JP2012202393A - Steam turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam turbine which has a reduced turbine exhaust loss by suppressing the generation of a pressure loss in an exhaust chamber.SOLUTION: The steam turbine 10 includes: an annular diffuser 50 which is provided downstream from a turbine final stage and is formed from a steam guide 30 and a bearing cone 40 inside the steam guide and discharges steam passing through the turbine final stage toward the radial-direction outside. The bearing cone 40 includes: a cylindrical constituent part 41 which is positioned on a turbine final stage side and provided in parallel with an axial direction of a turbine rotor 23; an expanded cylindrical constituent part 42 of which the one terminal side is connected to the cylindrical constituent part 41 and which is expanded in a trumpet shape toward the downstream side; and an exit side cylindrical constituent part 43 of which the one terminal side is connected to the expanded cylindrical constituent part 42 and which constitutes an exit of the annular diffuser 50.

Description

  Embodiments described herein relate generally to a steam turbine including an exhaust chamber.

Improving the thermal efficiency of steam turbines used in thermal power plants and the like is an important issue that leads to effective use of energy resources and reduction of carbon dioxide (CO ₂ ) emissions.

  An improvement in the thermal efficiency of a steam turbine can be achieved by effectively converting the given energy into mechanical work, which requires reducing various internal losses.

  The internal loss of a steam turbine is typified by the turbine blade row loss based on the profile loss due to the blade shape, steam secondary flow loss, steam leakage loss, steam wetting loss, etc., steam valves and crossover pipes. There are passage portion loss in passages other than the blade row, turbine exhaust loss due to the turbine exhaust chamber, and the like.

  Among these losses, the turbine exhaust loss is a large loss that accounts for 10 to 20% of the total internal loss. The turbine exhaust loss is a loss that occurs between the final stage outlet and the condenser inlet, and is further classified into a leaving loss, a hood loss, an annular area limiting loss, a turn-up loss, and the like. Of these, the hood loss is a pressure loss from the exhaust chamber to the condenser, and depends on the type, shape, and size of the exhaust chamber including the diffuser.

  In general, the pressure loss increases in proportion to the square of the steam flow velocity. Therefore, it is effective to reduce the steam flow velocity by increasing the size of the exhaust chamber within an allowable range. However, when the size of the exhaust chamber is increased, there are restrictions from the manufacturing cost and the layout space of the building. Such restrictions are also imposed when the size of the exhaust chamber is increased in order to reduce the hood loss. Therefore, it is important to have a shape with a small pressure loss with a limited exhaust chamber size.

  In order to reduce the pressure loss in the exhaust chamber, it is necessary to sufficiently reduce the steam velocity in the diffuser to restore the static pressure and reduce the pressure loss downstream thereof. For this reason, various studies have been made to reduce turbine exhaust loss.

JP 2006-283587 A

  However, in an exhaust chamber of a conventional steam turbine, particularly a double flow type steam turbine which takes a large annular area of the final stage rotor blade and can cope with a large steam flow rate, it expands in the axial direction of the turbine rotor while expanding. In the process of introducing the flowing steam into the condenser installed below the turbine rotor shaft, it is necessary to largely change the flow direction of the steam. In such an exhaust chamber of a conventional steam turbine, the flow direction is forcibly changed at a sufficiently high speed before the static pressure is sufficiently restored. Loss occurred, and it was difficult to sufficiently reduce the turbine exhaust loss.

  The problem to be solved by the present invention is to provide a steam turbine capable of suppressing generation of pressure loss in an exhaust chamber and reducing turbine exhaust loss.

  The steam turbine according to the embodiment is provided on the downstream side of the turbine final stage, and is formed by a steam guide and a bearing cone on the inner side thereof, and discharges steam that has passed through the turbine final stage toward the radially outer side. With a diffuser. The bearing cone is located on the turbine final stage side, and is connected to the cylindrical component provided in parallel to the axial direction of the turbine rotor, and one end side is connected to the cylindrical component, and is formed in a trumpet shape toward the downstream side. An enlarged cylindrical component that expands, and an outlet-side cylindrical component that is connected to the enlarged cylindrical component at one end and forms an outlet of the annular diffuser.

