KR20180032200A - Exhaust casing for a low pressure steam turbine system - Google Patents

Abstract

The present invention relates to an exhaust case (10) for a steam turbine system, wherein the exhaust case comprises an upper side wall (11), a side wall (12), an inner side surface (13), an outer side surface (14), a plurality of case reinforcement elements (15), and a guide rib (17). The guide rib (17) is attached to the inner side surface (13) of the upper side wall (11) of the exhaust case (10) to extend inward in the radial direction, and each of the case reinforcement elements (15) is fixed to the guide rib (17). The guide rib acts as a guide to allow steam moving in the substantially vertical upward direction to swing by 180 degrees and flow downward toward the outlet of an exhaust system. The guide rib fixes a reinforcement element to the upper side wall of the exhaust case and also serves as a connection element between case blocks. This configuration improves the steam flow efficiency, because the number of elements in the inner space of the exhaust case is reduced. Accordingly, a collision between such elements of the steam passing through the system is also reduced. As a result, the turbulent flow rate of steam is balanced, and a pressure loss caused by the collision is reduced. As a result, efficiency of an exhaust system and overall performance of a turbine are improved.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an exhaust case for a low-pressure steam turbine system,

The present invention relates to an exhaust case for a low-pressure steam turbine system, and a structure of guide ribs and reinforcement elements in the inner space of the exhaust case, and relates to increasing the steam flow efficiency while reducing pressure loss.

Steam passing through the steam turbine is guided through the exhaust system to the condenser, condensed and then returned to the system. Conventional exhaust systems include an annular diffuser, which includes inner and outer flow guides through which steam that has passed through the turbine stage is radially outwardly discharged. Conventional exhaust systems are oriented vertically or horizontally, typically in a vertical orientation. The conventional diffuser has a guide channel divided into an upper guide channel and a lower guide channel by a horizontal plane. Steam exiting the diffuser through the lower guide channel moves radially downward and simply continues in this direction and exits through the outlet towards the condenser. The vapor exiting the diffuser through the upper guide channel, however, moves substantially vertically upwards and 180 degrees to flow downward toward the outlet of the exhaust system. To do this, the steam is directed by collision with a guide block at the apex of the diffuser in the interior space of the exhaust system. Apart from the guide convex, the steam collides with the case itself and with other elements located in the inner space of the exhaust case. Other elements may be various connecting elements such as, for example, connecting individual blocks of the case or fixing ribs for fixing the reinforcing elements in the exhaust system. As a result, the vortex is formed in the exhaust case at the top of the diffuser outlet, and the vapor flow experiences a large pressure drop, which has an undesirable effect on the efficiency of the exhaust system and on the overall performance of the turbine.

For large steam turbines, the exhaust case may be made of several blocks that must be connected together. In the current practice, the blocks may be connected, for example, by connecting elements similar to the guide ribs apart from the actual guide ribs. This configuration increases the number of elements present in the inner space of the exhaust case, which increases the impact of steam and pressure loss. Further, the exhaust case must be reinforced because a vacuum state must be provided inside the exhaust case. The reinforcement is often provided by a plurality of reinforcing elements in the form of tubes or plates, which need to be secured to the case. The current practice is that each reinforcement element is secured to a separate fixed rib. Therefore, there are fixed ribs as many as the number of reinforcing elements. The reinforcing ribs are positioned perpendicular to the guide ribs, that is, parallel to the longitudinal axis of the steam turbine system. This configuration increases the number of elements present in the interior space of the exhaust case to an extreme extent, which increases the steam collision and pressure loss.

A disadvantage of the arrangement described above is that, due to many factors, it affects the efficiency of the exhaust system, not only because the steam collides with the guide ribs, but also with all other elements. This collision contributes to the formation of a vortex, leading to a large pressure loss in the vapor stream. As described above, this pressure loss affects the efficiency of the exhaust system and the overall performance of the turbine in an undesirable manner.

