JP2013177816A - Axial-flow turbomachine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a blade row structure of an axial-flow turbomachine with a simple structure which can reduce an exciting force acting on a moving blade at specific stationary blade post-flow frequencies, and decrease a resonant response even when the stationary blade post-flow frequency and a moving blade natural vibration frequency coincide with each other without reducing stage structure efficiency.SOLUTION: An axial-flow turbomachine including a stage structure having a stationary blade row comprising a plurality of stationary blades 3 provided in a circumferential direction, and a moving blade row comprising a plurality of moving blades 4 provided in the circumferential direction on a downstream side of a flow direction of a working fluid of the stationary blades. The stationary blades 3 configuring the stationary blade row are arranged to differ axial positions of stationary blade trailing edges in the circumferential direction so that stationary blade post-flow pitches 14 in a moving blade front edge line 15 are not uniform.

Description

  The present invention relates to a cascade structure of a stationary blade of an axial flow turbomachine.

  The axial-flow turbomachine has a structure composed of a stationary blade and a paragraph composed of a moving blade disposed on the downstream side of the stationary blade.

  The working fluid flowing in from the upstream side of the stationary blade passes through the space between the stationary blades and flows to the upstream side of the moving blade at a predetermined outlet angle. At that time, in a region downstream from the trailing edge of the stationary blade, a region where the speed is low, so-called stationary blade wake, is formed due to the influence of the boundary layer developed on the blade surface of the stationary blade.

  Since the number of stator blade wakes matches the number of stator blades that form the wake, the rotor blades pass through the stator blade wakes by the number of stator blades upstream of the rotor blades as they move around the turbine axis. Will do. At this time, the rotor blades are excited by a fluid excitation force having a stator blade wake frequency represented by the product of the rotational frequency and the number of stator blades.

  If the stationary blade wake frequency and the moving blade natural frequency match, an excessive fluctuating stress is generated in the moving blade due to resonance, and the moving blade may be fatigued. Conventionally, in order to prevent fatigue destruction of the moving blade, a design has been made to detune the wake frequency at the rated rotational speed and the natural frequency of the moving blade.

  In the detuned design, there is a problem that the number of stationary blades that can be selected at the time of design is limited in order to change the stationary blade wake frequency by adjusting the number of stationary blades so as not to coincide with the natural frequency of the moving blade.

  In addition, even if the stationary blade wake frequency and the natural frequency of the moving blade match, the moving blade has sufficient vibration resistance so that the moving blade does not undergo fatigue failure. There are problems such as increased costs and hindering performance improvement.

  As described above, in the stage design of an axial-flow turbomachine, the excitation force acting on the moving blade at the stationary blade wake frequency hinders the increase in material cost and the performance improvement. Is desired.

As a prior art in this technical field, there is JP-A-8-61002 (Patent Document 1).
In Patent Document 1, by providing three types of stationary blades arranged in the circumferential direction of the diaphragm, arranging the stationary blades at different pitches and attaching them to the diaphragm, the steam flow at the trailing edge of the stationary blade is slow. The vane wake generated by the part becomes a mixture of frequencies due to the above-mentioned pitch difference, so that it does not resonate with the natural frequency of the rotor blade by preventing the occurrence of a constant-blade wake wake excitation force. It is described.

Japanese Patent Laid-Open No. 8-61002

  In general steam turbines, a constant vane outflow is maintained at the same blade height cross-section so that the working fluid flowing in from the upstream side of the vane flows out at a predetermined angle so that the stage efficiency does not decrease. Since it is designed to have a corner, the throat / pitch ratio between each stationary blade must also be constant.

  Therefore, when stator blades are installed at a plurality of different pitches in the circumferential direction, each stator blade must have a different shape or installation angle, and the throat pitch ratio between each stator blade must be constant. Can be complicated.

  That is, in Patent Document 1, since three types of stationary blades having different pitches are employed, the stationary blade structure may be complicated and the manufacturing cost may increase.

