JPH0370087B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a steam control valve that controls the flow rate of steam flowing into a steam turbine.

[Conventional technology]

FIG. 11 shows a conventional steam control valve. A slidable valve element 4 is provided on the inner surface of a cylindrical sleeve 3 fixed between the valve case 1 and the upper lid 2, and when the valve stem 5 moves upward, a slidable valve element 4 is provided on the valve stem shoulder 12 and the valve element 4. The valve body 4 is raised by engagement with the protrusion 13, and the large valve seat 9 is placed in an open state. In Figure 11, the center line 20
The left side shows the valve fully open state, and the right side shows the valve fully open state. As is clear from this figure, in the fully open state, the small valve seat 8 and the large valve seat 9 are closed by pressing the valve stem 5 downward, and the inlet steam chamber 6 and pressure chamber 7 are connected to each other by the sleeve. 3 and valve body 4
The pressure is the same because the two communicate through the gap.
Then, when the valve stem 5 moves upward, the valve stem shoulder 12
Until the projection 13 comes into contact with the small valve seat, only the small valve seat is opened, and the valve body 4 is connected to the pressure chamber 7 and the outlet flow path 1.
The large valve seat 9 is in a closed state because it is pressed downward by the pressure difference between the large valve seat 9 and the large valve seat 9. When the valve stem further rises, the valve stem shoulder 12 and the protrusion 13 engage and move the valve body 4 upward, so that the large valve seat 9 opens.

[Problem that the invention seeks to solve]

FIG. 12 shows the pressure conditions in the inlet steam chamber 6, pressure chamber 7, and outlet flow path 11 when the valve is opened and closed. 12th
In the figure, P ₁ is the pressure in the inlet steam chamber 6, P ₂ is the pressure in the pressure chamber 7, and P ₃ is the pressure in the outlet flow path 11.
In such a conventional device, depending on the relationship between the pressure state and the amount of valve stem movement, vibration and noise of the valve become intense, which may cause problems in the operation of the steam turbine. This phenomenon occurs in a specific range (around section A in the figure) where the small valve seat 8 is fully opened and the large valve seat 9 is opened and the flow rate increases to some extent. In this case, the pressure in the inlet steam chamber 6 is P ₁ and the pressure _P3 of the outlet flow path 11, the state downstream of the large valve seat 9 is a supersonic flow. Originally, in a steam control valve that controls the steam flow rate, the condition that the downstream of the large valve seat 9 becomes a supersonic flow is unavoidable.
Various structural improvements have been made.

Tokukowa 5-44263 is the flow of the large valve seat 9 and the valve body 4.
It provides a structure that prevents resonance phenomena caused by interference with the space formed inside the device. In addition, special public service 1977-
20891 has a valve stem 5 in the gap between the sleeve 3 and the valve body.
A plurality of grooves are provided in the moving direction of the valve seat 8, and the grooves communicate the inlet steam chamber 6 and the pressure chamber 7.
Even if the valve body 4 is fully opened, the drop in pressure P ₂ in the pressure chamber 7 is reduced, the pressure difference P ₂ −P ₃ is increased, and the force pressing the valve body 4 downward is increased, thereby reducing the vibration received from the fluid. It has a structure that reduces vibration amplitude of the valve body 4 due to force.

In addition, related publicly known examples proposing a structure that improves the flow around the valve body and reduces vibration are JP-A-52-126530, JP-A-54-54332, and JP-A-Sho.
54-54333 etc.

However, since supersonic flow has complex unsteadiness due to the generation of shock waves and its interference with the flow channel walls, the above-mentioned known techniques can be used even under different usage conditions. It is not general enough to be applied. Therefore, there is a fundamental need for the development of a structure for stabilizing the supersonic flow.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a steam acceleration valve structure for reducing the vibration and noise of a steam control valve encountered during operation of a steam turbine.