An object of the present invention is to provide a guide rib and a reinforcing element in the inner space of the exhaust case to reduce the pressure loss and increase the steam flow efficiency.

The present invention provides an exhaust case for a low pressure steam turbine system including an upper side wall, a side wall, an inner side surface, an outer side surface, a plurality of case reinforcing elements, and a guide rib, wherein the guide rib is attached to an upper side wall of the exhaust case, And one or more reinforcing elements are fixed to the guide ribs. The vapor flow efficiency is improved by this configuration, because it reduces the number of elements in the interior space of the exhaust case. Thus, likewise, the collision of the steam passing through the system with these elements is reduced. As a result, the turbulent velocities of the steam are balanced and the pressure loss due to the collision is also reduced. As a result, the efficiency of the exhaust system and the overall performance of the turbine are improved. Above all, the vibrations of the system caused by turbulent steam flow are reduced, which improves the durability of the individual elements present in the system. The present invention also relates to a low-pressure steam turbine system including the above-described exhaust case.

A low pressure steam turbine system includes a low pressure steam turbine, a diffuser, and an exhaust case to cover the exhaust system. The diffuser may be a conventional diffuser and is located immediately behind the last row of blades of the steam turbine. The diffuser forms part of an exhaust system of the steam turbine system and includes an exhaust guide channel formed by an inner guide and an outer guide, the outer guide being spaced from the side wall of the exhaust case. As the steam passes through the last row of the steam turbine plate, the steam is directed through the guide channel and its outlet to the interior space of the exhaust system surrounded by the exhaust case. The exhaust system directs the steam to an industrial process using a condenser, heat exchanger or steam.

The steam turbine system may be divided into a top and a bottom by a horizontal plane including the longitudinal axis of the system. The steam turbine system may also be divided into a first half and a second half by a vertical plane that is symmetrical about a vertical plane including a transverse axis of the system and includes a transverse axis of the system. The exhaust case described below is provided in the upper first half to cover at least a portion of the steam turbine and to form an inner space of the exhaust case in the first half which is the upper part of the system. In the lower part of the exhaust system, which corresponds to the lower part of the steam turbine (below the horizontal plane of the longitudinal axis), the steam flows directly from the lower outlet of the diffuser to the outlet of the exhaust system and therefore does not need to guide the steam, No vortex is formed.

The steam turbine system includes at least one exhaust case, preferably two exhaust cases, which will be described below, wherein the two exhaust cases are mutually symmetrical with respect to a vertical plane including an axis transverse to each other. Two exhaust cases can cover the entire low pressure steam turbine system.

In one embodiment of the present invention, a steam turbine system includes a low pressure steam turbine exhaust system and a low pressure steam turbine system in one flow direction, which exhausts steam in a radial direction, .

The exhaust case of the exhaust system may have a substantially cylindrical shape. The cylindrical shape is preferred for a steam turbine system having vertically oriented exhaust outlets.

In one embodiment of the invention, the exhaust case of the steam turbine system may have a different shape, preferably a rectangular shape. The combination of a cylindrical exhaust case and a rectangular exhaust case is preferred for a steam turbine system with a horizontally oriented exhaust outlet.

The exhaust case of the exhaust system may comprise one or more blocks. Preferably, the case may include two blocks, i.e., a first block and a second block, but may also include two or more blocks. A configuration with more blocks is particularly desirable for large steam turbines.

The exhaust case includes an upper side wall and a side wall, both of which have an inner side surface and an outer side surface. The exhaust case may be made of creep-resistant materials such as, for example, steel or steel alloys.

