JP6145372B2 - Steam turbine blade and steam turbine using the same - Google Patents

Description

  The present invention relates to a moving blade of a steam turbine.

  In general, a steam turbine has a plurality of stages including a stationary blade and a moving blade in the axial direction of the turbine rotor, and an exhaust chamber is installed downstream thereof. The working steam is accelerated by a stationary blade serving as a throttle channel to increase kinetic energy, and power is generated by converting the kinetic energy into rotational motion by the moving blade.

  In such a steam turbine, increasing the turbine blade length in the final stage of the low-pressure turbine increases the effective flow path area and decreases the kinetic energy of the steam, thus reducing the kinetic energy exhausted without being used for power generation. As a result, the turbine efficiency is improved. Therefore, the blade length has been extended recently. However, as the blade length increases, the blade peripheral speed increases and the blade inflow Mach number exceeds one. When the inflow speed of steam into the blade exceeds the speed of sound, a shock wave is generated on the upstream side of the blade tip, and the turbine efficiency may be reduced due to shock wave loss.

  Conventionally, as a technique for reducing shock wave loss, for example, a technique for suppressing an increase in inflow velocity into a moving blade by controlling a flow pattern of a flow flowing into the moving blade has been devised (see Patent Document 1). ).

JP 2007-127132 A

  However, in recent years, due to the longer blades, it has become unavoidable that the velocity of steam flow into the blade exceeds the speed of sound. In the turbine rotor blade in which the inflow speed to the rotor blade exceeds the sonic speed and becomes supersonic, the blade shape of the portion into which the steam flows in supersonic has a supersonic wing shape with a sharp blade leading edge. When steam flows in at supersonic speed, a shock wave is generated upstream of the blade.However, in a supersonic blade with a sharp blade leading edge, the shock wave upstream of the blade adheres to the blade leading edge and flows downstream of the blade. An oblique shock wave is formed.

  By the way, the working steam in the final stage of the low-pressure turbine of the steam turbine is wet steam. The liquid film discharged from the rear end of the stationary blade installed on the upstream side of the rotor blade is accelerated and subdivided by the steam flowing out from the stator blade, and collides with the tip of the rotor blade. The tip of the rotor blade is designed so as not to be destroyed or damaged by the collision of the droplet. For example, if the blade base material strength is insufficient with respect to erosion, a strong shield material having high erosion resistance is applied to the blade leading edge. However, it is difficult to completely prevent erosion due to droplet collision, and the rotor blade is designed so that the blade does not break even if erosion progresses to some extent.

  The leading edge of the supersonic airfoil that has eroded is deformed into a blunt shape. When the supersonic flow collides with the blunt-shaped blade front edge, a shock wave is formed at a position separated from the front edge of the supersonic airfoil. This separation shock wave is formed perpendicular to the working steam flow direction than the oblique shock wave. For this reason, the separation shock wave interferes with the boundary layer on the pressure surface side of the adjacent moving blade, the flow field becomes unstable, and the potential for separating the steam flow from the moving blade increases. When the pattern of the shock wave in contact with the blade surface changes unsteadily, the fluid force applied to the blade by the working steam also changes unsteadily. Depending on the vibration characteristics of the blade, there is a possibility of resonance, but if the blade tip is damaged, it is designed to be detuned. However, in preparation for unforeseen circumstances, it is desirable to reduce the blade vibration potential as much as possible.

  Therefore, an object of the present invention is to reduce the vibration generation potential of a moving blade caused by a shock wave upstream of the moving blade in a steam turbine moving blade cascade in which wet steam flows in at supersonic speed.

  In order to solve the above-mentioned problems, the steam turbine rotor blade of the present invention is provided in front of a rotor blade provided adjacent to the blade pressure surface side at the blade height position where the working steam flows in at supersonic speed and adjacent to the blade pressure surface side. It is characterized in that a vortex generator is provided on the blade leading edge side from the intersection of the perpendicular drawn from the edge tip to the blade pressure surface and the blade pressure surface.

  ADVANTAGE OF THE INVENTION According to this invention, the vibration generation potential of a moving blade resulting from the shock wave upstream of a moving blade can be reduced in the steam turbine moving blade cascade in which wet steam flows in at supersonic speed.

It is a perspective view of the moving blade applied to the low pressure turbine last stage of a steam turbine. It is explanatory drawing explaining the blade cross section of the front-end | tip part of the conventional low pressure turbine final stage moving blade. It is explanatory drawing explaining the front-end | tip blade cross section of the low pressure turbine last stage moving blade when a blade front-edge edge has eroded. It is the perspective view explaining the principal part of the turbine rotor blade front-end | tip part in 1st Example of this invention. It is an expansion perspective view of the vortex generator provided in the turbine rotor blade in the 1st example of the present invention. It is explanatory drawing explaining the installation position of the vortex generator in 1st Example of this invention. It is explanatory drawing explaining the flow of the steam in the cascade structure to which the turbine rotor blade in the 1st Example of this invention is applied. It is explanatory drawing explaining the application example of the 1st Example of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings as appropriate. In addition, the same code | symbol is attached | subjected to the equivalent component through each drawing.

