JP2006118585A - Shaft sealing mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shaft sealing mechanism with leaf seals in a plurality of stages for reducing a difference in pressure which the final stage leaf seal bears without further increasing the number of stages in which the leaf seals are installed. <P>SOLUTION: On a stator 60, the first stage leaf seal 120, the second stage leaf seal 220 and the third stage leaf seal 320 in the final stage are installed along the axial direction of a rotating shaft 4 in sequence from a high pressure side region to a low pressure side region. A slight gap h<SB>1</SB>between both thin plates 121 of the first leaf seal 120, a slight gap h<SB>2</SB>between both thin plates 221 of the second leaf seal 220 and a slight gap h<SB>3</SB>between both thin plates 321 of the third leaf seal 320 are set larger in this order. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a shaft seal mechanism for a rotating shaft of a large fluid machine such as a gas turbine, a steam turbine, a compressor, a water turbine, a refrigerator, a pump, and the like, and in particular, is coaxial with the peripheral surface of the rotating shaft and the rotating shaft. The present invention relates to a shaft seal mechanism that suppresses leakage of working fluid from a high pressure side to a low pressure side in a gap with an inner peripheral surface of a stationary member that is stationary.

  In general, in a large fluid machine such as a gas turbine or a steam turbine, in addition to a main flow channel that essentially flows a working fluid such as compressed air, combustion gas, or steam (hereinafter sometimes simply referred to as “gas”), It is unavoidable that an annular gap is formed between the peripheral surface of the rotating shaft and the inner peripheral surface of a stationary member that is coaxial and stationary on the rotating shaft (for example, an annular member that holds the inner peripheral end of the stationary blade). Absent. If no measures are taken with respect to the gap, gas leaks inadvertently from the high-pressure side to the low-pressure side through the gap, resulting in a decrease in the efficiency of the fluid machine. Therefore, it is extremely important to minimize gas leakage through the gap, and in order to realize this, a shaft seal mechanism is applied to the gap.

  As the shaft seal mechanism, a non-contact type so-called labyrinth seal in which a plurality of fins protrude from the inner peripheral surface of a stationary member has been widely used. However, the labyrinth seal must be configured so that the tip of the fin does not come into contact with the peripheral surface of the rotating shaft even during axial vibration or thermal transient thermal deformation during the rotational transition period. As a result, there is a problem that gas leakage cannot be greatly suppressed.

  On the other hand, in recent years, as a shaft seal mechanism that can significantly reduce the amount of gas leakage, a so-called leaf seal having a structure in which flat thin plates having a certain width in the axial direction of the rotating shaft are arranged in the circumferential direction of the rotating shaft is provided. Yes (see, for example, Patent Document 1). Hereinafter, the detailed configuration of the leaf seal will be described with reference to FIGS. Here, as a large-sized fluid machine to which a leaf seal is applied, a typical gas turbine will be described as an example.

  A gas turbine Gt shown in FIG. 4 includes a compressor 1 that takes in a large amount of air and compresses it, a combustor 2 that mixes and burns fuel into the air compressed by the compressor 1, and a combustor 2. The generated high-temperature and high-pressure combustion gas is introduced into the turbine 3 that converts the thermal energy of the combustion gas into rotational energy, and the rotation that directly receives the rotational energy of the turbine 3 and transmits a part of it as power for the compressor 1. And a shaft 4.

  In the turbine 3, a plurality of rotor blades 10 provided in a plurality of stages in the axial direction on the rotating shaft 4 rotate together with the rotating shaft 4 by receiving the pressure of the sprayed combustion gas. Thus, power is generated by converting the thermal energy of the combustion gas into mechanical rotational energy called rotation of the rotating shaft 4. The rotational energy given to the rotating shaft 4 is taken out from the shaft end and used for power generation. In addition to the moving blade 10 on the rotating shaft 4 side, the turbine 3 is provided with a plurality of stationary blades 11 on the casing 9 side of the turbine 3. The moving blade 10 and the stationary blade 11 are connected to the rotating shaft. 4 are arranged alternately in the axial direction. The amount of combustion gas that leaks from the high pressure side to the low pressure side through the gap between the rotating shaft 4 and the stationary blade 11 (actually, an annular stationary member that holds the inner peripheral end of the stationary blade 11). A leaf seal 20 is provided as a shaft seal mechanism for reducing the above.

  The compressor 1 is coaxially connected to the turbine 3 at the rotating shaft 4, and uses the rotation of the rotating shaft 4 in the turbine 3 to suck and compress outside air into the combustor 2. Supply. In the compressor 1, similarly to the turbine 3, a plurality of moving blades 6 are provided on the rotating shaft 4, and a plurality of stationary blades 7 are provided on the casing 5 side of the compressor 1. The rotating shafts 4 are alternately arranged in the axial direction. The compressed air leaking from the high pressure side to the low pressure side through the gap between the rotating shaft 4 and the stationary blade 7 (here, actually, an annular stationary member that holds the inner peripheral end of the stationary blade 7). A leaf seal 20 is provided as a shaft seal mechanism for reducing the amount of leakage.

  Further, in the bearing portion 8 where the casing 5 of the compressor 1 supports the rotating shaft 4 and the bearing portion 12 where the casing 9 of the turbine 3 supports the rotating shaft 4, compressed air or A leaf seal 20 is provided as a shaft seal mechanism for preventing combustion gas from leaking.

