. The upper half casing 10 and the lower half casing 11 are divided into upper and lower portions at a height near the horizontal plane including the central axis of the turbine rotor 1. As shown in FIG. 2, the outer wall surface of the upper casing has an arcuate ceiling when viewed in a cross section along a plane orthogonal to the axis (center axis) O of the turbine rotor 1. One lower casing is formed of a frame having a rectangular horizontal cross section and a constant cross sectional area in the vertical direction, and is connected to the condenser 20 via a connecting cylinder 21 whose diameter increases toward the lower side. . The exhaust chamber 4 described above is formed by being surrounded by the exhaust chamber outer casing 5, the exhaust chamber inner casing 2, and the bearing cone 3.

  The bearing cone 3 is continuously provided on the inner peripheral portion of the outlet ring zone 13 of the final stage moving blade 8 of the turbine rotor 1. The steam guide 6 is continuously provided on the outer peripheral portion of the final stage moving blade outlet annulus 13 so as to surround the outer peripheral side of the bearing cone 3. The annular diffuser flow path formed between the steam guide 6 and the bearing cone 3 drives the turbine rotor 1 to blow out the exhaust gas that has passed through the outlet ring zone 13 of the final stage moving blade 8 into the exhaust chamber 4. . Further, the diffuser flow path formed by the steam guide 6 and the bearing cone 3 has a gradually increased flow area, and when passing through the diffuser flow path, the exhaust is decelerated and the energy of the deceleration is converted into pressure. The exhaust pressure is restored.

A major feature of the turbine exhaust device according to this embodiment having the above-described configuration is the configuration of the exhaust chamber outer casing 5. Specifically, the exhaust chamber outer casing 5 is configured such that the exhaust chamber width W of the lower half casing 11 taken in the direction orthogonal to the axis O of the turbine rotor 1 is Wc, and the width of the condenser 20 taken in the same direction is Wc, When the diameter of the circle C drawn by the center in the length direction of the blade length BH of the last stage moving blade 8 is PCD,
W <Wc (Formula 1)
W / PCD ≧ 3 (Formula 2)
Thus, the lower opening of the exhaust chamber outer casing 5 is widened to ensure a sufficient flow path area.

  In the turbine exhaust device of the present embodiment, the exhaust gas blown from the steam guide 6 to the exhaust chamber 4 spreads radially. Exhaust gas (downward flow 30) blown out from the lower half side of the steam guide 6 goes to the condenser 20 below as it is without changing the traveling direction so much. On the other hand, the exhaust gas (upward flow 31) blown out from the upper half side of the steam guide 6 reverses the traveling direction from the steam guide 6 to the turbine inlet side, and then turns downward along the upper half casing 10 to move downward. Join the stream 30 and head to the condenser 20. Although not shown in the drawing, the lateral flow that exits the steam guide 6 and extends in the horizontal direction turns downward while spreading in the width direction in the exhaust chamber 4, and then joins the downward flow and is guided to the condenser 20. .

  Thus, in the lower opening of the exhaust chamber outer casing 5, there is a tendency that the flow from the upper side and the side flow are mixed except for the flow region of the lower flow 30, and the pressure loss is caused by the stagnation of the flow and the interference of the merge region. Although it is easy to occur, in this embodiment, since the exhaust chamber outer casing 5 is formed so as to satisfy the conditions of the above (Formula 1) and (Formula 2), the flow area of the lower opening is sufficiently secured, In addition, the exhaust chamber 4 and the condenser 20 can be connected by a connecting cylinder 21 whose diameter increases as it goes downward, and an enlarged flow path can be formed. Therefore, the upward flow and the lateral flow after exiting the steam guide 6 can be efficiently turned downward, and the pressure loss can be reduced by suppressing the flow interference and the like, thereby providing a high pressure recovery coefficient. As a result, the turbine efficiency can be improved.

The selection of the exhaust chamber width W will be described.
In general, because the turbine building is narrow and does not have enough space, it is difficult to ensure a sufficient distance between the exhaust chamber ceiling and the turbine exit annulus, and the distance between the exhaust chamber ceiling and the turbine exit annulus becomes short. Tend to. In general, the shorter the distance between the ceiling of the exhaust chamber and the turbine outlet ring zone, the more of the flow exiting the exhaust chamber flows out from the lower half side of the steam guide.

