Balanced grid valve for steam extraction

Abstract

A balanced grid valve for steam extraction from a multi-stage steam turbine comprising a first balancing chamber and a second balancing chamber configured to receive high pressure steam through at least one duct, the balancing chambers preferably being in the form of annular grooves and positioned at two different radial distances from an axis of the valve to reduce mechanical strain on the valve.

Description

[Technical Field]

[0001] The subject matter disclosed herein relates to a balanced grid valve for steam extraction from a multi-stage steam turbine. [Background technology]

[0002] Steam turbines are often used to generate electrical energy by converting steam thermal energy into mechanical energy (turbine rotation).

[0003] Multi-stage steam turbines may include an extraction valve between the high-pressure and low-pressure turbine sections to extract steam from the steam cycle at a desired pressure. The extracted steam is primarily used for purposes other than turbine rotation. For example, the extracted steam may be used to process goods, such as in a paper mill or food factory, or may be used as a heating fluid. Therefore, it is desirable to extract steam at a desired pressure that is advantageously constant over time to ensure an extraction flow with desired characteristics and turbine efficiency.

[0004] This can be done by positioning a bleed valve between two intermediate turbine sections or stages, with a bleed manifold located upstream of the bleed valve, through which the steam bleed pressure can be adjusted. Typically, the bleed valve is a grid-type valve that includes a fixed grid and a rotating grid that cooperate to define a variable flow path depending on the relative positions of the fixed and rotating grids. By varying the flow path, the bleed valve can adjust the pressure at the bleed valve and, consequently, the pressure of the flow bled through the bleed manifold connected upstream of the valve.

[0005] Note that the steam pressures upstream and downstream of the bleed valve are different. In particular, the pressure difference between the steam upstream and downstream of the bleed valve increases as the value of the bleed steam mass flow rate increases. The pressure difference across the bleed valve creates an axial force on the valve surface exposed to the high-pressure steam. This force presses the rotating grid against the fixed grid, increasing the contact force between the two grids and, consequently, increasing the friction between the two grids.

[0006] For this reason, in known bleed valves, a pressure difference limit is provided so that the two grids can still rotate relative to each other. One known method for increasing the pressure difference limit of a bleed valve is to provide a balancing chamber between the grids, which is supplied with high-pressure steam, in order to locally separate the two grids and reduce the friction between them.

[0007] EP 1970543 (B1) discloses a device for adjusting the extraction pressure of a steam turbine having a fixed grid and a rotating grid, the fixed grid having grooves that act as balancing chambers when supplied with high-pressure steam extracted from a stage located upstream of the steam extraction nozzle in order to separate the grid and reduce the forces acting on the grid.

[0008] It should be noted that such localized separation of the grids results from forces generated locally in the balancing chamber. This creates an "umbrella effect" on the rotating grids as the forces are applied farther away from the grid's rotation axis, resulting in, for example, increased localized wear in the portions of the grid closer to the grid's rotation axis, i.e., farther from the force application area, and increased leakage in the portions closer to the balancing chamber, i.e., near the force application area. Furthermore, if too much force is applied, excessive friction occurs in the portions of the grids near the grid's rotation axis, preventing the grids from moving relative to each other. Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, currently available bleed valves have technical limitations in terms of pressure difference, in particular they can only operate at pressure differences of up to 10-15 bar.

[0010] Applicant has conducted testing and analysis and has recognized that it would be desirable to have a bleed valve capable of controlling the flow bleed from the main stream of a steam turbine, i.e., a valve that can operate at a larger pressure differential, e.g., up to 60 bar, to accommodate increased bleed pressure requirements (bleed pressure is the pressure in the section of the steam turbine in which the bleed valve is located). In particular, it is desirable for a balanced grid valve, which is a type of bleed valve, to be able to bleed a constant flow at increased bleed pressure.

[0011] According to one aspect, the subject matter disclosed herein relates to a balance grid valve having a first balancing chamber and a second balancing chamber. Each of the first and second balancing chambers is configured to receive a fluid at a sufficiently high pressure through at least one duct. In one embodiment, the fluid can be steam. Advantageously, the chambers are fluidly coupled to one another via one or more channels (or grooves). The balancing chambers function to reduce axial forces on the valve due to bleed pressure. The balancing chambers are positioned at two different radial distances from the central horizontal axis of the valve to reduce valve distortion. In particular, valve distortion can occur as an "umbrella effect," in which a valve region near the balancing chamber is pushed away from the valve support due to high pressure in the balancing chamber. Embodiments of the novel balance grid valve, including rotary equipment coupled thereto, provide multiple advantages, including that use of the novel balance grid valve described, shown, and / or claimed herein may facilitate lower peak pressures on the internal valve surfaces, thereby facilitating movement of the valve between open and closed positions and reducing wear on the valve components.

