JPS62251405A - Water drip fining device for steam turbine - Google Patents

Abstract

PURPOSE:To promote the reduction of erosion in a moving blade, by setting mutually opposed vibrators in a diaphragm and a supporting ring, which support stationary blade, and generating a stationary ultrasonic wave. CONSTITUTION:Vibrators 9', 9 are respectively set to a diaphragm 2 and a supporting ring 3, which support a stationary blade 1, and the vibrators 9', 9 are opposed to each other. While the vibrators 9, 9' are connected with a high frequency power source through high frequency power cables 11, 11', 12, 12'. And a stationary ultrasonic wave, which is generated between the vibrators 9, 9', makes fine a water drip jetted from a trailing edge of the stationary blade 1. In this way, erosion in a moving blade 4 can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a turbomachine that undergoes a phase change such as a steam turbine, and is particularly suitable for reducing the size of water droplets generated in a working fluid. This relates to a miniaturization device.

[Prior art] - In general, the low-pressure stage of a steam turbine and all stages of a nuclear power turbine are operated under humid steam conditions, so a considerable amount of water droplets are generated in the internal working steam, and furthermore, these water droplets are Collision with channel walls or wing surfaces.

Under the effects of accumulation, crushing, etc., it grows into coarse water droplets with a size of several tens of microns to several hundreds of microns. In this process, the steam dissipates energy due to the acceleration and atomization of water droplets, increasing the so-called wetness loss. In addition, there are many problems in terms of performance and reliability, such as when coarse water droplets collide with the rotor blades rotating at high speed, causing corrosion due to the two lotions.

Here, with reference to FIGS. 11 and 12, a brief explanation will be given of the erosion phenomenon and moisture loss caused by two lotions on turbine rotor blades due to the generation of water droplets.

FIG. 11 shows the stationary blade 1 and the diaphragm 2 that holds it.
and support ring 3. Moving blade 4 and disk 5 that holds it
A typical steam turbine stage structure consisting of
The figure is a view taken along arrow I-1 in FIG. 11. Some of the water droplets generated by condensate impact and flowing down the paragraph become static due to inertia force.
1 and 1' and are collected and accumulated to form a water film flow 6. This water film flow 6 behaves in a complicated manner on the blade surface, and jets out as a water mass 7 from the trailing edge of the stationary blades 1, 1'.
Coarse water droplets 8 are formed. For this reason, so-called moisture loss increases, such as requiring energy for jetting and accelerating water droplets. Furthermore, the coarse water droplets 8 reach the rotor blades 4, 4' without being sufficiently accelerated. Figure 12 shows velocity triangles for steam and water droplets. If the velocity v4 of water droplets is small compared to the absolute velocity Vs of steam at the exit of the stationary blade 4,
．． The relative velocity Ws of the steam flowing into 4' and the relative velocity W4 of the water droplets have the directions and magnitudes as shown in the figure from the relationship with the circumferential velocity U. That is, the water droplets 8 are at a velocity Wa greater than the steam velocity Ws with respect to the rotor blades 4, and
′ collides with the rear side. Due to this, the rotor blades 4, 4
Erosion action will occur at the inlet of the hole.

Performance and reliability are caused by such coarse water droplets.

One of the conventional methods to solve this problem is to use ultrasonic waves to make water droplets smaller.

For example, Japanese Patent Application Laid-Open No. 51-12005 discloses that an ultrasonic generator is arranged on the outer periphery of an inner casing to which stationary blades are fixed, and ultrasonic waves are propagated from this ultrasonic generator in the radial direction into the paragraph. This is to make the water film flow and coarse water droplets on the blade surface finer. However, the coarse water droplets within the paragraph flow in a spatially dispersed manner, and it is difficult to effectively refine the coarse water droplets using ultrasonic waves.

