JP2005127198A - Turbine and sealing structure of stationary blade root section and moving blade root section - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remarkably and securely reduce leak amount, reduce a manufacturing cost for a rotor disk, and facilitate setting and maintenance operations on the seal structure of the stationary blade/moving blade root pars of a turbine. <P>SOLUTION: A brush seal 9 and a fixed part 7 are installed on the inner ring 5 of the stationary blade root part, and the seal structure is formed in the clearance thereof from a rotor disk projected part 8 formed on the rotor disk 6 of a moving blade 1. A clearance between the tip of the brush seal 9 and the rotor disk projected part 8 is set to zero or a nearly zero in stationary operation. The rotor disk projected part 8 is formed in a tapered shape so that a clearance between the tip of the brush seal 9 and the rotor disk projected part 8 is increased at starting. Since a static blade side structure such as a casing is displaced in a direction shown by 10 along the axial direction according to its extension by heat, and a moving blade side structure such as a rotor is displaced in a direction shown by 11, and the clearance is adjusted. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a seal structure of a stationary blade and a blade root portion of a steam turbine, a gas turbine or the like.

Leakage loss generated from the gap between the stationary body and the rotating body accounts for a large proportion of the various losses generated in the turbine. For this reason, it is important to establish a high-performance sealing technique in order to greatly improve the internal efficiency of the turbine. Further, if the turbine efficiency is improved, energy resources can be saved and environmental destruction factors such as CO ₂ can be reduced.

  In particular, a gap exists at the root between the downstream side of the turbine and the upstream side of the moving blade. As an example of a steam turbine, when steam passes through the stationary blades of the turbine, leaked steam that passes through the gap between the inner ring and the rotor that restrains the inner peripheral edge of the stationary blade is generated, and this leaked steam is downstream of the stationary blade. Passes through the gap at the root portion existing between the side and the upstream side of the rotor blade, and merges with the steam that has passed through the stationary blade. Due to this merging, the steam flowing from the stationary blade outlet to the moving blade inlet causes a turbulence in the vicinity of the blade root, thereby reducing the internal efficiency of the turbine. For this reason, in order to improve the internal efficiency of the turbine, it is necessary to establish a high-performance sealing technique in the gap between the roots of the stationary blade and the moving blade.

  The sealing device for the base part between the stationary blades and the moving blades used in many turbines up to now has fins that are integrated with the inner ring in the radial direction on the downstream side base part of the stationary blades. At the base of the rotor blade upstream side, there is a protrusion for the purpose of forming a seal structure with the tip of the fin installed on the inner ring, and the gap between the seal surface of the protrusion and the tip of the fin is minimal It is set to be limited.

  When this fin is used at the root part between the stationary blade and moving blade of turbine equipment, the inner ring side fin end and the rotor side projection contact each other due to thermal and mechanical deformation of the inner ring and rotor during operation. As a result, the fins may be damaged, and if the operation is continued in the damaged state, the gap size at the root between the stationary and moving blades will increase significantly, resulting in a decrease in sealing performance and a decrease in internal efficiency. It is. In order to prevent this, it is necessary to secure a gap between the fin tip and the protrusion in consideration of the reduction in gap size due to deformation. For this reason, in the case of the conventional fin structure, it is inevitable that the internal efficiency of the turbine is reduced due to leakage at the root portion between the stationary blade and the moving blade.

  As a means for solving this problem, a hole having an appropriate cross-sectional area is provided in the rotor disk portion for fixing the rotor and the rotor blade, and the leaked steam passing through the gap between the inner ring and the rotor is caused to flow between the stationary blade and the rotor blade. There is a method of not passing through the gap. By this method, a reverse leak from the main flow passing through the stationary blades and the moving blades toward the rotor disk portion is generated, and the turbulence of the root portion steam flow can be suppressed to prevent the internal efficiency from being lowered.

  On the other hand, in this method, a part of the steam at the stationary blade outlet portion flows from the root gap to the rotor blade outlet portion through the hole in the rotor disk portion, and does not pass through the portion between the rotor blades. As the amount of steam flowing into the rotor blade inlet decreases, the work volume decreases, resulting in performance degradation. Even in this method, if the root fin is damaged, not only will it cause a serious accident, but if the operation is continued with the damage, the gap between the roots will increase and the amount of outflow steam will increase further. However, further efficiency reduction occurs.

  Further, in the case of the conventional sealing structure using fins as described above, the fins are integrated with the inner ring, and it is necessary to remove the entire inner ring in order to replace and repair the fins. In particular, the stationary vane is usually fixed to the inner ring by welding, and when the entire inner ring is replaced, the cutting operation of the stationary vane and the inner ring occurs. Therefore, a great deal of labor is required for these operations.