  Subsequently, as shown in FIGS. 5 and 6, the leaf seal 20 is inserted into the stator 60 which is a stationary member corresponding to the stationary blades 7 and 11 and the bearing portions 8 and 12 (see FIG. 4), and the rotating shaft 4. Is installed as a shaft seal mechanism for preventing gas leakage in the annular space in the gap between the peripheral surface of the stator 60 and the inner peripheral surface of the stator 60. The leaf seal 20 includes an annular thin plate group formed of a plurality of thin plates 21 stacked in a circumferential direction of the rotating shaft 4 with a minute gap therebetween (see FIG. 7A), and the thin plate group is divided into the thin plate 21. Each of the U-shaped retainers 22 and 23 sandwiched from both sides in the axial direction on the outer peripheral proximal end side, and one side and one retainer 22 located on the high pressure side (the gas pressure side) in the thin plate group The thin plate group is sandwiched between the divided annular high-pressure side plate 24 that is sandwiched and contacts one side of the thin plate group, the other side located on the low-pressure side (the low gas pressure side) of the thin plate group, and the other retainer 23. Of the divided annular low-pressure side plate 25 in contact with the other side, the connecting member 26 for connecting the retainers 22 and 23 on the outer peripheral side of the thin plate 21, and the rattling of the thin plates 21 held by the retainers 22 and 23. Spacer 27 for suppressing Comprises a leaf spring 28 which sheet group that is grasped by the retainer 22, 23 provide a biasing force to be constant position with respect to the rotation axis 4, a.

  As shown in FIG. 6, each thin plate 21 that is a constituent element of the thin plate group is an approximately T-shaped thin member whose width in the axial direction of the rotation shaft 4 at the outer peripheral side base end is wider than the width at the inner peripheral end side. It is made of a steel plate, and on both sides thereof, notches 21a and 21b are provided at the stepped portions of the width. Here, each thin plate 21 is made of a rolled steel plate having a thickness of about 0.1 mm (for example, a metal steel plate made of stainless steel, Inconel, Hastelloy, etc.), and is first die-cut with a press or the like to obtain a constant thickness. It is molded into a predetermined shape (T-shape). Then, as shown in FIG. 8, the thickness of the thin plate 21 is removed by etching and removing only one side (corresponding to the shaded portion 21d in FIG. 8) of the inner peripheral end side while leaving the outer peripheral base end portion as it is. A step is formed. However, it is also possible to simultaneously form such T-shaped contour formation and step formation by etching.

  Such thin plates 21 are stacked so as to have the same width in the axial direction of the rotary shaft 4, and as shown in FIG. 7B, welded to the outer peripheral base end and the side surface of the wide portion serving as the outer peripheral base end side. Wd is applied and fixed, whereby a thin plate group is formed. In addition, each thin plate 21 is designed to have a predetermined rigidity in the circumferential direction of the rotating shaft 4 determined by the etched thickness t on the inner peripheral end side, and the rotating shaft 4 with respect to the rotating direction of the rotating shaft 4. Is held by retainers 22 and 23 so that the angle θ formed with the peripheral surface of the above becomes an acute angle. In the thin plate group, the depth c of the portion 21d removed by etching of each thin plate 21 is a minute gap between the thin plates 21.

  The high-pressure side plate 24 and the low-pressure side plate 25 are provided with protrusions 24a and 25a that protrude in the axial direction of the rotary shaft 4 at the outer peripheral edge portions, and these protrusions 24a and 25a are notches of the thin plate group. The parts 21a and 21b are respectively fitted. Further, the retainer 22 located on the high pressure side has a concave groove 22a on the surface facing the one side which is the high pressure side on the outer peripheral base end side in the thin plate group, and the retainer 23 located on the other low pressure side is in the thin plate group. A groove 23a is provided on the surface facing the other side which is the low pressure side on the outer peripheral base end side. In the thin plate group in which the protrusions 24a and 25a of the high-pressure side plate 24 and the low-pressure side plate 25 are fitted into the notches 21a and 21b, one side which is the high-pressure side on the outer peripheral base end side is the concave groove 22a of the retainer 22. And the other side, which is the low-pressure side of the outer peripheral base end side, is fitted into the recessed groove 23 a of the retainer 23.

  Here, the inner diameter of the high-pressure side plate 24 is slightly larger than the diameter of the rotating shaft, and the inner diameter of the low-pressure side plate 25 is larger than the inner diameter of the high-pressure side plate 24 by a predetermined amount. Accordingly, the inner peripheral end portion of each thin plate 21 in the thin plate group has a much larger exposed area in the axial direction on the other side, which is the low pressure side, than one side, which is the high pressure side.

  A connecting member 26 is inserted between the retainers 22 and 23 in which the outer peripheral proximal end side of the thin plate group is fitted, and the connecting members 26 are welded to the retainers 22 and 23 so that the retainers 22 and 23 are fixed. Is done. A spacer 27 is inserted between the outer peripheral proximal end of the thin plate group and the retainers 22 and 23 to fill the gap between them. Furthermore, concave grooves 22b and 23b are provided on the outer peripheral sides of the retainers 22 and 23 into which the spacers 27 are inserted, and a leaf spring 28 is fitted into one concave groove formed by the concave grooves 22b and 23b. As a result, the leaf spring 28 is fixed to the outer peripheral side of the retainers 22 and 23.

