JP2012149614A - Axial flow turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an axial flow turbine that improves turbine efficiency by eliminating or reducing a shock wave loss and a loss due to peeling, etc. and enhances reliability of a moving wing by reducing the amount of erosion generated on the moving wing when increasing an annulus area of an axial flow turbine by enlarging the wing length or an average diameter.SOLUTION: The axial flow turbine is provided with a turbine station which comprises a static wing 7 fixed to an outer circumferential side static wing support 5 and a dynamic wing 8 fixed to a turbine rotor 2 on the actuation fluid flow direction downstream side. A hollow part 11 to which the working fluid having a higher temperature and a higher pressure than those of the working fluid flowing around the static wing 7 is introduced, and an injection port 12 which is communicated with the hollow part 11 and injects the working fluid introduced to the hollow part 11 to an working fluid main flow path 4 are formed on the outer circumferential side static wing support 5 of the turbine station having the static wing in which the radial direction height of a static wing outlet part is larger than the radial direction height of the static wing inlet part.

Description

  The present invention relates to an axial flow turbine such as a steam turbine.

  An axial turbine, such as a steam turbine, is fixed to a rotor that is rotatably supported by a bearing device, a casing that includes the rotor and has a working fluid main flow path in which a working fluid main flow flows, and a casing or a casing. A stationary blade fixed to the outer peripheral diaphragm and a moving blade fixed to the rotor. The axial turbine has a function of changing the kinetic energy generated when the working fluid expands from the high-pressure portion to the low-pressure portion in the casing into the rotational force of the rotor by the paragraph composed of the stationary blades and the moving blades.

  In such an axial turbine, there is a demand to increase the flow rate, which is the mass of the fluid flowing through the paragraph per unit time, in order to increase the output per stage. If the output per stage can be increased, for example, in the case of a multi-stage axial flow turbine such as a steam turbine for power generation, it is possible to increase the amount of power generation without changing the number of stages.

  In order to increase the flow rate of the working fluid flowing through the paragraph per unit time, it is effective to increase the ring zone area, which is the area seen from the rotation axis direction of the flow path through which the working fluid flows. In the case of an axial turbine, the annulus area is the product of the blade length and the average diameter obtained by adding the outer and inner diameters of the blades and dividing by two times the circle ratio. Therefore, in order to increase the ring zone area, the blade length and the average diameter are increased.

  However, in an axial flow turbine such as a steam turbine, when the ring zone area is increased, that is, the blade length and the average diameter are increased, the amount of erosion due to water droplets on the moving blade tip side increases. The amount of erosion increases in proportion to the third power of the blade tip peripheral speed. Therefore, when the blade length and the average diameter are increased, the peripheral speed of the rotor blade tip increases, and the amount of erosion increases accordingly. In general, droplets that cause erosion are re-released into the working fluid that flows through the working fluid main flow path from the side walls that make up the working fluid main flow path wall upstream of the rotor blades and the water film formed on the stationary blade surface. Is generated.

  As a conventional technique related to erosion countermeasures, as shown in Patent Document 1, a stationary blade is made hollow, an upstream high-temperature and high-pressure steam is introduced therein to evaporate a water film on the surface of the stationary blade, and then a high-temperature and high-pressure Some blow off steam from the trailing edge of the stationary blade into the flow path.

JP-A-50-112604

  The prior art described in Patent Document 1 aims to prevent erosion of the downstream rotor blade by re-evaporating a water film formed on the surface of the stationary blade.

  However, many water films exist not only on the blade surface but also on the outer peripheral side wall of the stationary blade, and it is considered that the influence of the water film on the outer peripheral side wall causes erosion at the tip of the moving blade. Therefore, when increasing the annulus area, that is, increasing the blade length and average diameter, measures must be taken especially for the water film on the outer peripheral side wall of the stationary blade to prevent an increase in the amount of erosion caused by water droplets on the blade tip side. However, Patent Document 1 does not consider this point.

  By the way, generally, the specific enthalpy H0 which is the sum of the enthalpy per unit mass (specific enthalpy) and the kinetic energy per unit mass divided by the square of the flow velocity divided by 2 at the entrance of the paragraph is close to the rotation axis. The value is almost constant from the inner circumference side to the outer circumference side. On the other hand, the specific enthalpy h1 between the stationary blade and the moving blade becomes larger toward the outer peripheral side than the inner peripheral side so as to balance with the swirling flow between the stationary blades. Therefore, the specific enthalpy difference H0-h1 becomes smaller toward the outer peripheral side. The velocity of the flow exiting the stationary blade is proportional to the square root of this specific enthalpy difference H0-h1. That is, the stationary blade outflow speed becomes smaller toward the outer peripheral side. As described in the background art, when the annulus area is increased, that is, when the blade length and the average diameter are increased, the specific enthalpy difference H0-h1 on the outer peripheral side becomes smaller and the stationary blade outflow velocity also becomes smaller. . Thus, by increasing the ring zone area, the specific enthalpy difference H0-h1 on the outer peripheral side and the stationary blade outflow speed are reduced. On the other hand, the rotor blade peripheral speed increases in proportion to the radius. These things can cause two more problems as described below.