  On the other hand, Patent Document 1 discloses a seal structure in which a protruding portion extending in the axial direction is provided on one of a turbine bucket wheel or a turbine bucket dovetail of a steam turbine and a brush seal is opposed to the protruding portion. This patent document 1 aims to eliminate the thermal curvature of the steam turbine rotor.

Special Table 2002-535563

  However, in Patent Document 1, since the gap between the protruding portion and the brush seal is constant, if the gap is set assuming steady operation, the gap becomes small at the time of start-up, and the seal structure wears. It can grow.

  The present invention relates to a seal structure of a root portion between a stationary blade and a moving blade, and provides a seal structure capable of reducing the amount of leakage and reducing wear of the seal structure.

  The present invention provides a sealing structure that seals leakage from a gap between a rotor that is a rotating body and an inner ring that fixes a stationary blade that is a stationary body, from the root portion on the downstream side of the stationary blade toward the root portion on the upstream side of the moving blade. In this structure, a brush seal made of bristles made of a flexible metal strand is projected, and the gap is configured to be different between startup and steady operation.

  In the following, an embodiment of a root seal portion between a stationary blade and a moving blade of a steam turbine facility will be described with reference to the drawings.

  One embodiment provided with the seal structure of the present invention is shown in FIGS. The seal structure of the present embodiment is a seal structure installed on the inner ring of the root portion of the steam turbine stationary blade. In FIG. 1, 1 is a moving blade (blade), 2 is a steam inflow direction, 3 is a stationary blade (nozzle) for guiding steam to the moving blade 1, and 4 is a casing (not shown) with an outer peripheral end of the stationary blade 3 An annular outer ring 5 for fixing, an annular inner ring for restraining the inner peripheral end of the stationary blade 3, 6 a disk for fixing the moving blade to the rotor (not shown), and 7 a root portion between the stationary blade and the moving blade. It is fixed to the annular inner ring 5 by a fixing part that supports the seal structure. A plurality of rotor blades 1 are arranged in the circumferential direction (rotation direction) of the rotor. The stationary blade 3 is disposed on the upstream side in the steam inflow direction 2 with respect to the moving blade 1 so as to correspond to the moving blade 1. The combination of the moving blade 1 and the stationary blade 3 is referred to as a “turbine stage”. Such turbine stages are arranged in a plurality of stages with respect to the axial direction of the rotor. Within each section of the steam turbine, the blade length of the moving blade 1 increases as it goes downstream of the steam flow. The steam induced by the stationary blade 3 rotates the rotor via the moving blade 1. A generator (not shown) is provided at the end of the rotor, and the generator generates electric power by converting rotational energy into electric energy.

  A fixing component 7 is fixed to the inner ring 5 by a detachable fixing method such as bolting, and a sealing member is further provided from the fixing component 7 toward a protruding portion 8 provided in the axial direction from the rotor disk portion. Is going down. As the seal member, only one brush seal 9 is arranged.

  In the case of a steam turbine, during operation, a hot elongation phenomenon occurs due to an increase in temperature due to inflow and rotation of steam with respect to a rotor to which a moving blade is fixed and a casing to which a stationary blade is fixed. For this reason, the relative positional relationship between the moving blade side structure and the stationary blade side structure changes during the time from the stop to the steady operation after starting. In particular, since the dimension in the axial direction of the steam turbine is larger than the dimension in the other direction, the displacement amount due to the thermal extension in the axial direction is the largest. For this reason, the axial position of the surface of the protrusion 8 that forms a seal structure between the tip of the brush seal 9 and the rotor disk protrusion 8 changes from the time of stop to the time of startup and the steady operation. These amounts of change can be obtained by calculation from the characteristics of the materials used for the casing and the rotor, the temperature during steady turbine operation, and the axial dimensions.

  On the other hand, when the rotor is stopped, unlike the steady operation, a portion of the seal structure that comes into contact with the rotor is generated due to the influence of deflection due to the weight of the rotor. For this reason, when the rotor rotates during startup, etc., the rotor and the sealing structure such as the fin / brush seal rotate while in contact with each other even in places where a sufficient gap can be secured during normal operation (rubbing phenomenon). The longer the rotation time, the greater the degree of aging due to wear of the seal structure.

  In this embodiment, the wear caused by the contact at the start-up is reduced. In this embodiment, the gap between the tip of the brush seal 9 and the rotor disk protrusion 8 is wide in the positional relationship at the time of startup and close to zero or nearly zero in the positional relationship during steady operation. The seal structure forming surface 8 is inclined, and the diameter of the seal structure forming surface from the rotor central axis is changed depending on the position. In this embodiment, the stationary blade side structure such as the casing is displaced in the direction indicated by reference numeral 10 along the axial direction as the heat extends, and the moving blade side structure such as the rotor is displaced in the direction indicated by reference numeral 11 on the contrary. This is an example in which a fixed point of a structure is set. FIG. 1 shows a state during stop and FIG. 2 shows a state during steady operation.