[Means for solving problems]

In order to achieve the above object, the present invention has an eleventh aspect.
Utilizing the fact that the sleeve 3 and the valve body 4 described in the figure change their positional relationship with each other when the valve is opened and closed,
A hole is provided in the sleeve 3 and the valve body 4 to communicate the inlet steam chamber 6 and the pressure chamber 7, and the opening area of the hole between the sleeve 3 and the valve body 4 changes when the valve is opened and closed. , the area of the hole in the sleeve 3, the hole in the valve body 4, and the valve stem 5 are adjusted so that the pressure _P2 in the pressure chamber 7 is at least twice the pressure _P3 in the outlet flow path 11.
and the valve body 4 to adjust the pressure in the pressure chamber 7 and allow pressure fluid to flow from the flow path 10 to the outlet flow path 11 at valve openings that cause severe valve vibration and noise. Make it squirt aggressively. By this,
The flow pattern downstream of the valve body is based on the large valve seat 9.
The supersonic flow with a high Matsuha number that has passed through becomes an annular flow, and the center part becomes a supersonic flow with a lower Matsuha number, and due to the interference effect at the annular boundary of both supersonic flows, the The flow is stabilized and low vibration and noise are achieved.

[Function] With the above structure, the pressure in the pressure chamber 7 is adjusted according to the opening degree of the valve, and the inlet steam chamber 6 and Since the structure is configured such that the steam passing area of the holes provided in the sleeve 3 and the valve body 4 for communication with the pressure chamber 7 is increased, the pressure in the pressure chamber 7 is reduced when the opening degree of the large valve seat 9 is small. can be made higher than in the case of conventional technology, and the flow path 10
Since the flow rate necessary for the supersonic jet flow from the outlet flow path 11 is ensured, the interference effect between the two supersonic flows in the outlet flow path 11 is satisfied, and the stabilization of the flow can be achieved.

By the way, the interference phenomenon at the boundary between two concentric supersonic flows ejected in an annular manner at the center and around it is caused by (a) the flow direction caused by the collision of the shock waves (high pressure) and expansion waves of both jets; pressure is equalized, and the intensity of shock wave reflection at the boundary is weakened.
(b) In an annular jet, the shock wave that concentrates at the center and becomes stronger is extinguished by the jet at the center, resulting in an axisymmetric flow that is close to a simple two-dimensional flow.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.

FIG. 1 is a sectional view showing an embodiment of a steam acceleration valve according to the present invention. In FIG. 1, the movable part is divided, and the left half shows the fully open state, and the right half shows the fully open state. In FIG. 1, the valve case 21 and the upper cover 2
2 forms an acceleration valve main body, and a sleeve 23, a valve body 24, and a valve rod 25 that can be operated from the outside are housed inside the main body. Also, valve stem 2
5 is provided with a shoulder portion 26, and when the valve stem 25 rises and the shoulder portion 26 comes into contact with the protrusion 27 of the valve body 24, the valve body 24 and the valve stem 25 move together. It is structured to do this. Sleeve 23 and valve body 2
The contact surface with 4 is configured to have a gap large enough to allow sliding. Furthermore, the valve body 24 has a small valve seat 3.
A plurality of holes 28 penetrating from the outer circumferential surface to the inner circumferential surface of the valve body 24 are provided on the upstream side of the valve body 24.
A plurality of holes 29 are provided to penetrate the sliding surface.
Note that the holes 28 and 29 are installed at the same position in the circumferential direction. In the fully open state shown in the right half of FIG. 1, the small valve seat 30 and the large valve seat 31 are in a closed state, and the inlet steam chamber 32 and the outlet flow path 35 are in a state of being cut off. Upper lid 22, sleeve 23
A pressure chamber 33 formed by the valve body 24 communicates with the inlet steam chamber 32 through a gap between the sliding surfaces of the sleeve 23 and the valve body 24 . Here, in the closed state, the holes 28 and 29 are set to be in a state of slight communication. Further, in the closed state, the valve stem shoulder portion 26 and the protrusion portion 27 are configured to have a gap g.