  As shown in FIG. 6, the leaf seal 20 having such a configuration is an annular mounting groove formed integrally with a split annular mounting piece 62 on the inner peripheral wall surface on the stator 60 side along the circumferential direction. 61, the retainers 22 and 23 are fitted along the circumferential direction. Here, the concave groove 61 is formed on the side surface facing the one side which is the high pressure side of the thin plate group so that the width on the outer peripheral side serving as the bottom is wider than the width on the inner peripheral side in the axial direction of the rotation shaft 4. The shape is provided with a step, and the surface 61 a on the outer peripheral side of the step is a sliding contact surface that is in sliding contact with the inner peripheral surface of the retainer 22 of the leaf seal 20. Further, the outer peripheral surface 61 b that is the bottom of the concave groove 61 is a sliding contact surface that comes into sliding contact with the leaf spring 28 provided on the outer peripheral side of the leaf seal 20. Further, the inner circumferential side width of the concave groove 61 is formed to be sufficiently wider than the width of the leaf seal 20 in the axial width of the rotating shaft 4.

  On the other hand, as shown in FIG. 6, in the axial direction of the rotating shaft 4, the mounting piece 62 is connected to the other side, which is the low pressure side of the thin plate group, so that the width on the outer peripheral side is narrower than the width on the inner peripheral side. A step is provided on the opposite side surface, and the outer surface 62a of the step is a sliding contact surface that is in sliding contact with the inner peripheral surface of the retainer 23 of the leaf seal 20. Further, in the mounting piece 62, the side surface 62 b facing the other side which is the low pressure side of the thin plate group is in contact with the low pressure side plate 25 in the wide inner peripheral side portion in the axial direction of the rotating shaft 4. It becomes the pressure receiving surface. Note that a labyrinth seal 62d is provided by projecting a part of the inner peripheral surface of the mounting piece 62. That is, the mounting piece 62 is installed on the downstream side of the leaf seal 20, and thereby, the labyrinth seal 62 d for further reducing the amount of gas leakage is installed downstream of the leaf seal 20.

  As described above, the leaf seal 20 is held together with the mounting piece 62 on the outer peripheral proximal end side with respect to the concave groove 61 of the stator 60. That is, the inner peripheral surfaces of the retainers 22 and 23 are in sliding contact with the sliding contact surface 61a of the recessed groove 61 and the sliding contact surface 62a of the mounting piece 62, and are fixed to the outer peripheral side of the retainers 22 and 23. Is in sliding contact with the sliding contact surface 61 b of the concave groove 61, so that the leaf seal 20 is maintained in a state of being fitted to the stator 60. Incidentally, since the leaf seal 20 is fitted into the concave groove 61 of the stator 60 using the mounting piece 62, the assembling work can be easily performed.

  At this time, the leaf seal 20 can move slightly in the axial direction of the rotary shaft 4 with respect to the inside of the concave groove 61. Therefore, when gas flows from the high pressure side region toward the low pressure side region, the gas pressure acts on each thin plate 21 of the leaf seal 20, so that the leaf seal 20 moves toward the low pressure side region, as will be described later. The low-pressure side plate 25 comes into contact with the pressure receiving surface 62 b of the mounting piece 62.

  Next, the operation of the leaf seal 20 configured as described above will be described. As shown in FIG. 9A, when a gas pressure from the high pressure side region toward the low pressure side region is applied to each thin plate 21, it is located on the inner peripheral end side and the highest pressure side region with respect to each thin plate 21. A gas pressure distribution 70a is formed in which the gas pressure is highest at the corner r1 and the gas pressure gradually decreases toward the diagonal corner r2. In FIG. 6, each thin plate 21 has a T-shape. However, in FIGS. 5 and 9, only a rectangular portion that causes bending is illustrated for convenience.

  Further, as shown in a cross-sectional view along the circumferential direction of the rotating shaft 4 shown in FIG. 9B, the surface of each thin plate 21 facing the rotating shaft 4 is a lower surface 21q, and the back side is an upper surface 21p. And when the gas pressure which goes to a low pressure side area | region from a high voltage | pressure side area | region is added with respect to each thin plate 21, and the gas pressure distribution 70a as shown to Fig.9 (a) is formed, arbitrary along the cross section of each thin plate 21 The gas pressure is adjusted so that the gas pressure applied to the lower surface 21q is higher than the gas pressure applied to the upper surface 21p at the position.

  At this time, the gas g flowing from the high pressure side region toward the low pressure side region flows from between the high pressure side plate 24 and the peripheral surface of the rotating shaft 4. As shown in FIG. 9A, the gas g flows between the peripheral surface of the rotating shaft 4 and the inner peripheral end of the thin plate 21, and the gap between the upper surface 21p and the lower surface 21q of each adjacent thin plate 21. , And flows radially from the corner r1 to the corner r2. As the gas g flows in this manner, a low-pressure region expands toward the outer peripheral base end of each thin plate 21. Therefore, as shown in FIG. 9B, the gas pressure distributions 70b and 70c applied perpendicularly to the upper surface 21p and the lower surface 21q of each thin plate 21 become larger and closer to the inner peripheral end portion of each thin plate 21 and each thin plate 21. It becomes a triangular distribution shape that becomes smaller as it goes toward the outer periphery base end.

