JP2004124813A - Moving blade of rotating machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide high performance for a gas turbine or a compressor by restraining a leaking flow running through a tip clearance and reducing energy loss due to leaking eddies. <P>SOLUTION: A protrusion strip (8) protruding in the form of an eave is formed in an area ranging from a tip portion (6) to a body portion (4a) of each of moving blades (4). The respective protrusions (8) inhibit a leaking flow of main flow gas passing through each of the tip clearances (▵). Each of the protrusion strips is formed so as to form a chord on a blade surface on the curved body side, and has such a tapered shape that the height protruding toward the diametrical outside may increase gradually. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a moving blade of a rotating machine, and more particularly, to a moving blade of a rotating machine such as a turbine, a compressor, and a blower that constitutes a turbo machine.
[0002]
[Prior art]
FIG. 3 is a schematic configuration diagram of a turbojet engine, which includes an air intake 31, a fan 32, a compressor 33, a combustor 34, a gas turbine 35, a jet nozzle 36, and the like. In such a turbojet engine, air is introduced into the engine from an air intake 31 by a fan 32, the air is compressed by a compressor 33, and fuel is burned in a combustor 34 to generate high-temperature combustion gas. The gas turbine 35 is driven by the generated combustion gas, the fan 32 and the compressor 33 are driven by the power of the gas turbine 35, and the combustion exhaust gas is ejected backward from the jet nozzle 36 to generate a propulsive force. ing.
[0003]
FIG. 4 is an enlarged view of a turbine portion of a turbofan engine having a high compression ratio. The turbine of this engine has a two-shaft structure of a high-pressure turbine for driving a compressor (not shown) and a low-pressure turbine for driving a fan.
As shown in the figure, there is a gap (tip clearance Δ) between the tip (tip portion 6) of the moving blade 4 and the inner peripheral surface of the casing 2, and the moving blade and the casing have different thermal expansion coefficients. Therefore, the size of the chip clearance Δ changes depending on the operating state of the engine. Reference numeral 5 denotes a stationary blade for a high-pressure turbine.
[0004]
Here, a shroud 3 is often formed on the moving blade of the low-pressure turbine in order to prevent loss due to mainstream gas leaking from the pressure side (ventral side) to the suction side (back side) through the chip clearance. . This shroud is a small segment attached to the tip of the moving blade, and when all the moving blades are assembled to the turbine disk and the adjacent shrouds are connected, a ring is formed at the outer peripheral end of the moving blade, so that the main flow from the tip clearance Gas (combustion gas) leakage can be suppressed. However, compared with the low pressure turbine blade (rotating at about 5,000 rpm), it rotates at a very high speed (rotating at about 20,000 rpm), and the high pressure turbine blade used under high temperature and high pressure conditions In general, a shroud is not formed in consideration of the effect of creep caused by the action of a large centrifugal force.
[0005]
Therefore, in the rotor blades 4 of the high-pressure turbine, an active clearance control method (ACC method) is employed in order to suppress the leakage of the mainstream gas from the chip clearance Δ. The ACC method is a method of taking out air from a compressor, sending it to the inside of a rotor blade or a casing to cool it, and controlling thermal expansion to narrow the chip clearance Δ to suppress leakage of mainstream gas. .
[0006]
In recent years, the load on the turbine has been increased to reduce the weight of the engine. That is, efforts have been made to reduce the number of blades in order to reduce the weight of the engine, while increasing the amount of work to be performed on one blade.