  The first is that the relative inflow Mach number of the moving blades becomes supersonic and the possibility of increased loss increases. Increasing the blade length and average diameter increases the peripheral speed, which is the rotational speed of the moving blade. The peripheral speed of the moving blade becomes the largest at the outer peripheral end having the largest radial position, that is, at the tip of the moving blade. When the peripheral speed Mach number obtained by dividing the peripheral speed of the tip by the sonic speed exceeds 1 and becomes supersonic, if the rotational direction component of the flow from the stationary blade is not sufficient, the relative velocity of the flow flowing into the moving blade will be Supersonic speed. As the radial position increases, the peripheral speed increases, and the stationary blade outflow speed decreases as the radial position increases. Therefore, the larger the radial position, the greater the possibility that the relative inflow speed with respect to the moving blade becomes supersonic. When the relative inflow velocity becomes supersonic, a shock wave accompanied by a discontinuous pressure rise occurs on the upstream side of the rotor blade. In addition to the entropy increase due to the shock wave itself, the shock wave interferes with the boundary layer of the blade surface, the boundary layer thickness increases due to the discontinuous pressure increase, and further entropy increase occurs due to peeling. Due to the entropy increase due to the shock wave, the rotational force corresponding to the increased flow rate, that is, the output may not increase even though the annular zone area of the turbine stage is increased and the flow rate of the working fluid is increased. Therefore, it is important to eliminate or weaken the shock wave generated at the moving blade inflow part in order to realize an increase in output per paragraph by increasing the ring area beyond the limit peripheral speed, and for that reason Therefore, it is necessary to reduce the relative inflow speed of the rotor blade.

  The second is that the possibility of delamination increases in the enlarged flow path portion on the outer peripheral side. When the annular zone area of the paragraph is increased, the expansion rate of the meridian plane passage, that is, the increase rate of the passage outlet channel height with respect to the paragraph inlet passage height increases. On the other hand, even if the annular zone area of the paragraph is increased, the axial length of the paragraph cannot generally be increased because the overall length of the turbine is limited. In general, this is realized by increasing the divergence angle of the meridional flow path shape at the outer peripheral end or inner peripheral end of the wing portion. Even if the divergence angle of the meridional flow channel shape is large, if the specific enthalpy difference H0-h1 of the stationary blade part is large, the flow is accelerated between the blades and no problem such as separation occurs. To increase the blade length and average diameter, the specific enthalpy difference H0-h1 of the outer stationary vane portion is reduced, and the acceleration of the flow is reduced at the enlarged flow passage portion at the outer peripheral end of the meridional flow passage. Therefore, the flow is separated from the blade surface and the side wall surface, and the possibility that the loss increases is increased.

  Therefore, the object of the present invention is to increase the blade length and average diameter even when the annular zone area of the axial flow turbine is increased. Eliminates or reduces the shock wave loss that occurs at the moving blade inflow part due to the increase in the diameter, and eliminates the loss due to separation that tends to occur because the specific enthalpy difference is small at the enlarged flow path part on the outer periphery of the stationary blade, or By reducing the size, the efficiency of the turbine is improved, and the reliability is improved by reducing the amount of erosion.

  In order to achieve the above object, the present invention provides a turbine stage having a stationary blade fixed to the outer peripheral side stationary blade support and a moving blade fixed to the rotor on the downstream side in the working fluid flow direction of the stationary blade. A turbine stage having a stationary blade having a stationary blade outlet portion whose radial height is greater than a radial height of the stationary blade inlet portion; A working fluid having a temperature higher than that of the working fluid flowing around the stationary blade is introduced to the outer peripheral side of the stationary blade, and the introduced working fluid is ejected from the outer peripheral side wall of the stationary blade toward the downstream side of the working fluid main flow path. It is characterized by providing.

  According to the present invention, even when the annular zone area of the axial flow turbine is increased by increasing the blade length and the average diameter, the moving blade peripheral speed is reduced even though the stationary blade outflow speed is reduced on the outer peripheral side. Eliminating or reducing the shock wave loss that occurs at the moving blade inflow part by increasing it, and eliminating or reducing the loss due to separation that tends to occur because the specific enthalpy difference is small at the enlarged flow path part on the outer periphery of the stationary blade By doing so, reliability can be improved by improving the efficiency of the turbine and reducing the amount of erosion.