It is a figure showing the meridional section of the perpendicular direction of the steam turbine of a 1st embodiment concerning the present invention. It is a figure which shows the meridional section of the orthogonal | vertical direction of the exhaust chamber in the steam turbine of 1st Embodiment which concerns on this invention. It is a figure which shows the meridional section of the perpendicular direction when the upper half part of the exhaust chamber in the steam turbine of 1st Embodiment which concerns on this invention is expanded. It is a figure which shows the meridional section of the perpendicular direction when the upper half part of the exhaust chamber in the steam turbine of 2nd Embodiment which concerns on this invention is expanded. It is a figure which shows the relationship between the ratio (L0 / L1) of the length L0 of the turbine cone axial direction of a bearing cone, and the length L1 of the cylindrical rotor axial direction of a cylindrical structure part, and a turbine exhaust loss. It is a figure which shows the relationship between ratio (R2 / R1) of the radius R2 of the circular arc of an exit side cylindrical structure part, and the radius R1 of the circular arc of an expansion cylindrical structure part, and a turbine exhaust loss. It is a figure which shows the relationship between the ratio (L0 / L4) of the length L0 of the turbine rotor axial direction of a bearing cone, and the length L4 of the enlarged cylindrical structure part in the turbine rotor axial direction, and a turbine exhaust loss. It is a figure which shows the relationship between inclination-angle (theta) with respect to the turbine rotor axial direction of an enlarged cylindrical structure part, and turbine exhaust loss.

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

(First embodiment)
FIG. 1 is a diagram showing a meridional section in the vertical direction of a steam turbine 10 according to a first embodiment of the present invention. Here, the steam turbine 10 will be described by exemplifying a double-flow exhaust type low-pressure turbine having a lower exhaust type exhaust chamber. In the following description, the same components are denoted by the same reference numerals, and redundant description is omitted or simplified.

  In the steam turbine 10, an inner casing 21 is provided in the outer casing 20. A turbine rotor 23 in which a rotor blade 22 is implanted is provided in the inner casing 21. A plurality of rotor blades 22 are implanted in the circumferential direction to constitute a rotor blade cascade, and the rotor blade cascade is provided in a plurality of stages in the turbine rotor axial direction. The turbine rotor 23 is rotatably supported by a rotor bearing 24.

  A nozzle 26 supported by diaphragms 25a and 25b is disposed on the inner periphery of the inner casing 21 so as to alternate with the rotor blades 22 in the turbine rotor axial direction. A plurality of nozzles 26 are implanted in the circumferential direction to form a nozzle blade row, and the nozzle blade row and the moving blade blade row located immediately downstream constitute one turbine stage. The inner casing 21 is supported by the outer casing 20.

  In the center of the steam turbine 10, an intake chamber 28 into which steam from the crossover pipe 27 is introduced is provided. Steam is distributed and introduced from the intake chamber 28 to the left and right turbine stages.

  On the downstream side of the final turbine stage, an annular diffuser 50 is formed by the steam guide 30 on the outer peripheral side and the bearing cone 40 on the inner peripheral side and discharges steam outward in the radial direction. . Note that a rotor bearing 24 and the like are provided inside the bearing cone 40.

  A condenser (not shown) is provided below the lower exhaust type exhaust chamber having the annular diffuser 50 (that is, below the turbine rotor 23).

  The outer casing 20, the inner casing 21, the steam guide 30, the bearing cone 40, and the like described above have a vertically split structure. For example, a cylindrical steam guide 30 is constituted by the steam guides 30 on the upper half side and the lower half side. Similarly, a cylindrical bearing cone 40 is constituted by the bearing cones 40 on the upper half side and the lower half side. And the annular diffuser 50 is comprised by the cylindrical steam guide 30 and the cylindrical bearing cone 40 provided in the inner side. The configurations of the upper half side and the lower half side of the steam guide 30 and the bearing cone 40 are the same.

  Here, the operation of the steam turbine 10 will be described.

  The steam that flows into the intake chamber 28 in the steam turbine 10 through the crossover pipe 27 branches and flows to the left and right turbine stages. Then, the turbine rotor 23 is rotated by passing through a steam flow path including the nozzle 26 and the moving blade 22 of each turbine stage while performing expansion work. The steam that has performed the expansion work passes through the annular diffuser 50 while restoring the static pressure, and is guided to a condenser (not shown) installed below the turbine rotor 23.

  When such a double-flow exhaust (double flow) type low-pressure turbine is used, the flow rate of the steam can be increased by flowing the steam introduced from the center in the turbine rotor axial direction in two directions toward both ends, The annular area of the last stage rotor blade of the single-flow exhaust (single flow) type low-pressure turbine can also be increased. However, when a double-flow exhaust type low-pressure turbine is used in this way, it is difficult to cause the exhaust steam from the turbine to flow out as it is in the axial direction of the turbine rotor. Normally, a condenser is installed below the turbine rotor 23. The exhaust chamber is a lower exhaust type.

