JPS5865905A - Control valve of steam turbine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a valve having an inlet opening on a side surface of a valve case, a valve body movable within a valve guide inside the valve case, and a valve seat provided inside the valve case. and a diffuser connected to the edge of the seat, and the valve guide, the valve body, the valve seat, and the diffuser relate to a control valve of a steam turbine disposed coaxially with the long axis of the valve case.

For example, the West German magazine Siemens-Zeitschbrift (8iemens-Zeitschbrift)
) 4 1 (1967), ``Steam Turbine with Steam Turbines'', pp. 75-76, such a control valve must, on the one hand, ensure the desired curvature characteristics by changing the stroke position of the valve body; On the other hand, pressure loss must be kept to a minimum in the fully open state.Furthermore, due to the size and capacity limitations of the valve operating device, the operating force must be small.For built-in valves mainly used in steam turbines, the operating force is is reduced by choosing a relatively small diameter of the valve body.Therefore, in the narrow cross-sectional area behind the valve seat, high flow velocities occur even in the fully open state of the control valve, and the pressure in the following line In order to reduce losses, the flow velocity is reduced with low losses in a diffuser connected after the valve seat.This cross-sectional change of the control valve, which can be understood as a tapering-to-diverging flow path, shows that the narrowest cross-section The pressure is lowest at , and increases along the diffuser.

When the flow is curtailed for control purposes and the valve element approaches the valve seat, the closer the valve element is to the valve seat, the more severe the separation of the flow from the wall surface occurs in the diffuser. Parts of the flow that exceed the average velocity are then slowed down by the generation of vortices.

The stronger the stroke, the more likely a supersonic flow will occur behind the valve seat, and this flow will be extinguished by a shock wave. However, two forms of flow velocity reduction and loss generation due to generation of vortices or generation of shock waves are unsteady with significant turbulence, pulsation, and fluctuations in the flow that first emerges as a free jet after the valve seat. Produce behavior.

Particularly strong fluctuations can also occur when the ripples are relatively small.

A characteristic of the flow inside a diffuser is that the alternation between the flow that adheres to the wall and the flow that has separated occurs stochastically, so that the start of flow separation occurs unsteadily. Because of this, pressure cannot be recovered in the diffuser.

? The strong pressure shock generated by this excites vibrations in the valve body.

An object of the present invention is to provide a control valve that reduces the fluctuating force that excites vibrations in a valve body.

This object is based on the present invention in the fjlf type valve mentioned above, in which the inlet is offset from the long sleeve of the valve case so that the inflowing flow is given a swirl about the long axis of the valve case. This is achieved through careful placement.

This invention is based on the knowledge that the flow after the crest point and inside the diffuser is stabilized by swirling, and that such swirling of flow I can be achieved by eccentrically arranging the inlet with respect to the long sleeve of the valve case. It is based on The centrifugal action created by the swirl pushes the flow outwards, avoiding separation of the flow from the diffuser walls.

To avoid additional pressure losses due to this, the strength of the swirl imparted to the flow must be limited. For this purpose, the eccentricity of the inlet should be adjusted to 10 to 50% of the inner diameter of the inlet.
It is better to set it in the range of %.

Next, the present invention will be explained in detail with reference to drawings of one embodiment of a control valve based on the present invention.゛In Fig. 1, only the main parts of the valve case 1 of the control valve are shown. Arrow S
The steam flow shown by flows into the valve case 1 through the side inlet 2, passes through the ring-shaped cross section formed by the tip 31 of the valve body 3 and the valve seat 4, and flows downward from the valve case 1. do. The outlet part is formed as a diffuser.

In this case, the cross-sectional change of the control valve is understood as a flow path that tapers and widens at the end, the valve seat 4 is provided in the tapered flow path section in front of the narrowest part f, and the flow path section that widens toward the end is formed by the diffuser 5. In this case, it is formed by a valve seat bushing 6 made of tapered material and pressed into the valve housing 1.

The valve body 3 is constructed as a piston and guided axially in a valve guide 7 which is constructed as a cylinder and is fixed to the valve housing 1 . The stroke position of the valve body 3, which determines the pattern of the steam flow S, is controlled by a valve operating device (not shown) via the valve stem 8, which is firmly connected to the valve body 3 in the long sleeve L of the valve case 1 (n direction). Set.

In order to reduce the fluctuating forces that excite vibrations in the valve body 3, the steam flow behind the valve seat 4 and into the diffuser 5 must be stabilized. This is achieved by the swirl shown by the linear arrow once imparted to the steam flow S. The swirling prevents the flow from separating from the walls of the diffuser 5 due to the centrifugal action produced in the steam flow S.

How to give swirl to the steam flow S will be explained with reference to FIG. 2. Therefore, the center line M1 of the inlet 2 is not arranged radially along the long axis of the valve case 1 as usual, but is arranged eccentrically by e with respect to the long axis.

The eccentricity i4-e thus produces an asymmetrical inflow relative to the valve case 1, which gives rise to the swivel shown in FIG. The strength of the swirl is limited to avoid additional pressure losses due to this rotation. This restriction is to ensure that the eccentric bone e does not exceed a suitable size, and in the illustrated embodiment the eccentricity e is approximately 15% of the inner diameter Di of the inlet 2.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of the main parts of one embodiment of a control valve according to the present invention, and FIG. 2 is a cross-sectional view taken along section line 1--n in FIG. In the drawing, ] is the valve case, 2 is the inlet, 3 is the valve body,
4 is the valve seat, 5 is the diffuser, 7 is the valve guide, D is the arrow indicating turning, Di is the inner diameter of the inlet, e is the amount of eccentricity, L is the long axis,
S is flow.

Claims (1)

[Claims] 1) An inlet opening on the side of the valve case, a valve seat provided in the valve case above the valve body movable within the valve guide inside the valve case, and a valve seat provided in the valve case behind the valve seat. In a control valve for a steam turbine, the valve guide, the valve body, the valve seat, and the diffuser are arranged coaxially with the long axis of the valve case, and the valve guide, the valve body, the valve seat, and the diffuser are arranged coaxially with the long axis of the valve case. A control valve for a steam turbine, characterized in that the inlet is disposed eccentrically with respect to the long axis of the valve case so as to provide rotation about the long axis of the case. 2. A control valve for a steam turbine according to claim 1, wherein the eccentricity of the inlet is in the range of 10 to 50 inches of the inner diameter of the inlet.