JP2012112271A - Turbine steam control valve and combined steam valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a turbine steam control valve, along with a combined steam valve using the same, capable of striking a balance between the reduction in pressure loss and the suppression of vibration.SOLUTION: A control valve 20 changes the area of a flow channel between a second valve seat 24 and a second valve element 22 by moving the second valve element 22 relative to the second valve seat 24 to control the amount of steam flowing in the flow channel. The second valve seat 24 has a shape having a diameter expanding from an upstream side toward a downstream side in the steam flow direction. The second valve element 22 is separated from a seat part 24A of the second valve seat 24 in a valve-opening state of the control valve 20, and abuts on the seat part 24A of the second valve seat 24 in a valve-closing state of the control valve 20.

Description

  The present invention relates to an adjusting valve for a steam turbine for adjusting the amount of steam supplied to a steam turbine such as a thermal power plant or a nuclear power plant, and a combined steam valve using the same.

  Steam turbines such as thermal power plants and nuclear power plants are provided with a number of steam valves in order to adjust the amount of steam according to load changes and to shut off the supply of steam in the event of an abnormality. Among them, the one that adjusts the amount of steam according to the load change is called a regulating valve, and the valve rod is moved by an actuator to change the flow path area between the valve seat and the valve body. Generally, the amount can be adjusted.

  Since the regulating valve has a function of adjusting the amount of steam, it is always operated at an intermediate opening (slightly open state), so that the steam flow tends to be disturbed after passing through the regulating valve. In particular, the steam control valve arranged upstream of the high-pressure chamber of the steam turbine and the intercept valve arranged upstream of the intermediate-pressure chamber handle high-pressure and large-flow steam, so that there is a gap between the valve body and the valve seat. It has been a problem that the turbulence of the flow accompanying the shock wave generated when the flowing steam is in a transonic state causes vibration of each part of the adjusting valve.

Therefore, conventionally, attempts have been made to reduce the vibration of each part of the adjustable valve by devising the shapes of the valve body and the valve seat. For example, Patent Documents 1 and 2 disclose steam valves in which the radius of curvature of the valve body is 0.52 to 0.6 times the seat diameter and the curvature radius of the valve seat is larger than 0.6 times the seat diameter. Has been.
FIG. 3 is a cross-sectional view schematically showing the steam valve described in Patent Documents 1 and 2. As shown in FIG. 3, the radius of curvature r of the valve body 102 is 0.52 to 0.6 times the seat diameter _{D 0,} the radius of curvature R of the valve seat 104 than 0.6 times the seat diameter _{D 0} It is getting bigger. Therefore, since the steam flow line 100 when the steam valve is slightly opened is in a state relatively along the movement direction Y of the valve body (so-called streamline 100 standing state), the steam flow is the valve seat. An annular flow adhering to the 104 side is formed, the steam flow is stabilized, and the vibration of each part of the steam valve can be reduced.

Japanese Patent Publication No. 58-44909 Japanese Patent No. 4185029

By the way, in the steam valve described in Patent Documents 1 and 2, the tangential direction of the valve seat 104 is relatively standing at the position where the valve seat 104 and the valve body 102 are in contact (seat position 103) (movement of the valve body 102). Therefore, the flow path area between the valve seat 104 and the valve body 102 is small, and the pressure loss tends to be large. For this reason, in order to reduce pressure loss, it is necessary to set the lift amount of the valve body 102 large. However, when the lift amount of the valve body 102 increases, the steam flow interferes on the downstream side of the seat position 103, the above-mentioned annular flow is disturbed, and vibrations of each part of the steam valve occur.
As described above, in the steam valves described in Patent Documents 1 and 2, it is difficult to achieve both reduction in pressure loss and reduction in vibration.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a steam turbine control valve capable of achieving both reduction in pressure loss and vibration suppression, and a combined steam valve using the same.

  The steam turbine control valve according to the present invention changes the area of the flow path between the valve seat and the valve body by moving the valve body relative to the valve seat, and the steam flowing through the flow path. A steam turbine adjusting valve that adjusts the amount, a valve seat that expands from an upstream side to a downstream side in a steam flow direction, and is separated from a seat portion of the valve seat in an open state, and in a closed state, the valve seat And a valve body in contact with the seat portion of the valve seat.