[Problem that the invention seeks to solve]

In the above-mentioned conventional technology, the ultrasonic waves generated from the ultrasonic generator are transmitted through the inner casing and propagated into the paragraph, but the propagation efficiency of the ultrasonic waves into the paragraph is low because the specific acoustic impedance of the steam is very small. In order to miniaturize the water droplets ejected from the trailing edges of the stator blades, which are directly involved in the erosion of the turbine rotor blades, a huge amount of power had to be supplied to the ultrasonic generator. .

In addition, in the above-mentioned conventional technology, it is possible to use an ultrasonic generator to vibrate the inner casing itself with ultrasonic waves and propagate the ultrasonic waves within the paragraph, but in order to vibrate the casing itself, it is still necessary to use an ultrasonic generator. The problem was that large amounts of power had to be supplied to the

An object of the present invention is to provide a steam turbine that can efficiently atomize water to reduce the erosive effect of turbine rotor blades due to erosion, and that has less energy loss.

[Means for solving problems]

In order to solve the above-mentioned problems and achieve the above-mentioned purpose (to efficiently miniaturize water droplets), the present invention provides a diaphragm having stator blades arranged in rows on its outer periphery, and a diaphragm in which moving blades are arranged in rows on its outer periphery. a support ring that supports one end of the stationary blade and faces the blade tip of the rotor blade; and a casing that surrounds each of the components described above; A vibrator is installed on one of the members fixed to the support ring, a vibrator is installed on either one of the support ring and the member fixed to it, both of the vibrators are installed, and both of the above oscillators facing each other, and means for applying an alternating voltage with a frequency in the ultrasonic range to at least one of the two oscillators to generate an ultrasonic standing wave between the two oscillators. In the device of the present invention configured as described above, when an ultrasonic standing wave is generated by both of the opposed vibrators, the trailing edge of the stationary blade When coarse water droplets ejected from the space pass through a space where the above-mentioned standing waves of ultrasonic waves are generated, the coarse water droplets are made fine by the strong standing waves of ultrasonic waves. Thereby, the speed difference between the steam flow and the water droplets can be reduced, and the erosion effect and energy loss caused by the 20-johns on the turbine rotor blades can be reduced.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to FIGS. 1 to 14.

FIG. 1 shows an example in which the present invention is applied to one stage of a typical steam turbine, showing a stator blade 1, a plurality of diaphragms 2 supporting the vanes, and a support ring 3. The main components such as the rotor blades 4 and the rotating disks 5 on which a plurality of rotor blades are fixed are the same as those of the conventional example shown in FIG. At a downstream position of the stationary vane 1 in the ring 3, vibrators 9.9' made of piezoelectric elements or the like are arranged in opposing manner, as shown in FIG. The vibrators 9, 9' are connected to the stator blade support ring 3. static wing 1
, and high frequency power all, 11' through the insulating hole 17 provided in the diaphragm 2.

12 and 12', it is configured to be connected to a high frequency power source located outside the casing (not shown).

In this patent, an ultrasonic standing wave is generated in the space between the vibrators 9 and 9' shown in FIG. 1, and coarse water droplets ejected from the trailing edge of the stationary blade 1 are made fine by the ultrasonic standing wave.

When a standing ultrasonic wave is generated, the intensity of the ultrasonic wave can be significantly increased compared to a steady traveling wave even if the power supplied to the transducer is constant. The conversion efficiency can be greatly improved.

Next, a method for generating an ultrasonic standing wave will be explained with reference to FIG. Figure 2 shows a vibrator 9°9', a high frequency power source 10.10' and a high frequency power line 11.11', 1
2.12' is a basic configuration diagram of the present patent.

The vibrators 9 and 9' are arranged facing each other with a distance between the vibrators.

It vibrates at a high frequency in the direction of arrows 16 and 16' shown in the drawing due to the high frequency power from the high frequency power source 10 and 10'. The high-frequency vibrations of the vibrators 9 and 9' generate ultrasonic waves 14 in the space where the vibrators 9 and 9' face each other. This ultrasound 1
4 generates an ultrasonic standing wave 15 at a certain frequency.