  Next, the configuration of the steam guide 30 and the bearing cone 40 that constitute the annular diffuser 50 will be described in detail.

  FIG. 2 is a diagram showing a meridional section in the vertical direction of the exhaust chamber in the steam turbine 10 according to the first embodiment of the present invention. FIG. 3 is a diagram showing a meridional section in the vertical direction when the upper half of the exhaust chamber in the steam turbine 10 of the first embodiment according to the present invention is enlarged.

  As shown in FIGS. 2 and 3, on the downstream side of the final turbine stage, steam that has passed through the final turbine stage formed by the steam guide 30 and the bearing cone 40 inside the steam guide 30 is radially outward. An annular diffuser 50 is formed to discharge toward it.

  As shown in FIG. 3, the bearing cone 40 includes three components: a cylindrical component 41, an enlarged cylindrical component 42, and an outlet side cylindrical component 43. As described above, the bearing cone 40 is not integrally formed in a cylindrical shape, but becomes a cylindrical shape by assembling the upper half side and the lower half side of the semi-cylindrical shape. In the steam guide 30 described later, as in the case of the bearing cone 40, the upper half side and the lower half side of the semi-cylindrical shape are assembled to form a cylindrical shape. Here, the bearing cone 40 and the steam guide 30 having a vertically split structure will be described based on a cylindrical structure after assembling the upper half side and the lower half side.

  In the bearing cone 40, the cylindrical component 41, the enlarged cylindrical component 42, and the outlet-side cylindrical component 43 may be integrally configured by being coupled to each other. Alternatively, the bearing cones 40 may be configured by being configured separately and contacting and fixing each. Further, for example, the bearing cone 40 may be configured by integrally configuring the enlarged cylindrical component 42 and the outlet-side cylindrical component 43 and contacting and fixing the cylindrical component 41 to the cylindrical component 41. . In any case, each connecting portion is connected so that the outer wall surface side (surface side in contact with steam (steam channel side)) is continuously smooth.

  The cylindrical component 41 is located on the final turbine stage side and is provided in parallel with the axial direction of the turbine rotor 23. That is, the cylindrical component 41 is provided in parallel to the axial direction of the turbine rotor 23 so as to surround the turbine rotor 23 and is configured in a right cylindrical shape.

  The length L1 (see FIG. 3) of the cylindrical component 41 in the turbine rotor axial direction is preferably 1/7 to 1/3 times the length L0 of the bearing cone 40 in the turbine rotor axial direction. More preferably, the length L1 of the cylindrical component 41 in the turbine rotor axial direction is 1/6 times to 1/4 times the length L0 of the bearing cone 40 in the turbine rotor axial direction.

  By setting the length L1 to be 1/7 times to 1/3 times the length L0, the steam speed is changed between the cylindrical component 41 and the enlarged cylindrical component 31 of the steam guide 30 described later. It can be sufficiently reduced and the static pressure can be recovered. Therefore, turbine exhaust loss can be reduced.

  Here, the length L0 of the bearing cone 40 in the axial direction of the turbine rotor is such that the outlet side cylindrical component 43 that contacts the vertical wall 20a of the outer casing 20 from the end of the cylindrical component 41 on the final turbine stage side. It is the length of the turbine rotor axial direction to the end edge. The vertical wall 20a is formed in a direction perpendicular to the turbine rotor axial direction, and constitutes an end of the outer casing 20 in the turbine rotor axial direction.

  The enlarged cylindrical component 42 is configured in an enlarged cylindrical shape that is connected at one end to the cylindrical component 41 and expands in a trumpet shape toward the downstream side. In other words, the enlarged cylindrical component 42 expands in a trumpet shape while spreading outward in the radial direction as it goes in the turbine exhaust direction and in the turbine rotor axial direction (right direction in FIGS. 2 and 3). In the cross-sectional view shown in FIG. 3, the outer wall surface (the surface on the side in contact with the steam (steam channel side)) of the enlarged cylindrical component 42 is formed by an arc having a radius R1.

  The outlet side cylindrical component 43 is configured in an enlarged cylindrical shape that is connected at one end to the enlarged cylindrical component 42 and expands in a trumpet shape toward the downstream side. Further, the outlet-side cylindrical component 43 is a part constituting the outlet of the annular diffuser 50, and the other end is joined to the vertical wall 20 a of the outer casing 20. In other words, the outlet side cylindrical component 43 expands in a trumpet shape while spreading outward in the radial direction as it goes in the turbine exhaust direction and in the turbine rotor axial direction (right direction in FIGS. 2 and 3). In the cross-sectional view shown in FIG. 3, the outer wall surface (surface on the side in contact with the steam (steam channel side)) of the outlet side cylindrical component 43 is formed by an arc having a radius R2.