  Conventionally, a configuration of a steam valve that uses a valve seat that gradually decreases in diameter from the upstream side to the downstream side and flows steam from the base of the valve body to the valve head has been established by those skilled in the art. It was. However, in the steam valve having such a configuration, there is a trade-off relationship between reduction of pressure loss and reduction of vibration, and it has been difficult to improve both at the same time by devising the shapes of the valve seat and the valve body. Therefore, the inventors of the present application have come up with the idea of the present invention by reviewing the configuration of the steam valve, which has been established among those skilled in the art, and conducting intensive studies.

According to the control valve for a steam turbine according to the present invention, since the valve seat whose diameter is increased from the upstream side to the downstream side of the steam flow is provided, the downstream side of the seat portion is more upstream than the upstream side of the seat portion of the valve seat. The steam passage area is larger. For this reason, when the steam supplied from the upstream side of the control valve passes through the seat portion of the valve seat, the flow velocity becomes slow, and the turbulence of the steam flow on the downstream side of the seat portion is suppressed. Therefore, even if the lift amount of the valve body is increased to reduce the pressure loss, the steam flow after passing through the seat portion maintains the state of the annular flow that remains attached to the valve seat. Can be suppressed.
The annular flow means that the vapor flow flows in an annular shape along the valve seat. In general, it is said that the formation of the annular flow stabilizes the steam flow and can suppress the vibration of each part of the adjusting valve.

  In the steam turbine control valve, the valve head of the valve body is preferably concave.

  As a result, the steam flow once stays in the concave portion of the valve head on the upstream side of the seat portion, and the steam flow is rectified so as to follow the valve seat, so that the annular flow can be further stabilized.

  The steam turbine control valve further includes a cylindrical valve body guide that is provided on an outer periphery of the valve body and guides the valve body, and the valve body and the valve body are provided at a valve head of the valve body. It is preferable that a balance hole is formed to communicate the internal space surrounded by the guide with the space upstream of the valve body, and the inner diameter of the valve body guide is larger than the diameter of the seat portion of the valve seat.

  Thus, by providing the balance hole, the vapor pressure in the internal space surrounded by the valve body and the valve body guide is equal to the upstream space of the valve body. Here, since the inner diameter of the valve body guide is larger than the diameter of the seat portion of the valve seat, the net steam force acting on the valve body as a whole is directed in the direction from the downstream side to the upstream side of the steam flow (i.e., adjustment). Valve closing direction). Thus, the net steam force acting on the valve body always pulls the valve body in the direction in which the adjusting valve is closed, so that the alignment of the valve body is improved, and the turbulence of the steam flow can be further suppressed.

  In the above-described steam turbine control valve, it is preferable that an angle formed by a central axis direction of the valve body with respect to a tangential direction in the seat portion extending upstream from the seat portion is 25 to 50 degrees.

  In this way, by setting the angle formed by the central axis direction of the valve body to the tangential direction of the seat portion to be 25 degrees or more, the flow passage area is rapidly expanded from the seat portion to the upstream side of the seat portion. In comparison, the flow velocity of the downstream steam flow can be sufficiently slowed to more reliably suppress the interference of the steam flow. On the other hand, by setting the angle to 50 degrees or less, jet collision can be avoided, fluid noise can be reduced, and noise can be reduced.

  A combined steam valve according to the present invention includes the above-described steam turbine control valve and a steam turbine stop valve disposed upstream of the steam turbine control valve, the steam turbine control valve and the steam turbine. The stop valve is provided in a common valve casing.

  This combination steam valve includes the above-described steam turbine control valve. Here, in the above-described steam turbine control valve, since the valve seat whose diameter is increased from the upstream side of the steam flow toward the downstream side is provided, the downstream side of the seat portion is more upstream than the upstream side of the seat portion of the valve seat. The steam has a larger flow path area. For this reason, when the steam supplied from the upstream side of the control valve passes through the seat portion of the valve seat, the flow velocity becomes slow, and the turbulence of the steam flow on the downstream side of the seat portion is suppressed. Therefore, even if the lift amount of the valve body is increased in order to reduce the pressure loss, the steam flow after passing through the seat portion maintains the state of the annular flow that remains attached to the valve seat. Vibration can be suppressed.

