JP2006307843A - Axial turbine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an axial turbine suppressing speed of flow flowing in a moving blade relative to the moving blade and improving turbine stage efficiency. <P>SOLUTION: In the axial turbine includes a plurality of stages, each of the plurality of stages having stationary blades 41 and moving blades 42 being located downstream of the stationary blades 41 along a flow direction of a working fluid, so as to be opposed to the stationary blades, each of the stationary blades is formed so that a stationary blade outer diameter line 4 which is an intersection line between the outer periphery of the stationary blade 41 constituting a stage having moving blades 42 longer than moving blades in a preceding stage and a plane containing the central axis 21 of the turbine, has a flow path constant diameter portion 60 that includes at least an outlet outer periphery 3 of the stationary blade 41 and that is parallel to the central axis 21 of the turbine. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an axial flow turbine such as a steam turbine or a gas turbine, and more particularly to an axial flow turbine (low pressure turbine) in a low pressure region.

  The axial flow turbine accelerates the working fluid by passing through the stationary blade and deflects it in the rotating direction of the turbine rotor, and imparts kinetic energy to the moving blade by the flow having the velocity component in the rotating direction to rotate the turbine rotor. In order to induce the flow of the working fluid that drives the turbine rotor, the height of the paragraph outlet passage measured in the radial direction of the turbine rotor in accordance with the high pressure of the paragraph inlet of the turbine compared to the paragraph outlet is It is higher than the paragraph inlet channel height. Therefore, at the outer periphery of the stationary blade ring zone of each paragraph, the flow path height increases monotonously from the inlet to the outlet of the paragraph, that is, the outlet portion of the stationary blade with respect to the radial height of the inlet portion of the stationary blade. The height in the radial direction is usually high (see Patent Document 1).

JP 2003-27901 A

  In a general turbine, as described above, the flow path height of the outer peripheral portion of the stationary blade ring zone monotonously increases toward the paragraph outlet, so that the flow that has passed through the stationary blade has a radially outward velocity component. Normally, a flow having a velocity component radially outward increases in relative velocity with respect to the blade. However, in the future, the turbine blades are expected to be longer for further performance improvement, and the peripheral speed of the outer periphery of the rotor blades may become higher. If the blade length is increased without extending the axial length with the current design, the inclination angle of the outer periphery of the stator blade annulus becomes steeper and the radially outward velocity component of the flow exiting the stator blade increases. . As a result, the relative speed of the flow flowing into the moving blades with respect to the moving blades exceeds the speed of sound, and the turbine efficiency may decrease due to factors such as the loss of shock waves on the moving blades.

  An object of the present invention is to provide an axial flow turbine capable of suppressing the relative speed of a flow flowing into a moving blade with respect to the moving blade and improving turbine stage efficiency.

  In order to achieve the above object, according to the present invention, in an axial flow turbine having a plurality of stages, a stationary blade having a radial height of an outlet portion of the stationary blade higher than a radial height of the inlet portion of the stationary blade is provided. The intersection line between the surface including the turbine central axis and the stationary blade outer peripheral portion includes a portion extending in the extending direction of the turbine central shaft including the stationary blade outlet.

  ADVANTAGE OF THE INVENTION According to this invention, the relative speed with respect to the moving blade of the flow which flows in into a moving blade can be suppressed, and turbine stage efficiency can be improved.

First, a basic structure of a turbine stage section of a general axial flow turbine will be described with reference to FIG.
As shown in FIG. 1, the turbine stage of the axial-flow turbine is located between a high-pressure part P0 on the upstream side in the flow direction of the working fluid (hereinafter simply referred to as upstream side) and a low-pressure part p1 on the downstream side. The turbine stage includes a stationary blade 41 fixed between the stationary body wall surface 6 and the inner peripheral diaphragm outer peripheral surface 7, and a moving blade 42 provided on the turbine rotor 15 rotating around the central shaft 21. A plurality of stages are provided in the flow direction. In each paragraph, the moving blade 42 is opposed to the downstream side of the stationary blade 41 in the flow direction of the working fluid (hereinafter simply referred to as the downstream side).

  The “stationary body wall surface 6” refers to an inner peripheral wall surface of a stationary body (excluding a stationary blade) that covers the turbine rotor 15 that is a rotating body. For example, a diaphragm (outer peripheral diaphragm) is annularly formed on the inner peripheral side of the casing. When attached, the inner peripheral wall surface of the outer peripheral diaphragm corresponds to the “stationary body wall surface 6”, and when the outer peripheral diaphragm is not provided, the inner peripheral wall surface of the casing corresponds to the “stationary body wall surface 6”. For later explanation, the portion of the stationary body wall surface 6 to which the stationary blade 41 is connected is referred to as “the stationary blade outer peripheral stationary wall surface 6a”, and the portion facing the outer peripheral side of the moving blade 42 is referred to as “the moving blade outer periphery”. The side stationary body wall surface 6b "is defined.

  With the above configuration, when the working fluid flow 20 is induced by the pressure difference P0-p1, the flow 20 is accelerated when passing through the stationary blade 41 and is deflected in the turbine circumferential direction. The flow passing through the stationary blade 41 and given the circumferential velocity component gives energy to the moving blade 42 and rotates the turbine rotor 15.

