JPH0263182B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention provides a steam turbine in which the efficiency of the steam turbine and the corrosion state of the rotor blades are monitored by understanding the particle size distribution and particle density of water droplets in the steam. relating to a steam monitoring device. [Technical background of the invention and its problems] Commercial thermal power turbines, nuclear power turbines, geothermal turbines, etc. are operated using so-called wet steam containing water droplets in the steam. To know the efficiency of such a steam turbine, it is necessary to know the energy of wet steam, that is, the sum of the energy of steam and the energy of water droplets. Since the energy possessed by water droplets is derived from the amount of water droplets, it is impossible to determine the accurate efficiency of a steam turbine unless the amount of water droplets is known. However, in the past, there was no way to accurately determine the amount of water droplets, so the efficiency of a steam turbine had to be estimated from the plant's electrical output, drain amount, etc., which lacked accuracy. . On the other hand, this type of steam turbine has a problem in that water droplets contained in the steam cause erosion of the rotor blades. In order to prevent such erosion of the rotor blades, it is essential not only to improve the material of the rotor blades and the structure of the steam turbine, but also to operate the turbine in proper conditions. It goes without saying that corrosion of rotor blades should be kept below the allowable value under design operating conditions, but during partial load operation or load fluctuations, there may be cases where the steam condition at the turbine inlet and the load are insufficiently matched, or if the steam condition If the temperature fluctuates transiently, the steam humidity may increase abnormally, leading to excessive erosion of the rotor blades. Therefore, there is a need for a device that can quantitatively monitor steam humidity at all times. However, steam wetness is also determined from the amount of water droplets in the steam turbine, and as there is no way to determine this, it is also impossible to accurately determine the amount of erosion on the rotor blades. Ta. [Object of the Invention] The present invention was made based on the above facts, and its purpose is to determine the efficiency of a steam turbine and the corrosion status of rotor blades from the particle size distribution and particle density of water droplets in the steam. An object of the present invention is to provide a steam monitoring device for a steam turbine that can be grasped and monitored. [Summary of the Invention] Generally, when a spherical particle with a particle size D is irradiated with parallel monochromatic light such as a laser beam, the scattered light intensity I (D, θ) generated in the direction of angle θ is calculated according to the Mie scattering theory. Therefore, it can be calculated accurately. Based on this, the applicant has determined the difference between the scattered light intensity i (D, θ) by one particle and the particle size distribution nr (D), which was determined based on the scattering theory of the laser light irradiated onto the particle group to be measured. Based on the following relationship, I(D)=∫i(D, θ)nr(D)dD...(1), we proposed a particle size measuring device that calculates the particle size distribution nr(D). . The present invention has been made to apply the above device to the field of steam turbines, and is characterized by the following configuration. That is, the present invention
A probe that can be inserted into the inside of a steam turbine is configured as follows at the tip of a cable consisting of an irradiation optical fiber and a plurality of light receiving optical fibers,
The steam to be measured is irradiated with a laser beam through the above-mentioned optical fiber for irradiation, and the scattered light for each scattering angle of the scattered light scattered by the steam to be measured is transmitted to the steam turbine using the optical fiber for reception. The light is then received to obtain a scattered light intensity distribution signal, and the particle size distribution and particle density are calculated from this scattered light intensity distribution signal. The probe includes a tip portion of the light irradiation fiber that is bent in a U-shape so as to rotate the traveling direction of the laser light traveling through the irradiation optical fiber by 180 degrees, and a It is characterized by comprising an optical system that shapes the light emitted from the tip and irradiates the vapor to be measured, and a tip of the light-receiving optical fiber that faces this optical system. [Effects of the Invention] According to the present invention, it is possible to accurately measure the particle size distribution and particle density of water droplets in a steam turbine.
It can be constantly and quantitatively monitored. Moreover, according to this invention, only the probe needs to be inserted inside the steam turbine, which is in a high temperature and humid environment, and other equipment is installed outside the steam turbine and the two are connected using optical fiber. This allows for highly reliable monitoring. Moreover, with such a configuration, there are also effects such as extremely easy attachment and detachment to the steam turbine. [Embodiments of the Invention] Hereinafter, a steam turbine steam monitoring device according to an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, 1 is a steam turbine to be monitored that is operated with wet steam. The steam monitoring device according to this embodiment includes a probe 2 whose tip end is inserted into the steam turbine 1, a device main body 3, and an irradiation optical fiber that optically connects these probes 2 and the device main body 3 . 4 and a plurality of light-receiving optical fibers 5 ₁ , 5 ₂ , 5 ₃ , ..., 5n, and air pipes 7 and 8 for sending air from the device main body 3 to the probe 2. ing. Light-receiving optical fiber 5 ₁ to 5n
It is desirable that the optical fiber be a large-diameter optical fiber with a diameter of 100 μm or more, for example. The apparatus main body 3 includes a laser light source 11 that supplies monochromatic laser light to the probe 2 via an irradiation optical fiber 4, and a lens 12 that focuses the light from the laser light source 11 onto the input end of the irradiation optical fiber 4. and interference filters 13 ₁ , 13 ₂ , 13 ₃ , . . . , 1 that transmit light of a specific wavelength to be subjected to measurement among the light emitted from the input ends of the light receiving optical fibers 5 ₁ to 5n.