[0012] According to another aspect, the subject matter disclosed herein relates to a steam turbine including an embodiment of the novel balance grid valve described, shown, and / or claimed herein, the balance grid valve having at least two balancing chambers. [Brief explanation of the drawings]

[0013] A complete understanding of the disclosed embodiments of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings. [Figure 1] FIG. 1 shows a cross-sectional view of a rotating machine, in particular a multi-stage steam turbine, provided with an embodiment of a balance grid valve. [Figure 2] FIG. 2 illustrates a partial cross-sectional view of an embodiment of a balance grid valve included in the turbine of FIG. [Figure 3A] FIG. 3A shows a first side view of the balance grid valve of FIG. 2, specifically the valve support side. [Figure 3B] FIG. 3B shows a second side view of the balance grid valve of FIG. 2, specifically the valve body side. [Figure 4] FIG. 4 shows a front view of the balanced grid valve of FIG. 2 partially opened, particularly the valve body side. [Figure 5] FIG. 5 shows a schematic diagram of the valve body of the balance grid valve of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0014] The subject matter disclosed herein relates to an innovative balance grid valve for a multi-stage steam turbine. The balance grid valve is positioned and coupled to a steam turbine so that steam flowing through the steam turbine can be bled at a higher pressure and away from the steam turbine relative to known bleed valves. The innovative balance grid valve, among other things, includes two balancing chambers at different radial distances from the horizontal central axis of the valve. Each of the two balancing chambers is configured to receive fluid bled from a final stage of a high-pressure section of the rotary equipment through at least one duct. In one embodiment, the rotary equipment is a multi-stage steam turbine, and the fluid is (or includes) high-pressure steam of at least 60 bar. In particular, the two balancing chambers can take the form of two annular concentric grooves, each having two different radii from the horizontal central axis of the valve.

[0015] Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the drawings. Each example is provided by way of explanation of the disclosure, not as a limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure.

[0016] Referring now to the drawings, Figure 1 illustrates, by way of example and not limitation, a portion of rotary equipment designated generally by reference numeral 1000. In one embodiment, rotary equipment 1000 is a multi-stage steam turbine. Multi-stage steam turbine 1000 is configured to process a fluid (steam) flow through flow expansion and to extract power from the flow expansion. Multi-stage steam turbine 1000 is further configured to extract a fluid (steam) flow exiting a final stage of the high-pressure section of turbine 1000 through an inventive balance grid valve 100.

[0017] A multi-stage steam turbine 1000 is provided with an embodiment of an innovative balance grid valve, generally designated by reference numeral 100. Balance grid valve 100 is configured to be disposed between two intermediate stages of multi-stage steam turbine 1000. Advantageously, balance grid valve 100 is disposed between high-pressure turbine section 800 and low-pressure turbine section 900, each turbine section having at least one stage, and preferably multiple stages in series.

[0018] The balance grid valve 100 is configured to bleed high-pressure steam, and preferably, the pressure of the bled steam is substantially constant over time. The multi-stage steam turbine 1000 includes a flange 400 fluidly coupled to the balance grid valve 100. In particular, the flange 400 is fluidly coupled to an annular chamber 600 that couples the final stage of the high-pressure turbine section 800 with the balance grid valve 100. In particular, the annular chamber 600 is the section of the multi-stage steam turbine 1000 from which the steam flow is bled. The large arrow in FIG. 1 emanating from the flange 400 indicates that through the flange 400, the balance grid valve 100 can supply the bled steam to one or more external units, for example, by connecting a manifold to the flange 400.

[0019] 2 shows a partial cross-sectional view of a multi-stage steam turbine 1000 equipped with an innovative embodiment of a balanced grid valve 100. In FIG. 2, only the upper portion of the valve 100 and a portion of the low-pressure turbine section 900 are shown, in particular, the valve support is integrated with the stator casing of the turbine section.