  Since the paragraph inlet portion has a higher pressure and a smaller specific volume of the working fluid than the paragraph outlet portion, the paragraph inlet passage height H1 is smaller than the paragraph outlet passage height H2. In other words, the outer peripheral portion of the stationary blade 41 and the stationary outer peripheral wall surface 6a of the moving blade have an outer diameter line 4 that is a line of intersection between the surface including the turbine central shaft 21 (the meridian surface) and the outer peripheral portion of the stationary blade 41. It is inclined radially outward from the moving blade outlet portion of the paragraph to the moving blade inlet portion constituting the same paragraph, and the radius of the annular flow path of the working fluid increases linearly (or monotonously) at the portion of the stationary blade 41. ing. That is, the radial height H3 of the outlet portion of the stationary blade is higher than the radial height (stage inlet channel height) H1 of the stationary blade inlet portion. Therefore, in a particularly long blade section of a general axial turbine, the radius of the outer peripheral portion of the stationary blade 41 (the point of the stationary blade trailing edge on the outer diameter line 4 or the stationary blade outer peripheral end trailing edge) 3 R <b> 1 is smaller than the radius R <b> 2 of the outer peripheral portion of the inlet of the moving blade 42 (the moving blade outer peripheral front edge) 11.

  The rotor blade outer peripheral speed Mach number obtained by dividing the rotational peripheral speed of the inlet peripheral part 11 of the moving blade 42 by the sound velocity of the fluid flowing into the outer peripheral end (the outer peripheral part in the effective length) of the moving blade 42 exceeds 1.0. Then, the relative speed of the working fluid flowing into the moving blade 42 with respect to the moving blade 42 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 42 becomes completely supersonic.

FIG. 2 is a graph showing changes in the relative Mach number (moving blade relative inflow velocity) of the working fluid with respect to the moving blade in the blade length direction.
The relative inflow speed of the rotor blade in the paragraph where the blade length is long and the peripheral speed Mach number of the rotor blade exceeds 1.0 tends to exceed 1.0 around the root and tip of the rotor blade as shown by the dotted line. In some cases, the working fluid having a relative velocity of supersonic velocity flows around the root portion and the tip portion of the rotor blade. When the relative inflow velocity of the blade reaches supersonic speed, the flow choke on the upstream side of the blade, so the flow rate cannot be determined by the blade throat (minimum distance between adjacent blades in the circumferential direction). The flow of the working fluid cannot be realized. Further, a large loss occurs due to the separation shock wave formed upstream of the moving blade leading edge interfering with the blade surface boundary layer. In particular, since the ring zone area is large and the flow rate of the working fluid is large on the blade tip side, the rate of performance degradation due to the working fluid flowing in at supersonic speed is large compared to the vicinity of the blade root. As described above, when the blade length is measured in a general turbine stage, the relative inflow speed of the working fluid with respect to the moving blade may reach supersonic speed, so that the stage performance may be remarkably deteriorated.

Next, the principle that the relative inflow speed of the moving blade is supersonic at the moving blade tip side in the turbine stage shown in FIG. 1 will be described with reference to FIG.
In FIG. 3, the working fluid exiting the flow path formed by the stationary blades 41a and 41b adjacent in the circumferential direction has a flow velocity c1 at the stationary blade outlet outer peripheral portion 3 (see FIG. 1). The flow velocity c1 includes a turning velocity ct1 that is a circumferential velocity component, an axial flow velocity cx1 that is an axial velocity component, and a radial velocity cr1 (not shown) that is a velocity component outward in the radial direction of the turbine (frontward in the direction orthogonal to the paper surface). Consists of. On the other hand, the flow that has passed through the stationary blades 41a and 41b at the flow velocity c1 flows into the outer peripheral side leading edge 11 (see FIG. 1) of the moving blades 42a and 42b at the flow velocity c2. Let ct2 be the turning speed component of the flow velocity c2.

Here, the swirl speeds ct1 and ct2 are determined from the law of conservation of angular momentum between the stationary blade and the moving blade, using the stationary blade outer peripheral edge radius R1 and the moving blade outer peripheral edge radius R2 (both see FIG. 1),
R1 × ct1 = R2 × ct2 (Formula 1)
The relationship is established.

In the axial turbine shown in FIG.
R1 <R2 (Formula 2)
Therefore, from (Expression 1) and (Expression 2), ct1> ct2 (Expression 3)
The relationship is guided.
Thus, the turning speed ct2 at the inlet of the moving blades 42a, 42b is smaller than the turning speed ct1 at the outlet of the stationary blades 41a, 41b.

  On the other hand, since the peripheral speed U of the moving blades 42a and 42b is high at the moving blade tip side, the relative inflow speed w2 of the working fluid to the moving blades 42a and 42b is opposite to the rotational direction of the moving blades 42a and 42b. It has a velocity component that is directed in the direction. Therefore, the moving blade relative inflow velocity w2 increases as the circumferential velocity component ct2 of the flow velocity c2 decreases.

  In consideration of the above relationship, when the turning speed ct1 given by the stationary blades 41a and 41b expands with a velocity component outward in the turbine radial direction and flows into the moving blades 42a and 42b, (Equation 3) As described, since the speed is reduced to ct2 (<ct1) according to the angular momentum conservation law, the moving blade relative inflow velocity w2 increases and becomes supersonic. That is, when the blade is made longer, if the working fluid that has passed through the outer periphery of the stationary blade 41 has a velocity component that is outward in the turbine radial direction, the moving blade relative inflow velocity w2 becomes supersonic. This contributes to a significant reduction in turbine stage efficiency.

Based on the above, embodiments of the axial flow turbine of the present invention will be described below.
FIG. 4 is a cross-sectional view showing the main structure of the axial turbine according to the embodiment of the present invention. In this figure, portions corresponding to the same portions as those in the previous drawings are given the same reference numerals and description thereof is omitted.
As shown in FIG. 4, in the present embodiment, the stationary blade outer diameter wire 4 includes the outlet portion (outlet outer peripheral portion 3) of the stationary blade 41, and the extending direction of the turbine central shaft 21 (the left-right direction in FIG. 4). The stationary blade 41 and the stationary blade outer peripheral side stationary body wall surface 6a are formed so as to have a portion 60 extending in the direction. In other words, if the point upstream from the stationary blade outlet outer peripheral portion 3 by the distance d along the stationary blade outer diameter line 4 is defined as the starting end (upstream end) 5 of the portion 60 extending along the turbine central axis 21, the starting end 5 In the section from the outer peripheral portion 3 to the stationary blade outlet, a cylindrical annular channel having a constant radius R3 is formed. That is, in the present embodiment, in the same turbine stage,
R1 = R3 (Formula 4)
The relationship is established.