[0007]
[Patent Document 1] JP-A-11-201092 [Patent Document 2] JP-A-58-113504
[Problems to be solved by the invention]
As described above, in the blade of a high-pressure turbine in which a shroud cannot be formed, the main flow gas flowing from the pressure side to the suction side of the blade through the tip clearance by making the tip clearance as small as possible by the ACC method. Efforts have been made to reduce the effects of vortices (called "leakage vortices"), but due to structural limitations, the effects of leakage vortices on turbine performance (as turbine loads increase) Deterioration) has become a serious problem. That is, as the load on the turbine increases, the pressure difference between the pressure side (ventral side) and the suction side (back side) of the blades increases. As a result, the moving blades of the high pressure turbine without the tip shroud use the ACC method. Also, the influence of the leakage vortex near the tip part was large, and this had the fact that the turbine performance was significantly deteriorated.
[0009]
In order to explain this more specifically, the result of analyzing the flow of the mainstream gas of the rotor blade of the turbine with a high load is shown in FIG. 5 using vectors. As shown in this figure, the mainstream gas is generated at the corner of the root portion 15 (root portion of the blade) in addition to the primary flow flowing along the blade surface between the adjacent moving blades 4. Separation flow A, {circle around (2)} radial flow B flowing radially along the wing surface, {circle around (3)} the tip clearance between the tip portion 6 and the inner peripheral surface of the casing 2 is changed from the pressure side (ventral side 4a) to the suction side. There was a leakage flow C flowing on the side (back side 4b) and the like, and due to these effects, a secondary flow that disturbed the primary flow of the mainstream gas was generated near the bucket 4.
[0010]
Among the secondary flows, the largest loss given to the primary flow is caused by the leakage flow C. In the conventional rotor blade, the interference between the leakage flow passing through the chip clearance and the high-speed primary flow (leakage vortex) ) Was the biggest factor that degraded the performance of the gas turbine.
[0011]
The present invention has been made to solve such a problem. That is, an object of the present invention is to reduce the leakage flow passing through the chip clearance, reduce the energy loss due to the leakage vortex, and increase the performance of a rotating machine capable of achieving high performance such as a gas turbine and a compressor. To provide wings.
[0012]
[Means for Solving the Problems]
According to the present invention, which achieves the above-mentioned object, the present invention passes through a tip clearance (Δ) formed between an inner peripheral surface of a casing (2) and a tip part (6) of a rotor blade (4), and from a ventral side (4a). A rotary machine having a tip clearance vortex reducing plate (8) that protrudes in an eaves-like shape from the tip portion to prevent leakage of mainstream gas flowing to the back side (4b). Provide moving blades.
[0013]
According to the present invention, a tip clearance vortex reduction plate formed by projecting a leakage flow of a mainstream gas leaking from a pressure side to a suction side from a tip clearance into an eaves-like shape on an abdominal side (pressure side) of a moving blade. The energy loss due to the generated leakage vortex can be reduced, and the performance of a rotating machine such as a turbine or a compressor can be improved.
In particular, according to the present invention, the pressure difference between the pressure side (ventral side) and the suction side (back side) of the blade is large, and the high-pressure turbine or high-pressure compression which cannot be sufficiently suppressed even by the ACC method. Leakage flow in the machine can be effectively reduced by the simple shape of the moving blade.
[0014]
Here, it is preferable that the tip clearance vortex reducing plate (8) is formed so as to form a chord on the curved wing surface on the ventral side (4a).
[0015]
The pressure difference between the positive pressure surface and the negative pressure surface is large, and the protrusion near the center in the primary flow direction of the large-curvature tip portion, which has conventionally caused a large amount of leakage, is large, and the small-curvature tip portion has a small leakage flow. By making the projections small, it is possible to effectively reduce the leakage flow, and at the same time, it is possible to minimize the increase in the weight of the bucket and the effect of centrifugal force accompanying the increase in the weight.
[0016]
In the present invention, the tip clearance vortex reduction plate is formed on the ventral side of the rotor blade, but is intended to prohibit the formation of the tip clearance vortex reduction plate on the back side in addition to the ventral side. is not.
[0017]
According to a preferred embodiment, the chip clearance vortex reducing plate (8) has a tapered shape that gradually increases the height of the protrusion toward the outside in the radial direction.