  FIG. 1 is a perspective view showing a turbine rotor blade applied to the final stage of the low-pressure turbine of the steam turbine of this embodiment. In FIG. 1, a part of the moving blade row fixed in the circumferential direction of the rotor is extracted and illustrated.

  The main components of the moving blade 1 applied to the final stage of the low-pressure turbine are the wing portion 2 twisted from the blade root to the blade tip, the integral cover portion 3 provided at the blade tip portion, and the blade back side of the blade intermediate portion. A projecting tie boss 4 and a platform 5 for supporting the wing 2 are shown. The outer peripheral surface of the platform 5 forms a channel wall surface on the radially inner peripheral side of the steam channel. An implanted portion 7 that fits the rotor blade 1 to the rotor is formed at the lower portion of the platform (inner side in the turbine radial direction).

  A plurality of disk grooves 8 are formed in the rotor circumferential direction in the disk portion 6 of the rotor to fit the implanted portion 7 of the blade 1 and fix the blade 1 to the rotor. The disk groove 8 is a groove that is straightly cut from one end surface side of the disk portion 6 in the turbine axial direction toward the other end surface side, and is a turbine along the turbine axial direction or with respect to the turbine axial direction. Inclined in the circumferential direction.

  The implanted portion 7 of the moving blade 1 is inserted into the disk groove 8 to engage the moving blade 1 and the rotor. Centrifugal force acting on the rotor blade 1 when the rotor rotates is supported by the rotor. As the rotational speed of the rotor increases, centrifugal force acts on the blade portion 2 from the blade root toward the blade tip. Since the wing part 2 is twisted, untwisting occurs in the wing part 2 due to centrifugal force. The integral cover 3 and the tie boss 4 are connected to the integral cover and the tie boss of the adjacent moving blades, respectively, in order to twist back the blades by untwisting. In FIG. 1, for example, the moving blade 1b is connected to the moving blade 1a and the moving blade 1c adjacent to both sides in the turbine circumferential direction by an integral cover 3 and a tie boss 4, respectively.

  FIG. 2 is a blade cross-sectional view of a tip portion of a conventional turbine blade. The blade shape of the moving blade shown in FIG. 2 is a supersonic blade shape used when the moving blade inflow velocity of the working steam becomes supersonic, and has a blade leading edge having a sharp cross section. . As shown in FIG. 2, a shock wave 11 is generated upstream of a moving blade having a supersonic blade shape. In a supersonic blade having a sharp blade leading edge, the shock wave 11 upstream of the blade row adheres to the tip of the blade leading edge and forms an oblique shock wave toward the downstream side in the working steam flow direction.

  FIG. 3 is a diagram showing a case where the turbine rotor blade shown in FIG. 2 is eroded by droplets. In the final stage of the low pressure turbine where the working steam is wet steam, the droplets discharged from the stationary blades ride on the steam flow and collide with the moving blade leading edge. The tip portion of the supersonic airfoil that has been eroded by the collision of the droplet gradually deforms from a sharp shape to a blunt shape. When the supersonic flow collides with the blunt-shaped blade leading edge, a shock wave 11 is formed at a position separated from the tip of the airfoil. Since this separation shock wave is formed more perpendicular to the working steam flow direction than the oblique shock wave, it interferes with the boundary layer on the pressure surface 9 side of the adjacent moving blade as shown in a circle A surrounded by a broken line, As a result, the flow field becomes unstable and the potential for flow separation increases. Further, when the pattern of the shock wave 11 in contact with the blade surface changes unsteadyly, the fluid force applied to the blade by the working steam also changes unsteadyly, which becomes a factor for increasing the vibration generation potential of the blade.

  Next, this embodiment will be described. FIG. 4 shows a perspective view of the tip of the turbine rotor blade in the present embodiment shown in FIG. In this embodiment, the pressure surface 9 at the tip of the moving blade has a vortex generator 12 that generates a minute vertical vortex on the blade surface. The vortex generator 12 is provided at a plurality of locations at regular intervals in the blade height direction.