  Here, the “portion 60 extending in the extending direction of the turbine central shaft 21” of the stationary blade outer diameter wire 4 is a portion extending substantially in parallel with the turbine central shaft 21, and has a constant radius R3 as described above. For the sake of convenience, in the following description, it will be referred to as the “flow channel equal diameter portion 60”.

  Further, the stationary blade 41 and the stationary blade outer peripheral side stationary body wall surface 6 a have a portion 61 in which the stationary blade outer diameter line 4 is inclined toward the outer peripheral side in the turbine radial direction toward the downstream side in the working fluid flow direction. Is also formed on the upstream side. In the portion 61 inclined to the outer peripheral side in the turbine radial direction, the diameter of the annular flow path formed by the stationary blade outer peripheral side stationary body wall surface 6a increases toward the downstream side. Is referred to as a flow passage diameter-expanding portion 61. The flow path enlarged diameter portion 61 is smoothly connected to the flow path same diameter portion 60.

In addition, the height in the turbine radial direction of the flow path same-diameter portion 60 (that is, the stationary blade outer peripheral trailing edge radius R1) is substantially equal to the height in the turbine radial direction of the effective length outer peripheral portion of the moving blade 42 in the same paragraph. In the present embodiment, the rotor blade 42 is provided with a connecting cover 12 at the tip for connecting with other rotor blades adjacent in the circumferential direction. Determined at the height of the peripheral surface. In this case, the height in the turbine radial direction of the effective length outer peripheral portion of the moving blade 42 is the moving blade outer peripheral leading edge radius R2. Therefore, in this embodiment,
R1 = R2 (Formula 5)
The relationship is established.
In addition, the effective length outer peripheral part of the moving blade 42 will be touched later in FIG. 6 and FIG.

  Here, the turbine stage shown in FIG. 4 has a moving blade 42 having a longer blade length than the moving blade of the previous paragraph. In the paragraph including the flow path same-diameter portion 60, the blade length of the moving blade 42 is long, and specifically, the working fluid flowing into the tip portion of the moving blade 42 at the rotational peripheral speed of the tip portion of the moving blade 42 during operation. It is a paragraph having a long blade whose peripheral tip Mach number divided by the speed of sound can exceed 1.0.

  In such a turbine stage, in the present embodiment, the annular flow path of the working fluid in the vicinity of the stationary blade outlet is a cylindrical flow path with R3 = R1. Therefore, the working fluid that has passed through the stationary blade 41 flows substantially parallel to the turbine central shaft 21 in which the velocity component outward in the turbine radial direction is suppressed. Therefore, as shown in FIG. 5, the swirl speed ct3 of the flow of the flow velocity c3 exiting the stationary blades 41a and 41b in the axial flow turbine of the present embodiment is not decelerated as the flow expands. It will flow in between the moving blades 42a and 42b with c3. As a result, the moving blade relative inflow velocity w3 can be suppressed below the sound velocity, and a designed flow pattern can be realized. Moreover, since the moving blade relative inflow speed w3 can be suppressed to a sound speed or less, shock wave loss can be significantly reduced.

  Further, in the present embodiment, the stationary blade outer peripheral trailing edge radius R1 is set to be substantially equal to the moving blade outer peripheral leading edge radius R2, so that it passes through the vicinity of the stationary blade outer peripheral portion and is substantially parallel to the turbine central shaft 21. The flowing working fluid flows into the vicinity of the outer peripheral portion of the rotor blade. Therefore, the working fluid can be allowed to flow into the effective length portion of the moving blade 42 in a well-balanced manner, and the performance of the moving blade 42 having a longer blade length can be maximized.

Here, FIG. 6 is an enlarged view of the tip portion of the moving blade 42 provided with the connection cover 12.
As described above, the cover 12 for connecting the adjacent blades in the circumferential direction is provided at the tip of the blade 42. In order to avoid excessive stress concentration, an R portion (building-up portion) 14 is provided at a joint portion between the connecting cover 12 and the moving blade 42. In this case, since the region of the height h of the R portion 14 on the turbine radial direction inner peripheral side from the tip side of the moving blade 42 is different from the originally designed blade shape, the energy of the working fluid is used as rotational power. It may not be appropriate to include it in the effective length that performs the function of conversion. Therefore, the effective long outer peripheral portion of the rotor blade 42 is located between the height position of the surface of the connecting cover 12 on the inner peripheral side in the turbine radial direction and the position on the inner peripheral side in the turbine radial direction by the height h of the R portion 14 therefrom. It shall be located between. That is, the outer peripheral portion of the moving blade effective length can be defined as being at a distance between (R2-h) and R2 from the blade root to the outside in the turbine radial direction.

Therefore, when the R portion 14 of the joint portion of the connection cover 12 is taken into consideration in terms of fluid dynamics, the stationary blade outer peripheral trailing edge radius R1 at which the effective effective length of the moving blade is maximized is strictly the outer peripheral surface of the moving blade. It is not necessary to make it equal to the leading edge radius R2, and the above (formula 5) is
0 ≦ R2−R1 <h (Formula 5 ′)
Is allowed in the range represented by

Further, from the fact that the flow path same-diameter portion 60 does not need to be strictly parallel to the turbine central shaft 21 as described above and the range of the effective length of the moving blade 42 described above, the above equation (4) is
-H <R3-R1 <h (Formula 4 ')
Is allowed in the range represented by In this case, R3 is related to R2 from (Equation 5 ′),
0 ≦ R2−R3 <2h (Formula 6)
The value is in the range represented by.