[0018]
By making the protruding height of the tip clearance vortex reduction plate a tapered shape that gradually increases toward the wing tip, as described later, the tip clearance tends to escape by a radial flow flowing in the radial direction along the wing surface. It is possible to effectively prevent the leakage flow and reduce the leakage flow that causes the largest loss to the primary flow, thereby improving the performance of the rotating machine.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In each of the drawings, the same reference numerals are used for parts common to the conventional example.
[0020]
The turbine of the present embodiment is an axial flow turbine, and has a casing having a gas flow path for gradually widening the cross-sectional area of the passage, and a stationary blade for a high-speed rotating high-pressure turbine provided in the gas flow path near the combustor outlet. A row 5 and a moving blade row 4, a plurality of stages of stationary blade rows 7 and a moving blade row 9 for a low-pressure turbine that rotates at a relatively low speed downstream thereof, and a rotor 11 to which the moving blades 4 and 9 are attached are provided. (See FIG. 4). This turbine is a high-load turbine that reduces the number of blades and increases the amount of work to be performed on one blade for the purpose of reducing the weight of the engine.
[0021]
FIG. 1 shows a perspective view (a) as viewed from the downstream side of the moving blade of this embodiment of the high-pressure turbine moving blade, and a ZZ sectional view (b) of (a). A plurality of blades are attached to the hub 13 at equal intervals in the circumferential direction, and have a shape in which the twist angle is large at the tip portion and small at the root portion 15 with respect to the axis. I have. Further, as shown in (b), the upstream side (left side in the figure) of the rotating blade in the rotation direction is the pressure side 4a (ventral side), and the downstream side in the rotation direction (the right side in the figure) is the suction side 4b (back side). Due to the rotation of the rotor blade, the static pressure on the pressure side is high and the static pressure on the suction side is low. In addition, this high-pressure turbine is a turbine in which the pressure difference is particularly large between the pressure side and the suction side as compared with a normal high-pressure turbine, and the load is increased.
[0022]
The moving blade 4 has a hollow structure as shown in FIG. 2 (a), and sends compressed air taken out from a compressor (not shown) to cool the inside of the moving blade 4 while moving the compressed air. The blades are protected from high-temperature combustion gas immediately after exiting the combustion chamber by jetting from the fine holes 17 formed in the blades 4 and film-cooling the outer peripheral surface of the blades. Similarly, the casing is also cooled by compressed air to control its thermal expansion, and the tip clearance formed between the inner peripheral surface of the casing and the tip of the rotor blade is controlled to be small, and the tip clearance is controlled. A device has been devised to minimize the leakage of combustion gas (mainstream gas) from the system (active clearance control method).
[0023]
As shown in FIGS. 1 and 2 (a), a tip clearance vortex reduction plate 8 which protrudes in an eave shape so as to form a chord on the curved wing surface of the ventral side 4a is provided on the tip portion of the rotor blade 4. Is formed.
[0024]
In a turbine blade with a high load, as shown in FIG. 5, it is possible to suppress the leakage flow flowing through the tip clearance from the pressure side 4a (belly side) to the suction side 4b (back side) of the blade. Since the ACC method still cannot sufficiently achieve this, the leakage flow flowing into the chip clearance from the pressure side is inhibited by the chip clearance vortex reduction plate 8. According to this rotor blade, the leakage flow can be effectively reduced by using the chip clearance vortex reducing plate 8 which can be formed at a low cost, and the operating efficiency of a high-pressure turbine with a high load is dramatically improved. Can be done.