[0020] According to this embodiment, the balance grid valve 100 includes a valve support 200 fixed to the multi-stage steam turbine 1000 and a valve body 300 rotatable relative to the valve support 200 about an axis R. As will become apparent below, the valve body 300 can be rotated to vary the steam flow through the balance grid valve 100. Specifically, rotating the valve body 300 reduces the passage area for steam flow in the balance grid valve 1000; reducing the passage area stacks the steam flow through the valve, thereby increasing the amount of steam flow extracted from the multi-stage steam turbine 1000.

[0021] Valve support 200 has first side 210 and second side 220. First side 210 is configured to be exposed to a first flow of steam processed by multi-stage steam turbine 1000, the first flow being at a first pressure, and first side 210 being subjected to the first pressure.

[0022] Valve body 300 has first side 310 and second side 320. First side 310 is configured to be exposed to a second flow of steam processed by multi-stage steam turbine 1000, the second flow being at a second pressure, and first side 310 experiencing the second pressure.

[0023] The second pressure is greater than the first pressure. In other words, the first side 210 of the valve support 200 is positioned to be coupled to the low-pressure turbine section 900 of the multi-stage steam turbine 1000, and the first side 310 of the valve body 300 is positioned to be coupled to the high-pressure turbine section 800 of the multi-stage steam turbine 1000.

[0024] Thus, the second side 220 of the valve support 200 faces and / or is positioned adjacent to the second side 320 of the valve body 300 .

[0025] 3A and 3B, a first side view of the balance grid valve 100, particularly the valve support 200 side, and a second side view of the balance grid valve 100, particularly the valve body 300 side, are shown, respectively. The valve support 200 is shown, by way of example, as a fixed ring-shaped valve support, and the valve body 300 is shown, by way of example, as a rotatable ring-shaped valve body. The ring-shaped valve support 200 and the ring-shaped valve body 300 share a common central horizontal axis R about which the valve support 200 and the valve body 300 are formed.

[0026] 3B, 4, and 5, the valve support 200 and the valve body 300 have openings 250, 350 configured to define an adjustable flow path for fluid flow, e.g., steam flow. In particular, the adjustable flow path is a function of the relative rotation angle X between the valve support 200 and the valve body 300, where, with non-limiting reference to FIG. 4, the relative rotation angle X is measured relative to any vertical orientation of the valve support 200 (see, e.g., the vertical dashed line where arrow X begins) and a new orientation obtained after rotating the valve body 300 by angle X relative to the valve support 200 (see, e.g., the diagonal dashed line where arrow X terminates). That is, arrow X is the relative rotation angle X of the valve body 300 relative to any vertical orientation of the valve support 200. Advantageously, the openings 250 on the valve support 200 correspond to the openings 350 on the valve body 300, such that there is at least a rotation angle at which the openings 350 completely overlap the openings 250. Instead, according to certain rotation angles, opening 350 partially overlaps opening 250. Finally, according to at least one rotation angle, opening 350 does not overlap opening 250 at all.

[0027] To regulate steam flow through the balanced grid valve 100, and thus the pressure of the steam bled through the flange 400, the valve body 300 can be rotated relative to the valve support 200, either manually or automatically via an actuator, to vary the relative rotation angle X and, therefore, the adjustable flow path defined by the openings 250 and 350. Advantageously, the valve body 300 is mechanically coupled to an actuator, particularly a linear actuator that converts linear motion into rotational motion. As shown in FIGS. 3B and 4 , the valve body 300 includes a connection device 330, such as a mechanical bracket, that is coupled to the linear actuator and transfers motion from the linear actuator to the valve body 300 to rotate it. In particular, the valve body 300 can be rotated during installation and / or operation. More specifically, during operation, the valve body 300 may be rotated one or more times; for example, the valve body 300 may make continuous slow rotations to complete one full stroke of relative rotation angle X once a day (a full stroke may be approximately 10°, in either case depending on the number of openings 250, 350 used), or it may make fast rotations, for example, three small rotations (less than 1°) per hour.

[0028] According to a non-limiting embodiment, and particularly as shown in Figure 5, the rotatable valve body 300 includes a first groove 360 and a second groove 380 disposed on the second side 320 of the valve body 300. Note that the first groove 360 is disposed at a first radial distance "r1" from the axis R, and the second groove 380 is disposed at a second radial distance "r2" from the axis R, where the first radial distance "r1" is greater than the second radial distance "r2."

[0029] Advantageously, the first groove 360 and the second groove 380 are annular grooves disposed about a central horizontal axis R. In particular, the first groove 360 and the second groove 380 define a first circle (having a radius "r1") and a second circle (having a radius "r2") that surround the axis R. Advantageously, the first groove 360 and the second groove 380 have the same width (defined in the radial direction) and depth (defined in the axial direction).