  Here, it is preferable that the radius R2 of the arc of the outlet side cylindrical component 43 is larger than the radius R1 of the arc of the enlarged cylindrical component 42. By configuring the radius R2 to be larger than the radius R1, the steam whose flow direction has been changed to the radially outer side in the enlarged cylindrical component 42 flows while gradually changing the flow direction to the radially outer side. be able to. Therefore, the occurrence of bending loss can be suppressed.

  Further, the value of the radius R1 of the arc of the enlarged cylindrical component 42 is equal to or less than the value of the length L0 of the bearing cone 40 in the turbine rotor axial direction, and the radius R2 of the arc of the outlet-side cylindrical component 43 is It is preferably 1.5 times or more the radius R1 of the arc of the enlarged cylindrical component 42. More preferably, the radius R2 of the arc of the outlet-side cylindrical component 43 is 1.5 to 2 times the radius R1 of the arc of the enlarged cylindrical component 42.

  Here, it is preferable to set the value of the radius R1 to be equal to or less than the value of the length L0, and the direction of the flow is a direction perpendicular to the axial direction of the turbine rotor 23 from the axial direction of the turbine rotor 23 in the annular diffuser 50. This is because it is desirable to completely convert to The reason why the radius R2 is preferably 1.5 times the radius R1 is the same as the reason for configuring the radius R2 to be larger than the radius R1.

  Further, the length L2 of the enlarged cylindrical component 42 in the axial direction of the turbine rotor is such that the flow direction in the enlarged cylindrical component 42 is changed from the axial direction of the turbine rotor 23 to the axial direction of the turbine rotor 23 as much as possible. For the reason that it is preferable to turn to an angle close to the vertical direction, it is preferable to set the outlet side cylindrical component 43 about 0.6 to 4 times the length L3 in the turbine rotor axial direction.

  As shown in FIG. 3, the steam guide 30 includes two parts, an enlarged cylindrical component 31 that functions as a second enlarged cylindrical component, and an enlarged cylindrical component 32 that functions as a third enlarged cylindrical component. It consists of components.

  The expansion cylindrical structure part 31 is located in the last turbine stage side, and is comprised in the expansion cylinder shape expanded linearly toward the downstream. In other words, the enlarged cylindrical component 31 linearly expands radially outward as it goes in the turbine exhaust direction and in the turbine rotor axial direction (right direction in FIGS. 2 and 3). Therefore, in the cross-sectional view shown in FIG. 3, the inner wall surface (surface on the side in contact with steam (steam channel side)) in the enlarged cylindrical component 31 is an inclined straight line that is inclined with respect to the turbine rotor axial direction.

  The length L4 of the enlarged cylindrical component 31 in the turbine rotor axial direction is preferably 1/7 to 1/3 times the length L0 of the bearing cone in the turbine rotor axial direction. Further, the length L4 of the enlarged cylindrical component 31 in the turbine rotor axial direction is more preferably 1/6 to 1/4 times the length L0 of the bearing cone in the turbine rotor axial direction.

  By setting the length L4 to be 1/7 times to 1/3 times the length L0, the steam velocity is sufficiently reduced between the enlarged cylindrical component 31 and the cylindrical component 41 described above. Static pressure can be recovered. Therefore, turbine exhaust loss can be reduced.

  The inclination angle θ of the enlarged cylindrical component 31 with respect to the turbine rotor axial direction is preferably 7 to 27 degrees. In addition, the inclination angle θ of the enlarged cylindrical component 31 with respect to the turbine rotor axial direction is more preferably 14 degrees to 20 degrees.

  It is preferable to set the inclination angle θ in the above-described range in that the steam speed is sufficiently reduced and the static pressure is restored between the enlarged cylindrical component 31 and the cylindrical component 41 described above. Because you can.

  The enlarged cylindrical component 32 is configured in an enlarged cylindrical shape that is connected to the enlarged cylindrical component 31 at one end side and expands in a trumpet shape toward the downstream side. In other words, the enlarged cylindrical component 32 expands in a trumpet shape while spreading outward in the radial direction as it goes in the turbine exhaust direction and in the turbine rotor axial direction (right direction in FIGS. 2 and 3). In the cross-sectional view shown in FIG. 3, the inner wall surface (the surface on the side in contact with the steam (steam channel side)) of the enlarged cylindrical component 32 is formed by an arc having a radius R3. Although the radius R3 is not particularly limited, it is desirable that the enlarged cylindrical component 32 forms a smooth flow path section together with the enlarged cylindrical component 42 and the outlet side cylindrical component 43. It is preferably set in a range larger than the radius R1 and smaller than the radius R2.