A vacuum state needs to be provided in the inner space of the exhaust case (typically a pressure of about 0.5 bar or less, preferably about 0.1 bar or less is used). Therefore, the exhaust case must be reinforced. The reinforcement is provided by a plurality of reinforcing elements located in the inner space of the exhaust case. The reinforcing element is preferably located between the upper side wall and the side wall of the exhaust case. The reinforcing element may be located between the connecting portion and the upper sidewall between the sidewall and the inner flow guide of the diffuser or between the upper sidewall and the inner flow guide of the diffuser. The reinforcing element may have any suitable shape, preferably in the form of a tube or a plate. The angle between the reinforcing element and the upper side wall is 20 to 60 degrees, preferably 30 to 50 degrees. The number of reinforcement elements shall be reduced as far as possible in relation to the reinforcement request. The appropriate number of reinforcing elements is 5 to 15, preferably 7 to 10. They may be made of the same material as the case of the exhaust system, for example, steel or steel alloy.

Further, the guide rib is located in the inner space formed by the exhaust case. The guide ribs are attached to the upper wall of the exhaust case and are oriented at right angles to the longitudinal axis of the system. The guide rib extends radially inward from the inner side of the upper wall toward the inner space of the exhaust system. Preferably, the guide rib extends from a horizontal plane of the longitudinal axis of the system and follows the cylindrical shape of the upper wall of the exhaust case.

In cross-section, the guide rib may have an I-shape or a T-shape. The guide ribs may be formed of a single plate or may comprise more than the same number of plates, preferably two, i.e., a first plate and a second plate. The T-shaped guide rib preferably comprises two L-shaped plates. The T-shaped guide rib may comprise an additional plate perpendicular to the plate of the I-shaped guide rib. The plate may be, for example, steel or a steel alloy, which is the same material as the exhaust case, and is connected together by bolts and / or welding. In terms of improving the steam flow, there is no difference between the I-shaped guide ribs and the T-shaped guide ribs. From a configuration point of view, I-shaped guide ribs are easy to manufacture. On the other hand, the T-shaped guide rib has the advantage of being easy to weld.

The height h of the guide rib 17 is given with respect to the height H between the horizontal plane of the longitudinal axis and the highest point of the upper wall. The height h of the guide rib may range from 0.05 * H to 0.15 * H , preferably 0.14 * H , more preferably about 0.1 * H. The reduction in pressure loss is higher within this range when compared to the outside range of this range. The reduction in pressure loss is maximal for h = 0.1 * H. The same height range can be applied to both I-shaped and T-shaped guide ribs. The width w of the T-shaped guide rib is equal to or less than 1.4 * h , preferably equal to or less than 1.2 * h , more preferably equal to or less than 1.0 * h .

The guide rib serves as a guide to cause the vapor leaving the outlet of the diffuser to be substantially vertically upwardly turned 180 degrees and flowing downward toward the outlet of the exhaust system. In order to improve the vapor flow which reduces the pressure loss caused by the formation of the vortex, the guide rib may be located at a specific position relative to the exhaust outlet of the diffuser or at a specific distance l from the side wall of the exhaust case. The position or distance l is determined based on the distance m between the end point of the outer guide of the guide channel and the inner surface of the side wall of the exhaust case. The optimum position distance l is preferably between 1.2 * m and 1.9 * m , preferably between 1.3 * m and 1.7 * m , more preferably between 1.4 * m and 1.6 * m it may be located in l * = 1.5 m from the inner surface of the side wall of the exhaust casing. Here, the parameter ( m) is defined as described above. The reduction in pressure loss is higher within this range when compared to the case where the guide ribs are located outside this range. The reduction in pressure loss is maximized at the desired position, l = 1.5 * m . The same position range can be applied for both I-shaped and T-shaped guide ribs.

The guide ribs also provide reinforcement for the scraper case of the steam turbine system. The guide ribs themselves provide reinforcement for the exhaust case. Further, the guide rib serves as a fixing element for fixing the reinforcing element to the upper side wall of the exhaust case, so that a separate fixing rib is not required. The reinforcing element is fixed to the guide rib. They may be fixed directly to the guide rib, or the support element may be provided to fix the reinforcement element to the guide rib. The support element may have a suitable shape and size. The height of the support element should be equal to or less than the height ( h) of the guide ribs, so as not to become another obstacle to the flowing vapors. The width of the supporting element shall be equal to or less than the height of the supporting element. One support element may be provided along the guide rib, or preferably a separate support element may be provided for each reinforcement element. The reinforcing element is fixed to the guide rib or the supporting element by conventional suitable means, for example bolts and / or welding, preferably both bolts and welding, to ensure a firm connection.

