JPS61149804A - Detecting method of moving blade position of axial flow turbo machine - Google Patents

Abstract

PURPOSE:To prevent a position shift and a contact accident by fitting plural arrays of diffraction gratings on the shroud surface of the tip of a moving blade, irradiating those diffraction gratings with laser light, and measuring the frequency of diffracted light and detecting the position of the moving blade. CONSTITUTION:Diffraction grating arrays 4 which differ in grating interval in the axial direction A are provided on the top surface of the shroud of the tip part of the moving blade 1 implanted in a disk 2, and the laser light 8 from a light source 5 is made incident on those diffraction grating arrays in a peripheral direction through an optical fiber 6 and a light emitting device 7. Then, the diffracted light 9 is photodetected by a photodetector 10, whose output is inputted to a frequency analyzer 13 through the optical fiber 6 and a photomultiplier 11. When the shroud 3 moves in the axial direction A, the irradiated diffraction grating 4 also shifts in position and the diffracted light varies in frequency, so the quantity of this variation is analyzed by the analyzer 13 to calculate the gap between a stationary part and a rotating part in the axial direction A. Further, light is made incident on the diffraction gratings 4 in the axial direction as well and then the deviation of the rotating part in a radial direction B is also detected from variation in the frequency of said diffracted light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention provides a method for detecting axial and radial position changes in wJ of an axial flow turbomachine in ms+=.
This invention relates to a position detection method.

[Technical background of the invention and points of interest]

Generally in axial flow turbo dA machines, the fi! During movement and when stopped, a relative displacement occurs in the axial direction between the casing held by the stationary part and the rotor held by the rotating part.

This relative misalignment is generally due to the circumference v! of the casing and rotor. This is thought to be due to differences in A temperature, coefficient of expansion, coefficient of heat transfer, thermal conductivity, or heat capacity. Also, during operation, the IdJJ! Since t receives centrifugal stress and thermal stress, it expands in the radial direction C2.

In this way, the relative misalignment that occurs between the casing and the rotor and rotor blades causes the tip fins to deteriorate.

Contact is caused at the shroud, labyrinth packing, etc. As a result, if the vibrations in the axial flow turbomachine increase and become too loose, there is a risk of causing accidents such as damage to contact parts. In order to avoid such accidents, there is a method of designing the gaps between each part to be larger, but this method increases the amount of working fluid that does not pass through the rotor blades and does not participate in the process, resulting in a decrease in efficiency. descend. Therefore, in order to improve the performance and reliability of axial flow turbomachines, it is necessary to reduce the gaps between each part as much as possible and constantly monitor changes in the gaps.

Until now, as a method of monitoring the gap, a laser beam is irradiated at a predetermined distance from the inner surface of the casing of an axial flow turbomachinery parallel to or nearly parallel to the rotation axis, and the tip of the rotor blade is checked to see if the tip of the rotor blade crosses the laser beam or not. A method for monitoring the size of the gap: A light emitter and a sensor that receives the light emitted from the light emitter and reflected at the tip of the rotor blade are installed on the inner wall of the casing, and the size of the gap at the tip of the rotor blade is monitored via this sensor. Methods to do this have been proposed. However, with these methods, it is impossible to detect any change in the gap in the axial direction, so contact accidents due to positional deviation in the axial direction cannot be avoided. Furthermore, the above-mentioned method cannot reveal the change in the gap in the radial direction in detail.

stomach.

[Purpose of the invention]

An object of the present invention is to provide a method for detecting the position of a rotor blade in an axial flow turbomachine, which can detect changes in the gap in the axial and radial directions between the stationary part and the rotating part of the axial flow turbomachine. It is in.