  According to the present invention, since the valve seat whose diameter is increased from the upstream side to the downstream side of the steam flow is provided, the flow path area of the steam on the downstream side of the seat portion is higher than the upstream side of the seat portion of the valve seat. Is big. For this reason, when the steam supplied from the upstream side of the control valve passes through the seat portion of the valve seat, the flow velocity becomes slow, and the turbulence of the steam flow on the downstream side of the seat portion is suppressed. Therefore, even if the lift amount of the valve body is increased to reduce the pressure loss, the steam flow after passing through the seat portion maintains the state of the annular flow that remains attached to the valve seat. Can be suppressed.

It is sectional drawing which shows the structural example of the combination steam valve provided with the regulating valve for steam turbines of this embodiment. It is an enlarged view which shows the periphery of the adjustment valve for steam turbines among the combination steam valves of FIG. It is sectional drawing which shows the conventional steam valve typically.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely illustrative examples. Only.

FIG. 1 is a cross-sectional view showing a configuration example of a combination steam valve provided with a steam turbine control valve of the present embodiment. FIG. 2 is an enlarged view showing the vicinity of a steam turbine adjusting valve in the combined steam valve of FIG. 1.
In the following, the steam turbine control valve incorporated in the combination steam valve will be described with reference to FIGS. 1 and 2. However, the steam turbine control valve according to the present invention is not limited to this example. It may be a separate valve independent of the stop valve.

  As shown in FIG. 1, the combination steam valve 1 includes a steam turbine stop valve 10 (hereinafter simply referred to as “stop valve 10”) and a steam turbine control valve 20 (hereinafter simply referred to as “control valve 20”). Are provided in a common valve casing 40. While the stop valve 10 plays a role of blocking the steam flow in an emergency, the control valve 20 adjusts the amount of steam according to the load change.

The valve casing 40 includes a steam inlet 46, a stop valve chamber 42, an intermediate flow path 48, an adjusting valve chamber 44, and a steam outlet 50 in order from the upstream side of the steam flow. A stop valve 10 is accommodated in the stop valve chamber 42, and an adjustment valve 20 is accommodated in the adjustment valve chamber 44. The stop valve chamber 42 and the adjustable valve chamber 44 are each closed by a bonnet 52 attached to the valve casing 40.
The steam supplied from the steam inlet 46 flows through the stop valve chamber 42, then flows into the control valve chamber 44 through the intermediate flow path 48, and is finally discharged from the steam outlet 50.

  The stop valve 10 housed in the stop valve chamber 42 includes a first valve body 12, a first valve seat 14 with which the first valve body 12 comes into contact when the valve is closed, and a first valve attached to the first valve body 12. It has a rod 16 and a guide bush 18 for guiding the first valve rod 16.

  The first valve body 12 includes a main valve 12A that contacts the seat portion 14A of the first valve seat 14 when the stop valve 10 is closed, and a sub valve 12B included in the main valve 12A. The inner wall surface 13 of the main valve 12A functions as a valve seat for the sub valve 12B.

  One end of the first valve rod 16 is attached to the sub-valve 12B of the first valve body 12, and the other end is connected to the actuator. The driving force of the actuator is transmitted to the auxiliary valve 12B of the first valve body 12 through the first valve rod 16.

A guide bush 18 that guides the first valve stem 16 is embedded in the bonnet 52. As a result, the first valve stem 16 driven by the actuator slides in the guide bush 18 and moves along the central axis C ₁ of the first valve stem 16.

  In the stop valve 10, the sub-valve 12B to which the first valve rod 16 is attached moves forward and backward independently up to a predetermined lift amount, but moves forward and backward together with the main valve 12A when the predetermined lift amount is reached. For this reason, when the sub valve 12B is moved in the valve opening direction (upward in FIG. 1) via the first valve rod 16 by the actuator, only the sub valve 12B moves until the predetermined lift amount, and the sub valve 12B Open first. Thereafter, when the auxiliary valve 12B is further moved in the valve opening direction via the first valve rod 16 by the actuator, the auxiliary valve 12B moves together with the main valve 12A at a predetermined lift amount, and the main valve 12A is also opened. It is. Thus, by opening the auxiliary valve 12B first, the pressure difference before and after the main valve 12A can be reduced, and the main valve 12A having a larger seat diameter than the auxiliary valve 12B can be opened with a small driving force. .