It is meridional sectional drawing showing the principal part structure of the turbine stage part of the axial flow turbine which concerns on the 1st Embodiment of this invention. It is a meridian plane sectional view showing the basic structure of the turbine paragraph part of a general steam turbine. It is the figure which showed the relationship between a stationary blade and a jet nozzle opening part on the stationary blade outer peripheral side wall surface of the axial flow turbine which concerns on the 1st Embodiment of this invention. It is the figure which showed the relationship different from FIG. 3 of the stationary blade and jet nozzle opening part on the stationary blade outer peripheral side wall surface of the axial flow turbine which concerns on the 1st Embodiment of this invention. FIG. 5 is a diagram of a stationary blade blade surface pressure distribution for determining the opening position shown in FIG. 4. It is the figure which showed the relationship different from FIG. 3 and FIG. 4 of a stationary blade and a jet nozzle opening part on the stationary blade outer peripheral side wall surface of the axial flow turbine which concerns on the 1st Embodiment of this invention. It is meridional sectional drawing explaining the shape of the jet nozzle opening part of the axial flow turbine which concerns on the 1st Embodiment of this invention. It is meridional sectional drawing explaining another shape of the jet nozzle opening part of the axial flow turbine which concerns on the 1st Embodiment of this invention. It is meridional sectional drawing explaining another shape of the jet-outlet opening part of the axial flow turbine which concerns on the 1st Embodiment of this invention. On the stationary blade outer peripheral side wall surface of the axial flow turbine according to the first embodiment of the present invention, the relationship between the stationary blade and the jet opening is shown in FIG. 3, FIG. 4 and FIG. It is the figure seen on the outer peripheral side wall. It is the figure which looked at the shape of the jet nozzle shown in FIG. 10 in the meridian plane. It is the figure which looked at the shape of the jet nozzle shown in FIG. 10 from the outer peripheral side. It is a blade height direction distribution of a moving blade relative inflow Mach number of a turbine stage part of a general axial flow turbine. It is a figure which represents typically the relationship between the flow which came out of the stationary blade, the moving blade peripheral speed, and the relative inflow speed of a moving blade when the peripheral speed of a moving blade is large. It is a figure which represents typically the effect which reduces the increase in the relative inflow speed of a moving blade when the peripheral speed of a moving blade is large by this invention. It is meridional plane sectional drawing showing the principal part structure of the axial flow turbine which concerns on the 2nd Embodiment of this invention.

  An embodiment of the present invention will be described below by taking the final stage of a steam turbine as an example. However, the effect of the present invention is not limited to the final paragraph as long as the exhaust chamber is replaced with the downstream inlet. Moreover, the effect of reducing the relative inflow speed of the moving blade and reducing the shock wave loss is effective regardless of the working fluid such as steam and air.

  First, the basic structure of a turbine stage section of a general steam turbine will be described with reference to FIG. FIG. 2 is a meridional cross-sectional view showing a basic structure of a turbine stage portion of a general steam turbine.

  The steam turbine 1 includes a turbine rotor 2 rotatably supported by a bearing device (not shown), a turbine casing 3 that includes the turbine rotor 2 and that has a working fluid main flow path 4 in which steam as a working fluid flows, The outer peripheral side diaphragm 5 which comprises the outer peripheral side wall surface of the working fluid main channel 4 formed in cyclic | annular form, and the inner peripheral side diaphragm 6 which comprises the inner peripheral side wall surface of the working fluid main channel 4 are provided. A hollow portion 23 is a space formed when the outer peripheral diaphragm and the stationary blade are assembled.

  An arrow 10 shown in FIG. 2 represents the flow direction of the steam flowing through the working fluid main channel 4. As shown in FIG. 2, the turbine stage of the steam turbine includes a high-pressure portion P0 on the upstream side (hereinafter simply referred to as upstream) in the working fluid flow direction inside the turbine casing 3 and a downstream side in the working fluid flow direction (hereinafter simply downstream). And the low-pressure part P1).

  The turbine stage includes a stationary blade 7 fixed between an outer peripheral diaphragm 5 and an inner peripheral diaphragm 6 fixed on the inner peripheral side of the turbine casing 3, and a turbine rotor 2 that rotates around the turbine central axis 20. And a moving blade 8 provided on the surface. In the case of a steam turbine in which the turbine stage is composed of a plurality of stages, this stage structure is provided by being repeated a plurality of times in the working fluid flow direction. In each paragraph, the moving blade faces the downstream side of the stationary blade.

  The steam turbine accelerates the steam flow induced by the differential pressure between the high pressure part P0 and the low pressure part P1 in the turbine casing 3 with the stationary blade 7 and converts it into rotational motion with the moving blade 8. A generator (not shown) is connected to the turbine rotor 2, and the rotational motion of the turbine rotor 2 is converted into electric power.

  Here, in the steam turbine, the outer peripheral diaphragm 5 may or may not be provided on the inner peripheral side of the turbine casing 3. When the outer peripheral diaphragm 5 is provided, the stationary blade 7 is supported by the outer peripheral diaphragm 5, and when the outer peripheral diaphragm 5 is not provided, the stationary blade 7 is supported by the inner peripheral side wall portion of the turbine casing 3. The Accordingly, a stationary body that supports the stationary blade 7 from the outer circumferential side is defined as an “outer circumferential stationary blade support”, and when the outer circumferential diaphragm 5 is provided, the outer circumferential diaphragm 5 is the “outer circumferential stationary blade support”. When the outer peripheral diaphragm 5 is not provided, the inner peripheral side wall portion of the turbine casing 3 corresponds to the “outer peripheral stationary blade support”.