  The gas pressure distributions 70b and 70c on the upper surface 21p and the lower surface 21q have substantially the same shape, but the thin plates 21 are arranged so that the angle θ with respect to the peripheral surface of the rotating shaft 4 is an acute angle. The relative positions of the gas pressure distributions 70b and 70c on 21p and the lower surface 21q are shifted from the thin plate 21. Thereby, a difference arises in the gas pressure of the upper surface 21p and the lower surface 21q in the arbitrary points P which go to the inner peripheral end side from the outer peripheral base end side of the thin plate 21. Thus, in each thin plate 21, the gas pressure applied to the lower surface 21q is higher than the gas pressure applied to the upper surface 21p, so that the gas pressure of the gas flowing between the peripheral surface of the rotating shaft 4 and the inner peripheral end of the thin plate 21 is reduced. The inner peripheral edge of each thin plate 21 is generated in the direction of floating from the rotary shaft 4.

  In this way, by generating a pressure difference between the upper surface 21p and the lower surface 21q of each thin plate 21, the inner peripheral end of each thin plate 21 is deformed so as to float above the peripheral surface of the rotating shaft 4. That is, when the rotation of the rotating shaft 4 is stopped, the inner peripheral end of the thin plate 21 is in contact with the peripheral surface of the rotating shaft 4 with a predetermined preload (see FIG. 7A). Since the inner peripheral end of the thin plate 21 is lifted by the dynamic pressure effect generated by the rotation, the thin plate 21 and the peripheral surface of the rotating shaft 4 are in a non-contact state (see FIG. 7C). Thus, the leaf seal 20 divides the space around the rotary shaft 4 into a high pressure side region and a low pressure side region, and seals the outer periphery of the rotary shaft 4.

  At this time, since the gas g flows from the high-pressure side region toward the low-pressure side region in this way, as shown in FIG. F acts. When the thin plate group receives the fluid force F, the leaf seal 20 moves from the high pressure side region toward the low pressure side region. Then, as shown in FIG. 10B, the position of the leaf seal 20 is regulated by the low pressure side plate 25 coming into contact with the pressure receiving surface 62b of the mounting piece 62. At this time, the low pressure side plate 25 is on the low pressure side in the thin plate group. The distance between the other side and the pressure receiving surface 62 b of the mounting piece 62 is equal to the thickness of the low-pressure side plate 25.

  This is because, since the inner diameter of the low-pressure side plate 25 is larger than the inner diameter of the thin plate group, there is an exposed area that does not contact the low-pressure side plate 25 on the inner peripheral end side of each thin plate 21 in the thin plate group. As a result, on the inner peripheral end side of each thin plate 21 in the thin plate group, a gap equal to the thickness of the low pressure side plate 25 is provided between the other side which is the low pressure side and the pressure receiving surface 62b of the mounting piece 62. It can be secured. On the other hand, since the inner diameter of the high-pressure side plate 24 is smaller than the inner diameter of the low-pressure side plate 25, as a result, on the inner peripheral end side of each thin plate 21 in the thin plate group, the exposed area on the high pressure side is the surface on the low pressure side. It becomes smaller than the departure area.

  Therefore, as shown in FIG. 9A, the gas g flowing into each thin plate 21 (thin plate group) through the gap between the inner peripheral surface of the high-pressure side plate 24 and the peripheral surface of the rotary shaft 4 is the upper surface 21 p of each thin plate 21. And the lower plate 21q flows widely in a diagonal direction, and a low pressure region spreads on the outer peripheral proximal end side of the thin plate 21, so that the inner peripheral end of each thin plate 21 floats from the peripheral surface of the rotating shaft 4, and the low pressure side It flows out through the gap between the inner peripheral surface of the side plate 25 and the peripheral surface of the rotating shaft 4. Thus, the high-pressure side plate 24 and the low-pressure side plate 25 are important for the leaf seal 20 that adjusts the amount of gas flowing into each thin plate 21 and the gas pressure in order to effectively float the inner peripheral end of each thin plate 21. Fulfills the functions.

  In the leaf seal 20 described above, each thin plate 21 has a T-shape, but may have a simple rectangular shape. Further, there may be no spacer 27 between the thin plate group and the retainers 22 and 23, or the retainers 22 and 23 and the connecting member 26 may be fixed with bolts, and there is no leaf spring 28. It does not matter.

Further, when the leaf seal 20 is assembled to a large fluid machine, it is difficult to insert the leaf seal 20 into the rotary shaft 4 along the axial direction in an annular state, so that the leaf seal 20 is annular along the peripheral surface of the rotary shaft 4. As shown in FIG. 11, the configured leaf seal 20 is actually composed of a plurality of divided bodies divided into 4 to 8 in the circumferential direction. At this time, the angle formed by each end face of each divided body with the circumferential surface of the rotating shaft 4 with respect to the rotation direction of the rotating shaft 4 is equal to the angle formed by each thin plate 21 with the circumferential surface of the rotating shaft 4.
JP 2002-13647 A

By the way, when the leaf seal 20 is to be installed in the stator 60 where the pressure difference between the high pressure side region and the low pressure side region is extremely large, it is difficult for one leaf seal 20 to withstand the pressure difference. For this reason, the leaf seals 20 are installed in a plurality of stages in the axial direction of the rotary shaft 4, and the leaf seals 20 share the pressure difference. As an example, FIG. 12 shows a situation where the leaf seals 20 are installed in three stages. Here, the first-stage leaf seal 120, the second-stage leaf seal 220, and the final-stage third-stage leaf seal 320 are installed in order from the high-pressure side region to the low-pressure side region. Yes. The gas at the pressure P ₁ existing on the high pressure side of the first-stage leaf seal 120 that is the high-pressure side region drops to the pressure P ₂ through the first-stage leaf seal 120, and further the second-stage leaf seal. The pressure drops to P ₃ through 220, and finally to the pressure P ₄ through the third-stage leaf seal 320 to reach the low pressure side region.

