JP4178545B2 - Rotating machine blade - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotating blade of a rotating machine, and more particularly to a rotating blade of a rotating machine such as a turbine, a compressor, or a blower that constitutes a turbomachine.
[0002]
[Prior art]
FIG. 3 is a schematic configuration diagram of a turbojet engine, which includes an air inlet 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 the air intake 31 by a fan 32, the air is compressed by a compressor 33, fuel is combusted in the combustor 34, and high-temperature combustion gas is generated. 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 rearward from the jet nozzle 36 to generate propulsive force. ing.
[0003]
FIG. 4 shows an enlarged view of the turbine portion of a turbofan engine with a high compression ratio. The engine turbine 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 portion (tip portion 6) of the moving blade 4 and the inner peripheral surface of the casing 2, and the thermal expansion coefficient differs between the moving blade and the casing. Therefore, the magnitude of the tip clearance Δ varies 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 clearance side (abdominal side) to the negative pressure surface side (back side) through the tip clearance. . This shroud is a small segment attached to the tip of the rotor blade. When all the rotor blades are assembled to the turbine disk and adjacent shrouds are joined together, they form a ring at the outer peripheral edge of the rotor blade. Gas (combustion gas) leakage can be suppressed. However, in comparison with low-pressure turbine blades (rotating at about 5,000 rpm), they rotate at a very high speed (rotating at about 20,000 rpm), and in high-pressure turbine blades 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]
Accordingly, the active clearance control method (ACC method) is employed in the moving blade 4 of the high pressure turbine in order to suppress leakage of the mainstream gas from the tip clearance Δ. The ACC method is a method of taking out air from the compressor, sending it into the rotor blades or casing, cooling it, and controlling the thermal expansion to narrow the tip clearance Δ and suppress mainstream gas leakage. .
[0006]
In recent years, the load of the turbine has been increased for the purpose of reducing the weight of the engine. That is, in order to reduce the weight of the engine, efforts are being made to reduce the number of blades while increasing the amount of work to be performed on one blade.
[0007]
[Patent Document 1]
JP-A-11-201092 [Patent Document 2]
Japanese Patent Application Laid-Open No. 58-113504
[Problems to be solved by the invention]
As described above, in a moving blade of a high-pressure turbine that cannot form a shroud, the mainstream gas that flows from the pressure surface side to the suction surface side of the blade through the tip clearance by narrowing the tip clearance as much as possible by the ACC method. Efforts to reduce the effects of vortices (called “leakage vortices”) are being made, but due to structural limitations, the impact of leakage vortices on turbine performance as turbines increase in load ( Deterioration) has become a serious problem. That is, as the turbine load increases, the pressure difference between the pressure surface side (abdominal side) and the suction surface side (back side) of the blade increases. As a result, the ACC method is used for moving blades of high-pressure turbines without tip shrouds. However, the influence of leakage vortices in the vicinity of the tip part was large, and there was a situation in which this significantly deteriorated the turbine performance.
[0009]
In order to explain more concretely, the result of analyzing the flow of the mainstream gas of the rotor blade of the turbine subjected to 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 (the root portion of the blade) in addition to the primary flow flowing along the blade surface between the adjacent blades 4. Separation flow A, (2) radial flow B flowing radially along the blade surface, (3) tip clearance between the tip portion 6 and the inner peripheral surface of the casing 2 from the pressure surface side (abdominal side 4a) to the suction surface There is a leakage flow C flowing on the side (back side 4b), and a secondary flow that disturbs the primary flow of the mainstream gas is generated in the vicinity of the rotor blade 4 due to these effects.
[0010]
Of the secondary flows, the loss given to the primary flow is the largest due to the leakage flow C. In the conventional rotor blade, the interference between the leakage flow passing through the tip clearance and the high-speed primary flow (leakage vortex) ) Was the biggest factor that deteriorated the performance of the gas turbine.
[0011]
The present invention has been made to solve such problems. That is, it is an object of the present invention to suppress the flow of leakage through the chip clearance, reduce energy loss due to leakage vortices, and achieve the performance of a rotating machine that can achieve high performance such as a gas turbine or a compressor. To provide wings.
[0012]
[Means for Solving the Problems]
The present invention that achieves the above object passes through the tip clearance (Δ) formed between the inner peripheral surface of the casing (2) and the tip portion (6) of the rotor blade (4) from the ventral side (4a). In order to inhibit the leakage flow of the mainstream gas flowing to the back side (4b), the tip clearance vortex reduction plate (8) protruding in a bowl shape from the tip portion to the ventral side is formed ,
The tip clearance vortex reduction plate extends from a first position to a second position;
The first position is a position downstream by a predetermined distance from the most upstream position in the moving blade, and the second position is a position upstream by a predetermined distance from the most downstream position in the moving blade,
The height at which the tip clearance vortex reduction plate (8) protrudes from the tip portion to the ventral side is relatively small in the vicinity of the first position and the second position, and the first position and the Provided is a rotor blade for a rotating machine blade characterized by being relatively large near the center between the second position . The first position may be a position close to the most upstream position, and the second position may be a position close to the most downstream position. The most upstream position may be an upstream end of the ventral end portion in the tip portion, and the most downstream position may be a downstream end of the ventral end portion in the tip portion.