  Therefore, in the present embodiment, first, a rectangular region having a short side as the distance L from the lower end of the steam guide 6 to the end surface of the lower half casing 11 facing the axial direction in the axial direction and a long side as the exhaust chamber width W is set downward. It is defined as a flow path through which the flow 30 flows. Further, the outflow area of the flow path of the lower flow 30 is Ao (= L × W), and the final stage motion obtained by the product of the blade height BH, the blade height center diameter PCD, and the circumferential ratio π of the final stage rotor blade 8. Let the area of the blade exit annulus 13 be Ai (= π × PCD × BH). At this time, if the flow path area Ao is larger than the final-stage exit annulus area Ai, the flow flowing out from the lower half side of the steam guide 6 is smoothly fed into the condenser 20 without interfering with other flows. .

From the above, the following (Formula 3) is established.
Ao / Ai = L × W / (π × PCD × BH)> 1 (Equation 3)
Further, since BH is generally the same as L, (Equation 3) can be generalized as the following equation.
Ao / Ai = W / (π × PCD)> 1 (Formula 4)
In Equation (4), when the circumference ratio π is 3, the above (Formula 2) is obtained.

The relationship between the exhaust chamber width W and the condenser width Wc will be described.
If the exhaust chamber width W is larger than the condenser width Wc (W> Wc), the flow area of the exhaust introduced into the condenser 20 from the exhaust chamber 4 is reduced in diameter downward, and the exhaust is compressed. This is not preferable. On the other hand, when the exhaust chamber width W is equal to the condenser width Wc (W = Wc), a straight wall surface in which the side wall surface of the exhaust chamber 4 and the wall surface of the condenser 20 are continuous is formed. In this case, the exhaust gas turning and flowing out from the exhaust chamber 4 along the side wall surface of the casing flows as it is along the side wall surface of the connecting cylinder 21 and the condenser 20, and the exhaust gas may drift near the wall surface.

  On the other hand, when W <Wc as in the present embodiment, the connecting cylinder 21 does not become a compression flow path, and the flow rate distribution of the exhaust gas that is turned from the exhaust chamber 4 along the side wall of the casing flows out to the connecting cylinder 21. It is made uniform when flowing in. From this, by forming the exhaust chamber outer casing 5 so as to satisfy the above (Formula 1) and (Formula 2), a high pressure recovery coefficient can be obtained and the turbine efficiency can be improved.

Furthermore, the effect in this embodiment is verified also by the flow analysis.
FIG. 3 is a graph showing fluctuations in the value of the pressure recovery coefficient Cp when the exhaust chamber width W is adjusted and the range of W / PCD is changed in the range of 2.5 to 4.5.
As shown in FIG. 3, as a result of the analysis, the value of the pressure recovery coefficient Cp is low in the range of W / PCD <3, Cp improves as the value of W / PCD approaches 3, and W / PCD> 3. Cp was almost constant over the range. This also shows that a high pressure recovery count can be obtained by forming the exhaust chamber outer casing 5 so as to satisfy the above (Formula 1) and (Formula 2).

FIG. 4B is a schematic diagram showing an overview structure viewed from the axial direction of a turbine exhaust device according to another embodiment of the present invention, and FIG. 4A is a diagram for explaining the structure. In these drawings, the same parts as those in the previous drawings are denoted by the same reference numerals, and description thereof is omitted.
In the present embodiment, when the exhaust chamber outer casing (see FIG. 4A) with W / PCD set to less than 3 is used as a reference, the upper half casing 10 has a height dimension H as a reference height dimension. While maintaining the same level, the curvature radius R2 of the cross section along the plane orthogonal to the axis of the turbine rotor is formed to be larger than the reference curvature radius R1.

  That is, when the exhaust chamber width is increased from the reference W1 to W2 (> W1), the curvature radius of the upper half casing 10 is changed from the reference R1 to R2 (> R1), and the height dimension H is not changed. The curvature center S is moved downward. Other configurations are the same as those in FIGS.

  By doing in this way, the exhaust chamber outer casing which satisfy | fills said (Formula 2) can be easily formed, making a height dimension comparable as a general thing. Therefore, by putting the exhaust chamber width W2 in a range that satisfies the above (Formula 1), the same effect as the embodiment shown in FIGS. 1 and 2 can be obtained.