  The inner peripheral side wall surface of the outer peripheral side stationary blade support body constitutes the outer peripheral side flow channel wall surface of the working fluid main flow channel 4. Therefore, the portion of the inner peripheral side wall surface of the outer peripheral side stationary blade support to which the stationary blade 7 is connected is defined as “the stationary blade outer peripheral side wall surface 9”. When the outer peripheral diaphragm 5 is provided, the portion of the inner peripheral side wall surface of the outer peripheral diaphragm 5 to which the stationary blade 7 is connected corresponds to the “static blade outer peripheral side wall surface 9”, and the outer peripheral diaphragm 5 is provided. If not, the portion of the inner peripheral side wall portion of the turbine casing 3 to which the stationary blade 7 is connected corresponds to the “static blade outer peripheral side wall surface 9”.

  As shown in FIG. 2, the paragraph inlet portion of the turbine stage has a smaller specific volume of the working fluid than the paragraph outlet portion, so the paragraph inlet channel height is smaller than the paragraph outlet channel height. That is, the outer peripheral portion of the stationary blade 7 has the same paragraph from the moving blade outlet portion of the previous paragraph in the outer diameter line that is the intersection line between the surface including the turbine central axis 20 (the meridian surface) and the outer peripheral portion of the stationary blade 7. It is inclined radially outward from the moving blade inlet portion to be configured, and the radius of the working fluid main flow path 4 increases linearly (or monotonically) in the portion of the stationary blade 7. In other words, the radial height of the outlet portion of the stationary blade is higher than the radial height of the inlet portion of the stationary blade (stage inlet channel height).

  Based on the above, embodiments of the present invention will be described below.

  FIG. 1 is a meridional cross-sectional view showing a main structure of a turbine stage part of a steam turbine according to an embodiment of the present invention. In this figure, parts corresponding to the same parts as in the previous figures are given the same reference numerals and description thereof is omitted.

  As shown in FIG. 1, in the present embodiment, the outer diaphragm 5 of the stationary blade 7 has a structure having a hollow part 11 connected in the circumferential direction, and the structure in which the hollow part 11 and the working fluid main channel 4 are communicated with each other. Have

  The hollow portion 11 is formed inside the outer peripheral diaphragm 5 that is the outer peripheral stationary blade support, and a high-temperature and high-pressure working fluid (steam) is introduced through a bleed portion 14 and a working fluid introduction passage 13 described later. Space. The hollow portion 11 is provided on the outer peripheral side of the stationary blade outer peripheral side wall surface 9 of the outer peripheral diaphragm 5, and is an annular space extending in the circumferential direction along the stationary blade outer peripheral side wall surface 9. It is. The hollow portion 11 is connected to a jet port 12 that passes through the outer peripheral diaphragm 5 and opens to the stationary blade outer peripheral side wall surface 9, and communicates with the working fluid main flow path 4 through the jet port 12. . Therefore, the high-temperature and high-pressure working fluid introduced into the hollow portion 11 through the extraction portion 14 and the working fluid introduction flow path 13 is ejected from the ejection port 12 toward the working fluid main flow path 4. The hollow portion 11 may be formed using a space formed when the stationary blade 7 is assembled to the outer peripheral diaphragm 5.

  In addition, a working fluid introduction flow path 13 is connected to the outer peripheral diaphragm 5 as a flow path for introducing high temperature and high pressure working fluid (steam) into the hollow portion 11. The working fluid introduction flow path 13 is connected to, for example, the bleed portion 14 of the upstream turbine stage, or the bleed portion 15 of the further upstream turbine stage, and the upstream high-temperature and high-pressure working fluid bleed at the bleed portion. Is introduced into the hollow portion 11. The steam introduced into the hollow part 11 from the extraction part 14 or 15 has higher temperature and pressure than the steam around the stationary blade 7 supported by the outer peripheral diaphragm 5 having the hollow part 11. Therefore, the steam introduced into the hollow portion 11 heats the outer peripheral side diaphragm 5 to be higher than the temperature of the main working fluid around the stationary blade 7 supported by the outer peripheral side diaphragm 5 having the hollow portion 11. Therefore, the water film flowing down the stationary blade outer peripheral side wall surface 9 at the same temperature as the working fluid mainstream temperature is heated by the stationary blade outer peripheral side wall surface 9 of the outer peripheral diaphragm 5 having the hollow portion 11, and a part thereof It evaporates, and the rest becomes a state where it tends to evaporate when it becomes hotter than the surrounding steam.

  In general, the water film flowing down the outer peripheral side wall surface 9 of the stationary blade is re-released into the main flow, for example, by being rolled up by a secondary flow vortex on the side wall surface, and collides with the tip of the moving blade to move. Causes wing erosion. Further, the amount of erosion increases in proportion to approximately the third power of the moving blade tip circumferential speed. Accordingly, when the blade length and the average diameter are increased, the moving blade tip peripheral speed is also increased, and the amount of erosion is accordingly increased. However, according to the present embodiment, since the amount of water film on the outer peripheral side wall surface 9 of the stationary blade is reduced, the amount of water droplets that collide with the moving blade, particularly the tip of the moving blade, is reduced, and the amount of erosion is reduced. Can do. Therefore, this embodiment is particularly suitable when the annular zone area of the axial flow turbine is increased by increasing the blade length and the average diameter.

