JPH10299910A - Steam governing valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smooth flow downstream of a valve element so as to prevent noise caused by the collision of jet and noise caused by the generation of a turbulent vortex by providing the bottom face part of the valve element with a flat face, and providing a circumferential groove of approximately angle shape or semicircular cross section near the outer periphery of the flat face. SOLUTION: A bottom face part of a valve element 1 of a steam governing valve is provided with a flat face 7, and a circumferential groove 9 is provided near the outer periphery of the flat face 7. In the bottom face part of the valve element 1, the radius of curvature R1 of the valve element 1 and the radius of curvature R2 of a valve seat 4 are set to be R1=R2, and the flat face 7 is formed in such a position that the distance h1 from a contact point between the valve element 1 and valve seat 4 is 0.05<h1 /d<0.1 to a valve nominal diameter (d). Steam flow around the valve therefore flows smoothly along the valve seat 4, and turbulence of steam flow caused by the collision of jet downstream of the valve is prevented. The groove part 9 is provided in such a way as to slow down the flow from the center part of the valve element 1 before joining main flow, so as to suppress the flow velocity of contraflow of circulating flow and to reduce the turbulence of the flow along the valve seat 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a low noise type steam control valve, and more particularly to a steam control valve for controlling the speed of a steam turbine used in a thermal power plant, a nuclear power plant, a combined cycle power plant, and the like.

[0002]

2. Description of the Related Art A large number of valves are employed in a steam turbine. Among these valves, a steam control valve which is exposed to high-temperature and high-pressure steam is subjected to the most severe operating conditions. Moreover, the steam control valve has a large influence on the entire steam turbine in terms of reliability, performance, and stable operation.

Conventionally, as a steam control valve of a high-output steam turbine, as shown in FIG. 4, a valve with a slave valve including a master valve 1 and a slave valve 2 has been used as a steam control valve. The child valve 2 is formed integrally with the valve stem 3, and the child valve 2 contacts the parent valve 1 by opening and closing the valve stem 3 in the axial direction of the valve, and controls the opening and closing of the parent valve 1. The speed of the steam turbine is controlled by controlling the flow rate of steam by a throat portion formed by the valve body and the valve seat.

In recent years, in order to suppress the vibration of the valve body, the bottom of the valve body is formed flat as shown in FIG. 6, for example, to prevent the vibration due to the turbulence of the steam flow. Has appeared. In addition, as a device related to this type of steam control valve, for example, Japanese Patent Application Laid-Open No. Sho 56-1099
No. 55 or JP-B-61-43589.

[0005]

The steam control valve is used in a state where a large pressure difference is generated between the inlet and the outlet of the valve in order to control the opening and closing of the valve according to the load of the steam turbine. For this reason, a large fluid force acts on the valve body, and the flow around the valve body becomes complicated, which causes vibration and noise. That is, since the steam control valve throttles and controls the flow rate of the steam, the pressure difference before and after the valve becomes very large, and in the throat portion formed by the valve body and the valve seat of the steam control valve, the steam flow becomes excessive. The flow becomes a sonic flow, and the pressure ratio before and after the valve and the area of the valve lift become large.

[0006] Fluid noise generated by fluid is known as Lighthil.
According to the study of l et al., it is known that the speed is proportional to the sixth to eighth power. Also, according to a study by Kojima et al., It is known that when the steam flows from the throat collide with each other, noise becomes larger than when they flow in parallel.

[0007] In the former valve described above, FIG.
As shown by an arrow 5 in FIG. 5, a steam flow collision occurs at the center of the bottom of the valve body, and the collision turbulence causes the valve body to generate vibration noise. On the other hand, in the latter, the collision of the steam flow does not occur at the center of the bottom of the valve body because the bottom of the valve body is cut, but when the operating conditions are different, as shown by the arrow 8 in FIG. A high-speed circulating flow is generated below the bottom portion, and when the circulating flow merges with the main flow at a large angle θ, the main flow is disturbed, and there is also a fear that noise may be generated.