  Furthermore, when different stator blades are arranged at different pitches in the circumferential direction, the flow rate of the working fluid is not uniform in the circumferential direction on the downstream side of the stator blades, resulting in an unbalanced flow, resulting in reduced paragraph efficiency and It is considered that there is a problem that a vibration problem occurs at a frequency different from the frequency.

  Therefore, the present invention reduces the excitation force acting on the moving blade at a specific stationary blade wake frequency without reducing the paragraph efficiency, and reduces the stationary blade wake frequency and the moving blade natural frequency. It is an object of the present invention to provide a stationary blade structure for an axial-flow turbomachine that can reduce the resonance response even when the values match.

  In order to solve the above-mentioned problems, the present invention comprises a stationary blade row composed of a plurality of stationary blades provided in the circumferential direction and a plurality of moving blades provided in the circumferential direction on the downstream side in the working fluid flow direction of the stationary blades. In an axial-flow turbomachine having a paragraph having a moving blade row, a plurality of stationary blades constituting the stationary blade row are arranged with their stationary blade trailing edge positions shifted from each other by a predetermined interval in the axial direction. Features.

  According to the present invention, a simple structure in which the blade shapes of all the stationary blades are constant, the excitation force acting on the moving blades at a specific stationary blade wake frequency is reduced without lowering the paragraph efficiency, and It is possible to provide a stationary blade structure of an axial-flow turbomachine that can reduce the resonance response even when the blade wake frequency and the blade natural frequency coincide with each other.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is an example of the paragraph structure of a steam turbine. It is an example of the expanded view which looked at the cascade structure of the general stationary blade from the turbine radial direction. It is the expanded view which looked at the example (Example 1) of the stationary blade cascade structure of the stationary blade which concerns on this invention from the turbine radial direction. It is a figure explaining the effect | action of this invention. It is a figure explaining the effect of the present invention. It is the expanded view which looked at the example (Example 2) of the stationary blade row | line | column structure of the steam turbine which concerns on this invention from the radial direction.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, although the Example described below is an example which applied this invention to the steam turbine as an example of an axial flow turbomachine, this invention is applicable not only to a steam turbine but to a gas turbine and a compressor. is there.

  A first embodiment of the present invention will be described. First, an example of a steam turbine to which the present invention is applied will be described.

  FIG. 1 is an example of a paragraph structure of a steam turbine that is an example of an axial-flow turbomachine. In FIG. 1, 1 is an outer ring of a diaphragm, 2 is an inner ring of a diaphragm, 3 is a stationary blade, 4 is a moving blade, 5 is a rotor, 6 is a shroud cover, an arrow indicated by 7 is a flow direction of steam as working fluid, 16 The central axes of the rotor 5 are shown respectively. In addition, as a definition of a direction, it is a turbine axial direction from the drawing left to the right, a turbine radial direction from the bottom to the top, and a circumferential direction from the front to the back.

A general steam turbine includes a stationary blade row that forms an annular flow path by fixing a plurality of stationary blades 3 in the circumferential direction between a diaphragm outer ring 1 and a diaphragm inner ring 2 that are assembled in an annular shape. A stage in which a plurality of blades 4 formed by fixing a plurality of blades 4 in the circumferential direction to the disk portion of the rotor 5 is combined in the axial direction in the axial direction. It has a structure with multiple lines. The diaphragm outer ring 1 is fixed to a casing (not shown) on the outer peripheral side.
Moreover, the outer peripheral side of the moving blade 4 is generally connected and fixed by a shroud cover 6.

  The stationary blade 3 plays a role of rectifying and accelerating the working fluid flowing from the upstream side of the stationary blade 3 in the flow direction. The energy of the working fluid accelerated by the stationary blade 3 is converted into rotational energy by the moving blade 4 to rotate the rotor 5 that is a rotating body. The rotor 5 is connected to a generator (not shown), and generates electricity by the rotation of the rotor 5.