FIG. 5B is a schematic diagram showing an overview structure viewed from the axial direction of a turbine exhaust device according to still another embodiment of the present invention, and FIG. 5A is a diagram for explaining the structure. In these drawings, the same parts as those in the previous drawings are denoted by the same reference numerals, and description thereof is omitted.
In the present embodiment, when the exhaust chamber outer casing (see FIG. 5A) with W / PCD set to less than 3 is used as a reference, the upper half casing 10 has a flat end 15 at the center in the width direction of the ceiling surface. Thus, the width dimension W2 is made larger than the reference width dimension W1 while the height dimension H is maintained at the reference height dimension.

  That is, in this embodiment, the general configuration of FIG. 5A serving as a reference is divided into two at the central portion in the width direction, and a size configuration having a flat end portion 15 interposed therebetween. Accordingly, the radius of curvature of the portion 16 located on both sides of the flat end portion 15 is the same radius of curvature R1 as the reference in FIG. 5A, and the exhaust chamber width W2 is wider than the reference width W1 by the width B of the flat end portion 15. (W2 = W1 + B). Other configurations are the same as those in FIGS.

  Even if comprised in this way, an exhaust chamber width | variety can be enlarged without enlarging a height dimension, and the exhaust chamber outer casing which satisfy | fills said (Formula 2) can be formed easily. Therefore, by putting the exhaust chamber width W2 in a range that satisfies the above (Formula 1), the same effect as the embodiment shown in FIGS. 1 and 2 can be obtained. Moreover, in the case of the present embodiment, the internal space of the exhaust chamber can be made larger than that of the embodiment of FIG. 4B (shown by the dotted line in FIG. 5B). Can further reduce the flow loss.

FIG. 6 is a schematic diagram showing an overview structure viewed from the axial direction of a turbine exhaust device according to still another embodiment of the present invention. In this figure, parts similar to those in the previous figures are given the same reference numerals, and description thereof is omitted.
In the present embodiment, the steam guide 6 is continuously provided on the outlet inner peripheral portion (the outer peripheral portion of the final stage rotor blade outlet ring zone 13) of the exhaust chamber inner casing 2, and radially from the rotation center O of the turbine rotor 1. The outermost peripheral part is located closer to the turbine rotor 1 than the bisection position of the line segment connecting the two points where the extending line intersects the outer peripheral part of the final stage rotor blade outlet ring zone 13 and the inner wall surface of the exhaust chamber outer casing 5 respectively. It is formed to do.

  For example, on the line connecting the exhaust chamber outer casing 5 and the rotation center O in a plane orthogonal to the rotation center (center axis) O of the turbine rotor 1, the outer peripheral portion (the inner diameter of the steam guide 6) ) And an intermediate point of the intersection β between the intersection α and the inner surface of the exhaust chamber outer casing 5 is γ. Then, when the intersection point β is moved from the lower end portion of one side wall of the exhaust chamber outer casing 5 to the lower end portion of the other side wall through the ceiling portion, the intermediate point γ becomes a locus A as indicated by a dotted line in FIG. Draw. Since the inner wall surface does not exist in the lower opening of the exhaust chamber outer casing 5, it is assumed that the side wall surface of the exhaust chamber outer casing 5 is longer in the vicinity of the lower end portion of the exhaust chamber outer casing 5. Assume a locus of point γ. In the present embodiment, the steam guide 6 is formed so that the outermost peripheral portion is within the locus A. Other configurations are the same as those of the previous embodiments.

  According to the present embodiment, the same effects as those of the respective embodiments described above can be obtained, and the steam flow that has exited the final stage rotor blade outlet annular zone 13 is prevented by preventing the steam guide 6 from protruding from the locus A. After turning from the axial direction to the radial direction, it is possible to secure a sufficient flow path area to go around to the back side (turbine inlet side) of the steam guide 6, so that the blockage of the flow can be reduced. Therefore, the flow loss in the exhaust chamber 4 can be reduced, and the turbine efficiency can be further improved.

This will be described with reference to FIG.
FIG. 7 is a side cross-sectional view of the upper half of the turbine exhaust device in the present embodiment.
In FIG. 7, a flow that flows out to the exhaust chamber 4 along the steam guide 6 is a, a flow that flows to the outer wall portion of the steam guide 6 after flowing out to the exhaust chamber, b is turned around the back side of the steam guide 6, and the turbine Let c denote the flow proceeding to the inlet side.