[Summary of the invention]

The method for detecting the rotor blade position of an axial flow turbomachine according to the present invention is #
A plurality of rows of diffraction gratings exhibiting a light reflecting function with different grating spacings depending on the axial position are installed on the shroud surface of the cutting tip, and these diffraction grating rows (using optical fibers from a laser light source device installed outside the knee machine) are installed on the shroud surface of the cutting tip. C; irradiate the inside of the machine with a laser beam of ζ2 degrees and measure the frequency of the diffracted light;
Therefore, the present invention is characterized in that the moving blade position can be detected.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on an embodiment ζ shown in the drawings. 1181 and 2, where the a-wing position detection method of the present invention is applied, -XI
is embedded in a disk 2 that is integrated with or fitted into a rotor (not shown). The tip of #wing 1 is connected to shroud 3
ζ; Therefore, it is bordered.

Mounted on the upper surface of the shroud 3 are diffraction grating arrays 4 having different grating intervals depending on their axial positions.

Here, the diffraction grating array 4 is a glass or metal plate with extremely finely spaced lines (thousands of lines/cIL) carved into it, and the flat area between the green and the lines emits light. reflect.

The difference in the grating spacing depending on the axial position is shown by the black and white bands on the diffraction grating 4 in Figure 41. For example, the diffraction grating 4a
The grating spacing is the finest, from diffraction grating 4b to grating 4e.
, a case in which the intervals become coarser as the grid progresses to 4d is shown.

On the other hand, the laser light emitted from the laser light source device 5 is guided to the light emitter 7 in the turbine by the optical fiber 642,
Furthermore, the diffraction grating 4 on the upper surface of the Nishroud 3 is irradiated. The irradiated laser light is reflected in the direction of mutual reinforcement due to interference ζ2. d, the incident angle of the laser beam is β, the reflection angle is β', and the wavelength of the laser beam is λ.The condition for mutual reinforcement due to interference is when the optical path difference is an integral multiple of the wavelength of the laser beam, so djcoaβ- d-coISβ/ = nλ (n ・
-・via ) ...(1). Diffracted light 9 is generated in the direction β' where equation (1) holds true.

Furthermore, since the diffraction grating 4 moves once with the shroud 3, the frequency of the diffracted light is shifted by the Doppler effect. That is, in FIG. 3, if the C1 frequency, which is the velocity of the incident light 8, is f1, and the frequency of the diffracted light 9 is f', and the moving speed of the diffraction grating 4 is V, then the frequency f' of the diffracted light due to the Doppler effect is "=c-" v, cos7s":8F(1+"cos〆)i =1+÷cos/' (2).The condition for mutual reinforcement due to interference is that when the diffraction grating is stationary, ), but when the diffraction grating rotates and the frequency of the diffracted light shifts, it is expressed by the following equation (wavelength of λ' second diffraction).

dcosβ=nλ, dcosβ'=nλ'
・-・-・13) Substitute equation (3) into equation (2) C2 and get [f
If i, then it becomes. If the frequency f of the incident light and the moving speed V of the diffraction grating are constant, it can be said that the frequency f' of the diffracted light changes depending on the grating spacing d for diffracted light of the same order (n is equal).

That is, in FIG. 1 C2, the upper surface of the shroud 3 (;
is the axial peer i! Since the diffraction gratings 4 with different grating spacings are installed, when the shroud 3 of the rotating part moves in the axial direction C2 with respect to the stationary part where the light emitter 7 is installed, the position of the diffraction grating 4 that is irradiated changes. moves, and as a result, the frequency of the diffracted light also changes. By adjusting the amount of change in frequency to the needle side, the axial gap between the stationary part and the rotating part can be determined.

In FIG. f11 and FIG. 2 C2, the diffracted light 9 is received by a light receiver 10, and is made to enter a photomultiplier tube 11 provided in an external device of the machine via an optical fiber 6.

The frequency of the diffracted light is very large (on the order of 10” Hz), and it is not possible to analyze the frequency up to t.
A heterodyne detection method is used to find the difference in Jif numbers between two beams of light. That is, the frequency-shifted diffracted light 9 and the reference source branched from the laser light source t device 5 are made to enter the photomultiplier tube 11 . Among the outputs of the photomultiplier tube ■, those with a frequency similar to that of light are attenuated and do not appear due to the characteristics of the photomultiplier tube 11, and as a result, components with a difference in frequency between the diffracted light beam 9 and the reference source stop appear. can get. This signal is passed to the frequency analyzer 13
By applying human power, it is possible to determine the magnitude of the frequency deviation of the diffracted light 9 and also to determine the distance of 1 m in the axial direction.