The conditions under which the ultrasonic wave 14 generates the standing wave 15 are expressed by the following equation.

Here, f is the frequency, C is the sound speed of the ultrasonic wave, L is the distance between opposing transducers, and n is a positive integer. The above formula means that a standing wave is generated when the distance between opposing oscillators is an integral multiple of the wavelength of the ultrasonic wave, and as shown in Figure 1, it is applied to the inside of a steam turbine stage. In the case, the oscillator 9.
Since the distance between the transducers 9' and the sound speed of the ultrasonic waves are known, by adjusting the high frequency applied to the transducers 9 and 9' so as to satisfy the condition of equation (1), the transducers 9 and 9' It is possible to generate a standing ultrasonic wave in the space between them.

For example, if the frequency is 500 KHz and the sound speed of the ultrasonic wave is approximately 340 m/s, the 1/4 wavelength of the ultrasonic wave is 0.17 mm, so even if the frequency is constant, the oscillators 9 and 9
If ' is moved within this range, it is possible to generate an ultrasonic standing wave between the transducers 9 and 9'.

Figure 3 shows the relationship between the frequency applied to the transducer 9.9' and the intensity of the ultrasonic wave generated from the transducer 9.9', with the horizontal axis representing the applied frequency f and the vertical axis representing the applied frequency f. Fo is the resonance frequency of the vibrator 9°9', Io is the strength of the ultrasonic wave at that time. As is clear from FIG. 3, even if the power supplied to the vibrators 9 and 9' is constant, the vibrator 9,
At a resonant frequency fo of 9', the intensity of the ultrasonic wave increases rapidly as Io. Therefore, if the resonance frequency of this vibrator 9.9' is configured to match the fast wave number f at which the ultrasonic standing wave is generated in equation (1), the intensity of the ultrasonic standing wave can be made even stronger. This makes it possible to improve the efficiency of water droplet miniaturization.

FIG. 4 is an enlarged view of the trailing edge of the stationary blade 1 shown in FIG. 1, showing the vibrator 9 disposed on the support ring 3. A vibrator 9' placed on the diaphragm 2 (not shown) is molded with an insulating waterproof agent made of epoxy resin or the like, and placed on the support ring 3 and the diaphragm 2.

A high frequency power source (not shown) whose frequency and applied voltage can be arbitrarily set is provided outside the casing, and the high frequency power line 11.11
', 12.12' to apply a high frequency voltage to the vibrator 9.9'. Adjust the frequency of the above high frequency power to mr as appropriate.
A standing wave 15 of ultrasonic waves is generated.

What does it mean to have the vibrators 9 and 9' facing each other?

This means that the other transducer is located within the reach of the ultrasonic waves generated by the other transducer, and does not necessarily have to be strictly geometrically facing each other.

The key is to face a situation that can generate a standing wave.

Since high-speed steam is flowing in the space where the above-mentioned standing waves are generated, there may be cases where the phenomenon of ultrasonic waves flowing cannot be ignored. In such a case, it is desirable to install the vibrator in advance in a direction biased toward the upstream side so that the ultrasonic waves carried by the steam flow reach the other vibrator.

On the other hand, the water droplets collected on the ventral surface of the stationary blade 1 accumulate to form a water film flow 6, which flows down along the ventral surface.

The water film that has reached the trailing edge becomes a water mass 7 from the trailing edge of the stationary blade l and is ejected into the steam to form coarse water droplets 8. When this coarse water droplet 8 passes through a space where the above-mentioned ultrasonic standing wave 15 is generated, the strong ultrasonic standing wave 15 causes
Negative pressure is generated in the liquid of the coarse water droplets 8, and voids are generated. This bubble is compressed by the compression phase of the sound pressure of the ultrasonic wave, and when the radius exceeds a certain radius, it does not disappear and vibrates within the sound field, that is, within the coarse water droplet. The stomata may collapse during this vibration.