Next, the operation of the steam control valve configured as described above will be explained. In the process from the closed state in the right half of FIG. 1 to the fully open state in the left half, when the valve stem 25 moves upward, only the valve stem 25 moves until the gap g disappears, and the valve body 24 3
It does not move because it is pressed downward by the force due to the pressure difference between 3 and the outlet flow path 35.
The large valve seat 31 remains closed. On the other hand, in the small valve seat 30, as the amount of movement of the valve stem 25 increases, the number of steam passages increases, and the valve seat 30 becomes fully open when the gap g becomes zero. Steam flow is inlet steam chamber 3
2, enters the pressure chamber 33 through the gap between the sliding surfaces of the sleeve 23 and the valve body 24, and is discharged from the flow path of the small valve seat 30, through the flow path 34, and into the outlet flow path 35. In this case, since the flow path area in the small valve seat 30 is larger than the flow path area due to the gap between the sliding surfaces of the sleeve 23 and the valve body 24, the gap g decreases to zero, and the small valve seat 30 In the process of fully opening, the pressure in the pressure chamber 33 gradually decreases. Next, the valve stem shoulder 26, the valve body 24, and the protrusion 27 come into contact (with a gap g
= 0), and when the valve stem 25 further rises, the valve stem 2
5 and the valve body 24 move as one,
As the large valve seat 31 moves toward the fully open state, the area of the flow path where the holes 28 and 29 communicate with each other increases. As a result, the pressure in the pressure chamber 33 is reduced to
It rises because the amount of steam flowing in from 8 increases.
If such an operating state is shown in terms of pressure changes in each part, it will be as shown in FIG. 2, which is significantly different from the case of the prior art shown in FIG. 12. That is, the pressure P ₁ in the inlet steam chamber 32 and the pressure P ₃ in the outlet flow path 35 are the same in FIG. 12 and FIG. 2, but the pressure P ₂ in the pressure chamber is different. In FIG. 2, which shows an embodiment of the invention, the area where valve vibration is likely to occur is located to the right of the figure (the state in which the valve stem is further raised) from the fully open position of the small valve seat shown in the figure. In part A) shown in the figure, the relationship P ₂ /P ₃ ≧2 is established. This P ₂ /P ₃ relationship can be maintained by appropriately determining the relationship between the flow path areas of the hole 28, the hole 29, and the small valve seat 30, and is the most different from the configuration of the prior art. This is the point. Note that the pressure P′ ₂ in Fig. 2 is the first
This is the pressure in the flow path 34 in the figure. The flow situation in the present invention, which is an operating state different from that in the prior art, is shown in FIG. 3 in comparison with that in the prior art. FIG. 3a shows the flow in the outlet channel 11 in the prior art shown in FIG. 11, in which flow 41 is the flow from the small valve seat, and flow 42 is the flow that has passed through the large valve seat. . In this case flow 4
Since 1 is the flow rate that has passed through the gap between the sliding surfaces of the sleeve 3 and the valve body 4, it is very small compared to the flow rate that has passed through the large valve seat. Therefore, the flows that have passed through the large valve seat merge at point a, and an unstable vortex flow 43 is generated upstream of point a, causing a shock wave 44 generated in the supersonic flow and the position of the shear flow boundary 45. oscillates and becomes a source of pressure fluctuations in the outlet flow path. FIG. 3b shows the flow in the outlet flow path in the structure of the present invention shown in FIG.
is the flow that passed through the large valve seat. In the present invention, the second
As shown in the figure, since the value of P ₂ /P ₃ is maintained at 2 or more, the flow 51 passing through the small valve seat becomes a supersonic flow, and in order to pass through the appropriately opened holes 28 and 29, the flow 51 becomes relatively fast. The high flow rate will mix in the exit channel with the supersonic flow that has passed through the large valve seat. In parallel supersonic flows, the different Matsuha numbers of the flows interfere with each other, changing the structure of shock waves generated in the flows. The present invention reduces pressure fluctuations and noise downstream of the valve by effectively utilizing the interference phenomenon of the two supersonic flows described above. 52) in Figure 3 b and small valve seat 3
As a condition for the flow from 0 (51 in Figure 3b), the Matsuha number of flow 52 in the range where vibration and noise occurs is 1.3 to 1.8, while the Matsuha number of flow 51 is 1.05 to 1.10. It is necessary that the Matsuha number slightly exceeds 1 in terms of degree. Under these conditions, the flow 51 from the small valve seat is reduced as shown in Figure 3b.
The shock wave 53 in is relatively weak due to the small Matsuha number, but by interfering with the flow 52 from the large valve seat via the shear flow layer 54, the shock wave within the flow 52 from the large valve seat is reduced. 55 is generated aperiodically, and the structure of the shock wave 55 becomes unclear. As a result, flow conditions throughout the channel are improved, and pressure fluctuations and noise due to supersonic speeds are reduced.

FIG. 4 shows a modified embodiment having the same effects as the embodiment of FIG. 1 as described above. The operating state in the embodiment of FIG. 4 is the same as that of FIG. 1, but
A flow passage 48 is provided downstream of the large valve seat 47 of the valve body 46.
It has a structure in which a plurality of grooves 49 are provided in the flow path of the flow from the large valve seat 47 on the outer peripheral side.