The present invention has been made in view of the above, and it is an object of the present invention to make the flow downstream of the valve body a smooth flow to prevent noise due to jet collision even when the operating conditions of the plant are different. Another object of the present invention is to provide a steam control valve of this type which can prevent noise due to generation of turbulent vortices due to turbulent flow and thereby reduce noise.

[0009]

That is, the present invention provides a steam control system in which a valve body is advanced or retracted in the axial direction of a valve seat to control a steam flow rate by a throttle amount of a throat formed by the valve body and the valve seat. In the valve, a flat surface is provided on the bottom surface of the valve body, and a circumferential groove having a substantially mountain-shaped or semi-circular cross section is provided near the outer periphery of the flat surface. This is to achieve the purpose.

[0010] In this case, the circumferential groove is formed with a depth h of the groove.
And the ratio between the nominal diameter d and the nominal diameter d is 0.03 <h2 / d. Further, the ratio between the distance h from the contact surface between the valve element and the valve seat to the valve element bottom and the nominal valve diameter d is 0.0
It is formed so as to be in the range of 5 <h / d <0.1.

That is, with the steam control valve formed as described above, a flat surface is provided on the bottom surface of the valve body,
A circumferential groove is provided in the vicinity of the outer periphery of the flat bottom surface of the valve body, so that the groove portion reduces the circulating flow area and the circulating flow merges at a small angle when merging with the main flow. The mainstream will not be disturbed,
Therefore, noise in the valve section can be reduced.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. FIGS. 1, 3 and 4 show the essential parts of the steam control valve in cross section. 1 is a valve body, 4 is a valve seat, and 3 is a valve stem. Radius of curvature R1 of the valve element 1
When the curvature radius R2 of the valve seat 4 and the curvature radius R2 of the valve seat 4 are in a relationship of R1 <R2, the pressure ratio and the valve lift condition are set such that the steam flow 5 flows along the valve body 1 by the Coanda effect and the jet collides downstream of the valve. The area is increased, and when the jet collides downstream of the valve in this way, the jet collision generates a larger noise than when the jet flows in parallel. In addition, this shape causes a relatively large noise due to the flow velocity at the valve throat.

In the present invention, as shown in FIG. 3 in an enlarged manner, a flat surface 7 is provided on the bottom surface of the valve body 1 and a circumferential groove 9 is formed near the outer periphery of the flat surface. Is provided. There are various possible shapes of the circumferential groove,
It is best if the cross section is substantially mountain-shaped or semi-circular.

In this case, the bottom surface of the valve body 1 has a valve body curvature radius R1 and a valve seat curvature radius R2 of R1 = R2, and the distance h from the contact point 6 between the valve body 1 and the valve seat 4 is equal to the valve height. Assuming a flat surface 7 at a position where 0.04 <h1 / d <0.09 with respect to the nominal diameter D, the steam flow around the valve flows smoothly along the valve seat as shown in FIG. The turbulence of the steam flow due to the collision of the jet flow downstream of the valve can be prevented.

That is, if the bottom of the valve body is made flat at the position where h1 / d <0.04, the flow after the throat becomes a flow that adheres to the valve body 1 or adheres to the valve body 1. The pressure ratio and the area of the valve lift that result in an unstable flow that changes unsteadily between the flowing flow and the flow adhering to the valve seat 5 increase. Further, if 0.09 <h1 / d, the flow velocity in the throat portion becomes high, and this causes the generated fluid noise to increase.

The jet from the throat formed by the valve element 1 and the valve seat 4 is an annular jet that is ejected in an annular shape. In this annular jet, there is a negative pressure area surrounded by the jet ejected from the throat. In the flow in the negative pressure region, a recirculating flow 8 is formed with a backflow flowing in a direction opposite to the main flow.
Here, as shown in FIG. 3, by providing a circumferential groove 9 in the flat portion 7 on the bottom surface of the valve body 1, the flow from the center of the valve body is decelerated before merging with the main flow, and the circulating flow 8 is formed. By suppressing the reverse flow velocity and reducing the recirculation area, turbulence of the flow along the valve seat can be reduced, contributing to noise reduction.