  FIG. 2 is an example of a development view in which the cascade structure of a general stationary blade 3 is viewed from the turbine radial direction. In FIG. 2, 10 is a stationary blade pitch, 11 is a stationary blade throat, 12 is a stationary blade trailing edge, 13 is a stationary blade trailing flow, 14 is a stationary blade trailing flow pitch, 15 is a moving blade leading edge line, and 17 is a blade. The installation angles are shown respectively. The stationary blade trailing edge line 12 here is a line connecting the trailing edge positions of the stationary blades 3, and the moving blade leading edge line 15 is a line connecting the leading edge positions of the moving blades 4. The blade installation angle 17 is an angle between a line connecting the leading edge and the trailing edge of the stationary blade 3 and the rotational direction (circumferential direction) of the turbine.

  In FIG. 2, a stationary blade row is configured by arranging a predetermined number of stationary blades 3 over the entire circumference of 360 °. In this stationary blade row, the stationary blade pitch 10 and the stationary blade throat 11 are arranged on the entire circumference so that the working fluid flowing in from the upstream side in the axial direction flows out from the stationary blade row at a predetermined angle over the entire circumference 360 °. It is constant. Moreover, since the axial position of the stationary blade trailing edge is constant in each stationary blade 3, the stationary blade trailing edge line 12 has a linear shape in the circumferential direction.

  That is, the stationary blade wake 13 formed on the downstream side of each stationary blade 3 also flows out at a constant angle over the entire circumference, so the stationary blade wake pitch 14 when reaching the moving blade leading edge line 15 is At regular intervals throughout the circumference.

  When the frequency at which the moving blade 4 passes through the stationary blade wake 13 at a constant interval matches the natural frequency of the moving blade 4 and the excitation force acting on the moving blade 4 is large, the resonance response increases. Since there is a possibility that the rotor blade 4 may be fatigued and destroyed, there is a problem that it is desired to reduce the excitation force acting at the frequency of the stationary blade wake 13.

  Therefore, the cascade structure of the stationary blade according to the present embodiment, which can reduce the excitation force at the stationary blade wake frequency, will be described.

  FIG. 3 is an example of a development view in which the cascade structure of the stationary blade of this embodiment is viewed from the turbine radial direction.

  As shown in FIG. 3, the present embodiment uses the same shape of the stationary blade 3 at 360 ° in the entire circumference, and periodically changes the installation angles to four types A, AB, B, and BA. In this arrangement, the axial positions of the trailing edges of the stationary blades are different in the circumferential direction. In order to minimize the influence of the unbalanced flow, the stationary blade pitch 10 is set at regular intervals on the entire circumference.

  Here, the axial position of the trailing edge of the stationary blade is varied in the circumferential direction and the working fluid 7 can be allowed to flow out from each stationary blade 3 at a predetermined angle, thereby affecting the paragraph efficiency. In order to obtain a structure that minimizes the above, it is necessary to keep each stationary blade throat 11 at a predetermined length. For this purpose, it is necessary to use at least four types of stationary blades 3 having different installation angles.

  As shown in FIG. 3, in the stationary blade 3 at the installation angle A, as it moves from the top of the drawing to the stationary blade 3 of the bottom of the drawing, the shaft in the blade row from the stationary blade arranged in the most downstream side in the axial direction in the blade row. The axial position of the trailing edge of the stationary blade gradually moves toward the upstream side toward the stationary blade disposed on the most upstream side in the direction. At this time, if the amount of axial movement of the adjacent stationary blade trailing edges is constant, that is, the inclination of the stationary blade trailing edge line 12 is constant, each stationary blade 3 having the same installation angle A can be used. The stationary blade throat 11 of the blade 3 can be maintained at a certain length. Therefore, it is possible to make it possible to allow the working fluid to flow out from each stationary blade 3 at a predetermined angle while moving the trailing edge of each stationary blade 3 in the axial direction.