Here, in general, from the viewpoint of reducing design man-hours and facilitating parts management, the first, second, and third-stage leaf seals 120, 220, and 320 are designed with the same dimensions as each other. The sealing performance with respect to the leakage amount of the working fluid (gas) is the same. Therefore, when the working fluid to be handled is a compressive fluid, the working fluid passes through the first-stage leaf seal 120, the second-stage leaf seal 220, and the third-stage leaf seal 320 in order. The pressure at each time point decreases monotonously and increases to P ₂ , P ₃ , and P ₄ . That is, compared with the pressure difference (P ₁ −P ₂ ) borne by the first-stage leaf seal 120 and the pressure difference borne by the second-stage leaf seal 220 (P ₂ −P ₃ ), A phenomenon occurs in which the pressure difference (P ₃ −P ₄ ) borne by a certain third-stage leaf seal 320 is significantly increased (see the lower graph in FIG. 12).

  In this case, particularly for the third-stage leaf seal 320 as the final stage, this may exceed the limit value of the pressure difference allowable in the design specifications. Conventionally, in order to avoid such a situation, the number of stages of the leaf seal 20 has been further increased. This is because the pressure difference borne by the last-stage leaf seal 20 can be reduced as the number of installation stages of the leaf seal 20 increases.

  However, if the number of installation stages of the leaf seal 20 is large, the number of parts increases accordingly, so that the manufacturing cost is deteriorated, which is disadvantageous in terms of economy. In addition, since it is necessary to secure a space in the axial direction for installing the leaf seal 20, an increase in the size of the fluid machine to which the leaf seal 20 is applied is caused in the axial direction, resulting in generation of axial vibration of the rotating shaft 4. Has the negative effect of becoming sensitive.

  Accordingly, the present invention has been made in view of the above problems, and is a shaft seal mechanism including a plurality of stages of leaf seals, which is not accompanied by further increase in the number of installation stages of the leaf seals. It aims at providing the shaft seal mechanism which can reduce the pressure difference which bears.

  In order to achieve the above object, the shaft seal mechanism according to the present invention provides a working fluid from a high pressure side to a low pressure side in a gap between a peripheral surface of a rotating shaft and an inner peripheral surface of a stationary member that is coaxial and stationary on the rotating shaft. A shaft seal mechanism that suppresses leakage of the rotary shaft, and has a certain width in the axial direction of the rotary shaft, and each of them has an acute angle with respect to the peripheral surface of the rotary shaft with a small gap therebetween in the circumferential direction of the rotary shaft. An annular thin plate group consisting of a plurality of flexible thin plates whose inner peripheral ends are in contact with the peripheral surface of the rotating shaft when rotation is stopped, and both sides of the thin plate group in the axial direction. An annular high-pressure side plate that has an inner diameter that is a predetermined amount larger than the diameter of the rotary shaft, and that is located on the low-pressure side of both sides in the axial direction of the thin plate group. A predetermined amount larger than the inner diameter of the high-pressure side plate. A shaft seal member comprising: an annular low-pressure side plate having a diameter; an annular holding member that integrally holds the thin plate group, the high-pressure side plate, and the low-pressure side plate at their outer peripheral portions; However, the shaft seal mechanism mounted in a plurality of stages in the axial direction has the following features.

  As a first feature point, each thin plate group in the shaft seal member of each stage has a narrower gap between the thin plates in the thin plate group closer to the high pressure side, and closer to the low pressure side. In the thin plate group, the minute gaps between the thin plates are wider. If it does in this way, in each shaft seal member, ie, each leaf seal, out of the gas which flowed in between the thin plates along the axial direction of the rotating shaft, it flows between the thin plates as it is and flows out. The volume flow rate of the gas is smaller as it is closer to the high pressure side, and conversely, it is increased as it is closer to the low pressure side. Therefore, as the working fluid passes through the leaf seals in order from the high pressure side to the low pressure side, the pressure at each point of time decreases substantially uniformly. Therefore, the pressure difference borne by the leaf seal at the final stage is almost equal to the pressure difference borne by the other leaf seals, and is reduced within the limit value in the design specifications.

  As a second feature point, each high-pressure side plate in the shaft seal member of each stage has a smaller inner diameter as the high-pressure side plate in the shaft seal member close to the high-pressure side, and the high-pressure side plate in the shaft seal member close to the low-pressure side. The inner diameter is larger. Even in this case, in the shaft seal member, that is, the leaf seal, the gas flowing between the thin plates in the axial direction between the thin plates flows in the axial direction between the thin plates as it flows out. The volume flow rate of the leaf seal decreases as it approaches the high pressure side, and conversely increases as it approaches the low pressure side. As a result, the sealing performance of the leaf seal increases as it approaches the high pressure side, and decreases as it approaches the low pressure side. Therefore, as in the case of the first feature point described above, the pressure difference borne by the final leaf seal is almost equal to the pressure difference borne by the other leaf seals, and is within the limit values in the design specifications. It is reduced.