FIG. 5 shows a single product from which the valve body 46 has been extracted, cut along the - plane in FIG. 4 and viewed in the direction of arrow V. Due to the relationship between the groove 49 and the convex portion 50, the cross section has a petal-like shape, and the flow from the large valve seat is divided into a plurality of parts in the circumferential direction and merges with the flow from the flow path 48. By adopting such a structure, the following effects are added compared to the embodiment shown in FIG. That is, in FIG. 4, the steam flow that has flowed into the inlet steam chamber 57 from the steam inlet pipe 56 passes through the large valve seat 47 and flows into the outlet flow path 58, but in this case, the flow becomes a spiral flow and flows toward the outlet. In the embodiment of FIG. 4, it is possible to eliminate the spiral flow, and the exit channel 58
The flow at is more stabilized than in the embodiment of FIG.

Next, a second embodiment for achieving the object of the present invention is shown in FIG. The difference in FIG. 6 compared to the first embodiment (FIG. 1) is that the valve body 24 in FIG. 1 has a different shape like the valve body 60 in FIG. The components and operation are the same as the embodiment of FIG. In the structure shown in FIG. 6, whereas the flow passage 34 in FIG. 1 is open from the small valve seat 30 to the outlet flow passage 35, a partition wall 62 between the flow passage 61 and the outlet flow passage 63 is provided on the downstream side of the flow passage 61. The partition wall 62 is provided in an integral structure with the valve body 60, and the shape of the partition wall 62 is approximately conical. A plurality of ejection holes 65 having the same diameter are provided, and the structure is such that the flow from the small valve seat 66 can be ejected into the outlet flow path 63.
Further, FIG. 7 shows an embodiment having a different structure that provides the same effect as the second embodiment shown in FIG. 6.
7, the difference from FIG. 6 is that in FIG. 6, the valve body 60 and the partition wall 62 are integrated, whereas in the embodiment of FIG. 7, the valve body 70 and the partition wall 71 are integrated.
are not integrated, but are separated by a sliding surface 72, and the partition wall 71 is connected to the valve case 74 by a support plate 73, so the structure is such that it does not operate in conjunction with the opening/closing operation of the valve body 70. be. The shape of the partition wall 71 is a hollow cone, and the hollow part 75 of the cone communicates with a flow passage 77 downstream of the small valve seat 76, and a plurality of jet holes 78 provided in the conical surface communicate with the flow passage 77 downstream of the small valve seat 76. The structure is such that the flow from the small valve seat 76 is ejected into the flow from the large valve seat 79. Note that FIG. 8 is a cross-sectional view taken along line AA in FIG. 7. In the embodiment shown in FIGS. 6 and 7 above, the large valve seats 64, 7
The feature is that the flow from the small valve seats 66, 76 is ejected almost orthogonally to the flow from the small valve seats 66, 76 from the plurality of small diameter ejection holes 65, 78, and the effect of this structure is ( 1) Because of the jet flow from the porous wall, the non-uniformity of the pressure on the wall caused by shock waves colliding with the wall in the supersonic flow is reduced, and the reflected waves from the wall are reduced. The flow is weakened and stabilized. (2) The main flow changes from the cylindrical jet in the conventional shape to an annular jet due to the jet from the wall, which reduces the concentration and reinforcement of shock waves in the center of the flow path that occurs with cylindrical jets, and the flow uniformity is promoted. Such effects and actions are illustrated in FIG. 9. In Fig. 9a, a flow 91 from the large valve seat and a flow 92 from the small valve seat
When jets are perpendicular to each other from a large number of jet holes provided in the partition wall 93, the pressure on the surface of the partition wall 93 is high at the position where the shock wave 94 of the flow 91 collides, so the amount of jet is small; Since the pressure is low on the surface of the partition wall 93, the amount of ejection increases.
This reduces the strength of the shock wave 94 generated at 1 (pressure ratio before and after the shock wave). The pressure change caused by this shock wave is shown on the center line of the flow as shown in Figure 9b.In the conventional structure, the pressure change caused by the shock wave continues over a long range on the downstream side, but in the proposed structure, the pressure change due to the shock wave continues in a long range on the downstream side. The pressure change is reduced in a small range on the downstream side, and the flow can be created with less pressure change on the downstream side. As a result, the noise generated by the jet flow is reduced, and the vibration of the valve body caused by pressure fluctuations and flow instability is reduced.