At this time, a shock wave is generated, and a large force acts locally on the coarse water droplet. When the large force generated by this shock wave becomes larger than the surface tension of the coarse water droplets 8, the coarse water droplets 8 become fine and form minute water droplets 19. In general, the diameter of water droplets ejected from the trailing edge of the stationary blade 1 is reduced when the above-mentioned miniaturization means are not applied.

The diameter of these water droplets is from several tens of microns to several hundred microns, but according to this embodiment, the diameter of these water droplets can be easily reduced to several microns or less. On the other hand, FIG. 5 shows the water droplet velocity V with respect to the water droplet diameter D-.
When the water droplet diameter D-, which shows the relationship between , and the steam velocity Vs, becomes less than 10-odd microns.

The difference between the steam flow velocity Vs and the water droplet velocity v4 becomes smaller, in other words, water droplets smaller than 10 microns follow the steam streamlines, so collisions with the downstream rotor blades 4 are significantly reduced, resulting in erosion and braking loss. Problems that impair performance and reliability can be alleviated.

FIG. 6 shows a second embodiment of the present invention. In the first embodiment, the vibrator 9 is attached to the stator blade support ring 3, and
′ are arranged facing the diaphragm 2, and the vibrator 9
, 9', but the ultrasonic standing wave 15 was generated between 6th and 9'.
In the illustrated embodiment, Shizurei Kobari 11'/ /f Q +-
io -1+-value-eO+-'46-h x 4ts The rotor 20 is arranged on the vibrator support plate 23 provided at any position in the radial direction of the trailing edge of the stator blade 1. . FIG. 7 is an enlarged perspective view of the vibrator support plate 23 portion of FIG. 6. As shown in FIG. 7, the shape of the vibrator support plate 23 is preferably approximately streamlined in order to reduce fluid loss. in general.

The blade length range in which the erosion phenomenon of steam turbine rotor blades occurs is as follows:
It is known that the distance is about 1/4 of the blade length from the tip of the rotor blade. The reason may be as follows. Since the water film flow 6 shown in FIG. 7 flows toward the radial outer circumference side due to the radial component of the steam flow, the amount of water that accumulates on the ventral side of the radial outer circumference side of the stationary blade 1 increases, and is ejected from this position. The number density of coarse water droplets increases. Therefore, as shown in FIG. 8, the humidity level Y, which is one of the causes of rotor blade erosion, increases near the tips of the stator blades, and as a result, as described above.

Erosion concentrates in a quarter of the tip of the rotor blade. Furthermore, since the circumferential speed at the tip of the rotor blade increases, the collision speed with water droplets increases, which is thought to promote erosion of the rotor blade. On the other hand, in general, ultrasonic waves are attenuated when they propagate through the air, and their intensity decreases in inverse proportion to the square of the propagation distance. For the reasons mentioned above, the vibrator support plate 23 shown in FIG.
If we generate an ultrasonic standing wave with a resonance frequency of ゜23,
Coarse water droplets ejected from the trailing edge of the stationary blade 1 can be made finer more efficiently. Further, in this embodiment, the vibrator 20 is arranged on the vibrator support plate 23, but the vibrator 20 is omitted, and the ultrasonic waves from the Il oscillator 9 and the ultrasonic waves reflected on the vibrator support plate 23 are A configuration in which a standing ultrasonic wave is generated between the vibrator 9 and the vibrator support plate 23 is also effective in making coarse water droplets fine.

As can be easily understood from the above example, the term "oscillator" in the present invention includes both a member that is supplied with electromagnetic energy and projects ultrasonic waves, and a member that receives and reflects ultrasonic waves. be.

FIG. 9 shows a third embodiment of the present invention.

In the second embodiment, the ultrasonic standing wave is projected in the radial direction, but in the third embodiment, the ultrasonic standing wave is generated in the circumferential direction. FIG. 10 is a sectional view taken along the line ■-■ in FIG. 9. In the third embodiment, in order to generate a standing ultrasonic wave in the circumferential direction, a vibrator 24 extending radially on the ventral and dorsal sides of the stationary blade 1 is used.
．． Place 25. The vibrators 24 and 25 are configured in a plate shape.