That is, in FIG. 1, the incident light 8 to the diffraction grating C2 is incident on the diffraction grating 4b, but when it enters the diffraction grating 4al due to the axial deviation of the one rotation part, the diffraction occurs. The frequency of the light 9 changes greatly from that when it is incident on the diffraction grating 4b. Therefore, by manually inputting this signal to the frequency analyzer 13, the magnitude of the frequency deviation of the diffracted light 9 can be determined, and the moving distance of the rotating part in the axial direction can be determined.

Next, another embodiment ζ shown in FIG. 4 will be described.

In the embodiments shown in FIGS. 1 and 21ζ2, only changes in the movement of the rotating part in the axial direction are detected, but changes in the radial direction cannot be detected. Therefore, in the embodiment shown in FIG. 44, the laser beam 8 is made incident on the diffraction grating 4 from the axial direction.

In this embodiment, when the rotating part extends in the radial direction as shown by the dotted line, the incident light 8 changes from the solid line incident light to the dotted line incident light, and the incident light changes from the diffraction grating 4b irradiated to the diffraction grating 46. The rounded, diffracted light 90 frequency also changes. The deviation in the radial direction of the rotation part can be detected by the frequency change of the diffracted light 9.

In this embodiment, changes in the axial direction can also be detected.

In another embodiment shown in FIG. 5, a light emitter 7a that emits light from the circumference of the diffraction grating 4 and a light emitter 7b that emits light from the axial direction are provided. That is, laser beams with different frequencies are oscillated by 28 laser beam fA devices 5a and 5b, and are passed through optical fibers 6a + 6b to a light emitter 7.
b, led to 7m. The incident light 8a*8b irradiated by the diffraction grating 41 from the two light emitters 7a, 7b is reflected in respective directions as diffracted light 9m, 9b which has been subjected to a sinusoidal frequency shift as described above.

The two diffracted lights 9a and 9b are transmitted to the receivers 10a and lOb.
Through the optical fiber cta, eb+ = photomultiplier tube 11a.

11b Two people are shot.

In addition, the reference beam 12 (12b) which is obtained by branching the laser beams from the two laser light source devices i5a and 5b is also emitted from the photomultiplier tubes 11a and llb 4.The photomultiplier tube L
la.

By inputting the flb signal to the frequency analyzers 13&, 13b1), the magnitude of the frequency deviation of the diffracted lights 9a and 9b can be determined. Furthermore, it is difficult to determine the axial and radial gaps between the stationary part and the rotating part (by manually inputting this signal to the calculation d 15 ).

Furthermore, by manually inputting this signal to the computer 15, the axial and radial gaps between the stationary part and the rotating part can be determined. Note that the gap amount at each point at a steady state when the machine is stationary is input in advance to the calculator 15, and the gap amount can be monitored in real time, and in the case of an abnormality,
It is possible to issue operation control signals such as a reduction in rotation speed. In addition, the use of laser beams with 1:2 different frequencies as a laser light source is achieved by changing the circumference a and a level of the two diffracted beams 9+a and 9b. Decame to avoid.

Furthermore, in another example C2 shown in Figure 6, the configuration is such that a number of laser beams with different frequencies are obtained from one laser light source device 715. The laser beam oscillated from the laser light source device VT5 is incident on the ultrasonic light modulator 16. An S!lb element such as a crystal oscillator is installed at the bottom of the ultrasonic light modulator 16. An oscillator 17 applies high frequency abrasive pressure to both sides of the vibrator.

As a result, the piezoelectric reverse effect (; therefore, the vibrator vibrates at a high speed in the thickness direction, and a traveling ultra-f wave is generated in the medium in the ultrasonic optical modulator 16.