In one embodiment, the reinforcing element can penetrate the guide rib and be attached to the upper wall located on the side of the guide rib spaced from the side wall. In this case, the penetrating reinforcing elements and the guide ribs are fixed to each other by, for example, welding. In order to fix the reinforcement element to the upper side wall, a separate support element is required. However, the size of these base elements can be reduced because the connection by welding with the guide ribs of the reinforcing elements provides additional fixation.

In any case, this arrangement is advantageous because the guide ribs provide a fixing element for the reinforcing element, since it does not require a separate fixing element. Thus, the number of elements in the exhaust chamber interior space is reduced, which results in a reduction of vapor impact with these elements in the interior space, thereby reducing the pressure loss in the exhaust system.

The guide ribs are attached to the upper wall in any one of the following ways. One plate of the guide rib is attached to the inner surface of the upper side wall or one plate of the guide rib is used as a connecting element for connecting the individual blocks of the exhaust case. Alternatively, the first plate is attached to the first block of the exhaust case and the second plate is attached to the second block of the exhaust case. The connection between the rib and the case block is provided by conventional suitable means such as, for example, bolts and / or welding, preferably by means of both bolts and welding, in order to ensure a secure and sealed connection. This configuration in which the guide ribs provide the connection of the case blocks is advantageous because it does not require a separate connecting element to connect the individual blocks of K. Thus, the number of elements in the exhaust chamber inner space is reduced, which leads to a reduction in collision between these elements in the steam and the inner space, and a reduction in the pressure loss in the exhaust system.

The guide rib serves as a guide which causes the vapor moving in the substantially vertical upward direction to turn 180 degrees and to flow downward toward the outlet of the exhaust system. The guide rib serves as a reinforcing element and also serves as a fixing element for fixing the reinforcing element to the upper side wall of the exhaust case and serves as a connecting element between the case blocks. If the reinforcing element is fixed directly to the guide rib or through the supporting element, no further ribs or fixing elements are required. Similarly, if the case block is directly connected by the guide ribs, no further connecting elements are required. Thus, whether individually applied or applied in combination, any arrangement described above increases the vapor flow efficiency, because it reduces the number of elements in the interior space of the exhaust case. Thus, the collision of steam passing through the system with these elements is likewise reduced. Thus, the turbulence velocity of the steam is balanced and the pressure loss caused by the collision is also reduced. As a result, the efficiency of the exhaust system and the overall performance of the turbine are improved. Above all, the vibration of the system caused by the turbulent steam flow is reduced, thereby improving the durability of the individual elements present in the system.

1 shows a vertical section of a first half which is the top of a steam turbine system and shows an exhaust system with an exhaust case.
Figure 2 shows a 3D model of two connected exhaust cases providing a cover of the overall steam turbine system.
Figure 3 shows a dependency of a normalized loss coefficient on the position of the guide rib from the inner side of the sidewall.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described, by way of example, with reference to the accompanying drawings, in which a preferred embodiment of a slicer for a low pressure steam turbine system is illustrated. However, these examples are not to be construed as limiting the scope of the claims.

The low pressure steam turbine system of FIG. 1 includes a low pressure steam turbine 1, a diffuser 22, and an exhaust case 10 covering the exhaust system 10. The diffuser 22 may be a conventional diffuser and is positioned immediately behind the last row of blades 24 of the steam turbine 1. The diffuser 22 includes an exhaust guide channel 19 formed by an inner guide 20 and an outer guide 21. The steam passes through the last row of the blades 24 of the steam turbine 1 and is directed to the inner space 18 of the exhaust system surrounded by the exhaust case 10 through the guide channel 19 and its outlet 23.