In the embodiment described above, since the flow downstream of the valve is stabilized, vibrations of movable parts such as the valve stem and valve body can be reduced compared to the conventional technology, and noise generated from the flow can be reduced. It is also effective in reducing A concrete example of these effects is the first
It will look like Figure 0. Figure 10a shows the relationship between the valve stem lift and the pressure at each part shown in Figure 2, and the Matsuha number M _n of the jet from the large valve seat and the Matsuha number of the jet from the small valve seat.
Fig. _10b shows the vibration acceleration of the valve body. Also, Figure 10c
shows the noise level under the conditions of Matsuha numbers M _n and M _s . As is clear from Figures 10b and c,
In the range where vibration generation troubles occur frequently with conventional technology, with this generation it is possible to suppress vibration acceleration to about 1/2.

It was confirmed that the noise level of the embodiment shown in FIG. 1 was reduced by about 10 decibels compared to the noise level of the conventional example shown in FIG.

〔Effect of the invention〕

As detailed above, the steam control valve of the present invention has
This has an excellent practical effect in that the vibration of the steam control valve and the generation of noise during operation of the steam turbine can be significantly reduced.

[Brief explanation of drawings]

Fig. 1 is a sectional view of one embodiment of the steam control valve of the present invention, Fig. 2 is a chart for explaining the effects of the above embodiment, Fig. 3 is a qualitative explanatory diagram of steam flow, and Fig. 4 is a sectional view of an embodiment different from the above, and the fifth
The figure is a bottom view of the valve body in the embodiment shown in Fig. 4 as seen from below, Figs. 6 and 7 are sectional views of embodiments different from the above, and Fig. 8 is A in Fig. 7. -A sectional view. FIG. 9 and FIG. 10 are diagrams for explaining the functions and effects of the above embodiment, respectively. FIG. 11 is a sectional view of a conventional steam control valve, and FIG. 12 is a chart for explaining the operation of the conventional example. 23...Sleeve, 24...Valve body, 25...Valve stem, 26...Valve stem shoulder, 27...Protrusion, 28...
...hole, 29 ... hole, 30 ... small valve seat, 31 ... large valve seat, 32 ... inlet steam chamber, 33 ... pressure chamber, 3
4...Flow path, 35...Outlet flow path.

Claims (1)

[Scope of Claims] 1. A steam inlet chamber connected to an outlet flow path is provided in the valve case, a sleeve is fixed in the steam inlet chamber, and a sleeve is slidably fitted inside the sleeve, A cylindrical valve body is provided that blocks the steam inlet chamber and the outlet flow path when the large valve seat formed at the tip comes into contact with the opposing part of the valve case, and the cylindrical valve body is inserted concentrically, and when the shoulder formed on the outer periphery abuts the protrusion formed on the inner periphery of the cylindrical valve body, both members interlock and the shoulder formed on the outer periphery In a steam control valve provided with a valve stem that blocks the cylindrical valve body and the outlet flow path when the small valve seat abuts the opposing portion of the cylindrical valve body, the cylindrical wall of the sleeve, and A through hole is provided in each of the cylinder walls of the cylindrical valve body, and the overlap between the two through holes changes as the valve body opens and closes, and the pressure inside the cylindrical valve body is controlled by the valve. A flow path formed by the area of both of the through holes, the valve stem inserted into the cylindrical valve body, and the inner surface of the cylindrical valve body so that the pressure at the downstream side of the body is at least twice as high as the pressure downstream of the body. A steam control valve characterized by comprising an area. 2. The change in the degree of overlapping of both through holes is such that when the Matsuha number of the main stream flowing around the outer periphery of the cylindrical valve body is 1 or more, the Matsuha number of the jet flowing out from the center hole of the cylindrical valve body is The steam control valve according to claim 1, wherein the steam control valve is set to be 1.05 to 1.10 compared to the mainstream Matsuha number. 3. A conical partition wall is provided near the boundary where the main flow flowing out from the periphery of the cylindrical valve body and the jet flow flowing out from the central hole of the valve body merge, and a plurality of through holes are provided in the partition wall. The steam control valve according to claim 1, characterized in that the steam control valve is provided with: 4. The steam control valve according to claim 3, wherein the conical perforated partition wall is fixed to the valve body. 5. The steam control valve according to claim 3, wherein the conical perforated partition wall is fixed to the valve casing.