  Subsequently, in order to return the axial position of the trailing edge of the stationary blade that has moved upstream to the original axial position at the entire circumference of 360 °, the lower position of the stationary blade 3 at the installation angle A is reversed. Of the stationary blade trailing edge from the stationary blade disposed on the most upstream side in the axial direction in the cascade toward the stationary blade disposed on the most downstream side in the axial direction. It is necessary to make the structure such that the position gradually moves downstream. At this time, in order to allow the working fluid to flow out from each stationary blade 3 at a predetermined angle, it is necessary to use the stationary blade 3 having an installation angle B different from the installation angle A. In addition, since the stationary blade 3 with the installation angle A and the installation angle B is switched and the stationary blades 3 having the installation angles AB and BA are used, a total of four types of stationary blades 3 having different installation angles are required. The installation angle AB is an angle that is set in order to smoothly switch from the stationary blade having the installation angle A to the stationary blade having the installation angle B, and is an angle determined by the balance between the installation angles A and B. Similarly, the installation angle BA is an angle set in order to smoothly switch from the stationary blade with the installation angle B to the stationary blade with the installation angle A, and is an angle determined by the balance between the installation angles A and B.

  Here, in the present embodiment, the stationary blades 3 having different installation angles on the entire circumference of 360 ° are arranged in one cycle of A → AB → B → BA → A. For example, A → AB → B → BA → It may be arranged in a plurality of cycles such that A → AB → B → BA → A. Moreover, although four types of stationary blades 3 having different installation angles are used, it is not always necessary to have four types.

  FIG. 4 is a diagram for explaining the operation of this embodiment.

  In the stationary blade structure of the present embodiment, the axial position of the stationary blade trailing edge in each stationary blade 3 is different in the circumferential direction. Therefore, as shown in FIG. It can be seen that the stationary blade wake 13 at the moving blade leading edge line 15 is displaced in the circumferential direction compared to the stationary blade structure in which is constant over the entire circumference.

  That is, in this embodiment, the stationary blade wake 13 flowing into the moving blade 4 is different from the stationary blade structure in which the stationary blade trailing edge pitch 14 is constant along the entire circumference of the stationary blade trailing edge. There are also a plurality of stationary blade wake frequencies calculated from the stationary blade wake pitch 14.

  Next, the effect of the present embodiment will be described. FIG. 5 shows a comparison of the conventional vane structure and the vane structure of this embodiment with respect to the velocity amplitude of the vane wake 13 with respect to the frequency. In addition, about a present Example, it compares about the result at the time of changing the axial direction movement amount of a stationary blade trailing edge into three steps, small, medium, and large.

  As shown in FIG. 5, in the conventional stationary blade structure in which the axial position of the stationary blade trailing edge is not moved, the velocity amplitude is increased only by the stationary blade wake frequency. On the other hand, in the amplitude of the present embodiment for moving the axial position, the velocity amplitude at the stationary blade wake frequency decreases as the amount of movement increases, and velocity amplitude is also generated at other frequency components. .

  Here, if the velocity amplitude of the stationary blade wake 13 at the stationary blade wake frequency decreases, the excitation force acting on the moving blade 4 also decreases. Therefore, by using the stationary blade structure of this embodiment, Even when the flow frequency and the natural frequency of the moving blade coincide with each other, the resonance response can be reduced.

  In addition, according to the present embodiment, the throat pitch ratio is constant, the flow rate of the working fluid can be made uniform in the circumferential direction on the downstream side of the stationary blade, the unbalanced flow is suppressed, and the paragraph efficiency is reduced. Can be suppressed, and a stationary blade having the same shape can be used, so that the manufacturing cost can be reduced.

  Therefore, with a simple structure in which the blade shapes of the stationary blades used in the blade row are the same, while suppressing the decrease in the paragraph efficiency, the excitation force acting on the moving blades at a certain stationary blade wake frequency is reduced, The resonance response can be reduced even when the stationary blade wake frequency and the moving blade natural frequency match.

  Next, a second embodiment of the present invention will be described. FIG. 6 is a view showing the stationary blade structure of the present embodiment in which the axial movement amount of adjacent stationary blade trailing edges is not constant. Here, the same components as those described in the first embodiment are denoted by the same reference numerals, description thereof is omitted, and portions different from those in the first embodiment are described.

  In FIG. 6, since the stationary blade trailing edge has a different stationary blade structure in the circumferential direction, the same effect as the embodiment described above can be obtained. However, the difference from the first embodiment is that the amount of axial movement of the adjacent stationary blade trailing edge is not constant, and the inclination of the stationary blade trailing edge line 12 is not constant.

