RU2743873C2 - Balanced rotary control valve - Google Patents

Abstract

FIELD: mechanic engineering.SUBSTANCE: disclosed is a balanced rotary control valve mainly for steam turbines comprising a valve chest, an inlet and outlet pipe, a rod, an axle-box, a valve chest cover characterized in that for the outlet of steam a cylindrical cup with diffuser part and windows on inlet cylindrical part of diffuser the area of which exceeds the interior cross-sectional area of cylindrical cup by 50-60% and said windows are overlapped by rotatable diaphragm with windows identical to windows on inlet cylindrical part of diffuser with rod being used for rotation of diaphragm connected to rotatable diaphragm via splined coupling and ring valve being designed on rod from the side of axle-box overlapping ring hemispheric bypass on end surface of axle-box.EFFECT: technical result aims at reduction of dynamic loads introduced to rod and when fully opened, valve has minimum possible hydraulic resistance, which leads to improved performance of high-pressure turbine cylinder.1 cl, 3 dwg

Description

The invention relates to the field of power engineering and is devoted to increasing the reliability and reducing the hydraulic resistance of control valves designed primarily for steam turbines.

In terms of functionality, an analogue for the new valve under consideration can be an unloaded control valve, which is used on the turbines of the Leningrad Metal Plant, shown in figure 1 (Zaryankin A.E., Simonov B.P., "Regulating and stop-control valves of steam turbines", Publishing house MPEI 2005)

In figure 1, the following designations are adopted.

1 - poppet valve

2 - the cylindrical part of the spool (nut)

3 - unloading valve

4 - stock

5 - bushing limiting the travel of the unloading valve

6 - guide cylinder

7 - windows for supplying steam to the inner part of the valve

8 - windows for supplying steam to windows 7 in the cylindrical part of the spool

9 - the inner cavity of the valve

10 - protective glass

At the initial moment of opening the valve, when the unloader valve, when it rises within the limits defined by the restricting sleeve 5, provides the connection of the internal cavity of the valve 9 with the space behind the valve, the pressures are equalized between these cavities and, accordingly, the force required to lift the spool 1 sharply decreases. However, as the valve rises, the pressure behind it increases and the force pressing the valve spool to the head 3 of the stem 4 sharply decreases and if there are high pressure pulsations in the flow, spontaneous movement of the spool is possible within the free travel of the unloading valve. In the presented design, to prevent the development of self-oscillations, additional loading by steam force is used at large valve lifts.

For this purpose, at approximately half opening of the valve, the window 7 on the cylindrical part of the spool is connected to the ports 8 in the guide cylinder 6 and an intensive secondary flow of steam occurs through the inner cavity 9 and the seat of the unloading valve into the diffuser part of the seat.

At the same time, the pressure inside the valve increases and the force increases, pressing the valve spool against the stem head, preventing its spontaneous axial movement. The main disadvantage of the valve under consideration with flow-through loading with an additional axial force is that when the steam passing through the inner part of the valve is mixed with the main part of the steam passing between the valve and the seat, very large pressure pulsations occur (up to 10% of the initial steam pressure) (Kostyuk A.G., Kushenko A.I., Nekrasov A.V., Medvedev S.V. "Experimental analysis of pressure pulsations of steam-conducting parts of a turbine unit" Heat power engineering 2000, No. 6 pp. 50-57) and as a result, high dynamic loads arise on all parts of the control valve, significantly reducing its vibration reliability.

In addition, the highly unstable steam flow after the valve, entering the nozzle apparatus of the first stage of the turbine, negatively affects its reliability.

The disadvantages of the valve include the fact that with a poppet-shaped spool, the hydraulic resistance of the valve is at the level of 5% of the initial steam pressure.

According to the degree of compliance of the control valve with complex and numerous operational requirements, we will take the valve shown in figure 2 as a prototype, where the following designations are adopted

2 - cylindrical part (nut) of the spool

3 - unloading valve

4 - stock

6 - guide cylinder

9 - the inner cavity of the valve

11 - profiled spool

12 - unloading valve saddle

13 - diffuser valve seat

14 - bushing

15 - perforation hole

16 - axle box

17 - damper chamber

(Zaryankin A.E., Simonov B.P. "Regulating and stop-regulating valves of steam turbines" Publishing house MPEI 2005)

In contrast to the analogue (figure 1), in this case, both the unloading system and the valve loading system with additional steam force have been fundamentally changed when it rises above 50% of the total opening.

Here, the standard system for unloading the valve from axial forces is displaced inside the valve, and between the seat 12 of the unloading valve 3 and the profiled spool 11, a damper chamber 17 is formed, connected to the space behind the valve by two belts of perforation 15, through the holes of which steam is released from the inner cavity 9, in diffuser seat 12 of the valve spool.