  In addition, at the outlet of the annular diffuser 50, for example, the edge on the outlet side of the enlarged cylindrical component 32 is on the outlet side of the outlet-side cylindrical component 43 so that the flow of steam flows radially outward. It is preferable to be configured so that the horizontal direction position is the same as the end edge of. That is, the radial distance from the turbine rotor shaft of the outlet-side edge of the enlarged cylindrical component 32 and the radial distance from the turbine rotor shaft of the outlet-side edge of the outlet-side cylindrical component 43 Are preferably constructed equally.

  Next, the steam flow in the annular diffuser 50 will be described.

  The steam that has flowed into the annular diffuser 50 from the final turbine stage is decelerated in the linear diffuser portion formed between the cylindrical component 41 and the enlarged cylindrical component 31, and flows while recovering the static pressure. At this time, since the flow direction is not changed, no bending loss occurs and the static pressure can be sufficiently recovered.

  The steam whose velocity is reduced is guided between the enlarged cylindrical component 42 and the enlarged cylindrical component 32, and the flow direction is changed radially outward. At this time, since the steam is decelerated, it is possible to suppress the occurrence of bending loss.

  Subsequently, the steam is guided between the outlet side cylindrical component 43 and the enlarged cylindrical component 32, and the flow direction is gradually changed toward the radially outer side. Since the radius R2 of the arc of the outlet side cylindrical component 43 is configured to be larger than the radius R1 as described above, it is possible to suppress the occurrence of bending loss. Further, at the outlet of the annular diffuser 50, a flow of steam rectified in a radially outer direction, in other words, in a direction perpendicular to the axial direction of the turbine rotor 23 is obtained.

  Since the steam flowing out from the annular diffuser 50 is rectified, the flow is led to a condenser (not shown) without greatly disturbing the flow. Therefore, occurrence of pressure loss between the annular diffuser 50 and the condenser is also suppressed.

  As described above, according to the steam turbine 10 of the first embodiment, the turbine exhaust loss in the annular diffuser 50 in the exhaust chamber can be reduced. Further, since the flow of steam at the outlet of the annular diffuser 50 can be rectified, the turbine exhaust loss between the annular diffuser 50 and the condenser can be reduced.

(Second Embodiment)
The steam turbine 11 of the second embodiment is the same as the configuration of the steam turbine 10 of the first embodiment except for the configuration of the outlet side cylindrical component 43 of the bearing cone 40. The different configurations will be mainly described.

  FIG. 4 is a diagram showing a meridional section in the vertical direction when the upper half portion of the exhaust chamber in the steam turbine 11 of the second embodiment according to the present invention is enlarged.

  As shown in FIG. 4, on the downstream side of the final turbine stage, steam formed by a steam guide 30 and a bearing cone 40 inside the steam guide 30 and exhausted through the final turbine stage is discharged radially outward. An annular diffuser 50 is formed.

  As shown in FIG. 4, the bearing cone 40 includes three components: a cylindrical component 41, an enlarged cylindrical component 42, and an outlet side cylindrical component 43. In addition, the structure of the cylindrical structure part 41 and the expansion cylindrical structure part 42 is the same as the structure in the steam turbine 10 of 1st Embodiment.

  Here, the value of the radius R1 of the arc of the enlarged cylindrical component 42 is preferably equal to or less than the value of the length L0 of the bearing cone 40 in the turbine rotor axial direction. It is preferable to set the value of the radius R1 to be equal to or less than the value of the length L0. The flow direction in the annular diffuser 50 is completely changed from the axial direction of the turbine rotor 23 to the direction perpendicular to the axial direction of the turbine rotor 23. This is because it is desirable to turn around.

  The outlet-side cylindrical component 43 is connected to the enlarged cylindrical component 42 at one end side, and has an enlarged cylindrical shape that linearly expands toward the downstream side in the tangential direction at the connection edge of the enlarged cylindrical component 42. It is configured. In other words, the outlet side cylindrical component 43 linearly expands radially outward as it goes in the turbine exhaust direction and in the turbine rotor axial direction (right direction in FIG. 4). Therefore, in the cross-sectional view shown in FIG. 4, the outer wall surface (surface on the side in contact with steam (steam channel side)) in the outlet-side cylindrical component 43 is an inclined straight line that is inclined with respect to the turbine rotor axial direction. .