[0025]
The reason why the tip clearance vortex reducing plate 8 is formed so as to project in a chord on the blade surface on the ventral side 4a of the rotor blade 4 is that the horizontal axis is a dimensionless code (X / XB) and the vertical axis is a dimensionless dimension. As can be seen from FIG. 2B, which is a distribution diagram of the static pressure on the blade surface of the turbine rotor blade expressed as the pressure (P / PT), the curvature is large, so that the pressure difference between the pressure side and the suction side becomes large. The portion, that is, the projection near the center in the primary flow direction of the blade (X / XB is around 0.5) is large, the curvature is small, and therefore the pressure difference between the pressure side and the suction side is small, that is, the blade By making the protrusions on the upstream and downstream sides in the primary flow direction small, it is possible to effectively reduce the leakage flow that proceeds radially outward on the pressure surface and exits the chip clearance and flows into the suction surface side. And at the same time minimize the weight increase of the rotor blades. It is to suppress to.
[0026]
Here, as shown in FIG. 1B, the tip clearance vortex reducing plate 8 of this embodiment has a tapered shape in which the protruding height gradually increases toward the blade tip. The radial flow B flowing outward in the radial direction along the blade surface 4a of the rotor blade 4 progresses in the direction opposite to the rotation direction of the turbine along the inclination of the chip clearance vortex reducing plate 8 near the tip portion 6. The direction is changed, and it collides with the leakage flow C heading toward the chip clearance along the inner peripheral surface of the casing 2 and impedes its entry.
[0027]
As described above, according to the rotor blade 4 of the present embodiment, conventionally, both the radial flow B and the leakage flow C enter the chip clearance to generate a leakage vortex, thereby deteriorating the performance of the turbine. Is used to obstruct the leakage flow C, thereby canceling both flows, reducing the leakage flow that passes through the chip clearance and forms a secondary flow, and improves the performance of the rotating machine.
[0028]
Although the above-described embodiment is directed to a high-pressure turbine with a high load, the present invention is not limited to this, and is applicable not only to a gas turbine but also to a compressor or a blower as long as it is a moving blade of a rotary machine. It is possible, of course, to variously change the application range and the like without departing from the gist of the present invention.
[0029]
【The invention's effect】
As described above, according to the rotating blade of the rotating machine of the present invention, by suppressing the leakage flow passing through the chip clearance and reducing the energy loss due to the leakage vortex, the performance of a gas turbine, a compressor, and the like can be improved. Can be achieved.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a moving blade of a high-pressure turbine according to an embodiment.
FIG. 2 is a sectional view of a cooling blade (a) and a distribution diagram of a blade surface static pressure (b).
FIG. 3 is a schematic configuration diagram of a turbojet engine.
FIG. 4 is an enlarged view of a turbine portion of the turbofan engine.
FIG. 5 is a diagram showing a flow of a mainstream gas of a rotor blade of a turbine with a high load, using vectors.
[Explanation of symbols]
2 Casing 4 Moving blade 4a Ventral side (pressure side)
4b Back side (negative pressure side)
Reference Signs List 5 Stator vane for high-pressure turbine 6 Tip part 7 Stator vane row for low-pressure turbine 8 Plate for tip clearance vortex reduction 9 Row of blades for low-pressure turbine 11 Turbine disk 13 Hub 15 Root part 17 Pores 31 Air intake 32 Fan 33 Compression Machine 34 Combustor 35 Gas turbine 36 Jet nozzle A Separation flow B Radial flow C Leakage flow Δ Chip clearance

Claims (3)

Mainstream gas flowing from the ventral side (4a) to the dorsal side (4b) through the tip clearance (Δ) formed between the inner peripheral surface of the casing (2) and the tip part (6) of the bucket (4). A rotating blade of a rotary machine, wherein a tip clearance vortex reducing plate (8) projecting in an eaves-like shape from the tip portion to the abdomen side is formed to inhibit leakage flow of the rotating machine. The rotating blade of a rotary machine according to claim 1, wherein the tip clearance vortex reducing plate (8) is formed so as to form a chord on a curved wing surface on the ventral side (4a). The rotating blade of a rotary machine according to claim 1, wherein the tip clearance vortex reducing plate has a tapered shape that gradually increases a height protruding radially outward.

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