  That is, when the connecting blade is provided at the tip of the moving blade as in this example, the inclination of the flow path same-diameter portion 60 is such that the flow path same-diameter portion 60 is located at the height position of the inner peripheral surface of the connection cover 12 and from there. It is preferable that the inclination is in a range that falls between the height h of the R portion 14 and the position on the inner circumferential side in the turbine radial direction, but in the case of inclining in the direction of expanding the annular flow path toward the downstream side, The start end 5 of the flow path same-diameter portion 60 is allowed even when it is between the height position of the inner peripheral surface of the connecting cover 12 and the position on the inner peripheral side in the turbine radial direction by the height 2h.

Here, FIG. 7 is an explanatory view of the axial region (length) of the flow path same-diameter portion 60, and the outer peripheral portions of the stationary blades 41a and 41b adjacent in the circumferential direction are viewed from the radially outer side (the connecting cover 12). Is schematically shown).
As shown in FIG. 7, a throttle channel 102 is formed between the stationary blades 41a and 41b. The throat 103, which is a line that minimizes the distance between the stationary blades 41 a and 41 b, intersects the blade suction surface 105 at a point 104. In this case, the working fluid is accelerated to the throat 103 having the minimum channel width along the throttle channel 102 formed between the stationary blades 41a and 41b. Inflow.

  That is, the working fluid passing through the throat portion is guided by being restrained by the stationary blade, but the flow after passing through the throat portion becomes free. In the present embodiment, the flow that has passed through the throat portion is guided to the effective length of the moving blade by suppressing the velocity component in the radial direction by the flow path same-diameter portion 60. It is important to flow into the moving blade 42 without greatly changing the. In consideration of this, it is desirable that the flow path same-diameter portion 60 includes the throat 103 in which the working fluid is most accelerated in the throttle flow path 103.

  That is, since the throat 103 located on the most upstream side of the throat 103 is the throat point 104 on the stationary blade suction surface side, the starting end 5 (see FIG. 4) of the flow path same-diameter portion 60 is negative in the outer peripheral portion of the stationary blade. It is desirable that it extends from the axial position of the throat point 104 on the pressure side or from the upstream side to the outlet outer peripheral portion 3. Specifically, as shown in FIG. 8, the start end 5 of the same-diameter portion 60 of the flow path is on the surface 106 passing through the point 104 and orthogonal to the turbine central shaft 21 or on the upstream side thereof. Is desirable. For example, in FIG. 8, when the x-coordinate with the direction toward the downstream side is positive and the distance in the x-axis direction from the starting end 5 to the surface 106 is α, the flow path same diameter portion 60 is secured so that α ≧ 0. To do. As a result, the working fluid reaches the same diameter portion 60 of the flow path and is given the maximum acceleration force by the throttle flow path 102 in a state where the outer peripheral side of the flow is constrained, so the diameter of the working fluid after exiting the stationary blade 41 The outward speed component is more effectively suppressed.

  Further, as described above, in the turbine stage to which the present invention is applied, the radial velocity component of the outlet flow is suppressed. In the axial turbine of the present invention having a plurality of paragraphs, when the features described in FIGS. 4 to 8 are applied to the final paragraph, there is only an exhaust diffuser (not shown) further downstream of the final paragraph. Therefore, there is no problem even if the velocity component in the radial direction of the working fluid that has passed is small.

  However, in an axial turbine having a plurality of paragraphs, the blade length may increase in the downstream paragraph in order to expand the working fluid and increase the specific volume of the working fluid. Therefore, in a paragraph in which a paragraph continues on the downstream side (that is, a paragraph other than the final stage), the working fluid smoothly flows into the downstream paragraph when the working fluid has a radially outward velocity component at the paragraph outlet. In that sense, the features of the present invention are most effective when applied only to the turbine final stage. However, if the wings are further increased in the future, the effect is expected even when the present invention is applied to paragraphs in the vicinity including the final stage. Further, the present invention is desirable when applied to a turbine having a low rotational speed (1500 rpm or 1800 rpm) and a relative speed of the working fluid with respect to the tip of the moving blade is slower than the sonic speed, such as a steam turbine used in a current nuclear power generation facility or the like. The effect is difficult to obtain. However, there is a possibility that the steam turbine used in the nuclear power generation facility in the future will have the same rotational speed (3000 rpm or 3600 rpm) as the steam turbine of the thermal power plant, in which case the present invention can be applied, The desired effect is obtained.

FIG. 9 is a cross-sectional view showing the main structure of a configuration example of the axial turbine according to the present invention in which the present invention is applied only to the turbine final stage.
As shown in FIG. 9, in this example, in the axial flow turbine having the n-stage turbine stage, only the final stage stationary blade 41 _n constituting the turbine final stage (n-th stage) has the channel same-diameter portion 60 on the outer peripheral portion. Have. It also applies to the previous example of FIG. 4, but when the connection cover is provided on the blade tip as in this embodiment, the inner circumferential surface of the connection cover 12 _n of the final stage moving blade 42 _n is the flow path of the final stage stationary blade 41 _n Similar to the same-diameter portion 60, it has a cylindrical shape. That is, the outer diameter line 13 _n, which is an intersecting line with the surface including the turbine rotating shaft 21, extends in the extending direction of the turbine central shaft 21, and the effective length of the final stage moving blade 42 _n is substantially constant.