  FIG. 5 is an enlarged perspective view of the vortex generator 12. The vortex generator 12 has a shape that is narrowed toward the upstream side, and the width w of the bottom surface k and the height h, which is the distance between the front long side j and the blade pressure surface, decrease toward the blade leading edge. This is a wedge-shaped projection. As shown, the front long side j of the vortex generator is installed so as to be parallel to the flow. The flow in the vicinity of the blade surface is turned to the mainstream side by the vortex generator 12. The maximum angle turning to the mainstream side is the vortex generator wedge angle i. The vortex generator wedge angle i is designed by the vortex generator 12 at an angle at which the working steam Mach number after turning can be supersonic. Therefore, the wedge angle is on the order of several degrees to at most ten degrees, and the increase in loss due to the oblique shock wave generated in the turning portion is also slight. The working steam that has passed through the vortex generator side face l flows downstream from the vortex generator in the working steam flow direction. At this time, the downstream of the vortex generator rear surface m becomes a separated flow, and the working steam flowing out downstream of the vortex generator forms a vertical vortex. By this vertical vortex, the working steam on the blade boundary layer is mixed in the vertical direction of the blade surface, supplied with momentum, and activated. As a result, separation of the steam flow downstream of the vortex generator 12 in the working steam flow direction can be suppressed.

  Note that a fillet, that is, a smooth curved surface, may be formed at a joint portion where the vortex generator side surface l, the vortex generator back surface m, and the blade pressure surface intersect each other. In the case where a fillet is provided, the height h decreases toward the leading edge of the blade in a range excluding the fillet region.

  Next, the installation position of the vortex generator 12 will be described with reference to FIG. Basically, it is installed on the pressure surface 9 side at the blade height position where supersonic inflow occurs. The position on the pressure surface is a perpendicular line n down to the pressure surface 9 so as to intersect the pressure surface 9 perpendicularly from the tip of the leading edge of the blade adjacent to the pressure surface (the blade 1c in the case of FIG. 6). If the vortex generator 12 is installed upstream of the intersection point p between the pressure surface 9 and the pressure surface 9, the boundary layer activation causes the blade force to be unsteady due to interference between the separation shock wave and the boundary layer on the adjacent pressure surface. The potential that changes to can be reduced.

  More preferably, a straight line portion q in which the pressure surface is formed in a straight line is formed on the upstream side of the pressure surface from the intersection p of the perpendicular line n and the pressure surface 9 dropped from the adjacent blade tip on the pressure surface side to the pressure surface 9. The leading edge side end of the pressure surface straight line portion q from a point separated from the intersection p by the length of the perpendicular n, that is, a distance equivalent to the shortest distance between the blade leading edge tip of the adjacent moving blade and the pressure surface. In the meantime, the vortex generator 12 is provided. It is preferable to provide the vortex generator 12 at this position. When the space between the shock wave and the boundary layer interferes with the vortex generator and the vortex generator is curved in a convex shape, the working steam is accelerated. This is because the formed vertical vortex is rectified and the effect of boundary layer activation is weakened. Further, when the shock wave and the boundary layer interfere with each other and separation occurs on the blade surface, the separation region spreads upstream. At this time, if the vortex generator 12 is included in the separation region, the effect of the boundary layer activation may be weakened.

  Next, the function and effect of this embodiment will be described with reference to FIG.

  FIG. 7A is a view showing a blade cross section of a turbine blade having a sharp blade leading edge before erosion in the first embodiment. In this embodiment, the moving blade inflow Mach number of steam exceeds 1.0, is supersonic, and a shock wave 11a is generated in front of the moving blade. Since the airfoil shown in the figure has a supersonic blade shape with a sharp leading edge, the shock wave 11a in front of the blade adheres to the leading edge without detaching from the leading edge of the blade, and starts downstream from the leading edge. An oblique shock wave is formed on the side. Further, an oblique shock wave 11b is also generated from the turning portion of the vortex generator 12 having a wedge shape.

  FIG. 7B is a diagram showing the blade cross section when the leading edge of the blade is blunted due to erosion or the like in the first embodiment. Since the blade leading edge has a blunt shape, the shock wave 11a in front of the blade leaves the blade leading edge. This separation shock wave collides with the pressure surface side of the adjacent wing substantially perpendicularly. In this embodiment, the vortex generator 12 is provided on the upstream side of the intersection of the separation shock wave and the pressure surface, so that the longitudinal vortex 13 is generated from the vortex generator 12. Since the boundary layer on the pressure surface 9 is activated by the longitudinal vortex of the longitudinal vortex 13, the site where the shock wave and the pressure surface boundary layer interfere with each other is stabilized. Therefore, unsteady separation due to interference between the separation shock wave 11a and the pressure surface boundary layer is suppressed, the potential of the blade force fluctuating unsteadyly is reduced, and the force acting on the blade is kept constant. Therefore, the vibration generation potential of the moving blade can be reduced.