They are molded with an insulating waterproof agent 26, 27 such as epoxy resin, and fixed to the stator vane 1.1' in such a manner that they face each other like vibrators 24, 25 shown in FIG. Vibrator 24.
25 may be placed at relatively opposing positions,
It is clear that there is no need to limit its location. A high frequency power source outside the casing applies a frequency to the vibrator 24.25 that is the resonant frequency of the vibrator 24.25 and that generates an ultrasonic standing wave between the vibrator 24.25, Between the vibrators 24 and 25, that is, between the stator blades 1 and 1
' generates an ultrasonic standing wave in the circumferential direction of the stationary blades 1, 1.
By making the coarse water droplets passing through the flow path between the rotor blades finer, it is possible to reduce erosion of the rotor blades and energy loss, improve performance, and provide a highly reliable steam turbine.

The material of the vibrator used in the first to third embodiments of the present invention is as follows:
As described above, a piezoelectric element, an electrostrictive element, or the like is used.

A piezoelectric element or an electrostrictive element has a critical temperature called the Curie point at which it loses one polarization and piezoelectricity.

Therefore, when these elements are used in a turbine casing as in the present invention, it is necessary to use elements that have a single Curie point higher than the ambient temperature.

For example, the curri point of barium titanate is approximately 120°C, so it cannot be used at very high temperatures, but lead zirconate titanate has a curri point of over 200°C, so it can be used in hot water. . In any case, since the atmospheric temperature in the stage where the working steam becomes wet steam containing water droplets in the steam turbine low pressure stage is 100°C or less,
As the vibrator of the present invention, barium titanate, lead zirconate titanate, etc. can be used.

Further, since barium titanate is porcelain, it has the advantage that it can be sintered into any shape.

Here, to briefly describe the directivity of ultrasonic waves, the directivity of ultrasonic waves is generally very good, and the opening angle θ of the ultrasonic waves is expressed by the following equation.

Here, λ is the wavelength of the ultrasonic wave, and R is the radius of the sound source, that is, the vibrator. Equation (2) shows that if the wavelength λ is smaller than the radius R of the transducer, θ will also be smaller, which means that the ultrasonic waves have sharp directivity.As in this patent, the wavelength of high-frequency sound waves can be made very short. Therefore, the directivity of the ultrasonic waves generated from the vibrator becomes very sharp, which makes it easy to focus powerful ultrasonic waves, which is advantageous for making water droplets smaller.

In addition, in order to further focus the ultrasonic waves and improve the water droplet miniaturization efficiency, the shape of the vibrator 9 shown in FIG. 4 is formed into a substantially cylindrical shape as shown in FIG. A shaped groove 28 is formed. When the vibrator 9 vibrates in the thickness direction of the vibrator 9 as shown by the arrow 16, the ultrasonic waves generated from the vibrating surface 29 of the vibrator 9 are emitted so as to be focused at a certain point as shown by the arrow 30. Therefore, if the hemispherical groove 28 is formed by taking into account the aperture angle θ of the ultrasonic waves in equation (2) described above, it becomes possible to project ultrasonic waves without an aperture angle, which improves the efficiency of water droplet miniaturization. It is valid. Also, the 14th vibrator
If the vibrator is formed into a hammer-shaped bow-shaped vibrator 31, 32 as shown in the figure, it will be more effective in reducing the size of water inside the casing of a steam turbine. FIG. 15 shows an example in which the cubic vibrators 31 and 32 shown in FIG. 14 are applied to miniaturize water droplets inside a steam turbine. That is, the oscillator 31 of the aircraft shadow is arranged at a position downstream of the stator blade of the stator blade support ring 3, and the volume-shaped oscillator 32 is placed opposite the position downstream of the stator blade of the diaphragm 2, and the hammer-shaped oscillators 31, 32 A standing wave of ultrasonic waves is generated in the space between the two, and the water droplets that pass through it are miniaturized. @Figure 16 is a sectional view taken along ■-■ in Figure 15, where the cubic vibrator 31°32 is extended in the circumferential direction as shown in the figure.
The cubic transducers 31 and 32 are formed to generate a planar ultrasonic standing wave downstream of the plurality of stator blades.