  An enlarged view of the seal structure in FIG. 1 is shown in FIG. When the motor is stopped, the tip of the brush seal 9 is in contact with the rotor disk protrusion 8 at an interval a so that no contact occurs even when the actuator is started (this is due to the shaft deflection due to the shape, material, span length, etc. of the rotor). It is set in a state that is maintained), and when it reaches the rated operating state after startup, it is affected by the displacement due to thermal expansion in the axial direction of the moving blade side and stationary blade side structures. The positional relationship moves in the axial direction by the distance b. This b can be predicted from the material, dimensions, etc. as described above, and by determining the gap dimension a between the brush seal 9 and the rotor disk protrusion 8 at the time of stopping so that the rubbing phenomenon does not occur, tan θ = From the a / b equation, the inclination angle θ of the rotor disk protrusion can be determined.

  In this embodiment, the amount of steam flowing through the turbine stage is smaller at startup than in steady operation, and the loss due to leakage is less than in steady operation, so the gap in the seal structure is wide. There is little loss. As the amount of steam flowing through the paragraph increases, the gap of this seal structure gradually narrows, and becomes zero or nearly zero during steady operation, and the sealing performance is always compared to the case where the gap dimension is nearly zero. However, since the wear at the time of start-up described above can be avoided, the contact time between the brush seal 9 and the rotor disk protrusion 8 can be shortened. A longer service life can be realized, and as a result, the maintainability of the turbine is improved.

  Further, according to the present embodiment, even if the gap between the brush seal 9 and the protruding portion 8 decreases due to thermal and mechanical deformation of the rotor and the casing and the like, even if both contact with a strong force, the spring is applied to the brush seal 9. Since there is an action, they are not damaged, and a good sealing performance can be ensured at the same time, and at the same time, the gap management between them becomes easy.

  The fixed part 7 has a detachable structure, and even when replacement is necessary due to wear of the brush seal 9, only the fixed part 7 needs to be replaced, and the inner ring 5 does not need to be removed.

  Further, in the present embodiment, since the gap between the tip of the brush seal 9 and the protrusion 8 at the base of the rotor blade is almost zero, the amount of leaked steam passing through this gap is smaller than that of a seal structure using ordinary fins. Since it can be made almost zero, there is no need to provide a hole that has been machined in the rotor disk for the purpose of suppressing leaked steam that has conventionally been blown between the stationary blade and the moving blade. This not only reduces the processing cost of the rotor disk, but also prevents a decrease in the disk strength associated with the setting of the holes, and has a positive effect on the strength design on the disk side. .

  Another embodiment of the present invention will be described with reference to FIGS. In this embodiment, the brush seal 9 and the fixed component 7 fixed to the inner ring portion on the stationary blade outlet side are fixed so that the brush seal is oriented parallel to the axial direction, and the tip of the brush seal 9 is the rotor disk. A seal structure is formed with the upstream surface of the rotor blade 6.

  In this embodiment, in the same manner as in the above-described embodiment, the change in the relative position in the axial direction of the casing and the rotor caused by the thermal expansion that occurs until the turbine facility starts from the stop and reaches the steady operation is considered. The position of the brush seal 9 is set so that the gap of the seal structure portion is large at the time of stopping, and the gap decreases as the state of steady operation approaches, and the gap approaches zero or nearly zero during steady operation. FIG. 4 shows a state at the time of stopping, and FIG. 5 shows a state at the time of steady operation. In this case, the fixed points with respect to the foundations of the respective structures are set so that the axial displacement due to the thermal extension is in the direction indicated by 10 on the casing side and the direction indicated by 11 on the rotor side. An enlarged view is shown in FIG.

  In this embodiment, the life of the brush seal 9 is not only increased by reducing the contact time of the tip of the brush seal 9 with the rotor disk 6 as in the above-described embodiment, but also has a sealing structure forming surface. Installation of the protrusion 8 becomes unnecessary. Thereby, it is possible to reduce the processing cost of the disk rotor.

  However, in this embodiment, unlike the above-described embodiment, the seal structure gap dimension c when stopped is always equal to the displacement dimension b due to thermal elongation. If it is too large, the turbulence of the steam in the turbine at the time of start-up may be caused, which may affect the start-up time. In that case, as shown in the example shown in FIG. 7, by providing a disk rotor groove 12 having a certain depth in the vicinity of the brush seal tip contact portion of the disk rotor, the gap c of the seal structure at the time of stop is set to the amount of leaked steam. It is possible to secure an appropriate value calculated so that is within the allowable range. The setting position and width of the disk rotor groove 12 are approximately the same as the starting / stopping gap a when set in the radial direction, for example, so as to cover a small amount of radial displacement at the starting / stopping. The gap may be set to a dimension that can be secured in the radial direction.