When such supersonic waves propagate through a medium, a density difference occurs in the medium, and the refractive index of the medium changes. As a result, the ultrasonic waves act as a diffraction grating, and when the source is incident, the light is strongly diffracted only in a specific direction. Furthermore, since sound waves are elastic waves that propagate in a medium, the diffraction grating can be considered to be moving at the speed of sound. Therefore, as mentioned above (; due to the Doppler effect, the frequency of the diffracted light is biased.
If it is 0, the frequencies of the +1st-order diffracted light 18 and the 1st-order diffracted light 19 are as follows.

-j+fo and f-fo, respectively, and the frequency of the 0th order diffracted light does not change and remains f. Figure 6 4 = As shown, ±1st order diffraction sources 18.19 are used as incident light 8,
By using the 0th-order diffracted light as the reference light, the axial and radial gaps between the stationary part and the rotating part can be determined as in the case of FIG. 5.

〔Effect of the invention〕

As described above, in the present invention 12, in the axial flow turbomachine, the laser light guided into the machine from the laser light source fi, it located outside the machine using an optical fiber is directed to the tip of the sb. By irradiating two diffraction gratings 1 with different grating intervals depending on the position in one direction attached to the shroud surface and measuring the frequency of the diffracted light. Since it can be constantly monitored, it is possible to prevent contact accidents caused by relative positional deviation ζ.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an am position detection device that makes use of the wJX position habituation method for an axial flow turbo machine according to the present invention, and FIG. Figure 3 is a schematic diagram illustrating the function of the diffraction grating used in the second embodiment of the present invention, and Figure 4 is a rounded schematic diagram illustrating another embodiment of the present invention. FIG. I5 and FIG. 6 are schematic configuration diagrams showing other different 4M examples of the present invention. 1-... Moving blade 2... Disk 3... Sheet 4... Diffraction grating 5... Laser light source device 6... Original fiber 7... Light emitter 8.
...Incoming light 9... Diffracted light 10... Light receiver 11... Optical multiplier tube 12... Reference light 13...
-Frequency analyzer 14...Casing 15...Computer 16...Ultrasonic light modulator 17...Oscillator 18...+1st order diffracted light 19...-1
Next-order diffracted light “addition… 0th-order diffracted light 21… Lens (8733) Agent: Patent attorney Yoshiaki Inomata (and 1 others)
Name) Figure 1 Figure 2 Figure 3 Figure 4! ? Figure 5

Claims (5)

[Claims] (1) In an axial flow turbomachine that has rotor blades whose tips are bound by a shroud, a diffraction grating array is attached to the shroud surface that exhibits the function of reflecting multiple lights with different grating intervals depending on the axial position, and this shroud is The moving blade position is determined by irradiating the diffraction grating array on the surface with laser light guided into the machine using an optical fiber from a laser light source device located outside the machine, and measuring the frequency of the diffracted light from the diffraction grating array. A method for detecting the position of rotor blades in axial flow turbomachinery, characterized by detecting the position of moving blades in axial flow turbomachinery. (2) Claim 1, characterized in that the diffraction grating array on the shroud surface is irradiated with laser light from the circumferential direction thereof.
A method for detecting the position of a rotor blade in a trickle turbomachine as described in . (3) A method for detecting a rotor blade position of an axial flow turbomachine according to claim 1, characterized in that a laser beam is irradiated onto a diffraction grating array on a shroud surface from an axial direction thereof. (4) The method for detecting the position of a rotor blade for an axial flow turbomachine according to claim 1, characterized in that the diffraction grating array on the shroud surface is irradiated with laser light from both the circumferential direction and the axial direction. (5) A plurality of laser beams are irradiated onto the diffraction grating array on the shroud surface by frequency modulating and splitting the laser beam from the laser light source device using an ultrasonic modulator. A method for detecting the position of rotor blades in axial flow turbomachinery.