The exhaust case 10 is provided in a first half which is the upper part of the steam turbine system and which covers at least a portion of the steam turbine 1 as part of a horizontal plane including the longitudinal axis 25 of the system, Which forms an inner space 18 of the exhaust case 10 at the top of the system where the steam exits the outlet 23 of the diffuser 22 and enters the lower portion of the vapor system below the horizontal plane of the longitudinal axis And is turned 180 degrees toward the outlet 26.

The exhaust case 10 is substantially cylindrical and includes an upper wall 11 and a side wall 12. The case 10 of the exhaust system has an inner side 13 and an outer side 14. The exhaust case 10 is made of an anti-creep material such as, for example, steel or a steel alloy.

The reinforcement of the exhaust case 10 is provided by the guide ribs 17 themselves and by a plurality of reinforcing elements 15 which are preferably arranged in the interior of the upper wall 11 and the side wall 12 of the exhaust case 10 And is located between the connecting places of the flow guide (20). The reinforcing element 15 has a tube shape or a plate shape, but is preferably a tube. The optimum number of reinforcing elements 15 is 5 to 15, preferably 7 to 10, and in the embodiment 11 reinforcing elements are provided. They are preferably made of an anti-creep material such as, for example, steel or a steel alloy, similar to the material of the case 10 of the exhaust system.

The guide ribs 17 are attached to the upper side wall 11 of the exhaust case 10 and are oriented at right angles to the longitudinal axis 25 of the system and extend from the inner side 13 of the upper side wall 11 And extend radially inward toward the inner side 18. The guide ribs 17 extend from the horizontal plane of the longitudinal axis 25 of the system and follow the cylindrical shape of the upper wall 11 of the exhaust case 10 and this is shown in the 3D model of FIG.

An embodiment with T-shaped guide ribs 17 is shown in FIG. 1, but the T-shaped ribs may be replaced with I-shaped ribs. Preferably, the T-shaped guide ribs 17 comprise two identical plates, namely a first plate 171 and a second plate 172. The plate may be, for example, steel or a steel alloy, which is the same material as the exhaust case, and is connected together by bolts and / or welding.

The height h of the guide rib 17 is given in relation to the height H between the horizontal plane of the longitudinal axis 25 and the highest point of the upper wall 11. The height h of the guide rib 17 is 0.05 * H to < RTI ID = 0.0 > 0.15 * H , preferably 0.14 * H , more preferably 0.1 * H. In the illustrated embodiment, the height of the guide rib 17 is 0.1 * H. A range of the same height can be applied to both the I-shaped and T-shaped guide ribs 17. The width w of the T-shaped guide rib 17 is equal to or less than 1.4 * h , preferably equal to or less than 1.2 * h , more preferably equal to or less than 1.0 * h .

The guide rib 17 is provided at a specific position with respect to the exhaust outlet 23 of the diffuser 22. This particular position is there at a distance (l), the distance (l) is the exhaust casing (10) 1.2 * m, and 1.9 * m, preferably between 1.3 * m, and 1.7 * m from the inner surface of the side wall 12 of the More preferably between 1.4 * m and 1.6 * m , More preferably l = 1.5 * m . The parameter m is defined as the distance between the end point of the outer guide 21 of the guide channel 19 and the inner surface 13 of the side wall 12 of the exhaust case 10. [ The above-mentioned position range is based on the measurement of the loss coefficient (representing the pressure loss of the steam flow) for various positions of the guide rib 17. The results of this measurement are shown in FIG. 3, which shows the dependence of the normalized loss factor on the highest value on the position of the guide rib 17 of the inner side 13 of the side wall 12. According to these measurements, the pressure loss of the guide ribs 17 located between 1.2 * m and 1.9 * m is relatively small compared to the pressure loss measured outside this range.