[0030] More advantageously, the opening 350 in the valve body 300 is disposed between the first groove 360 and the second groove 380. In other words, the center of the opening 350 in the valve body 300 is disposed a third radial distance from the axis R, the third radial distance being greater than the second radial distance "r2" but less than the first radial distance "r1." Advantageously, the opening 250 in the valve support 200 is disposed at the same third radial distance from the axis R as the opening 350 in the valve body 300 and can have the same shape.

[0031] With non-limiting reference to FIG. 2, the first groove 360 and the second groove 380 are configured to form a first balancing chamber 460 and a second balancing chamber 480 when the valve body 300 is coupled with the valve support 200.

[0032] The first groove 360 is configured to receive steam at a third pressure such that the first balancing chamber 460 is subjected to a third pressure, the third pressure being greater than the second pressure (i.e., the pressure upstream of the valve). The second groove 380 is configured to receive steam at a fourth pressure such that the second balancing chamber 480 is subjected to a fourth pressure, the fourth pressure being greater than the second pressure (i.e., the pressure upstream of the valve).

[0033] 5, the valve 100, and in particular the valve body 300, further comprises an inner channel 370 fluidly coupling the first groove 360 and the second groove 380, where advantageously the third pressure is equal to or substantially equal to the fourth pressure. In particular, the first groove 360 is configured to receive steam at the third pressure, with the steam flowing through the inner channel 370 and being supplied to the second groove 380. It should be noted that if no pressure loss is caused by flowing through the inner channel 370, the steam received by the second groove 380 (i.e., into the second chamber 480) will be at the same third pressure as the steam received by the first groove 360 (i.e., into the first chamber 460).

[0034] With the above-described configuration, when the first groove 360 and the second groove 380 receive steam, the balanced grid valve 100 has two substantially equal forces above and below the opening 350 in the valve body 300 ("above" and "below" being defined relative to the radial extension of the opening 350).

[0035] According to some alternative embodiments, the first and second grooves are located on the valve support and the inner channel and are configured to form first and second balancing chambers when the valve body is coupled with the valve support. According to some other alternative embodiments, the first groove is located on the valve support or the valve body, and conversely, the second groove is located on the valve body or the valve support.

[0036] 1 , the multi-stage steam turbine 1000 further comprises a duct 500. The duct 500 has a first end positioned to be fluidly coupled to a stage of the multi-stage steam turbine 1000 located upstream of the balance grid valve 100, specifically to a high-pressure stage of the high-pressure turbine section 800.

[0037] The duct 500 has a second end arranged to be fluidly coupled to the balance grid valve 100, in particular to a flange 520. Advantageously, the flange 520 is provided with a suitable seal to prevent steam leakage. The flange 520 is fluidly coupled to the first groove 360. The duct 500 is arranged to supply steam to the first groove 360 at a third pressure, for example, the pressure of a high-pressure stage of the high-pressure turbine section 800 to which the first end is coupled.

[0038] Advantageously, the duct 500 is provided with a valve 510 , in particular a regulating valve, for regulating the steam flowing through the duct 500 and supplied to the balance grid valve 100 .

[0039] 1 and 2 , in operation, a fluid such as steam enters an inlet of rotary equipment 1000, which may be a multi-stage steam turbine, expands through rotary equipment 1000, particularly through the blades of the equipment, and exits through an outlet of rotary equipment 1000. Steam flowing through rotary equipment 1000 is extracted from an intermediate section of the equipment through balance grid valve 100. Valve 100 has openings 250, 350 through which a portion of the steam can flow to continue its expansion, and an annular chamber 600 upstream of valve 100 from which a portion of the steam is extracted. Balance grid valve 100 has grooves 360, 380, and at least a portion of the steam flowing upstream of valve 100, preferably taken from or near the inlet of rotary equipment 1000, can be injected through duct 500. In particular, duct 500 is provided with valve 510 that regulates the steam supplied to grooves 360, 380 of valve 100. Preferably, steam is supplied to the grooves 360, 380 only when the valve body 300 is rotated relative to the valve support 200 to reduce friction therebetween. More preferably, the valve 510 allows steam to be supplied to the grooves 360, 380 when actuated by an actuator receiving a digital control signal or when actuated manually.