  Here, in order to minimize the reduction in the paragraph efficiency, the length of the stationary blade throat 11 is adjusted by each stationary blade 3 so that the working fluid 7 can flow out at a predetermined angle as in the first embodiment. It is necessary to.

  In the present embodiment, since the stationary blade pitch 10 is constant and the axial movement amount of the stationary blade trailing edge is not constant, the stationary blades 3 having the same installation angle are simply arranged adjacent to each other as in the first embodiment. Then, the length of the stationary blade throat 11 cannot be kept constant.

  In order to keep the length of the stationary blade throat 11 constant, it is necessary to change the shape of each stationary blade 3 or to change the installation angle of each stationary blade 3, but when the shape of each stationary blade 3 is changed, Since an unbalanced flow may occur on the downstream side of the stationary blade 3, the present embodiment has a stationary blade structure in which the installation angle of each stationary blade 3 is changed.

  However, if the axial movement amount of the adjacent stationary blade trailing edges is too large, not only the installation angle of the stationary blade 3 needs to be significantly changed, but also the stationary blade throat 11 moves to the upstream side of the blade, Performance may be degraded, which is not desirable.

  Therefore, the axial movement amount of the stationary blade trailing edge is larger than the stationary blade manufacturing tolerance of a general axial flow turbomachine so that the interval of the stationary blade wake pitch 14 becomes non-uniform, and It is desirable that the stationary blade throat 11 be within a range that does not move too far upstream of the stationary blade 3.

  As an advantage of the present embodiment, since the axial movement amount of the stationary blade trailing edge is not constant, a larger number of different stationary blade wake pitches 14 are formed compared to the first embodiment. The frequency can also be varied to many frequencies.

  That is, since the velocity amplitude of the stationary blade wake 13 at the stationary blade wake frequency is reduced as compared with the first embodiment, the excitation force at the stationary blade wake frequency acting on the moving blade 4 can be further reduced. It becomes.

  Further, in this embodiment, since the shape of each stationary blade 3 is the same as that of the known example in which the stationary blades are installed at a plurality of different pitches in the circumferential direction, the working fluid 7 of the stationary blade 3 is the same. Since the unbalanced flow on the downstream side can be suppressed, there is an advantage that not only performance degradation can be minimized, but also manufacturing is easy.

  As mentioned above, although the Example of this invention was described, this invention is not limited to an above-described Example, Various modifications are included. For example, in FIG. 3 of the first embodiment, all the stationary blades 3 have a structure in which the axial position of the stationary blade trailing edge is different, but it is not necessarily different in all the stationary blades, and in a certain region in the circumferential direction. A composite structure in which the axial position of the trailing edge of the stationary blade is the same and the axial position of the trailing edge of the stationary blade is different in different regions as shown in FIG. In short, it is effective if the stator blade 3 having a different axial position of the trailing edge of the stator blade is included.

  In the embodiments of the present invention, the diaphragm-structured steam turbine has been described as an example. However, the present invention is not limited to the diaphragm-structured steam turbine. It is done.

DESCRIPTION OF SYMBOLS 1 Diaphragm outer ring 2 Diaphragm inner ring 3 Stator blade 4 Rotor blade 5 Rotor 6 Shroud cover 10 Stator blade pitch 11 Stator blade throat 12 Stator blade trailing edge 13 Stator blade trailing flow 14 Stator blade trailing pitch 15 Rotor leading edge 16 Rotor Center axis

Claims (2)

A shaft provided with a paragraph having a stationary blade row composed of a plurality of stationary blades provided in the circumferential direction and a moving blade row composed of a plurality of moving blades provided in the circumferential direction on the downstream side in the working fluid flow direction of the stationary blades A flow turbomachine,
A plurality of stationary blades constituting the stationary blade row are arranged such that the stationary blade trailing edge positions are shifted from each other by a predetermined interval in the axial direction. An axial-flow turbomachine according to claim 1,
The stationary blade row is installed at different installation angles depending on the axial position of the stationary blade trailing edge so that the stationary blade trailing edge interval and the stationary blade throat length of adjacent stationary blades are constant over the entire circumference. An axial-flow turbomachine characterized by