When the valve is lifted over 50% of its full opening, the holes in the cylindrical nut 2 are closed by the sleeve 14 and the pressure in the internal cavity 9 of the valve increases to the initial steam pressure, ensuring reliable pressing of the spool 11 to the head 3 of the rod 4.

With the help of perforation holes on the profiled streamlined surface of the spool 11, closed to a common damper chamber 17, pressure pulsations are damped, which provides a sharp decrease in the dynamic forces perceived by the rod 4.

In addition, with the help of perforation holes on the spool 11 and on the surface of the diffuser seat 13, the circumferential irregularity of the steam flow is reduced, and when supersonic speeds occur (turbine start-up modes), these holes play the role of absorbers of the wave structure of the flow that occurs in the region of supersonic speeds.

The features of the prototype include the profiling of the streamlined surface of the spool Ne of the inlet section of the seat 13 from the condition of an uninterrupted flow of steam in the valve axisymmetric channel, which is formed when the valve rises between the indicated surfaces and 100% centering of the spool 11 inside the guide cylinder 6. Such alignment is achieved by performing on the outer cylindrical part of the spool of the centering sector with an angle of 60 °, the radius of which coincides with the radius of the inner surface of the guide cylinder 6.

By means of these design changes, the valve in question meets almost all operational requirements, having the following characteristics.

1 - The hydraulic resistance at full opening in the absence of a protective grid does not exceed 2% of the initial vapor pressure

2 - Allows any degree of unloading from axial forces without the danger of developing axial self-oscillations

3 - The dynamic forces acting on the valve stem do not exceed 0.5% of the maximum static stem forces

4 - Maintains the original centering of the spool relative to the seat during the entire operation time, which provides it with a high density

5 - Compared to standard valves, it has a reduced acoustic emission. The disadvantages of this valve include:

- common to all angle valves (except for valves with liquid metal stem seals) disadvantage, consisting in the leakage of steam along the stem;

- a relatively complex design that increases the cost of the valve;

- a common drawback for all existing unloading valves - a strong dependence of the valve's power characteristic on the initial steam pressure and the position of the valve spool.

The technical problem solved in the present invention consists in eliminating the noted disadvantages. In the new valve, all these disadvantages are absent, while maintaining all the above advantages of the prototype. A longitudinal section of the new valve is shown in figure 3, where the following designations are adopted.

4 - stock

16 - axle box

17 - cylindrical glass with a diffuser

18 - annular rotary diaphragm

19 - splined coupling

20 - ring valve

21 - windows at the entrance of the cylindrical glass

22 - windows on a cylindrical annular diaphragm

23 - annular hemispherical saddle

24 - valve box

25 - inlet pipe

26 - valve box cover

27 - outlet branch pipe

The main part of the new valve is a cylindrical cup with a diaphragm 17, pressed into the valve housing 24.

For the passage of steam inside the cylindrical glass 17, windows 21 are made on its lateral surface. Their total area F ₀ in order to maximize the reduction of hydraulic resistance must exceed the inner transverse area of the glass 17 by at least 50-60%.

Thus, with diffuser steam removal from the valve box, the total area of the windows 21 should be equal to

(n - число окон на цилиндрической поверхности стакана, l₀ - высота, a h₀ - ширина этих окон, a D₀ - внутренний диаметр цилиндрического стакана 17).

(n is the number of windows on the cylindrical surface of the glass, l ₀ is the height, ah ₀ is the width of these windows, and D ₀ is the inner diameter of the cylindrical glass 17).

Since the total width of the window for the passage of steam cannot occupy more than half the length of the inner bypass of the cylindrical glass 17 with an inner diameter D ₀ , the width of one window h ₀ will be equal to

Then, substituting (3) into (2), we obtain

From relation (4) it follows that the height of the windows l ₀ in the cylindrical inlet part of the diffuser does not depend on their width h ₀ , which is determined by the inner diameter of the inlet section of the diffuser D ₀ and the adopted number of windows n ₀ .

The outer cylindrical part of the glass 17 is closed by a rotary diaphragm 18, on the cylindrical part of which the above-mentioned windows for the passage of steam are made. Their number n ₁ is equal to the number of windows on the surface of the glass 17, and the configuration of the windows on the rotary part of the diaphragm is identical with the windows on the inlet cylindrical part of the diffuser.

However, in order to reliably overlap the windows at the entrance to the diffuser by the rotary diaphragm, the windows on the diaphragm should be made with a slightly smaller area and their linear dimensions l ₁ and h ₁ should be taken equal

l ₁ = 0.95 * l ₀ and h ₁ = 0.95 * h ₀ (where h ₁ is the width of the windows on the rotary diaphragm 18)

those. enter 5% overlap between the windows in question.

An annular rotary diaphragm 18 is connected to the stem 4 by means of a spline coupling 19, which allows axial displacement of the stem 4.