  Further, the outlet-side cylindrical component 43 is also a part constituting the outlet of the annular diffuser, and the other end is joined to the vertical wall 20 a of the outer casing 20.

  The length L2 of the enlarged cylindrical component 42 in the turbine rotor axial direction is a direction in which the flow direction in the enlarged cylindrical component 42 is as vertical as possible from the axial direction of the turbine rotor 23 to the axial direction of the turbine rotor 23. Therefore, it is preferable to set the outlet side cylindrical component 43 about 0.6 to 4 times the length L3 in the turbine rotor axial direction.

  The configuration of the steam guide 30 is the same as the configuration in the steam turbine 10 of the first embodiment.

  Next, the steam flow in the annular diffuser 50 will be described.

  The steam that has flowed into the annular diffuser 50 from the final turbine stage is decelerated in the linear diffuser portion formed between the cylindrical component 41 and the enlarged cylindrical component 31, and flows while recovering the static pressure. At this time, since the flow direction is not changed, no bending loss occurs and the static pressure can be sufficiently recovered.

  The steam whose velocity is reduced is guided between the enlarged cylindrical component 42 and the enlarged cylindrical component 32, and the flow direction is changed radially outward. At this time, since the steam is decelerated, it is possible to suppress the occurrence of bending loss.

  Subsequently, the steam is guided between the outlet side cylindrical component 43 and the enlarged cylindrical component 32, and the flow direction is gradually changed toward the radially outer side. Therefore, it is possible to suppress the occurrence of bending loss. Further, at the outlet of the annular diffuser 50, a flow of steam rectified in a radially outer direction, in other words, in a direction perpendicular to the axial direction of the turbine rotor 23 is obtained.

  Since the steam flowing out from the annular diffuser 50 is rectified, the flow is led to a condenser (not shown) without greatly disturbing the flow. Therefore, occurrence of pressure loss between the annular diffuser 50 and the condenser is also suppressed.

  As described above, according to the steam turbine 11 of the second embodiment, the turbine exhaust loss in the annular diffuser 50 in the exhaust chamber can be reduced. Further, since the flow of steam at the outlet of the annular diffuser 50 can be rectified, the turbine exhaust loss between the annular diffuser 50 and the condenser can be reduced.

  In the above-described embodiment, the steam turbines 10 and 11 have been described by exemplifying a double-flow exhaust type low-pressure turbine having a lower exhaust type exhaust chamber. However, the present embodiment is, for example, a single-flow type It can also be applied to other low pressure turbines.

(Evaluation of turbine exhaust loss)
Here, (1) the ratio (L0 / L1) between the length L0 of the bearing cone 40 in the turbine rotor axial direction and the length L1 of the cylindrical component 41 in the turbine rotor axial direction, (2) the outlet side cylindrical configuration The ratio (R2 / R1) between the radius R2 of the arc of the portion 43 and the radius R1 of the arc of the enlarged cylindrical component 42, (3) the length L0 of the bearing cone in the axial direction of the turbine rotor and the The ratio of the length L4 in the turbine rotor axial direction (L0 / L4) and (4) the inclination angle θ of the enlarged cylindrical component 31 with respect to the turbine rotor axial direction were evaluated with respect to the turbine exhaust loss. Here, the outlet side cylindrical component 43 has an enlarged cylindrical configuration that expands in a trumpet shape while spreading outward in the radial direction, as shown in the first embodiment.

(1) Ratio between the length L0 of the bearing cone 40 in the turbine rotor axial direction and the length L1 of the cylindrical component 41 in the turbine rotor axial direction (L0 / L1)
FIG. 5 is a diagram showing the relationship between the ratio (L0 / L1) between the length L0 of the bearing cone 40 in the turbine rotor axial direction and the length L1 of the cylindrical component 41 in the turbine rotor axial direction and the turbine exhaust loss. is there. This relationship is a result obtained in an actual machine. At this time, the ratio of radius R2 to radius R1 (R2 / R1) was 1.5, the ratio of length L0 to length L4 (L0 / L4) was 5, and the inclination angle θ was 17 degrees.

  In FIG. 5, the ratio (L0 / L1) between the length L0 and the length L1 is shown, and therefore the ratio (L1) between the length L1 and the length L0 shown as a preferable range in the above-described embodiment. / L0).