A cylindrical strainer 17 for removing foreign substances contained in the steam is provided on the outer periphery of the stop valve 10. Since the foreign material having a predetermined size or larger is removed by the strainer 17, the steam turbine to which each part (stop valve 10 and adjusting valve 20) and the combined steam valve 1 of the combined steam valve 1 downstream of the strainer 17 are connected is connected. It can be protected from failure due to foreign matter.
A baffle plate 19 is provided on the side of the stop valve chamber 42 far from the steam inlet 46. The baffle plate 19 is disposed between the outer peripheral surface of the strainer 17 and the inner wall surface of the stop valve chamber 42, and rectifies the steam flow that bypasses the outer periphery of the strainer 17.

  An adjusting valve 20 is provided on the downstream side of the stop valve 10. As shown in FIGS. 1 and 2, the control valve 20 includes a second valve body 22 (corresponding to “valve body”) and a second valve seat 24 (“valve seat”) with which the second valve body 22 abuts when the valve is closed. ), A second valve rod 26 attached to the second valve body 22, and a guide bush 28 for guiding the second valve rod 26.

Conventionally, a steam valve that uses a valve seat that gradually decreases in diameter from the upstream side toward the downstream side and that allows steam to flow from the base of the valve body toward the valve head has been established by those skilled in the art. On the other hand, in the present embodiment, from the viewpoint of the stabilization of the annular flow, the second valve seat 24 of the adjusting valve 20 is shaped to expand from the upstream side to the downstream side, and the second valve body 22 Steam is allowed to flow from the valve head 23 toward the base.
Thus, since the second valve seat 24 of the control valve 20 has a shape that gradually increases in diameter from the upstream side to the downstream side in the steam flow direction, from the upstream side of the seat portion 24A of the second valve seat 24. Also, the flow path area of the steam is larger on the downstream side of the seat portion 24A. For this reason, when the steam supplied from the intermediate flow path 48 passes through the seat portion 24A of the second valve seat 24, the flow velocity becomes slow, and the steam flow is disturbed on the downstream side of the seat portion of the second valve seat 24. It is suppressed. Therefore, the state of the annular flow in which the steam flow that has passed through the seat portion 24 </ b> A of the second valve seat 24 remains attached to the second valve seat 24 is maintained, and the vibration of each portion of the combination steam valve 1 can be suppressed.

The angle formed by the tangent line T in the seat portion 24A extending upstream from the seat portion 24A of the second valve seat 24 with respect to the central axis of the second valve body 22 (that is, the central axis C ₂ of the second valve rod 26). θ (see FIG. 2) is preferably 25 to 50 degrees. Thus, by setting the angle θ formed by the tangent line T of the seat portion 24A to the central axis of the second valve body 22 to be 25 degrees or more, the flow passage area is rapidly expanded with the seat portion 24A as a boundary. Compared to the upstream side of the portion 24A, the flow velocity of the downstream steam flow can be sufficiently slowed down, and the interference of the steam flow can be more reliably suppressed. On the other hand, by setting the angle θ to 50 degrees or less, jet collision can be avoided, fluid noise can be reduced, and noise can be reduced.

Moreover, the 2nd valve seat 24 of the adjustment valve 20 is provided as the common valve seat 4 integrated with the 1st valve seat 14 of the stop valve 10, as shown in FIG. The common valve seat 4 is provided over the entire length of the intermediate flow path 48 and is fixed to the inner wall of the valve casing 40.
Thus, by sharing the first valve seat 14 of the stop valve 10 and the second valve seat 24 of the control valve 20, the number of parts is reduced and the efficiency of the assembly work of the combination steam valve 1 is improved. In addition, since there is no seam between the first valve seat 14 and the second valve seat 24, the steam flow is not disturbed at the seam portion.