  According to the above-described embodiment, it is possible to make the amount of leaked steam at the root portion between the stationary blade and the moving blade close to zero, which makes it possible to reduce the processing cost of the rotor disk and remove the seal structure portion. Maintenance can be improved by using a possible structure.

  All of the embodiments according to the present invention described above are intended for the stationary blades and moving blades of a steam turbine, but the same effect can be obtained by applying the present invention to an axial flow turbine such as a gas turbine.

  According to the present invention, the high-performance sealing effect of the brush seal is sufficiently exerted on the root portion between the stationary blade and the moving blade of the turbine. As a result, since leakage loss is suppressed, turbine efficiency is improved. In addition, during maintenance, only the fixing part of the brush seal can be removed from the inner ring that fixes the stationary blade, so that maintenance work is facilitated. Furthermore, along with the improvement of the sealing effect, the drilling of the rotor disk part, which was installed for the purpose of preventing the efficiency reduction in the conventional fin structure, is no longer necessary, reducing the machining cost of the turbine and increasing the strength of the rotor disk. Can be improved. Further, by reducing the contact time at the tip of the brush seal and avoiding rubbing, it is possible to extend the life of the brush seal and further reduce maintenance costs.

It is a figure which shows the state at the time of a turbine stop among the schematic diagrams showing one Example of this invention. It is a figure which shows the state at the time of turbine steady operation among the schematic diagrams showing one Example of this invention. It is an enlarged view of the seal structure part vicinity among the schematic diagrams showing one Example of this invention. It is a figure which shows the state at the time of a turbine stop among the schematic diagrams showing the 2nd Example of this invention. It is a figure which shows the state at the time of turbine steady operation among the schematic diagrams showing the 2nd Example of this invention. It is an enlarged view of the seal structure part vicinity among the schematic diagrams showing the 2nd Example of this invention. It is a schematic diagram showing the 3rd example of the present invention, and is an enlarged view near a seal structure part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Rotor blade, 2 ... Steam inflow direction, 3 ... Stator blade, 4 ... Outer ring, 5 ... Inner ring, 6 ... Rotor disk, 7 ... Fixed part, 8 ... Projection part, 9 ... Brush seal, 10 ... Stator blade side structure 11: Displacement direction due to the thermal extension of the blade, 11... Displacement direction due to the thermal extension of the rotor blade side structure, 12.

Claims (5)

  A plurality of moving blades provided along the circumferential direction of the turbine rotor, a stationary blade provided upstream of the moving blade, a casing containing the moving blade and the stationary blade, and an inner periphery of the stationary blade And an annular inner ring and an outer ring that are constrained at the outer peripheral end and held by the casing, and a brush seal that is installed at the root part of the inner ring on the stationary blade outlet side and forms a seal structure The brush seal is installed in the radial direction of the turbine rotor, and has a surface that forms a seal structure with the end of the brush seal at the rotor blade root portion of the rotor disk that fixes the rotor blade. A turbine provided with a protrusion having a shape in which a diameter dimension from a rotor shaft center changes according to a position in an axial direction.   A plurality of moving blades provided along the circumferential direction of the turbine rotor, a stationary blade provided upstream of the moving blade, a casing containing the moving blade and the stationary blade, and an inner periphery of the stationary blade And an annular inner ring and an outer ring that are restrained at the outer peripheral end and held by the casing, and a brush seal that is installed at the root part of the inner ring on the stationary blade outlet side and forms a seal structure The brush seal is installed in the axial direction of the turbine rotor, and forms a seal structure with the upstream surface of the rotor blade root portion of the rotor disk that fixes the rotor blade.   The turbine according to claim 2, wherein a groove having a certain depth is set on a contact surface of the disk rotor at a position where a tip structure of the brush seal and a seal structure are formed.   4. The component for fixing the brush seal according to claim 1, wherein the component that fixes the brush seal is fixed to the stationary blade or the root of the moving blade by a detachable fixing method such as bolting. 5. Turbine. A plurality of moving blades provided along the circumferential direction of the turbine rotor, a stationary blade provided upstream of the moving blade, a casing containing the moving blade and the stationary blade, and an inner periphery of the stationary blade And a stationary blade root portion and a rotor blade root portion sealing structure having an annular inner ring and an outer ring held by the casing for the purpose of restraining at the outer peripheral end,
The seal structure is formed of a brush seal, and the gap is substantially zero during steady operation, and the gap is large at startup.

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