  The working fluid introduced into the hollow portion 11 is discharged into the working fluid main flow through the ejection port 12. According to the present embodiment, the working fluid introduced into the hollow portion 11 is discharged from the stationary blade outer peripheral side wall surface 9, so that the working fluid flows into the main flow compared to discharging from the trailing edge of the stationary blade. The influence of can be reduced. Therefore, the loss due to the turbulence of the main flow of the working fluid can be reduced, and the decrease in turbine efficiency can be suppressed.

  The working fluid introduced into the hollow part 11 is not between the turbine stage itself having the hollow part 11 and the turbine stage immediately downstream thereof, but is provided on the upstream side of the turbine stage having the hollow part 11. It is necessary to bleed from the bleed parts 14 and 15 in between. This is because the temperature of the working fluid flowing between the turbine stage itself and the turbine stage immediately downstream thereof is substantially the same as the temperature of the main working fluid around the stationary blade 7 supported by the outer peripheral diaphragm 5 having the hollow portion 11. Therefore, even if this working fluid is introduced into the hollow portion 11, the temperature of the outer peripheral diaphragm 5 is higher than the temperature of the main working fluid around the stationary blade 7 supported by the outer peripheral diaphragm 5 having the hollow portion 11. Because it is difficult to do. In addition, since the pressure is substantially the same, it is difficult to discharge the working fluid from the ejection port from the hollow portion 11 toward the working fluid main flow path.

  The working fluid introduction channel 13 may be configured by forming a part of the channel in the turbine casing 3 and separately providing a piping member for the other part of the channel.

  Further, in the steam turbine not provided with the outer peripheral side diaphragm 5, the hollow portion 11, the jet port 12, and the working fluid introduction flow path 13 may be provided directly in the turbine casing 3.

  Further, the working fluid introduced into the hollow portion 11 may be introduced from the outside rather than in the working fluid main stream as long as it is at a higher temperature and pressure than the working fluid flowing down the turbine stage having the hollow portion 11.

  Next, in order to explain further effects of the present embodiment, the problem of supersonic inflow of the working fluid into the moving blade will be described here.

  FIG. 14 is a schematic diagram of a general speed triangle between the stationary and moving blades when the peripheral speed of the moving blade increases because the radial position of the outer peripheral end increases as the blade length and average radius increase. is there. The high-pressure P0 steam 30 is accelerated and turned by the stationary blade 7 to become a flow of velocity V. When this flow V is viewed in a relative coordinate system that rotates together with the moving blade 8, the moving blade 8 rotates in the direction 31 and the circumferential speed U. Therefore, as shown in FIG. The moving blade relative inflow velocity is a flow of velocity W. A triangle composed of the vector V, the vector U, and the vector W is called a velocity triangle. As is apparent from the velocity triangle, the relative flow velocity W flowing into the moving blade increases as the moving blade peripheral speed U increases. In order to reduce the moving blade relative inflow velocity W, it is necessary to increase the stationary blade outflow velocity V. In order to increase the stationary blade outflow velocity V when the state quantity of steam at the paragraph inlet is fixed, the specific enthalpy h1 between the stationary and moving blades is decreased and the specific enthalpy difference Δh between the stationary blades is increased. Although it is necessary, the specific enthalpy h1 between the stationary blades and the moving blades increases with the swirl velocity field at the stationary blade outlet toward the outer periphery, and the longer the blade length, the stronger the influence of the swirl velocity field and the smaller h1. Becomes difficult. That is, it becomes difficult to increase V.

  Since the radial position of the outer peripheral edge of the moving blade is increased by increasing the blade length and the average radius, the peripheral speed of the moving blade is increased, and the speed of the inlet outer periphery of the moving blade 8 is increased by the sound speed of the working fluid flowing into the moving blade 8. When the outer peripheral edge peripheral speed Mach number obtained by dividing the rotational peripheral speed exceeds 1.0, the relative speed of the working fluid flowing into the moving blade 8 with respect to the moving blade 8 may become supersonic. When the outer peripheral edge peripheral speed Mach number of the moving blade exceeds 1.7, the relative velocity of the working fluid with respect to the moving blade 8 is completely supersonic. When the relative velocity of the working fluid with respect to the moving blades becomes supersonic, shock waves are generated at the leading and trailing edges of the moving blades, resulting in shock wave loss. Therefore, the turbine efficiency is reduced.

  FIG. 13 shows the blade height direction distribution of the blade relative inflow Mach number Mr1 when the blade peripheral speed increases because the radial position of the outer peripheral end increases as the blade length and average radius increase. . As described with reference to FIG. 14, it can be seen that on the outer peripheral side, the Mach number exceeds 1.0 and supersonic inflow occurs.

  Here, in order to increase the specific enthalpy difference Δh of the stationary vane on the outer peripheral side, if the enthalpy difference H0-h2 itself in the paragraph is increased, the relative inflow Mach number of the inner peripheral blade exceeds 1.0 and the supersonic inflow occurs. Therefore, it is difficult to solve the supersonic inflow problem by increasing the enthalpy difference of the entire paragraph.