The stationary blade of the upstream stage from the final stage has an outer diameter line (only the outer diameter line 4 _n-1 of the stationary blade 41 _n-1 of the (n-1) th paragraph) is directed toward the downstream side. It is formed so as to incline outward in the direction. That is, in this configuration example, in the paragraphs other than the final stage, the stationary body wall surface 6 is formed in a cylindrical shape that extends downstream. Also, the inner peripheral surface of the connecting cover of the moving blades of the paragraphs other than the final stage (only the connecting cover 12 _n-1 of the moving blade 42 _n-1 of the (n-1) th paragraph) is the stationary blade of the same paragraph. It is formed in a cylindrical shape that spreads downstream as in the case of the outer diameter line. That is, (only external diameter line 13 _n-1 of the connection cover 12 _n-1 shown) external diameter line is a line of intersection between the plane containing the turbine rotation shaft 21 is inclined radially outwardly toward the downstream side Yes.

Then, the extension line of the outer diameter line of the stationary blade finally moves to the outer diameter line of the moving blade of the same paragraph, and the extension line of the outer diameter line of the moving blade finally moves to the outer diameter line of the stationary blade of the next paragraph. The extension line of the outer diameter line 13 _n-1 of the blade 42 _{n-1 is connected to} the outer diameter line of the final stage stationary blade 41 _n (flow path enlarged portion 61) to some extent smoothly, and the flow path of the final stage stationary blade 41 _{n is} the same. On the upstream side of the starting end 5 of the diameter portion 60, the annular flow path of the working fluid is expanded. By configuring in this way, the flow of the working fluid has a radially outward velocity component 101 until it reaches the same-diameter portion 60 of the flow path, and causes separation or the like when flowing into the entrance of each paragraph. no smoothly distributed, it is possible to yet finally speed relative to a long final stage moving blade 42 _n of blade length by passage constant diameter portion 60 is suppressed remarkably improve the turbine stage efficiency. That is, in the paragraph where the relative speed of the working fluid to the tip of the moving blade is less likely to reach the sonic speed upstream of the final stage, the configuration is focused on the smoothness of introduction of the working fluid into the next blade row.

  Here, the case where the present invention is applied to an axial flow turbine in which a connecting cover is provided at the tip of a moving blade has been described as an example. However, the present invention describes an axial flow turbine in which the tip of a moving blade is not constrained by a connecting cover. The same effect can be obtained. When the moving blade 42 does not have the connection cover 12 and the tip of the moving blade 42 is a free end, the effective length outer peripheral portion of the moving blade 42 is the tip (outer peripheral portion) of the moving blade 42. In this case, since the stationary blade outer peripheral side trailing edge radius R1 at which the effective length of the moving blade 42 is utilized to the maximum is equal to the moving blade outer peripheral side leading edge radius R2, the above (Expression 4) and (Expression 5) are By satisfying the condition, the moving blade relative inflow speed can be suppressed to a sound speed or less, and the effective length of the moving blade 42 can be utilized to the maximum. However, in the relationship defined in (Expression 4) and (Expression 5), a difference in manufacturing error range (depending on the blade length, for example, about 1 to 2 mm) is allowed. FIG. 10 is a cross-sectional view showing the main structure of a structural example of the axial flow turbine of the present invention in the case where the tip has a moving blade 42 ′ that is a connection cover and is not connected to an adjacent blade.

Further, the shape of the stationary body wall surface 6 will be further examined.
For example, as shown in FIG. 11, when the stationary blade outer peripheral side trailing edge radius R1 is larger than the moving blade outer peripheral side leading edge radius R2, the relative inflow velocity w3 of the moving blade inlet 11 is suppressed to subsonic speed. The flow passing through the outer peripheral portion flows toward the seal gap 16 formed between the tip end portion of the moving blade 42 (strictly, the outer peripheral portion of the connection cover 12) and the moving blade side stationary body wall surface 6b. In this case, the flow that has passed through the outer peripheral portion of the stationary blade 41 passes through the seal gap 16 and is not effectively used for rotating the turbine rotor 15. From this, in order to make the best use of the effective length of the moving blade 42, it is preferable to satisfy (Equation 5 ') and (Equation 6) when the connecting blade is provided at the moving blade tip, and it is connected to the moving blade tip. When the cover is not provided, it is preferable to satisfy (Equation 5).

  In this case, because of the structure, it is necessary to ensure a required gap between the outer peripheral portion of the rotor blade effective length and the rotor blade side stationary body wall surface 6b. When the radial position is set to be approximately the same as the effective length outer peripheral portion of the moving blade of the same paragraph, the moving blade side stationary body wall surface 6b of the paragraph having the flow path same-diameter portion 60 is inevitably more than the flow path same-diameter portion 60. Is also located radially outward. In other words, by providing steps on the stationary body wall surface 6 on the stationary blade side and the moving blade side in this way, the working fluid rectified by the stationary blade side stationary body wall surface 6a can be efficiently guided to the moving blade effective length.

  In addition, the axial flow turbine of this Embodiment demonstrated above can suppress a moving blade relative inflow speed more effectively by carrying out various design changes. Hereinafter, modifications in which such effective configurations are combined will be sequentially described.

FIG. 12 is a graph showing the shape change of the stationary blade 41 in the blade length direction as a ratio of the throat to the pitch.
In the embodiment shown in FIG. 4, as indicated by a solid line in FIG. 12, the ratio s / t of the stationary blade throat s to the pitch t is smaller on the outer peripheral side than the intermediate portion in the blade length direction. By forming the stationary blade 41 by twisting it, the moving blade relative inflow speed can be further reduced.