  As a third feature point, each low-pressure side plate in the shaft seal member of each stage is thinner in the axial direction than the low-pressure side plate in the shaft seal member close to the high-pressure side, and is close to the high-pressure side. The low-pressure side plate of the member is thicker in the axial direction. In this way, in the shaft seal member, that is, the leaf seal, the volume of the gas flowing out and flowing out between the thin plates among the gases flowing in along the axial direction of the rotating shaft between the thin plates. The closer the flow rate is to the high pressure side, the smaller the flow rate, and the higher the flow rate to the low pressure side. Therefore, as in the case of the first feature point described above, the pressure difference borne by the final leaf seal is almost equal to the pressure difference borne by the other leaf seals, and is within the limit values in the design specifications. It is reduced.

  According to the shaft seal mechanism of the present invention, the pressure difference borne by the leaf seal at the final stage can be reduced without further increasing the number of leaf seals installed. Of course, there is no increase in the size of the fluid machine to which the leaf seal is applied in the axial direction.

  Hereinafter, a shaft seal mechanism employing a leaf seal as an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a state in which a plurality of leaf seals are installed in the present embodiment, FIG. 2 is a sectional view along the axial direction of a rotating shaft for explaining the characteristics of each leaf seal, and FIG. 3 is each leaf seal. It is sectional drawing in alignment with the radial direction of the rotating shaft for demonstrating the characteristic of these. In the figure, parts having the same names and the same functions as those in FIGS. 4 to 12 are denoted by the same reference numerals, and redundant description will be omitted as appropriate, and feature points of the present invention will be noted. In particular, in the present embodiment, the case where the leaf seals 20 are installed in three stages and the pressure difference between the high pressure side region and the low pressure side region is shared by these leaf seals 20 is shown as an example.

As shown in FIG. 1, the stator 60 includes a first-stage leaf seal 120 and a second-stage leaf seal 220 in order from the high-pressure side region to the low-pressure side region along the axial direction of the rotating shaft 4. , And a third-stage leaf seal 320, which is the final stage, is installed. The gas at the pressure P ₁ existing on the high pressure side of the first-stage leaf seal 120 that is the high-pressure side region drops to the pressure P ₂ through the first-stage leaf seal 120, and further the second-stage leaf seal. The pressure drops to P ₃ through 220, and finally to the pressure P ₄ through the third-stage leaf seal 320 to reach the low pressure side region.

In the present embodiment, on the assumption that the working fluid to be handled is a compressive fluid, in order to reduce the pressure difference (P ₃ −P ₄ ) borne by the third-stage leaf seal 320 as the final stage, The pressure difference (P ₃ −P ₄ ), the pressure difference borne by the first stage leaf seal 120 (P ₁ −P ₂ ), and the pressure difference borne by the second stage leaf seal 220 (P ₂ − P ₃ ) is made substantially equivalent (see the lower graph in FIG. 1). The method will be described subsequently.

  In each of the first, second, and third stage leaf seals 120, 220, and 320, the following expressions (1) and (2) are satisfied as the characteristics.

G1 _i = k1 · b _i · h _i ³ · (P _i ² −P _{i + 1} ² ) / L _i (1)
Here, i is 1, 2, 3,..., N, and represents the i-th leaf seal 20. In this embodiment, n = 3 is final. As shown in FIGS. 2 and 3, G 1 _i is the same among the thin plates 121, 221, 321 among the gases flowing in along the axial direction of the rotary shaft 4 between the thin plates 121, 221, 321. It is the volume flow rate of the gas which flows out and flows out between. k1 is a coefficient. b _i is the radial width of the exposed region formed by the inner peripheral ends of the thin plates 121, 221, 321 and the inner periphery of the high-pressure side plates 124, 224, 324. h _i is a minute gap between the thin plates 121, 221, and 321. P _i is the pressure on the high pressure side of the leaf seals 120, 220, and 320, and P _{i + 1} is the pressure on the low pressure side. L _i is the width in the axial direction of each of the thin plates 121, 221 and 321.

G2 _i = k 2 · e _i · PM _i (2)
However, i is 1, 2, 3,..., N as in the case of the above formula (1), and represents the leaf seal 20 at the i-th stage. In this embodiment, n = 3 is final. As shown in FIG. 2, G2 _i spreads between the thin plates 121, 221, and 321 among the gases flowing along the axial direction of the rotation shaft 4 between the thin plates 121, 221, and 321. Is the volumetric flow rate of the gas flowing out. k2 is a coefficient. e _i is the thickness in the axial direction of the low pressure side plate 125, 225, 325. PM _i is the pressure in the vicinity of the inner periphery of the low pressure side plates 125, 225, 325 on the low pressure side of the leaf seals 120, 220, 320.

Here, the sealing performance of the leaf seals 120, 220, and 320 is set so as to be higher as it is closer to the high pressure side region, and conversely, as it is closer to the low pressure side region. In the above equation (1), the volume flow rate G1 _i of the gas may be less as the leaf seal 20 is closer to the high-pressure side region and conversely as the leaf seal 20 is closer to the low-pressure side region. Specifically, the minute gaps h _i between the thin plates 21 are narrower as the leaf seal 20 is closer to the high-pressure side region and wider as the leaf seal 20 is closer to the low-pressure side region. In other words, the small gap h ₁ of the first leaf seal 120, minute gap h ₂ of the second leaf seal 220 is set so as to spread in the order of the small gap h ₃ of the third leaf seal 320.