  Returning to the description of the present embodiment. FIG. 3 shows the relationship between the stationary blade 7 and the opening 16 of the jet outlet 12 for discharging the high-temperature and high-pressure working fluid on the stationary blade outer peripheral side wall surface 9. The opening 16 of the jet port 12 is provided in the vicinity of a portion called a throat having the narrowest flow path between the stationary blades. The shape of the opening 16 is a slit along the throat. Further, as shown in FIG. 1, the outer peripheral portion of the stationary blade 7 has an outer diameter line that is an intersection line between the surface including the turbine central axis 20 (the meridian surface) and the outer peripheral portion of the stationary blade 7. Inclined radially outward from the blade outlet portion to the moving blade inlet portion constituting the same paragraph, and the radius of the working fluid main flow path 4 increases linearly (or monotonously) in the portion of the stationary blade 7. In other words, the radial height of the outlet portion of the stationary blade is higher than the radial height of the inlet portion of the stationary blade (stage inlet channel height). Therefore, the slit-shaped opening 16 itself is opened toward the turbine central axis. The turbine shaft direction is not necessarily required, and the turbine shaft may be opened slightly toward the outer periphery. By opening the opening 16 toward the turbine central axis direction or slightly toward the outer peripheral side, the working fluid in the hollow portion 11 is ejected toward the downstream side in the flow direction of the working fluid main flow, and the working fluid is ejected from the opening. Can be made to flow along the outer peripheral side wall surface, and the influence on the flow of the working fluid can be reduced.

  The reason why the opening 16 of the jet nozzle 12 is provided in the vicinity of the narrowest part called the throat of the flow path between the stationary blades will be described. In the inter-blade flow path of the stationary blade, the pressure is reduced from the stationary blade inlet portion to the throat portion because the flow passage area is reduced, and the pressure is almost constant at the throat. On the other hand, the pressure increases rather than the meridian spread. Therefore, when the radius of the working fluid main flow path 4 is increased and the angle of expansion of the outer peripheral side wall surface to the outer peripheral side is large, the pressure rise is increased, the side wall boundary layer of the outer peripheral side wall surface is rolled up, and the strong secondary A flow vortex is generated. If the spread angle of the outer peripheral side wall surface to the outer peripheral side is further increased due to the increase in the length of the blade, the separation may occur. In the present embodiment, since the opening 16 is provided in the throat portion, the kinetic energy is given to the flow near the side wall by the blowing of the working fluid from the throat portion, and the flow is accelerated. Peeling can be suppressed. Further, when the high-temperature working fluid is ejected and mixed with the water film on the side wall, the water film evaporates, and the water film that cannot be completely evaporated is refined by vigorous mixing with the jet from the opening 16. And released into the mainstream. The refined droplets flow at almost the same speed as the main working fluid flow, and most of them flow between the blades without colliding with the blades, so that the amount of erosion can be reduced. Therefore, according to the present embodiment, by providing the opening 16 of the spout 12 in the vicinity of the portion called the throat where the flow path between the stationary blades is the narrowest, the outer peripheral side of the outer peripheral side wall surface due to the longer blades. Even when the divergence angle increases, the increase in the boundary layer thickness and the separation can be suppressed, and the turbine efficiency can be improved.

Next, FIG. 15 schematically shows the effect of reducing the increase in the relative inflow speed of the moving blade according to the present embodiment. According to the present embodiment, the opening 16 of the jet nozzle 12 is provided in the vicinity of a portion called the throat where the flow path between the stationary blades is the narrowest, and the shape of the opening 16 is directed to the turbine axial direction or the outer peripheral side. By opening the slit along the throat, the flow velocity of the outer stationary vane outflow speed can be increased from V1 to V2 by the blowout flow from the jet outlet 12. By accelerating the flow velocity of the outer peripheral stationary blade outflow velocity from V1 to V2, the swirl velocity component can be increased from VT1 to VT2, and the relative velocity flowing into the moving blades even though the circumferential velocity U is the same. W1 can be decelerated to W2. According to this embodiment, the relative speed W1 flowing into the moving blade can be reduced to W2, thereby avoiding supersonic inflow. Therefore, it is possible to suppress the generation of shock waves at the moving blade inlet and to avoid an increase in loss associated therewith.
This effect is particularly suitable for the final stage of the low-pressure turbine.

  Next, FIG. 4 shows a different relationship from FIG. 3 between the stationary blade 7 and the jet port 12 for discharging the high-temperature and high-pressure working fluid on the stationary blade outer peripheral side wall surface 9.

  When the expansion angle of the outer peripheral side wall on the meridian plane is large, the expansion channel in the blade height direction is large, even though it is a throttle channel between the stationary blades. It may become. In that case, the secondary flow may be rolled up or separated from the side wall upstream of the throat between the stationary blades. In that case, the effect of this embodiment demonstrated previously can be acquired more reliably by installing the slit which ejects a high temperature / high pressure working fluid from the hollow part 11 of the outer peripheral side diaphragm 5 more upstream. In that case, the opening 16 of the ejection port 12 is provided upstream of the throat portion in the working fluid flow direction, and in the blade surface static pressure distribution of the stationary blade shown in FIG. 5, the pressure P6 of the blade positive pressure surface 24 and the blade negative pressure surface 25. If the pressure P5 of the two adjacent stationary blades is equal to each other and provided at a position along a line connecting the blade pressure surface 24 and the blade suction surface 25 facing each other, the blowing flow is more likely to flow along the main flow between the blades. Become. In this case, the shape of the opening 16 is a slit shape that opens toward the turbine axial direction or the outer peripheral side and connects the points where the pressure P6 of the blade positive pressure surface 24 and the pressure P5 of the blade negative pressure surface 25 become equal. Is desirable.