  As shown in FIG. 5, when the value of (L0 / L1) is about 5, the maximum static pressure recovery amount is reached, and when the value deviates from that, the static pressure recovery amount decreases and the turbine exhaust loss increases. This is because if the length of the linear diffuser formed between the cylindrical component 41 and the enlarged cylindrical component 31 in the turbine rotor axial direction is too short, the steam is not sufficiently decelerated and the static pressure is sufficient. Indicates that it will not be recovered. On the other hand, if the length of the linear diffuser in the axial direction of the turbine rotor is too long, a sufficient distance in the axial direction of the turbine rotor is not obtained downstream of the linear diffuser. Indicates an increase.

  Here, in the normal turbine design standard, a static pressure recovery amount reduced by 20% from the maximum static pressure recovery amount is allowed. In FIG. 5, the static pressure recovery amount reduced by 20% from the maximum static pressure recovery amount is indicated by a broken line. Therefore, by setting the value of (L0 / L1) in the range of 3 to 7, it is possible to obtain a static pressure recovery amount equal to or greater than the turbine design reference value described above, and to reduce turbine exhaust loss.

(2) Ratio of the radius R2 of the arc of the outlet side cylindrical component 43 and the radius R1 of the arc of the enlarged cylindrical component 42 (R2 / R1)
FIG. 6 is a diagram showing the relationship between the ratio (R2 / R1) between the radius R2 of the arc of the outlet-side cylindrical component 43 and the radius R1 of the arc of the enlarged cylindrical component 42 and the turbine exhaust loss. This relationship is a result obtained in an actual machine. At this time, the ratio of the length L0 to the length L1 (L0 / L1) was 5, the ratio of the length L0 to the length L4 (L0 / L4) was 5, and the inclination angle θ was 17 degrees.

  As shown in FIG. 6, when the value of (R2 / R1) is up to 1.5, the turbine exhaust loss rapidly decreases as (R2 / R1) decreases. This is because when the value of (R2 / R1) is small, the radius R1 of the arc of the enlarged cylindrical component 42 is larger than the radius R2 of the arc of the outlet-side cylindrical component 43. For this reason, the flow is suddenly bent outward in the radial direction, a bending loss occurs, a rectifying effect cannot be obtained, and the turbine exhaust loss increases.

  From this result, it is understood that the turbine exhaust loss can be suppressed by setting the value of (R2 / R1) to 1.5 or more.

(3) Ratio between the length L0 of the bearing cone in the turbine rotor axial direction and the length L4 of the enlarged cylindrical component 31 in the turbine rotor axial direction (L0 / L4)
FIG. 7 is a diagram showing the relationship between the ratio (L0 / L4) of the length L0 of the bearing cone 40 in the turbine rotor axial direction and the length L4 of the enlarged cylindrical component 31 in the turbine rotor axial direction and the turbine exhaust loss. is there. This relationship is a result obtained in an actual machine. At this time, the ratio (L0 / L1) between the length L0 and the length L1 was 5, the ratio (R2 / R1) between the radius R2 and the radius R1 was 1.5, and the inclination angle θ was 17 degrees.

  In addition, in FIG. 7, since it has shown by ratio (L0 / L4) of length L0 and length L4, ratio (L4) of length L4 shown as a preferable range in embodiment mentioned above. / L0).

  As shown in FIG. 7, when the value of (L0 / L4) is about 5, the maximum static pressure recovery amount is reached, and when deviating from this, the static pressure recovery amount decreases and the turbine exhaust loss increases. This is because if the length of the linear diffuser formed between the cylindrical component 41 and the enlarged cylindrical component 31 in the turbine rotor axial direction is too short, the steam is not sufficiently decelerated and the static pressure is sufficient. Indicates that it will not be recovered. On the other hand, if the length of the linear diffuser in the axial direction of the turbine rotor is too long, a sufficient distance in the axial direction of the turbine rotor is not obtained downstream of the linear diffuser. Indicates an increase.

  Here, in the normal turbine design standard, a static pressure recovery amount reduced by 20% from the maximum static pressure recovery amount is allowed. In FIG. 5, the static pressure recovery amount reduced by 20% from the maximum static pressure recovery amount is indicated by a broken line. Therefore, by setting the value of (L0 / L4) in the range of 3 to 7, it is possible to obtain a static pressure recovery amount equal to or greater than the turbine design reference value described above, and to reduce turbine exhaust loss.