The common valve seat 4 is preferably fixed to the inner wall of the valve casing 40 only on the upstream side in the steam flow direction from the seat portion 14A of the first valve seat 14. For example, the common valve seat 4 may be fixed to the inner wall of the valve casing 40 by the fastening member 6 at a position upstream of the seat portion 14A.
In this manner, the common valve seat 4 is fixed to the inner wall of the valve casing 40 only on the upstream side of the seat portion 14A of the stop valve 10 and not on the downstream side of the seat portion 14A of the stop valve 10. By doing so, the steam flow is not disturbed by the fastening member 6 for fixing. Further, only one side (stop valve 10 side) of the common valve seat 4 is fixed by the fastening member 6, and the opposite side of the common valve seat 4 can be freely thermally expanded starting from the fixing point by the fastening member 6. When the valve 20 is started and stopped, the common valve seat 4 can be prevented from being damaged due to thermal stress generated by a sudden temperature change. Furthermore, when the combination steam valve 1 is installed vertically (arranged along the vertical direction), the common valve seat 4 is removed from the stop valve 10 side, whereby the second valve body 22 and the like of the lower adjusting valve 20 are stopped. The combination steam valve 1 can be easily disassembled.

  The second valve body 22 that comes into contact with the second valve seat 24 when the valve is closed has a concave valve head 23 on the distal end side (side closer to the second valve seat 24). Thus, by making the valve head 23 of the second valve body 22 into a concave shape, as shown by the streamline 100 in FIG. 2, the valve head 23 on the upstream side of the seat portion 24 </ b> A of the second valve seat 24. The steam flow once stays in the concave portion of the gas and is rectified so that the steam flow follows the second valve seat 24. Therefore, the annular flow can be further stabilized.

As shown in FIG. 2, a cylindrical valve body guide 30 that guides the second valve body 22 is provided on the outer periphery of the second valve body 22. The inner diameter _{D G} of the valve body guide 30 is greater than the diameter (seat diameter) _{D 0} of the seat portion 24A of the second valve seat 24. The valve head 23 of the second valve body 22 is formed with a balance hole 34 that communicates the internal space 32 surrounded by the second valve body 22 and the valve body guide 30 to the intermediate flow path 48.

Thus, by providing the balance hole 34, the vapor pressure in the internal space 32 surrounded by the second valve body 22 and the valve body guide 30 and the intermediate flow path 48 on the upstream side of the second valve body 22 are equal. become. Here, than the diameter D ₀ of the seat portion 24A of the second valve seat 24, because there is the larger inner diameter D _G of the valve body guide 30, the steam forces the net acting on the second valve body 22 as a whole, a vapor stream Direction from the downstream side to the upstream side (that is, the valve closing direction of the adjusting valve). Thus, since the second valve body 22 is always pulled in the direction in which the control valve 20 is closed by the net steam force acting on the second valve body 22 of the control valve 20, the alignment of the second valve body 22 is improved. The turbulence of the steam flow can be further suppressed.

A second valve rod 26 is attached to the second valve body 22. As shown in FIG. 1, the second valve rod 26 of the control valve 20 and the first valve rod 16 of the stop valve 10 extend in opposite directions with the intermediate flow path 48 interposed therebetween. Therefore, the overall shape of the combination steam valve 1 is substantially linear extending along the intermediate flow path 48, and space can be saved when a plurality of combination steam valves 1 are laid out around the turbine casing. It becomes possible.
In the example shown in FIG. 1, the second valve rod 26 of the adjusting valve 20 is arranged so that the central axis C ₂ thereof substantially coincides with the central axis C ₁ of the first valve rod 16 of the stop valve 10. Yes.

  The second valve rod 26 is connected to the actuator at the end opposite to the end to which the second valve body 22 is attached. The driving force of the actuator is transmitted to the second valve body 22 via the second valve rod 26.

A guide bush 28 for guiding the second valve stem 26 is embedded in the bonnet 52. As a result, the second valve stem 26 driven by the actuator slides in the guide bush 28 and moves along the central axis C ₂ of the second valve stem 26.