The guide ribs 17 serve as fixing elements for fixing the reinforcing elements 15 to the upper side wall 11 of the exhaust case 10. The reinforcing element 15 may be fixed directly by the guide rib 17 or may be provided to allow the reinforcing element 15 to be fixed to the guide rib 17, . The backing element 16 may have any suitable shape and size. The height of the support element 16 may preferably be equal to or less than the height h of the guide ribs. The width of the backing element 15 is preferably equal to or less than the height of the backing element 16. One support element 16 may be provided along the guide ribs 17 (not shown), or preferably a separate support element 16 may be provided for each reinforcement element 15. The reinforcing element 15 is secured to the guide rib 17 by conventional suitable means such as, for example, bolts and / or welding, preferably by means of both bolts and welding, to ensure a firm connection, Can be fixed to the element (15).

The reinforcing element 15 can be attached to the upper wall 11 on the side of the guide rib 17 through the guide rib 17 and the guide rib 17 can be attached to the side wall 12, As shown in Fig.

In a preferred embodiment, the case 10 of the exhaust system comprises one or more blocks. Preferably, the first block 10a and the second block 10b include two blocks. As shown in FIG. 1, the first block 10a and the second block 10b may be connected together. Preferably, the first plate 171 of the guide rib 17 may be attached to the first block 10a of the exhaust case 10 and the second plate 172 may be attached to the second block 10a of the exhaust case 10, May be attached to block 10b. The connection between the ribs 17 and the case blocks 10a and 10b can be achieved by means of any suitable means, such as bolts and / or welding, preferably in the form of a bolt and welding, Provided by appropriate means.

Finally, the 3D model of FIG. 2 shows a preferred embodiment of a low pressure steam turbine system with two connected exhaust cases.

10: exhaust case 15: reinforcing element
16: Support element 17: Guide rib

Claims (9)

An exhaust case (10) for a low pressure steam turbine system,
The upper and lower walls 11 and 12,
The inner side surface 13 and the outer side surface 14,
A plurality of reinforcing elements 15,
And a guide rib (17) attached to an upper wall (11) of the exhaust case (10) and extending radially inwardly,
Characterized in that at least one reinforcing element (15) is fixed to the guide rib (17). The method according to claim 1,
The guide ribs 17 is located at a distance in the range between 1.2 * m, and 1.9 * m from the inner surface 13 of the side wall 12 of the turbine case 10, the parameter (m) is the side wall 12 Is defined as the distance from the inner side (13) of the outer guide (21) of the diffuser (22) of the steam turbine system to the end point of the steam turbine system. 3. The method according to claim 1 or 2,
The height of the guide ribs 17 is in the range of 0.05 * H to 0.15 * H , where H is the height of the steam turbine system between the horizontal plane of the longitudinal axis 25 and the highest point of the top wall 11 (10) for a low pressure steam turbine system. 12. A compound according to any one of the preceding claims,
Characterized in that the guide ribs (17) comprise at least one plate with an I-shape or the guide ribs (17) comprise two plates which are T-shaped and perpendicular to each other. An exhaust case (10) for a turbine system. 12. A compound according to any one of the preceding claims,
Characterized in that each said case reinforcing element (15) is fixed to said guide rib (17) via a separate supporting element (16). 6. The method of claim 5,
Wherein the height of each of the base elements 16 is equal to or less than the height h of the guide ribs 17 and the width of the base element 16 is equal to or less than the height of the base element 16 (10) for a low-pressure steam turbine system. 5. The method according to any one of claims 1 to 4,
At least one of the reinforcing elements 15 is fixed to the upper wall 11 on the side of the guide rib 17 through the guide rib 17 and the guide rib 17 is fixed to the exhaust case 10. The exhaust case (10) for a low pressure steam turbine system as claimed in claim 1, 12. A compound according to any one of the preceding claims,
Further comprising at least two case blocks (10a, 10b)
The first plate of the guide rib 17 is attached to the first block 10a of the exhaust case 10 and the second plate 172 of the guide rib 17 is attached to the first block 10a of the exhaust case 10, (10) for a low-pressure steam turbine system. A steam turbine system comprising at least one exhaust case (10) according to any one of the preceding claims.

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