In forming such a minute gap h _i between the thin plates 21, as shown in FIGS. 7 and 8, the leaf seal 20 closer to the high-pressure side region has a shallow etching depth c, that is, each thin plate. The thickness t of the etched inner peripheral end 21 is increased, and conversely, the leaf seal 20 closer to the low pressure side region has a deeper etching depth c of each thin plate 21, that is, the etched inner peripheral end of each thin plate 21. It is sufficient to reduce the thickness t on the side.

Alternatively, the leaf seal 20 closer to the high pressure side region extends the inner peripheral end of each thin plate 21 toward the rotation shaft 4, and conversely, the leaf seal 20 closer to the low pressure side region extends the inner peripheral end of each thin plate 21 from the rotation shaft 4. Shrinking is enough. Depending on the expansion and contraction of the thin plate 21, and mutual contact increasing or decreasing at the inner peripheral edge side of the planar plates 21, as a result, because the small gap h _i of the planar plates 21 each other on average to Semahiro.

With this configuration, as the working fluid passes through the first-stage leaf seal 120, the second-stage leaf seal 220, and the third-stage leaf seal 320 in order, the pressure at each time point is increased. It decreases almost uniformly to P ₂ , P ₃ , and P ₄ . Therefore, even if the number of installation stages of the leaf seal 20 is not further increased, the pressure difference (P ₁ −P ₂ ) borne by the third-stage leaf seal 320 as the final stage is the other first and second leafs. The pressure differences (P ₂ −P ₃ ) and (P ₃ −P ₄ ) borne by the seals 120 and 220 are almost equal to each other, and are reduced within the limit values in the design specifications. Of course, the size of the fluid machine to which the leaf seal 20 is applied is not increased in the axial direction, and there is no concern about the occurrence of shaft vibration of the rotating shaft 4.

As another configuration, in order to set the seal performance of the leaf seals 120, 220, and 320 so that the seal performance near the high-pressure side region is high, and conversely, the seal performance of the leaf seals 120, 220, and 320 is low as it is close to the low-pressure side region. ), The width of the exposed region of the leaf seal 20 is decreased so that the volume flow rate G1 _i of the gas is smaller as the leaf seal 20 is closer to the high-pressure side region, and conversely is larger as the leaf seal 20 is closer to the low-pressure side region. b _i is narrower leaf seal 20 closer to the high pressure side region, may be made wider as the leaf seal 20 is close to the low pressure side region conversely. That is, the width b ₁ of the exposed area at the first leaf seal 120, the width b ₂ of the exposed area at the second leaf seal 220, and the width b ₃ of the exposed area at the third leaf seal 320. Set to spread in order. It is sufficient that the leaf seal 20 closer to the high pressure side region has a smaller inner diameter of the high pressure side plate 24 and the leaf seal 20 closer to the low pressure side region has a larger inner diameter.

As another configuration, in order to set the sealing performance of the leaf seals 120, 220, and 320 so that the sealing performance near the high-pressure side region is higher and conversely the one near the low-pressure side region is lower, the above formula (2 ), The volume flow rate G2 _i of the gas may be smaller as the leaf seal 20 is closer to the high pressure side region, and conversely, may be larger as the leaf seal 20 is closer to the low pressure side region. Specifically, the thickness e _i of the low-pressure side plate 25 is thinner as the leaf seal 20 is closer to the high-pressure side region, and conversely is thicker as the leaf seal 20 is closer to the low-pressure side region. In other words, the thickness e ₁ of the low pressure side plate 125 of the first leaf seal 120, the thickness e ₂ of the low pressure side plate 225 of the second leaf seal 220, the low pressure side plate 325 in the third leaf seal 320 The thickness e ₃ is set so as to increase in this order.

Even in such a configuration, as the working fluid passes through the first-stage leaf seal 120, the second-stage leaf seal 220, and the third-stage leaf seal 320 in order, the pressure at each time point Is reduced almost uniformly to P ₂ , P ₃ , and P ₄ , so that the same effect as described above is obtained.

  In the present embodiment, the configuration in which the leaf seals 20 are arranged in three stages has been described. However, the number of stages may be two, or four or more.

  In addition, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, although the thing which employ | adopted the leaf seal is illustrated in the gas turbine shown in FIG. 4, it is not limited to it, Large-sized fluid machinery, such as a steam turbine, a compressor, a water turbine, a refrigerator, and a pump, is illustrated. As described above, it can be widely used for converting energy into work depending on the relationship between the rotation of the shaft and the flow of the working fluid. It can also be used to suppress the flow of the working fluid in the axial direction along the peripheral surface of the rotating shaft.

  The present invention is useful as a shaft seal mechanism for a rotating shaft of a large fluid machine.

It is a figure which shows the condition which installed the leaf seal in multiple stages in this invention. It is sectional drawing in alignment with the axial direction of the rotating shaft for demonstrating the characteristic of each leaf seal in this invention. It is sectional drawing in alignment with the radial direction of the rotating shaft for demonstrating the characteristic of each leaf seal in this invention. It is the schematic which shows the structure of the gas turbine which is an example of the large sized fluid machine provided with the conventional general leaf seal. It is a perspective view which shows the basic composition of the conventional general leaf seal. It is sectional drawing which follows the axial direction of the rotating shaft which shows the principal part of the large sized fluid machine provided with the conventional general leaf seal. It is the side view and sectional drawing which follow the circumferential direction of the rotating shaft which shows the basic composition of the conventional general leaf seal. It is a side view of the thin plate which is a component of the conventional general leaf seal. It is a schematic diagram for demonstrating the effect | action of the conventional general leaf seal. It is a schematic diagram for demonstrating the effect | action of the conventional general leaf seal. It is a top view which shows the state which has arrange | positioned the conventional general leaf seal in cyclic | annular form. It is a figure which shows the condition which installed the leaf seal in multiple steps in the past.