[0013]
According to the present invention, a chip clearance vortex reduction plate formed by projecting a mainstream gas leakage flow leaking from the pressure clearance side to the suction pressure side from the tip clearance in a bowl shape on the ventral side (positive pressure surface side) of the moving blade. It is possible to improve the performance of a rotating machine such as a turbine or a compressor by reducing the energy loss due to the leaked vortex generated.
In particular, according to the present invention, the pressure difference between the pressure surface side (abdominal side) and the suction surface side (back side) of the blade is large, and the high pressure turbine and the high pressure compression that have not been sufficiently suppressed even by the ACC method. Leakage flow in the machine can be effectively reduced by a moving blade having a simple shape.
[0014]
Here, it is preferable that the tip clearance vortex reducing plate (8) is formed so as to form a string on the curved blade surface (4a).
[0015]
The pressure difference between the positive pressure surface and the negative pressure surface is large, and there is a large protrusion at the center of the primary flow direction of the tip portion with a large curvature, where a large amount of leakage has occurred in the past. By making the protrusions small, the leakage flow can be effectively reduced, and at the same time, the weight of the moving blade and the influence of the centrifugal force accompanying the weight increase can be minimized.
[0016]
In the present invention, the tip clearance vortex reduction plate is formed on the ventral side of the rotor blade, but it is intended to prohibit the formation of the tip clearance vortex reduction plate on the dorsal 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 protruding outward in the radial direction.
[0018]
By making the protruding height of the tip clearance vortex reducing plate gradually increase toward the blade tip, as will be described later, it tries to escape the tip clearance by the radial flow flowing in the radial direction along the blade surface. The performance of the rotating machine can be improved by effectively inhibiting the leakage flow and reducing the leakage flow that causes the largest loss to the primary flow.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected and used for the part which is common in a prior art example.
[0020]
The turbine of the present embodiment is an axial turbine, and has a casing having a gas flow passage that gradually widens the cross-sectional area of the inside, and a stationary blade for a high-pressure turbine that rotates at a high speed provided in the gas flow passage near the combustor outlet. A row 5 and a moving blade row 4, a plurality of stationary blade rows 7 and a moving blade row 9 for a low-pressure turbine rotating at a relatively low speed downstream thereof, a rotor 11 to which the moving blades 4 and 9 are attached, and the like. (See FIG. 4). This turbine is a high-load turbine in which the number of blades is decreased and the amount of work to be performed by one blade is increased in order to reduce the weight of the engine.
[0021]
FIG. 1 shows a perspective view (a) of the high-pressure turbine rotor blade as viewed from the downstream side of the rotor blade of this embodiment and a ZZ cross-sectional view (b) of FIG. A plurality of blades are attached to the hub 13 at equal intervals in the circumferential direction, and the tip portion has a larger twist angle and the root portion 15 has a smaller twist angle with respect to the axial center. Yes. Further, as shown in (b), the upstream side in the rotational direction (left side in the figure) of the rotor blade is the pressure surface side 4a (belly side), and the downstream side in the rotational direction (right side in the figure) is the suction side 4b (back side). The static pressure on the pressure surface side is high and the static pressure on the suction surface side is low due to the rotation of the moving blade. Further, this high-pressure turbine is a turbine in which the pressure difference between the pressure surface side and the suction surface side is larger than that of 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). The compressed air taken out from a compressor (not shown) is fed into the moving blade 4 to cool the moving blade 4, and the compressed air is moved. The blade is protected from the high-temperature combustion gas immediately after leaving the combustion chamber by ejecting from the pore 17 formed in the blade 4 and film cooling the outer peripheral surface of the blade. 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 portion of the rotor blade is controlled to be narrow. Has been devised to reduce the leakage of combustion gas (mainstream gas) as much as possible (active clearance control method).
[0023]
As shown in FIGS. 1 and 2A, the tip portion of the moving blade 4 has a tip clearance vortex reduction plate 8 that protrudes in a hook shape so as to form a string on the curved blade surface of the ventral side 4a. Is formed.
[0024]
In the turbine blade having a high load, as shown in FIG. 5, the leakage flow flowing through the tip clearance from the pressure surface side 4a (abdominal side) to the suction surface side 4b (back side) of the blade is suppressed. Since the ACC method cannot be achieved sufficiently, the leakage flow flowing into the chip clearance from the pressure surface 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 reduction plate 8 that can be formed at low cost, and the operating efficiency of a high-pressure turbine with a particularly high load is dramatically improved. Can be made.