  Next, FIG. 6 shows a modification of the jet nozzle 12 in which a plurality of jet nozzles 12 for discharging high-temperature and high-pressure steam on the stationary blade outer peripheral side wall surface 9 are provided. As the opening 16a of the jet 12 installed on the most downstream side, the opening structure of the jet 12 shown in FIG. 3 or FIG. 4 described above may be employed. Moreover, what is necessary is just to employ | adopt the opening part structure of the jet nozzle 12 shown in FIG. 4 as the opening part 16b of the jet nozzle 12 provided in the upstream of the jet nozzle 12 installed in the most downstream side. Providing a plurality of jet outlets 12 as in this modification leads to an increase in the manufacturing process, but the effect of avoiding supersonic inflow, suppressing secondary flow roll-up and separation, and reducing the amount of erosion of this embodiment. Can be obtained larger.

  FIG. 10 shows still another relationship between the stationary blade 7 and the ejection port 12 for discharging the high-temperature and high-pressure working fluid on the stationary blade outer peripheral side wall surface 9. In order to provide the slit-shaped opening 16 between the vanes of the stationary blades, it is necessary to manufacture slits between the stationary blades. In the structure of FIG. 10, the opening 16 is provided in the shape of a slit extending in the circumferential direction in the downstream portion of the stationary blade outlet. And the guide plate 17 which matches the flow direction which blows off from the opening part 16 with the stationary blade outflow direction inside the opening part 16 is provided. FIG. 11 is a diagram of the structure of FIG. 10 viewed from the meridian plane, and FIG. 12 is a diagram of the structure of FIG. 10 cut by a plane 51 from the outer peripheral side indicated by the arrow 50 in FIG. In FIG. 12, the airfoil of the stationary blade 7 that is actually on the inner peripheral side of the surface 51 is indicated by a dotted line.

  As shown in FIG. 11, the jet nozzle 12 passes through the outer peripheral diaphragm 5 in the turbine axial direction and communicates with the hollow portion 11 and the working fluid main flow path 4. Therefore, the opening 16 opens in the turbine axial direction. In addition, as shown in FIG. 12, the flow direction of the jet flow 18 can be changed by providing a plurality of guide plates 17 at an interval in the circumferential direction by tilting the guide plate 17 in the jet direction of the stationary blade inside the jet port 12. It becomes possible to match the outflow direction of the main working fluid from the stationary blade 7.

  Next, FIG. 7 shows in detail the shape of the opening 16 of the ejection port 12 for ejecting the working fluid (shape of the ejection port). The downstream side wall surface of the opening 16 is formed in a curved shape so that the outer diameter of the opening increases toward the downstream side in the turbine axial direction so that the jet flow 18 flows along the side wall surface 9 on the outer peripheral side of the stationary blade. To do. On the meridian plane, the downstream side wall surface of the opening 16 is a curved portion 19.

  Further, as shown in FIG. 8, the curved surface portion formed on the downstream side wall surface of the opening portion 16 is ejected by making the width in the downstream turbine axial direction smaller than the upstream side when viewed on the meridian surface. The flow 8 flows more reliably along the outer peripheral side wall surface 9.

  Further, as shown in FIG. 9, a protrusion that turns the direction of the jet flow 8 flowing out from the opening 16 toward the stationary blade outer peripheral side wall on the downstream side of the opening, on the upstream side wall of the opening 16. By providing 21 as a flow guide, it is possible to flow the jet flow 18 along the outer peripheral side wall surface 9 more reliably.

    Next, a second embodiment of the present invention will be described.

  FIG. 16 is a meridional cross-sectional view illustrating a main structure of a turbine stage portion of the axial turbine according to the embodiment of the present invention. In this figure, parts corresponding to the same parts as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In this embodiment, in addition to the structure of the first embodiment described above, a porous sheet-like structure 22 is provided on the stationary blade outer peripheral side wall surface 9 of the outer peripheral diaphragm 5 by coating or the like. Since the sheet-like structure 22 is porous, the water film flowing on the stationary blade outer peripheral side wall surface 9 enters the sheet-like structure 22. Therefore, the area for the droplets to receive heat increases from the outer peripheral diaphragm 5 whose temperature has been increased by the high-temperature working medium introduced into the hollow portion 11, and more water film can be evaporated.

  As described above, the embodiment of the present invention has been described by taking a steam turbine using steam as a working medium as an example of an axial flow turbine. However, the present invention is not limited to this, and moisture is added to the working medium. The present invention can also be applied to an axial flow turbine, such as a high humidity gas turbine.