Explanation of symbols

4 Rotating shaft 20, 120, 220, 320 Leaf seal 21, 121, 221, 321 Thin plate 22, 23, 122, 123, 222, 223, 322, 323 Retainer 24, 124, 224, 324 High pressure side plate 25, 125, 225,325 Low pressure side plate 60 Stator 61, 161, 261, 361 Mounting groove 62, 162, 262, 362 Mounting piece

Claims (3)

A shaft seal mechanism that suppresses leakage of working fluid from the high pressure side to the low pressure side in the gap between the peripheral surface of the rotating shaft and the inner peripheral surface of a stationary member that is coaxial and stationary with respect to the rotating shaft,
Each inner peripheral end rotates while having a certain width in the axial direction of the rotating shaft and being stacked at an acute angle with respect to the peripheral surface of the rotating shaft, with each having a small gap in the circumferential direction of the rotating shaft. An annular thin plate group consisting of a large number of flexible thin plates that come into contact with the peripheral surface of the rotating shaft when stopped, and one side located on the high pressure side of both sides of the thin plate group in the axial direction. An annular high-pressure side plate having an inner diameter larger than the diameter of the rotary shaft by contact with the other side located on the low-pressure side of both sides of the thin plate group in the axial direction, and the inner diameter of the high-pressure side plate A shaft seal member comprising: an annular low-pressure side plate having an inner diameter larger than the predetermined amount; an annular holding member that integrally holds the thin plate group, the high-pressure side plate, and the low-pressure side plate at their outer peripheral portions. Multiple steps in the axial direction with respect to the stationary member In the shaft sealing mechanism,
Each thin plate group in the shaft seal member of each stage is such that the fine gap between the thin plates is narrower as the thin plate group is closer to the high pressure side, and the thin plate group is closer to the low pressure side. The shaft seal mechanism is characterized by a wide micro gap. A shaft seal mechanism that suppresses leakage of working fluid from the high pressure side to the low pressure side in the gap between the peripheral surface of the rotating shaft and the inner peripheral surface of a stationary member that is coaxial and stationary with respect to the rotating shaft,
Each inner peripheral end rotates while having a certain width in the axial direction of the rotating shaft and being stacked at an acute angle with respect to the peripheral surface of the rotating shaft, with each having a small gap in the circumferential direction of the rotating shaft. An annular thin plate group consisting of a large number of flexible thin plates that come into contact with the peripheral surface of the rotating shaft when stopped, and one side located on the high pressure side of both sides of the thin plate group in the axial direction. An annular high-pressure side plate having an inner diameter larger than the diameter of the rotary shaft by contact with the other side located on the low-pressure side of both sides of the thin plate group in the axial direction, and the inner diameter of the high-pressure side plate A shaft seal member comprising: an annular low-pressure side plate having an inner diameter larger than the predetermined amount; an annular holding member that integrally holds the thin plate group, the high-pressure side plate, and the low-pressure side plate at their outer peripheral portions. Multiple steps in the axial direction with respect to the stationary member In the shaft sealing mechanism,
Each of the high-pressure side plates in the shaft seal member of each stage has a smaller inner diameter as the high-pressure side plate in the shaft seal member closer to the high-pressure side, and a larger inner diameter as the high-pressure side plate in the shaft seal member closer to the low-pressure side. Shaft seal mechanism. A shaft seal mechanism that suppresses leakage of working fluid from the high pressure side to the low pressure side in the gap between the peripheral surface of the rotating shaft and the inner peripheral surface of a stationary member that is coaxial and stationary with respect to the rotating shaft,
Each inner peripheral end rotates while having a certain width in the axial direction of the rotary shaft and being stacked at an acute angle with respect to the peripheral surface of the rotary shaft, with each having a minute gap in the circumferential direction of the rotary shaft. An annular thin plate group consisting of a large number of flexible thin plates that come into contact with the peripheral surface of the rotating shaft when stopped, and one side located on the high pressure side of both sides of the thin plate group in the axial direction. An annular high-pressure side plate having an inner diameter larger than the diameter of the rotary shaft by contact with the other side located on the low-pressure side of both sides of the thin plate group in the axial direction, and the inner diameter of the high-pressure side plate A shaft seal member comprising: an annular low-pressure side plate having an inner diameter larger than the predetermined amount; an annular holding member that integrally holds the thin plate group, the high-pressure side plate, and the low-pressure side plate at their outer peripheral portions. Multiple steps in the axial direction with respect to the stationary member In the shaft sealing mechanism,
Each low-pressure side plate in the shaft seal member of each stage is thinner in the axial direction as the low-pressure side plate in the shaft seal member closer to the high-pressure side, and is lower in the axial direction as the low-pressure side plate in the shaft seal member closer to the high-pressure side. A shaft seal mechanism characterized by having a large thickness at the shaft.

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