[0025]
The tip clearance vortex reduction plate 8 is shaped so as to form a chord on the blade surface on the ventral side 4a of the rotor blade 4. The horizontal axis is a dimensionless code (X / XB) and the vertical axis is dimensionless. As can be seen from FIG. 2 (b), which is a blade surface static pressure distribution diagram of the turbine rotor blade expressed as pressure (P / PT), the curvature is large, and therefore the pressure difference between the pressure surface side and the suction surface side becomes large. The portion, that is, the protrusion near the center of the primary flow direction of the moving blade (X / XB is around 0.5) is large and the curvature is small, so that the pressure difference between the pressure surface side and the suction surface side is small, that is, the blade surface By forming 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 to the pressure side of the pressure surface and exits the tip clearance and flows into the suction surface side. At the same time, minimizing the weight increase of the blade It is to suppress to.
[0026]
Here, as shown in FIG. 1B, the tip clearance vortex reduction plate 8 of the present embodiment has a tapered shape in which the protruding height gradually increases toward the blade tip. The radial flow B flowing radially outward along the blade side 4a blade surface of the moving blade 4 travels in the vicinity of the tip portion 6 along the inclination of the tip clearance vortex reduction plate 8 on the opposite side of the turbine rotation direction. The direction is changed, and it collides with the leakage flow C toward the tip clearance along the inner peripheral surface of the casing 2 and inhibits its entry.
[0027]
As described above, according to the moving blade 4 of the present embodiment, conventionally, both the radial flow B and the leakage flow C enter the tip clearance to generate a leakage vortex, which deteriorates the performance of the turbine. By using the radial flow B for the inhibition of the leakage flow C, both flows can be offset, and the leakage flow that forms the secondary flow through the tip clearance can be reduced to improve the performance of the rotating machine.
[0028]
In addition, although the Example mentioned above is a thing about the high pressure turbine made high load, this invention is not limited to this, If it is a moving blade of a rotary machine, it is applied also to a compressor, an air blower, etc. besides a gas turbine. Needless to say, the scope of application and the like can be variously changed without departing from the gist of the present invention.
[0029]
【The invention's effect】
As described above, according to the rotor blade of the rotating machine of the present invention, the leakage flow passing through the tip clearance is suppressed, and the energy loss due to the leakage vortex is reduced, thereby improving the performance of the gas turbine, the compressor, and the like. Can be achieved.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a moving blade of a high-pressure turbine according to the present embodiment.
FIG. 2 is a sectional view of a cooling blade (a) and a blade surface static pressure distribution diagram (b).
FIG. 3 is a schematic configuration diagram of a turbojet engine.
FIG. 4 is an enlarged view of a turbine portion of a turbofan engine.
FIG. 5 is a diagram showing the flow of mainstream gas in a moving blade of a turbine subjected to high load using vectors.
[Explanation of symbols]
2 Casing 4 Rotor blade 4a Ventral side (positive pressure side)
4b Back side (negative pressure side)
5 High pressure turbine stationary blade 6 Tip portion 7 Low pressure turbine stationary blade row 8 Tip clearance vortex reduction plate 9 Low pressure turbine blade row 11 Turbine disk 13 Hub 15 Route portion 17 Fine hole 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 (5)

Mainstream gas flowing from the ventral side (4a) to the back side (4b) through the tip clearance (Δ) formed between the inner peripheral surface of the casing (2) and the tip portion (6) of the rotor blade (4). In order to inhibit the leakage flow of the tip, a tip clearance vortex reduction plate (8) projecting in a bowl shape from the tip part to the ventral side is formed ,
The tip clearance vortex reduction plate extends from a first position to a second position;
The first position is a position downstream by a predetermined distance from the most upstream position in the moving blade, and the second position is a position upstream by a predetermined distance from the most downstream position in the moving blade,
The height at which the tip clearance vortex reduction plate (8) protrudes from the tip portion to the ventral side is relatively small in the vicinity of the first position and the second position, and the first position and the A rotating blade of a rotating machine, characterized in that it is relatively large near the center between the second position .   The blade of a rotary machine according to claim 1, wherein the tip clearance vortex reducing plate (8) is formed to form a chord on the curved blade surface (4a).   The rotor blade of a rotary machine according to claim 1 or 2, wherein the tip clearance vortex reduction plate (8) has a tapered shape that gradually increases the height of the tip clearance vortex. The first position is a position close to the most upstream position, and the second position is a position close to the most downstream position. Rotor blades for rotating machinery. The most upstream position is an upstream end of a ventral end portion in the tip portion, and the most downstream position is a downstream end of the ventral end portion in the tip portion. A rotating blade of a rotating machine according to the item.

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