As described above, in the present embodiment, the regulating valve 20 includes the second valve seat 24 whose diameter increases from the upstream side to the downstream side in the steam flow direction, and the second valve seat when the regulating valve 20 is open. And a second valve body 22 that contacts the seat portion 24A of the second valve seat 24 in a closed state of the control valve 20.
According to this embodiment, since the second valve seat 24 whose diameter is increased from the upstream side to the downstream side of the steam flow is provided, the seat portion 24A is more upstream than the upstream side of the seat portion 24A of the second valve seat 24. The flow path area of the steam is larger on the downstream side. For this reason, the steam supplied from the upstream side of the control valve 20 has a low flow velocity when passing through the seat portion 24A of the second valve seat 24, and the turbulence of the steam flow on the downstream side of the seat portion 24A is suppressed. . Therefore, even if the lift amount of the second valve body 22 is increased to reduce the pressure loss, the state of the annular flow in which the steam flow after passing through the seat portion 24A remains attached to the second valve seat 24 is maintained. Therefore, the vibration of each part of the adjusting valve 20 can be suppressed.
In addition, according to the calculation result using the Computational Fluid Dynamics (CFD) performed by the inventor of the present application, the control valve 20 of the present embodiment has a noise (about 10 dB) compared to the control valve of the conventional configuration ( Vibration) reduction effect was obtained.

  Although an example of the present invention has been described in detail above, the present invention is not limited to this, and it goes without saying that various improvements and modifications may be made without departing from the gist of the present invention.

  For example, in the above-described embodiment, the control valve 20 provided in the valve casing 40 common to the stop valve 10 has been described. However, the control valve for a steam turbine according to the present invention is a separate valve independent of the stop valve. Also good.

  In the above-described embodiment, the control valve 20 having the configuration shown in FIG. 2 has been described. However, in the steam turbine control valve according to the present invention, the valve seat expands from the upstream side to the downstream side in the steam flow direction. The shape is not particularly limited as long as the shape is a diameter, and various configurations can be adopted.

DESCRIPTION OF SYMBOLS 1 Combination steam valve 4 Common valve seat 6 Fastening member 10 Stop valve 12 1st valve body 12A Main valve 12B Sub valve 14 1st valve seat 14A Seat part 16 1st valve rod 17 Strainer 18 Guide bush 19 Baffle plate 20 Adjusting valve 22 Second valve element 23 Valve head 24 Second valve seat 24A Seat part 26 Second valve rod 28 Guide bush 30 Valve element guide 32 Internal space 34 Balance hole 40 Valve casing 42 Stop valve chamber 44 Adjustable valve chamber 46 Steam inlet 48 Intermediate flow path 50 Steam outlet 52 Bonnet 100 Streamline

Claims (5)

This is a regulating valve for a steam turbine that adjusts the amount of steam flowing through the flow path by changing the area of the flow path between the valve seat and the valve body by moving the valve body relative to the valve seat. And
A valve seat whose diameter increases from the upstream side toward the downstream side in the steam flow direction;
A steam turbine control valve, comprising: a valve body that is separated from a seat portion of the valve seat in a valve-open state and abuts against a seat portion of the valve seat in a valve-closed state.   The valve for a steam turbine according to claim 1, wherein a valve head of the valve body has a concave shape. A cylindrical valve body guide that is provided on an outer periphery of the valve body and guides the valve body;
The valve head of the valve body is formed with a balance hole that communicates the internal space surrounded by the valve body and the valve body guide to the upstream space of the valve body,
The regulating valve for a steam turbine according to claim 1 or 2, wherein an inner diameter of the valve body guide is larger than a diameter of a seat portion of the valve seat.   The angle which the central axis direction of the said valve body makes with respect to the tangential direction in the said sheet | seat part extended from the said sheet | seat part is 25-50 degrees, The any one of Claim 1 thru | or 3 characterized by the above-mentioned. The adjusting valve for a steam turbine according to the item. A steam turbine control valve according to any one of claims 1 to 4,
A steam turbine stop valve disposed upstream of the steam turbine control valve;
The combined steam valve, wherein the steam turbine control valve and the steam turbine stop valve are provided in a common valve casing.

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