  Here, the stationary blade throat s is a portion where the flow area is the smallest in the flow path formed between the stationary blades 41a and 41b adjacent in the circumferential direction as shown in FIG. 13 (that is, the stationary blade 41a, 41b). On the other hand, the pitch t indicates the circumferential interval between the stationary blades 41a and 41b.

  In general, the throat pitch ratio s / t is designed to be small on the blade inner peripheral side and larger on the outer peripheral side as shown by the dotted line in FIG. When the tip peripheral speed Mach number of the moving blade exceeds 1.0, in addition to the fulfillment of the condition (Formula 4), the stationary blade throat pitch ratio s / t is decreased on the outer peripheral side as shown by the solid line in FIG. By forming the stationary blade as described above, the working fluid becomes a stationary blade outflow angle a5 (<a4) as shown in FIG. a4 is the stationary blade outflow angle of the working fluid when the stationary blade shape shown by the dotted line in FIG. 12 is used. Further, the swirl speed ct5 of the flow at the flow velocity c5 flowing out from the vane 41a, 41b is larger than the swirl speed ct4 of the working fluid when the vane shape shown by the dotted line is used, as much as the stationary blade throat s is reduced. Become. Therefore, the moving blade relative inflow speed w4 in this modification can be made smaller than the moving blade relative inflow speed w5 of the working fluid when the stationary blade shape shown by the dotted line in FIG. 12 is used. That is, even in comparison with the axial turbine shown in FIG. 4, this modification can reduce the relative inflow speed of the moving blades.

FIG. 15 is a diagram showing a change in the blade length direction of the static pressure between the stationary blade and the moving blade in the turbine stage.
As shown in FIG. 15, the static pressure between the stationary blade and the moving blade in the turbine stage is greatly increased on the outer peripheral side due to the swirling flow generated by passing through the stationary blade, and is decreased on the inner peripheral side. Therefore, on the inner peripheral side where the peripheral speed of the moving blade is slow, the stationary blade outflow speed c6 is larger than the moving blade peripheral speed U6, as shown in FIG. Supersonic speed.

  FIG. 17 is a graph showing the blade length direction change of the moving blade relative inflow speed (Mach number). The change in the blade length direction of the moving blade relative inflow speed when the blade length is increased in a general axial turbine is indicated by a dotted line. Show. As can be seen from this graph, when the blades are made longer with a general axial turbine due to the factors described in FIGS. 15 and 16, the relative inflow speed of the moving blades not only on the outer peripheral side but also on the inner peripheral side of the moving blades. May exceed the speed of sound. The supersonic inflow of the working fluid to the outer peripheral side of the moving blade is countered by suppressing the velocity component outward in the turbine radial direction of the flow passing through the outer peripheral side of the stationary blade as described above.

FIG. 18 is a conceptual diagram showing the configuration of a stationary blade for suppressing supersonic inflow of the working fluid to the inner peripheral side of the moving blade.
In FIG. 18, the stationary blade 41 is formed to be curved so that the trailing edge 2 of the intermediate portion in the blade length direction protrudes in the moving blade rotation direction W. However, although the stationary blade 41 is curved in this example, the stationary blade 41 may be bent so that the trailing edge 2 of the blade length direction intermediate portion protrudes in the moving blade rotating direction W. In any case, the outer peripheral side of the stationary blade 41 extends substantially in the turbine radial direction, and the inner peripheral side portion of the stationary blade 41 moves outward in the turbine radial direction with respect to the reference line 50 extending in the turbine radial direction. It is inclined to.

  By curving (or bending) the stationary blade 41 as shown in FIG. 18, a pressure gradient that increases inward in the radial direction is generated in the inner peripheral side portion of the stationary blade, and between the stationary blade and the moving blade in the turbine stage. The static pressure on the inner circumference increases. Thereby, the stationary blade outlet flow velocity c6 shown in FIG. 16 can be reduced, and the moving blade relative inflow velocity w6 can be suppressed to a sound velocity or less. Therefore, by combining the stationary blade configuration shown in FIG. 18 with the embodiment of FIG. 4, even if the blade length is further increased, the relative inflow of the moving blades in the entire region of the moving blade length direction as shown by the solid line in FIG. The speed can be suppressed below the sound speed. Therefore, the designed flow pattern can be more reliably realized, and the shock wave loss can be further reduced.

FIG. 19 is a cross-sectional view showing a main part structure of still another modified example of the axial turbine according to the present invention.
As shown in FIG. 19, in the present example, the stationary blade outer diameter wire 4 is upstream of the flow path same diameter portion 60 and passes through the turbine radial outside of the flow path same diameter portion 60 toward the downstream side. The stationary blade 41 and the stationary body wall surface 6 are formed so as to have a portion 62 directed radially inward. In addition, in the portion 62 heading toward the inner radial side in the turbine radial direction, the annular flow path formed by the stationary blade outer peripheral stationary body wall surface 6a is reduced toward the downstream side. Is referred to as a flow path reduced diameter portion 62.

That is, the flow path diameter reducing portion 62 is located between the flow path diameter increasing portion 61 and the flow path same diameter portion 60 and is given a convex curvature upward in the turbine radial direction. It bends in the vicinity and continues smoothly to the same-diameter portion 60 of the flow path. It continues as it is with respect to the flow path enlarged diameter part 61. FIG. The radius R4 of the outermost periphery of the flow path reduced diameter portion 62 is
R4> R3 (Formula 7)
Satisfy the relationship. Other configurations are the same as those shown in FIG.