[0040] In some embodiments, the multi-stage steam turbine 1000 may include a first duct fluidly connected to the first groove 360 and a first high-pressure stage of the high-pressure section 800 of the multi-stage steam turbine 1000, and a second duct fluidly connected to the second groove 380 and a second high-pressure stage of the high-pressure section 800 of the multi-stage steam turbine 1000, wherein the first duct is arranged to supply steam to the first groove 360 at a third pressure, particularly at the pressure of the first high-pressure stage, and the second duct is arranged to supply steam to the second groove 380 at a fourth pressure, particularly at the pressure of the second high-pressure stage.

[0041] It should also be noted that the first and second high pressure stages do not have to correspond to the first and second high pressure stages located immediately downstream of the inlet of the high pressure section 800 of the multi-stage steam turbine 1000.

Claims

1. 1. A balance grid valve (100) for steam extraction from a multi-stage steam turbine (1000), the multi-stage steam turbine (1000) configured to process a steam flow, the balance grid valve (100) configured to be positioned intermediate two turbines of the multi-stage steam turbine (1000), the balance grid valve comprising: a valve support (200) having a first side (210) and a second side (220), said first side (210) being adapted to be exposed to steam at a first pressure, said valve support (200) being fixed and ring-shaped; a valve body (300) having a first side (310) and a second side (320), said first side (310) being configured to be exposed to said steam at a second pressure, said valve body (300) being rotatable and ring-shaped; the second pressure is greater than the first pressure; the valve support (200) and the valve body (300) are mechanically coupled, and the second side (220) of the valve support (200) faces the second side (320) of the valve body (300); The valve body (300) is rotatable relative to the valve support (200) about an axis (R); the valve support (200) and the valve body (300) have openings (250, 350), the openings (250, 350) configured to define a flow path that is adjustable depending on the relative rotation angle between the valve support (200) and the valve body (300); the valve support (200) and / or the valve body (300) comprise a first groove (360) and a second groove (380), the first groove (360) and the second groove (380) being disposed on the second side (320) of the valve body (300) and / or the second side (220) of the valve support (200); the first groove (360) and the second groove (380) are configured to form a first balancing chamber (460) and a second balancing chamber (480), respectively, between the valve support (200) and the valve body (300); the first groove (360) has a first radial distance (r1) from the axis (R), and the second groove (380) has a second radial distance (r2) from the axis (R), the first radial distance (r1) being greater than the second radial distance (r2); the first groove (360) is configured to receive the steam at a third pressure; the second groove (380) is configured to receive the steam at a fourth pressure; the third pressure is greater than the second pressure; the fourth pressure is greater than the second pressure; the valve further comprises at least one duct (500), the duct (500) being fluidly coupled to the first groove (360) and / or the second groove (380) and configured to supply the steam at the third pressure and / or the fourth pressure; A balanced grid valve (100), wherein the valve support (200) and / or the valve body (300) further comprises at least one inner channel (370) fluidly coupling the first groove (360) to the second groove (380).

2. The balanced grid valve (100) of claim 1, wherein the third pressure is substantially equal to the fourth pressure.

3. The balanced grid valve (100) of claim 1, wherein the first groove (360) and the second groove (380) are annular grooves surrounding the axis (R).

4. The balanced grid valve (100) of any one of claims 1 to 3, wherein the opening (250, 350) of the valve support (200) and / or the valve body (300) is disposed between the first groove (360) and the second groove (380).

5. 2. The balanced grid valve (100) of claim 1, wherein the at least one inner channel (370) is disposed between two adjacent openings (250, 350) of the valve support (200) and / or the valve body (300).

6. The balanced grid valve (100) of claim 1, wherein the duct (500) is configured to be fluidly coupled to a stage of the multi-stage steam turbine (1000) located upstream of the balanced grid valve (100).

7. The balanced grid valve (100) according to claim 1, wherein the duct (500) is provided with a valve (510), in particular a regulating valve.

8. 10. A multi-stage steam turbine (1000) comprising the balance grid valve of claim 1, wherein the balance grid valve is disposed intermediate two turbines included in the multi-stage steam turbine (1000).

9. 9. The multi-stage steam turbine of claim 8, wherein the duct is fluidly coupled at a first end to a stage of the multi-stage steam turbine located upstream of the balance grid valve, and at a second end to the first groove and / or the second groove.

10. The multi-stage steam turbine (1000) of claim 9, wherein the duct (500) is provided with a valve (510), in particular a regulating valve.

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