  In order to use the steam guide 6 as a diffuser, the larger the diameter, the more pressure recovery can be promoted. However, since the outer casing 5 is limited in size, the larger the diameter of the steam guide 6 is, the more it is. There is a possibility that the area of the flow path through which the flows b and c pass is narrowed and a local high flow velocity region is generated due to the blockage of the flow or the restriction of the extreme flow path area, and the performance is deteriorated. Therefore, in the present embodiment, by securing the portion outside the trajectory A as a flow path for the flows b and c, the blockage of the flow can be reliably prevented. Further, by making the diameter of the steam guide 6 as large as possible within the range of the trajectory A, a sufficient pressure recovery effect can be expected. Therefore, it is possible to secure both the performance of the steam guide 6 as the diffuser and the performance of the entire exhaust chamber, and further improve the performance as the turbine exhaust device.

It is a sectional side view of the turbine exhaust apparatus which concerns on one Embodiment of this invention. FIG. 2 is a front view showing a part of the appearance of a turbine exhaust device according to an embodiment of the present invention as seen from the right side in FIG. 1. It is a graph showing the fluctuation | variation of the value of the pressure recovery coefficient Cp when the exhaust chamber width W is adjusted and the range of W / PCD is changed in the range of 2.5-4.5. It is the schematic diagram showing the general-view structure seen from the axial direction of the turbine exhaust apparatus which concerns on other embodiment of this invention, and the figure for the description. It is the schematic diagram showing the general-view structure seen from the axial direction of the turbine exhaust apparatus which concerns on further another embodiment of this invention, and the figure for the description. It is a schematic diagram showing the general-view structure seen from the axial direction of the turbine exhaust apparatus which concerns on further another embodiment of this invention. It is a sectional side view of the upper half part of the turbine exhaust apparatus which concerns on further another embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Turbine rotor 5 Exhaust chamber outer casing 10 Upper half casing 11 Lower half casing 13 Final stage blade exit annular zone 14 Ceiling surface 15 Flat end 20 Condenser 21 Connecting cylinder BH Final stage blade height H Height of upper half casing Dimension O Rotational center PCD Final stage blade height center diameter R1, 2, Radius of curvature W Exhaust chamber width Wc Condenser width α Intersection β Intersection γ Midpoint

Claims (4)

In the turbine exhaust device for guiding the steam flow that has passed through the final stage of the steam turbine to a condenser provided below the steam turbine,
An exhaust chamber outer casing comprising an upper half casing surrounding the turbine rotor of the steam turbine and a lower half casing connected to the lower side of the upper half casing;
The lower half casing is connected to the condenser via a connecting cylinder that widens downward.
When the width of the condenser taken in the direction perpendicular to the axis of the turbine rotor is Wc, and the diameter of the circle drawn by the blade length direction center of the last stage rotor blade of the steam turbine is PCD, the same direction The exhaust chamber width W of the lower half casing taken is
W <Wc,
W / PCD ≧ 3
A turbine exhaust system that is configured to satisfy the following condition. 2. The turbine exhaust system according to claim 1, wherein when the ratio of the exhaust chamber width W to the turbine final stage blade height central diameter PCD is set to a ratio W / PCD of less than 3, the upper half The casing is characterized in that a height dimension is substantially the same as the reference, and a curvature radius of a cross section along a plane orthogonal to the axis of the turbine rotor is larger than the reference. Turbine exhaust system. 2. The turbine exhaust system according to claim 1, wherein when the ratio of the exhaust chamber width W to the turbine final stage blade height central diameter PCD is set to a ratio W / PCD of less than 3, the upper half The turbine is characterized in that a flat end portion is interposed at a center portion in the width direction of the ceiling surface, thereby ensuring a width direction dimension larger than the reference while maintaining a height dimension at the reference level. Exhaust system.   2. The turbine exhaust device according to claim 1, wherein a line extending radially from the rotation center of the turbine rotor is continuously provided at an outlet inner peripheral portion of an exhaust chamber inner casing including the turbine rotor, and an outlet ring zone of the turbine rotor is provided. A steam guide formed so that the outermost peripheral portion is positioned closer to the turbine rotor than the bisection position of a line segment connecting two points intersecting the outer peripheral portion and the inner wall surface of the outer casing. Turbine exhaust device characterized.

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