These cubic vibrators 31 and 32 are arranged around the entire periphery of the diaphragm 2 and the support ring 3, and the adjacent cubic vibrators 31 and 32
If configured to be connected in parallel to the high frequency power [33°34], it is possible to reduce the number of high frequency power lines 11, 12 and insulation holes 17 for applying high frequency power to the monolithic oscillators 31, 32. At the same time, it is possible to generate a standing ultrasonic wave around the entire circumference of the steam turbine, which is more effective in making the water droplets inside the steam turbine smaller, reduces rotor blade erosion and control loss, and provides high performance and reliability. It becomes possible to provide a steam turbine device.

〔Effect of the invention〕

As described in detail above, the water droplet atomization device for a steam turbine according to the present invention prevents corrosion of rotor blades due to the lotion present inside the casing of a turbomachine such as a steam turbine that undergoes a phase change of steam. This has the effect that water droplets that cause braking loss, particularly coarse water droplets ejected from the trailing edge of the blade row of a turbomachine, can be efficiently miniaturized with low power.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the structure of the first embodiment of the present invention, Figure 2 is an explanatory diagram of the basic configuration of the present invention, and Figure 3 is for explaining the intensity of sound waves at the resonance point of the vibrator. Figure 4 is a partially enlarged view of Figure 1, Figure 5 is an explanatory diagram showing the relationship between water droplet diameter and its velocity, and Figure 6 shows the structure of the second embodiment of the present invention. 7 is a partially enlarged perspective view of FIG. 6, FIG. 8 is a chart showing the relationship between blade length and humidity, and FIG. 9 is a sectional view showing the structure of the third embodiment of the present invention. , Fig. 10 is a diagram showing the flow situation inside the stage of a conventional steam turbine similar to the ■-■ arrow view in Fig. 9, and Fig. 12 is the 1-1 arrow view in Fig. 11. It is a diagram. FIGS. 13 and 14 are explanatory diagrams of vibrators in different embodiments from those described above, respectively. 1.1'... Stationary blade, 2... Diaphragm, 3...
Support ring, 9.9', 20.24, 31.32...
- Vibrator, 11.12...High frequency power line, 13...
Transducer spacing, 15...Ultrasonic standing wave. Haku1mokusuji 2 Zushi. Nad- Horse Figure 6 Right 1st Ward High 11th Figure 13 (A) (
3) Bleaching 14 stitches (A) (B) z

Claims (1)

[Scope of Claims] 1. A diaphragm with stator blades arranged in rows on its outer periphery, a disk with rotor blades arranged in rows on its outer periphery, and a blade tip of the rotor blade that supports one end of the stator blade. A steam turbine comprising a support ring facing the diaphragm and a casing surrounding each of the above-mentioned components, in which a vibrator is installed on either the diaphragm or the member fixed thereto, and the support ring and A vibrator is installed on either one of the members fixed to this, both of the vibrators are made to face each other, and an alternating voltage having a frequency in the ultrasonic range is applied to at least one of the two vibrators. A water droplet atomization device for a steam turbine, characterized in that a means is provided to generate an ultrasonic standing wave between both of the vibrators. 2. Both of the opposed vibrators have at least one
It is arranged near the rear end of the row of stator blades of the paragraph, and is characterized by being configured to generate a standing wave of ultrasonic waves over the entire circumference of the row of stator blades arranged in rows around the outer periphery of the diaphragm. A water droplet atomization device for a steam turbine according to claim 1. 3. The water droplet atomization device for a steam turbine according to claim 1 or 2, wherein the vibrator uses a piezoelectric element.