  Since the flow passing through the stationary blade outer peripheral side flows along the stationary blade outer diameter line 4, a curvature that is convex toward the inner peripheral side in the turbine radial direction is once given when passing through the flow path reduced diameter portion 62. By imparting such a convex curvature to the inner peripheral side to the flow, the turbine stage has the effect of causing the flow to expand toward the outer peripheral side in the radial direction of the turbine by the centrifugal force between the stationary blade 41 and the moving blade 42. Can be relaxed. As can be seen from the graph of the change in the blade length direction of the static pressure distribution between the stationary blade and the moving blade shown in FIG. 20, the static pressure between the stationary blade and the moving blade of a general axial flow turbine. The distribution increases in pressure from the inner circumference side toward the outer circumference side as indicated by the dotted line. On the other hand, the static pressure distribution between the stationary blades and the moving blades in the axial flow turbine having the configuration shown in FIG. 19 shows that the static pressure increases in the region on the outer peripheral side in the turbine radial direction as shown by the solid line in FIG. It is suppressed. Therefore, by combining the configuration of FIG. 19 with the configuration of FIG. 4, the same effect as the configuration of FIG. 4 can be obtained, and the flow velocity of the flow flowing out from the outer peripheral side of the stationary blade can be further increased, and the relative flow velocity of the moving blade can be increased. Further reduction can be achieved.

  In the above description, the case where the flow passage diameter-expanding portion 61 is provided in the stationary blade outer diameter wire 4 has been described as an example of each figure. However, the velocity component outward in the turbine radial direction of the flow that has passed through the stationary blade is described. As long as it is suppressed, it is sufficient that the flow path same-diameter portion 60 including at least the stationary blade outer peripheral rear edge portion 3 is provided. Therefore, it is not always necessary to provide the flow path enlarged portion 61 on the stationary blade outer diameter wire 4, and in some cases, it may be configured to be provided between the stationary blade inlet portion and the moving blade outlet portion of all the stages. It is done. In this case, the same effect can be obtained.

  In addition, although the case where the stationary blade outer periphery trailing edge radius R1 is substantially equal to the moving blade outer periphery leading edge radius R2 (or the effective outer periphery radius of the moving blade) has been illustrated and explained in the drawings, this condition is shown in the drawings. As long as the velocity component outward in the radial direction of the turbine is suppressed, it does not necessarily have to be satisfied by design. As long as the relative inflow speed of the moving blade is kept below the sonic speed without giving a radially outward velocity component to the flow, it is sufficient if the flow path same diameter portion 60 is provided at least downstream of the stationary blade outer diameter line 4. The relationship between the outer peripheral trailing edge radius R1 and the moving blade outer peripheral leading edge radius R2 (or the moving blade effective length outer peripheral radius) is not necessarily within the range of (Equation 5 ′).

It is sectional drawing showing the basic structure of the turbine stage part of a general axial flow turbine. It is the graph showing the change to the moving blade length direction of the moving blade relative inflow speed of the working fluid with respect to a moving blade. It is explanatory drawing of the principle in which a rotor blade relative inflow speed becomes supersonic in a rotor blade front end side in a turbine stage. It is sectional drawing showing the principal part structure of the axial flow turbine which concerns on one embodiment of this invention. It is a conceptual diagram showing the moving blade relative inflow speed in the axial turbine which concerns on one embodiment of this invention. It is an enlarged view of a rotor blade tip provided with a connection cover. It is explanatory drawing of the axial direction area | region (length) of a flow path same diameter part. It is explanatory drawing of the axial direction area | region (length) of a flow path same diameter part. It is sectional drawing showing the principal part structure of the structural example of the axial flow turbine of this invention which applied this invention only to the turbine last stage. It is sectional drawing showing the principal part structure of the structural example of the axial-flow turbine of this invention which has a moving blade which is not connected with the adjacent blade | wing by the connection cover. It is sectional drawing showing the comparative example of the axial flow turbine of this invention. It is the graph which represented the shape change of the blade length direction of the stationary blade of the axial flow turbine which concerns on one modification of this invention with ratio of throat and pitch. It is a stationary blade sectional view of the axial flow turbine concerning one modification of the present invention. It is a conceptual diagram showing the moving blade relative inflow speed in the axial flow turbine which concerns on one modification of this invention. It is a graph showing the blade direction change of the static pressure between stationary blades. It is a conceptual diagram showing the moving blade relative inflow speed in the inner peripheral side of a moving blade. It is the graph showing the change to the moving blade length direction of the moving blade relative inflow speed of the working fluid with respect to a moving blade. It is the conceptual diagram showing the structure of the stationary blade of the other modification which suppresses the supersonic inflow of the working fluid to a moving blade inner peripheral side. It is sectional drawing showing the principal part structure of the other modification of the axial flow turbine of this invention. It is a graph showing the blade length direction change of the static pressure between stationary blades in the axial turbine which concerns on the further another modification of this invention.

Explanation of symbols

3 Stator blade outlet outer peripheral portion 4 Stator blade outer diameter wire 5 Start end 6 of the same diameter portion of the flow path Stationary body wall surface 6a Stator blade side stationary body wall surface 6b Rotor blade side stationary body wall surface 11 Rotor blade inlet outer periphery portion 12 Connecting cover 14 R portion 21 Turbine Central shaft 41 Stator blade 41 'Stator blade 42 Rotor blade 42' Rotor blade 60 Flow path same-diameter portion 61 Channel diameter-expanded portion 62 Channel diameter-reduced portion 103 Throat 103 Point on the blade negative pressure surface side of throat 105 Pressure face h Height of R part i Maximum blade thickness R1 Blade outer periphery trailing edge radius R2 Blade outer periphery leading edge radius s Blade throat t Valve blade pitch

Claims (13)