The stem 4 is made together with the annular valve 20 facing the valve box 26, and in the axle box 16 there is an annular hemispherical seat 23, which is closed by the annular valve 20, thereby eliminating steam leakage along the drive stem 4.

The stem 4 is connected to the stem of the valve drive system by means of a rotary coupling that converts the translational movement of the stem of the drive system into rotational movements of the stem 4, connected by the splined coupling 19 with a rotary annular diaphragm 18.

The considered device operates as follows. In the closed state, the rotary annular diaphragm 18 completely covers the windows 21 in the nozzle 17, thereby blocking the access of steam to the flow path of the turbine.

When steam is supplied to the valve box 24, a buoyant force Ryo acts on the stem 4, equal to

(Р ₀ - steam pressure in the valve box, В - atmospheric pressure, d - stem diameter)

Under the action of this force, the annular valve 20 is pressed against the annular hemispherical seat 23, ensuring a complete stem seal.

When the servo motor of the valve is turned on, the stem 4 rotates and as the angle of rotation increases, it increases the degree of opening of the windows 21, thereby increasing the passage of steam into the turbine. The rotation sector of the control rotary diaphragm 18 depends on the number of inlet windows 21 in the cylindrical part of the nozzle 17. With one window (half of the cylindrical surface of the rotary diaphragm is open for steam passage), the angle of rotation of the diaphragm 18 is 180 °, with two windows the angle of rotation of the diaphragm is 90 ° with four windows 45 °, with eight windows 22.5 °, and so on.

It is important to note that in the proposed valve the force required to rotate the diaphragm 18 does not depend on the initial vapor pressure in the valve box and is determined only by the friction forces between the inner surface of the cylindrical part of the rotary diaphragm 18 and the outer cylindrical surface of the glass 17 and the friction force of the annular valve 20 when it movement along the annular seat 23, made in the axle box 16.

In this case, the required power of the servo motor is sharply reduced and, accordingly, allows a relatively low pressure in the turbine control system, which significantly increases the reliability of the entire hydraulic part of the control system.

Compared to the prototype (figure 2), the valve is extremely simple to manufacture, practically does not require periodic repairs, is easily disassembled, does not transfer dynamic loads to the rod and, when fully opened, has the lowest possible hydraulic resistance, which leads to an increase in the efficiency of the high-pressure cylinder of the turbine.

Thus, a new control valve completely unloaded from axial forces is proposed, mainly for steam turbines containing a valve box, an inlet pipe, an outlet pipe, a valve box cover, a drive rod, characterized in that steam is removed from the valve box through a cylindrical sleeve containing a series windows for steam passage, which are overlapped by a cylindrical rotary diaphragm with windows of the same configuration as the windows on the cylindrical surface of the glass, and to rotate the cylindrical diaphragm, a rotary rod is used, connected to the rotary diaphragm by a splined coupling, and the rotary rod is made together with a sealing with a disk, on the side of which, facing the valve box, there is a hemispherical ring, which is included in the corresponding hemispherical annular inflow on the axle box.

It should also be noted that the dimensions of the windows for the passage of steam on the cylindrical inlet of the diffuser and on the rotary diaphragm are determined by the following relations.

l ₀ = 0.75 * D ₀ h ₀ = s ₁ * D ₀ / 2n = 1.57 D ₀ / n l ₁ = 0.95 * l ₀ h ₁ = 0.95 * l ₀

Where l ₀ and h ₀ are the height and width of the windows on the cylindrical inlet of the diffuser, l ₁ and h ₁ are the height and width of the windows on the rotary diaphragm, n is the number of windows, D ₂ is the inner diameter of the narrow section of the glass, D ₀ is the inner diameter the cylindrical part of the glass.

Sources of information used

1. Zaryankin A.E., Simonov B.P. Regulating and locking - regulating valves of steam turbines. Publishing house MEI. 2005 year

2. Kostyuk A.G., Kumenko A.I., Nekrasov A.V., Medvedev S.V. Experimental analysis of pressure pulsations of steam-conducting elements of a turbine unit. Heat engineering 2000, No. 6 p. 50-57.

Claims (1)

An unbalanced rotary control valve, mainly for steam turbines, containing a valve box, inlet and outlet pipes, stem, axle box, valve box cover, characterized in that a cylindrical nozzle with a diffuser part and windows on the inlet cylindrical part of the diffuser is used to exit the steam from the valve, the area of which is 50-60% greater than the inner transverse area of the cylindrical glass, and these windows are covered by a rotary diaphragm with windows identical to the windows on the inlet cylindrical part of the diffuser, and the diaphragm is rotated using a rod connected to the rotary diaphragm by a splined coupling, and on the rod from the side the axle box is made of an annular valve that overlaps the annular hemispherical seat on the end surface of the axle box.

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