DESCRIPTION OF SYMBOLS 1 Steam turbine 2 Turbine rotor 3 Turbine casing 4 Working fluid main flow path 5 Outer peripheral side diaphragm 6 Inner peripheral side diaphragm 7 Stator blade 8 Moving blade 9 Stator blade outer peripheral side wall surface 11, 23 Hollow part 12 Jet port 13 Working fluid introduction flow path 14, 15 Extraction part 16 Opening part 17 Guide plate 18 Ejection flow 19 Curve part 21 Projection part 22 Sheet-like structure 24 Blade pressure surface 25 Blade suction surface

Claims (15)

An axial flow turbine comprising a turbine stage having a stationary blade fixed to an outer peripheral stationary blade support and a moving blade fixed to a rotor on the downstream side in the working fluid flow direction of the stationary blade,
The turbine stage having a stationary blade having a stationary blade outlet portion whose radial height is larger than a radial height of the stationary blade inlet portion is arranged on the outer peripheral side of the stationary blade outer peripheral side wall of the outer peripheral side stationary blade support. A working fluid having a temperature higher than that of the working fluid flowing around the stationary blades of the paragraph is introduced, and the introduced working fluid is ejected from the outer peripheral side wall of the stationary blade toward the downstream side of the working fluid main flow path. A featured axial turbine. The axial turbine according to claim 1,
The working fluid introduced into the outer peripheral side of the stationary blade outer peripheral side wall of the outer peripheral side stationary blade support is introduced from the bleed portion of the upstream turbine stage provided upstream in the working fluid flow direction of the turbine stage. A featured axial turbine. The axial turbine according to claim 2, wherein
An axial flow characterized in that the working fluid introduced to the outer peripheral side of the outer peripheral side wall of the outer peripheral side stationary blade support is ejected along the throat portion where the flow path width between the stationary blades is the narrowest. Turbine. The axial turbine according to claim 2, wherein
The working fluid introduced to the outer peripheral side of the stationary blade outer peripheral side wall of the outer peripheral stationary blade support is ejected along a line connecting the pressure points of the adjacent stationary blades facing the pressure surface and the suction surface equal to each other. An axial flow turbine characterized by: The axial turbine according to claim 2, wherein
Ejecting the working fluid introduced to the outer peripheral side of the stationary blade outer peripheral side wall of the outer peripheral stationary blade support along the stationary blade outflow direction of the main working fluid from the downstream side in the working fluid flow direction of the stationary blade. A featured axial turbine. The axial flow turbine according to any one of claims 1 to 5,
In the turbine stage, the rotor blade tip peripheral speed Mach number obtained by dividing the rotational peripheral speed of the tip of the blade by the sound speed of the working fluid flowing into the blade tip exceeds 1.0. Flow turbine. An axial flow turbine comprising a turbine stage having a stationary blade fixed to an outer peripheral stationary blade support and a moving blade fixed to a rotor on the downstream side in the working fluid flow direction of the stationary blade,
From the working fluid flowing around the stationary blades of the turbine stage, the outer stationary blade support of the turbine stage having the stationary blades having the radial height of the stationary blade outlet part larger than the radial height of the stationary blade inlet part. A shaft formed with a hollow portion into which a high-temperature and high-pressure working fluid is introduced, and a jet port that communicates with the hollow portion and ejects the working fluid introduced into the hollow portion into the working fluid main flow path. Flow turbine. The axial turbine according to claim 7, wherein
An axial flow turbine characterized by introducing a working fluid extracted by a bleed portion of a turbine stage provided upstream in a flow direction of a working fluid of a turbine stage having the hollow part into the hollow part. The axial turbine according to claim 8, wherein
The axial flow turbine is characterized in that the jet outlet has a slit-like opening that opens along a throat portion where the flow path width between the stationary blades is the narrowest. The axial turbine according to claim 8, wherein
2. The axial flow turbine according to claim 1, wherein the jet nozzle has a slit-like opening that connects the pressure surfaces of the adjacent stationary blades facing each other at the same pressure and suction surfaces. The axial turbine according to claim 8, wherein
The jet port is provided on the downstream side of the stationary blade in the working fluid flow direction, and has a slit-like opening that extends and opens in the turbine circumferential direction.
An axial flow turbine characterized in that a guide plate for turning the flow direction of the working fluid flowing out from the opening to the stationary blade outflow direction of the working fluid main flow is provided in the jet outlet. The axial turbine according to any one of claims 9 to 11,
An axial flow turbine characterized in that the downstream side wall surface of the opening of the jet outlet is formed in a curved shape so that the outer diameter of the opening of the jet outlet increases toward the downstream side in the turbine axial direction. The axial turbine according to claim 12, wherein
Provided on the upstream side wall of the opening of the jet outlet is a flow guide that turns the flow direction of the working fluid flowing out from the opening toward the stationary blade outer peripheral side wall on the downstream side of the opening. An axial flow turbine characterized by The axial turbine according to any one of claims 7 to 13,
In the turbine stage having the hollow portion, the rotor blade tip peripheral speed Mach number obtained by dividing the rotational peripheral speed of the tip of the blade by the sound speed of the working fluid flowing into the blade tip exceeds 1.0. A featured axial turbine. The axial turbine according to any one of claims 7 to 14,
An axial flow turbine comprising a porous sheet provided on a stationary blade outer peripheral side wall surface of the outer peripheral side stationary blade support.

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