(4) Inclination angle θ of the enlarged cylindrical component 31 with respect to the turbine rotor axial direction
FIG. 8 is a diagram showing the relationship between the inclination angle θ of the enlarged cylindrical component 31 with respect to the turbine rotor axial direction and the turbine exhaust loss. This relationship is a result obtained in an actual machine. At this time, the ratio (L0 / L1) between the length L0 and the length L1 is 5, the ratio (R2 / R1) between the radius R2 and the radius R1 is 1.5, and the ratio between the length L0 and the length L4 (L0). / L4) was set to 5.

  As shown in FIG. 8, when the inclination angle θ is about 14 to 19 degrees, the maximum static pressure recovery amount is reached. This is because if the expansion of the flow path in the linear diffuser formed between the cylindrical component 41 and the enlarged cylindrical component 31 is small, the steam is not sufficiently decelerated and the static pressure is not sufficiently recovered. Is shown. On the other hand, if the expansion of the flow path in the linear diffuser portion is too large, the flow is separated and a pressure loss called expansion loss occurs, which indicates that the turbine exhaust loss increases.

  Here, in the normal turbine design standard, a static pressure recovery amount reduced by 20% from the maximum static pressure recovery amount is allowed. In FIG. 8, the static pressure recovery amount reduced by 20% from the maximum static pressure recovery amount is indicated by a broken line. Therefore, by setting the inclination angle θ in the range of 7 to 27 degrees, it is possible to obtain a static pressure recovery amount equal to or greater than the turbine design reference value described above, and to reduce turbine exhaust loss.

  According to the embodiment described above, generation of pressure loss in the exhaust chamber can be suppressed, and turbine exhaust loss can be reduced.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention.

  DESCRIPTION OF SYMBOLS 10, 11 ... Steam turbine, 20 ... Outer casing, 20a ... Vertical wall, 21 ... Inner casing, 22 ... Rotor blade, 23 ... Turbine rotor, 24 ... Rotor bearing, 25a, 25b ... Diaphragm, 26 ... Nozzle, 27 ... Cross Over pipe, 28 ... Intake chamber, 30 ... Steam guide, 31, 32, 42 ... Expanded cylindrical component, 40 ... Bearing cone, 41 ... Cylindrical component, 43 ... Outlet cylindrical component, 50 ... Annular diffuser .

Claims (9)

The steam turbine is provided with an annular diffuser that is provided on the downstream side of the final stage of the turbine and is formed by a steam guide and a bearing cone inside thereof, and discharges the steam that has passed through the final stage of the turbine radially outward. And
The bearing cone is
A cylindrical component located on the turbine final stage side and provided parallel to the axial direction of the turbine rotor;
One end side is connected to the cylindrical component, and an expanded cylindrical component that expands in a trumpet shape toward the downstream side;
One end side is connected to the said expansion | swelling cylindrical structure part, The exit side cylindrical structure part which comprises the exit of the said annular diffuser is comprised, The steam turbine characterized by these.   The steam turbine according to claim 1, wherein the outlet-side cylindrical component is configured to expand in a trumpet shape toward the downstream side.   3. The steam turbine according to claim 2, wherein a radius of a circular arc on the flow path side in the outlet-side cylindrical structural portion is larger than a radius of a circular arc on the flow path side in the enlarged cylindrical structural portion.   The radius of the arc on the flow path side in the enlarged cylindrical component is equal to or less than the value of the length of the bearing cone in the turbine rotor axial direction, and the radius of the arc on the flow channel side in the outlet side cylindrical component is The steam turbine according to claim 2, wherein the steam turbine has a radius of 1.5 times or more the radius of the circular arc on the flow path side in the enlarged cylindrical component.   The said exit side cylindrical structure part is comprised so that it may expand linearly toward the downstream in the tangential direction in the connection end edge of the said expanded cylindrical structure part. Steam turbine.   The length in the turbine rotor axial direction of the cylindrical component is 1/7 to 1/3 times the length of the bearing cone in the turbine rotor axial direction. The steam turbine according to claim 1. The steam guide is
A second enlarged cylindrical component located on the turbine last paragraph side and linearly expanding toward the downstream side;
One end side is connected to the said 2nd expansion cylindrical structure part, The 3rd expansion cylindrical structure part which expands in a trumpet shape toward the downstream is comprised, The any one of Claim 1 thru | or 6 characterized by the above-mentioned. The steam turbine according to claim 1.   The length in the turbine rotor axial direction of the second enlarged cylindrical component is 1/7 to 1/3 times the length of the bearing cone in the turbine rotor axial direction. The described steam turbine.   The steam turbine according to claim 7 or 8, wherein an inclination angle of the second enlarged cylindrical component portion with respect to the turbine rotor axial direction is 7 to 27 degrees.

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