  In addition, since the front long side angle of the vortex generator is formed so that the flow along the front long side of the vortex generator 12 also becomes a supersonic flow, the wedge angle of the vortex generator is on the order of a maximum of tens of degrees. There is also a small loss due to the oblique shock wave 11b.

In the arrangement of the vortex generator 12 shown in FIG. 4, the vortex generator wedge angle i formed by the front long side j of the vortex generator 12 and the blade pressure surface is smaller as the vortex generator is arranged on the inner peripheral side. You may form as follows.
The vortex generator 12 is intended to suppress unsteady fluctuations in blade force due to the interference between the shock wave and the boundary layer. The larger the vortex generator wedge angle i and the vortex generator wedge height h, the more Great effect. However, if the vortex generator wedge angle i and the vortex generator wedge height h are increased, loss increases due to entropy increase due to shock waves generated by the vortex generator 12 itself and mixing of the boundary layer. I can't make it bigger. Depending on the blade inflow Mach number, the vortex generator wedge angle i should be optimized to balance unsteady fluctuations in blade force and increased loss.

  The inflow Mach number to the moving blade tends to increase as the outer peripheral side having a higher peripheral speed. On the inner circumference side where the inflow Mach number is small, the separation shock wave is formed perpendicular to the adjacent pressure surface, but the pressure ratio before and after the shock wave is small, so the interference between the shock wave and the boundary layer is slight. Therefore, for suppressing unsteady fluctuations in blade force, the inner vortex generator can obtain the same effect as the outer vortex generator even if the vortex generator wedge angle i is reduced. Rather, as much as the loss is reduced, it can contribute to improving the characteristics of the blade.

  Further, as shown in FIG. 8, the vortex generators 12 may be arranged in a zigzag pattern in three rows in the height direction. In contrast to FIG. 4 in which the vortex generators 12 are arranged in a row in the radial direction, the boundary layer is activated, so that the effect of suppressing unsteady fluctuations in blade force due to interference between the shock wave and the boundary layer is enhanced.

  In the example of FIG. 8 as well, the vortex generator wedge angle i formed by the front long side j of the vortex generator 12 and the blade pressure surface may be formed to be smaller as the vortex generator arranged on the inner peripheral side. good.

  In the present embodiment, the vortex generator 12 is described as a wedge-shaped protrusion, but the shape of the protrusion is not necessarily limited to the wedge shape.

  As described above, in the above-described embodiments, the case where the present invention is applied to the final stage of the low-pressure turbine has been described. If the rotor blade peripheral speed Mach number divided by the rotational peripheral speed of the section exceeds 1.0, it is roughly applicable.

DESCRIPTION OF SYMBOLS 1 Rotating blade 2 Blade | wing part 3 Integral cover part 4 Thai boss 5 Platform 6 Disc part 7 Implanted part 8 Disc groove 9 Pressure surface 10 Negative pressure surface 11 Shock wave 12 Vortex generator

Claims (8)

A steam turbine rotor blade whose steam blade inflow Mach number exceeds 1.0 in a partial range in the blade height direction,
A normal line descending from the tip of the leading edge of the blade provided adjacent to the blade pressure surface side at the blade height position where the blade inflow Mach number exceeds 1.0 and the blade pressure surface side. A steam turbine rotor blade comprising a vortex generator on a blade leading edge side with respect to an intersection of the blade pressure surfaces. The steam turbine blade according to claim 1,
The blade pressure surface has a straight portion formed linearly toward the blade leading edge on the leading edge side of the intersection,
The steam turbine rotor blade according to claim 1, wherein the vortex generator is provided in the straight portion. The steam turbine rotor blade according to claim 2,
The steam turbine rotor blade according to claim 1, wherein the vortex generator is provided in the straight portion on the leading edge side from the intersection point along the blade pressure surface with a distance equal to the perpendicular length. In the steam turbine rotor blade according to any one of claims 1 to 3,
The vortex generator is a wedge-shaped protrusion whose width and height decrease toward the blade leading edge side,
A plurality of blade heights are provided.
The vortex generator wedge angle formed by the front long side of the vortex generator having a wedge shape and the blade pressure surface is formed to be smaller as the vortex generator provided on the base side in the blade height direction. A characteristic steam turbine blade. In the steam turbine rotor blade according to any one of claims 1 to 4,
A plurality of the vortex generators are provided in the blade height direction and are arranged in two or more rows and in a staggered manner. In the steam turbine rotor blade according to any one of claims 1 to 5,
The steam turbine blade according to claim 1, wherein the steam is wet steam. The steam turbine rotor blade according to any one of claims 1 to 6,
The steam turbine rotor blade is a rotor blade applied to a final stage of a low-pressure turbine.   A steam turbine comprising the steam turbine blade according to any one of claims 1 to 6.