In the axial flow turbine having a plurality of paragraphs composed of a stationary blade and a moving blade facing the downstream side in the working fluid flow direction of the stationary blade,
A stationary blade having a radial height of an outlet portion of the stationary blade higher than a radial height of the inlet portion of the stationary blade is such that an intersection line between a surface including the turbine center axis and the outer peripheral portion of the stationary blade is Including a portion extending in the extending direction of the turbine central axis, and
The stationary body wall surface facing the outer peripheral side of the moving blade of the stage having a portion extending in the extending direction of the turbine central axis is located radially outside the portion extending in the extending direction of the turbine central axis,
When the portion of the blade length that effectively functions to convert the working fluid energy into rotational power is defined as the blade effective length, the turbine radial height of the portion extending in the extending direction of the turbine central axis Is an axial flow turbine characterized in that it is set to the height in the turbine radial direction of the outer peripheral portion of the moving blade effective length of the moving blade of the same paragraph. In the axial flow turbine having a plurality of paragraphs composed of a stationary blade and a moving blade facing the downstream side in the working fluid flow direction of the stationary blade,
A stationary blade having a radial height of an outlet portion of the stationary blade higher than a radial height of the inlet portion of the stationary blade is such that an intersection line between a surface including the turbine center axis and the outer peripheral portion of the stationary blade is Including a portion extending in the extending direction of the turbine central axis, and
The stationary blade of the upstream stage with respect to the upstream side of the stage having a portion extending in the extending direction of the turbine central axis is inclined radially outward toward the downstream side of the intersection of the surface including the turbine central axis and the outer peripheral portion of the stationary blade Is formed to
The axial flow turbine characterized in that a portion extending in the extending direction of the turbine central shaft is formed only in the final stage stationary blade. In the axial flow turbine having a plurality of paragraphs composed of a stationary blade and a moving blade facing the downstream side in the working fluid flow direction of the stationary blade,
A stationary blade having a radial height of an outlet portion of the stationary blade higher than a radial height of the inlet portion of the stationary blade is such that an intersection line between a surface including the turbine center axis and the outer peripheral portion of the stationary blade is Including a portion extending in the extending direction of the turbine central axis, and
The portion extending in the extending direction of the turbine central axis extends from the axial position of the point on the suction surface side of the outer peripheral portion of the stationary blade where the distance from the stationary blade adjacent in the circumferential direction is the minimum, or from the upstream side. An axial-flow turbine characterized by that. In the axial flow turbine having a plurality of paragraphs composed of a stationary blade and a moving blade facing the downstream side in the working fluid flow direction of the stationary blade,
A stationary blade having a radial height of an outlet portion of the stationary blade higher than a radial height of the inlet portion of the stationary blade is such that an intersection line between a surface including the turbine center axis and the outer peripheral portion of the stationary blade is Including a portion extending in the extending direction of the turbine central axis, and
In the paragraph including the portion extending in the extending direction of the turbine central axis, the rotor blade tip peripheral speed Mach number obtained by dividing the rotational peripheral speed of the blade tip by the sound speed of the working fluid flowing into the blade tip is 1.0. An axial turbine characterized by exceeding.   5. The axial flow turbine according to claim 2, wherein a portion of the blade length of the moving blade that functions effectively for converting the energy of the working fluid into rotational power is defined as the moving blade effective length. The axial radial turbine characterized in that the turbine radial height of the portion extending in the extending direction of the central axis is set to the turbine radial height of the outer peripheral portion of the moving blade effective length of the moving blade of the same stage.   6. The axial flow turbine according to claim 5, wherein when the moving blade is provided with a connecting cover connected to another moving blade adjacent in the circumferential direction, an effective length outer peripheral portion of the moving blade is connected to the connecting cover. The axial flow turbine is located between the height position of the inner peripheral surface of the turbine and the position on the inner peripheral side in the turbine radial direction by the height of the R portion of the joint portion between the connecting cover and the moving blade. .   6. The axial flow turbine according to claim 5, wherein when the tip of the moving blade is a free end, the outer peripheral portion of the flow path effective range of the moving blade is the tip of the moving blade. .   The axial flow turbine according to any one of claims 1 to 4, wherein when the moving blade is provided with a connecting cover connected to another moving blade adjacent in the circumferential direction at a tip, the portion extending in the extending direction of the turbine central shaft Is a range in which the portion falls between the height position of the inner peripheral surface of the connection cover and the position on the inner peripheral side in the turbine radial direction by the height of the R portion of the connection portion between the connection cover and the moving blade. An axial-flow turbine characterized by having an inclination.   5. The axial flow turbine according to claim 1, wherein a portion extending in the extending direction of the turbine central shaft is formed only in a final stage stationary blade. 6.   5. The axial flow turbine according to claim 1, wherein the stationary blade is upstream of a portion where an intersecting line between a surface including the turbine central axis and the outer peripheral portion of the stationary blade extends in the extending direction of the turbine central shaft. The axial flow turbine is characterized in that it has a portion inclined toward the outer peripheral side in the radial direction of the turbine toward the downstream side.   The axial turbine according to claim 10, wherein the stationary blade passes through the outer side in the turbine radial direction with respect to the intersection of the surface including the turbine central axis and the outer peripheral portion of the stationary blade extending in the extending direction of the turbine central axis. An axial-flow turbine characterized by having a portion for reducing a flow path toward a portion extending in the extending direction of the turbine central shaft.   In the axial turbine according to any one of claims 1 to 4, a value obtained by dividing the minimum gap between the stationary blades adjacent in the circumferential direction by the circumferential interval of the stationary blade is more than the intermediate portion in the blade length direction of the stationary blade. An axial-flow turbine characterized in that the stationary blade is formed so as to be smaller on the outer peripheral side.   5. The axial turbine according to claim 1, wherein the stationary blade is inclined in the moving blade rotating direction toward the outer peripheral side in the turbine radial direction, and the blade length direction intermediate portion protrudes in the moving blade rotating direction. An axial turbine characterized by being curved or bent.

Images