At this time, it is desirable that the depth of the groove is 0.03 <h2 / d in order to make the recirculation area smaller. Also, the merging section 1 where the circulating flow 8 and the main stream 10 merge.
In 1, the angle θ formed between the circulating flow 8 and the main flow 10 becomes an acute angle, and the merging of the circulating flow 8 and the main flow 10 is made more smoothly,
The generation of turbulent vortices due to merging is reduced.

While the above description has been made with reference to a valve with a child valve used for a steam control valve, the same effect can be obtained even if the gist of the present invention is adopted for another valve type having no child valve. Of course.

As described above, in the steam control valve formed as described above, the bottom surface of the valve element is formed in a circular shape, and the ratio of the depth h2 to the nominal valve diameter d is 0.03 <h2. / D, the flow velocity of the steam flow in the throat portion formed by the valve body and the valve seat is reduced, and the steam flow pattern follows the valve body. The flow does not flow, and the flow does not collide at the lower part of the valve body, so that the noise caused by the collision that occurred conventionally can be reduced, and the valve of a steam turbine used in thermal power, nuclear power, and combined cycle power plants Fluid noise generated by the surrounding steam flow can be reduced.

[0020]

As described above, according to the present invention, even when the operating conditions of the plant are different, the flow downstream of the valve body is made a smooth flow to prevent the noise due to the collision of the jet, and the flow is disturbed. Accordingly, it is possible to obtain a steam control valve of this type which can prevent noise due to generation of turbulent vortices and thereby reduce noise.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view showing one embodiment of a steam control valve of the present invention.

FIG. 2 is a vertical sectional side view showing a conventional steam control valve.

FIG. 3 is an enlarged sectional view showing a main part of the steam control valve of the present invention.

FIG. 4 is a vertical side view showing a conventional steam control valve.

FIG. 5 is an enlarged sectional view showing a main part of the steam control valve of the present invention.

FIG. 6 is a cross-sectional view showing the periphery of a conventional steam control valve.

[Explanation of symbols]

1 ... valve body (parent valve), 2 ... small valve, 3 ... valve stem, 4 ... valve seat, 5
... Steam flow, 6 ... Point of contact between valve body and valve seat, 7 ... Flat surface, 8 ...
Recirculation flow, 9: groove, 10: main flow, 11: junction.

 ──────────────────────────────────────────────────の Continued on the front page (72) Fumio Kato Inventor 7-2-1, Omika-cho, Hitachi City, Ibaraki Pref.

Claims (4)

[Claims] 1. A steam control valve for controlling a steam flow rate by controlling a steam flow by a throttling amount of a throat formed by a valve body and a valve seat by moving a valve body toward and away from an axial center of a valve seat. And a circumferential groove having a substantially mountain-shaped or semi-circular cross section in the vicinity of the outer periphery of the flat surface. 2. A steam control valve in which a valve body is advanced and retracted in the axial center direction of a valve seat to control a steam flow rate by a throttle amount of a throat portion formed by the valve body and the valve seat. It is formed in a plane, and a circumferential groove is provided in the vicinity of the outer periphery of the plane portion. The circumferential groove is formed so that the ratio of the groove depth h to the nominal valve diameter d is 0.03 <h2 / d. A steam control valve characterized by being formed. 3. The steam control valve according to claim 2, wherein the circumferential groove has a substantially mountain-shaped or semi-circular cross-sectional shape. 4. The ratio of the distance h from the contact surface between the valve element and the valve seat to the valve element bottom to the nominal valve diameter d is 0.05 <h / d.
4. The steam control valve according to claim 2, which is formed in a range of <0.1.