JPH09296869A - Large-diameter control valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate any control at a minute open area by forming a valve element of a large-diameter control valve into a profile type of valve seat form. SOLUTION: A valve element 1 has one contact point to a valve seat 2 and it is formed into a profile shape as finely increasing a clearance along a valve seat diameter ϕd. Therefore, when a valve element 1 is lifted, a minimal opening part between the valve seat 2 and the valve element 1 shifts as finely increasing the profile along the circular arc of a radius R1 of the valve seat 2. With this shifting, opening is controlled, and a flow gain is also controlled. When the valve seat 2 is of a projection type, an end part of the valve element 1 is formed into a recess type of a radius R3 being larger in curvature than a projection part of the projection type. With this formation, in a minute open area, an increase in a passage area to the valve opening is made to be smallness as compared with the conventional plug valve, and thus it is possible to cope with the promotion of a large diameter in the control valve.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a large diameter control valve for a steam turbine or the like.

[0002]

2. Description of the Related Art There are various shapes such as a conventional cylindrical shape and a plug shape as the valve body shape of a large diameter control valve of a steam turbine. FIG. 3 is a cross-sectional view of a conventional plug having a very general plug shape. The inlet of the valve diameter φd is a valve seat 11, and the valve seat 11 is formed in an arc having a radius R _1. There is. Further, the valve body 12 is formed by an arc having a radius R ₂ larger than the arc of the valve seat 11, and the radius R of the valve seat 11 is
It touches at the center of ₁ arc. The diameter of the contact point between the valve body 12 and the valve seat 11 is φD _S , which is the minimum opening due to the lift of the valve rod in the slightly open region.

Now, the valve lift in the slightly open region is L, the opening length is H,
If the contact angle with the valve seat is θ, then H = L / sin θ, and the passage area (side area of the head cone) A is naturally proportional to the opening length H, so the road area A is also proportional to the valve lift L. To do.
The passage area / valve opening is called a flow rate gain, and is a value that is a proportional number of the passage area and the valve opening.

[0004]

As described above, in the plug valve, the relationship between the valve lift and the flow rate increases in proportion to the valve shift diameter in the fine opening range. Therefore, the valve diameter becomes large, and it becomes very difficult to control in the slightly open region. The present invention has been made to solve such a drawback, and an object thereof is to facilitate control in a slightly open region.

[0005]

The structure of the present invention for achieving the above object is characterized in that the valve body of the large-diameter control valve is formed in a valve seat profile.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIG. The profile is formed while slightly increasing the gap along the valve seat diameter φd. Therefore, when the valve body 1 is lifted, the minimum opening portion between the valve seat 2 and the valve body 1 moves along the arc of the radius R ₁ of the valve seat 2 while the profile slightly increases, so that the opening degree is suppressed. To be done. That is, the flow rate gain is suppressed.

When the valve seat 2 has a convex shape as shown in FIG. 1, the end portion of the valve body 1 is formed in a concave shape having a radius R _{3 having} a larger curvature than the convex shape of the convex shape. FIG. 2 is a relationship diagram of the passage area and the valve opening degree of the profile valve of the present invention and the conventional plug valve. In contrast to the plug valve increasing in proportion as shown by the solid line,
In the profile valve of the present invention, the increase of the passage area with respect to the valve opening degree is small in the fine opening region A where the profile is effective along the arc of the valve seat.

[0008]

As described above, according to the present invention, since the valve element is formed in the shape of the valve seat profile, the increase in the passage area with respect to the valve opening becomes smaller than that of the conventional plug valve, and the This has the effect that control in the open region becomes easy and the control valve can have a large diameter.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a comparison diagram of the present invention and a conventional example.

FIG. 3 is a cross-sectional view showing a conventional example.

[Explanation of symbols]

 1 valve body 2 valve seat

Claims (2)

[Claims] 1. A large-diameter control valve, wherein the valve body of the large-diameter control valve is formed in a valve-seat profile shape. 2. When the profile of the valve seat shape is convex, the end portion of the valve body is formed in a concave shape having a larger curvature than the convex portion of the convex shape. Large diameter control valve.