3n, photodetectors 14 ₁ , 14 ₂ , 14 ₃ , ..., 14n that receive and photoelectrically convert the light transmitted through these interference filters 13 ₁ - 13n, and the outputs of these photodetectors 14 ₁ - 14n at a predetermined amplification factor. Amplifiers 15 ₁ , 15 ₂ , 15 ₃ ,
..., 15n, and an arithmetic unit 16 that inputs the output signals from these amplifiers 15 ₁ to 15n to calculate the particle size distribution and particle density of water droplets of the steam to be measured, and is connected to one end of the air pipes 7 and 8. It consists of a compressor 17. Further, the probe 2 is specifically constructed as shown in FIG. In other words, 21 in the figure is
Irradiation optical fiber 4 and light reception optical fiber 5 ₁
This is a fiber accommodation tube that collectively accommodates the tips of ~5n. The fiber housing tube 21 has a hole 2 at its tip through which the tip of the irradiation optical fiber 4 can pass.
2 and an opening 23 to be described later, and a support arm 24 extending toward the distal end side is provided protrudingly. The tip of the irradiation optical fiber 4 passes through the hole 22 and enters the optical fiber housing tube 21.
The mounting plate 26 extends from the tip of the optical fiber receiving tube 21, is covered with a flexible light-shielding tube 25, rotates the tip by 180 degrees, and emits the laser beam toward the opening 23 of the optical fiber housing tube 21. via the support arm 2
It is fixed at 4. A collimator lens 27 is provided at the tip of the irradiation optical fiber 4 for shaping the laser beam emitted therefrom into a parallel beam. The collimator lens 27 and the tip of the irradiation optical fiber 4 are housed inside a cylindrical body 28.
An annular member 29 is attached to the output end of the cylinder 28 . As shown in detail in FIG. 3, this annular member 29 is a portion located on the inner surface of a hole 32 of a hollow annular body 31 formed with a thick wall on one side in the radial direction and a thin wall on the other side. An air outlet 33 extending in the circumferential direction is formed in the circumferential direction. Then, air A is introduced from the compressor 17 through an air pipe 7 connected to a thin walled portion of the outer peripheral surface of the hollow annular body 31, and the air A is jetted from the air jet port 33. This makes it possible to form an air curtain in the hole 32. A cylindrical optical shield 34 is provided at a position facing the output end of the annular member 29 . This optical shield 34
is fixed to the support arm 24 via a support plate 35. The relative position between this optical shield 34 and the collimator lens 27 is determined by the support plates 26, 3.
The screws 36, 37 fixing the support arm 5 to the support arm 24 allow for adjustment. The optical shield 34 is
Light is introduced into the interior through an opening 38 on the proximal end, and is emitted from an opening 39 on the distal end. The diameter of the opening 39 is set to be slightly larger than the diameter of the laser beam emitted from the collimator lens 27. An introduction hole 40 for introducing air is provided on the side surface of the optical shield 34, and one end of the air pipe 8 is connected to this introduction hole 40. The opening 23 of the optical fiber housing tube 21 faces the output end of the optical shield 34 via the measurement region P. This opening 23 is formed so that its width increases as it goes deeper, and the light receiving ends of the light receiving optical fibers 5 ₁ to 5n are placed inside the opening 23 at an equal distance from the measurement area P and at a scattering angle of 0°. θ ₁ , θ ₂ , ..., θn−1
It is designed to be placed at the position of . Their relative positions are determined by the support member 41.
Note that the opening 23 (second
The inner surface of the portion Q) surrounded by the dashed line in the figure is coated with black matte coating to prevent stray light. Next, the operation of the steam monitoring device according to this embodiment configured as described above will be explained. Monochromatic laser light generated by oscillation of the laser light source 11 is guided into the irradiation optical fiber 4 through the lens 12 and formed into a parallel laser beam with a predetermined cross-sectional area by the collimator lens 27. At this time, scattered light may be generated by bubbles inside the collimator lens 27, but most of this scattered light is blocked by the optical shield 34. Therefore, the measurement area P passes through the opening 39 of the optical shield 34.
Most of what is irradiated is the parallel beam component. Incidentally, the light emitting end of the cylindrical body 28 in which the collimator lens 27 is housed and the openings 38 and 39 of the optical shield 34 are in contact with the steam. Therefore, there is a possibility that water droplets in the steam may adhere to these parts and hinder the progress of the laser beam. However, in the present embodiment, air A is sent from the compressor 17 into the annular member 29 and the optical shield 34, and an air curtain is formed in the annular member 29, and the optical shield 34, the hole 3 is opened by blowing air from inside.
2 and the openings 38 and 39 can be removed. When the laser beam C passes through such an air-purged optical system and irradiates the measurement area P, the laser beam C is scattered by the vapor R to be measured, and the scattered light C' carrying the measurement information is scattered. The light is input to each of the light receiving optical fibers 5 ₁ to 5n. Each light receiving optical fiber 5 ₁
Scattered light C′ at each scattering angle guided to the outside of the steam turbine 1 by the interference filter 13
₁ to 13n, photoelectrically converted by detectors 14 ₁ to 14n, further amplified by amplifiers 15 ₁ to 15n, and inputted to arithmetic unit 16 as a scattered light intensity distribution signal Ir(θ). The calculation device 16 calculates the particle size distribution nr(D) from the input signal Ir(θ) by, for example, the logarithmic bound integral equation method or the logarithmic distribution function approximation method based on the above-mentioned (1). By the way, since the scattered light intensity distribution signal Ir(θ) is a relative value, the particle size distribution nr(D) is also a relative value. Here, the particle size distribution nr(D) is normalized to be ∫nr(D)dD=1 (2). The absolute particle size distribution n(D) and particle density N ₀ can be calculated by the following method. One method is to convert the measured relative scattered light intensity distribution Ir(D) into a scattered light intensity distribution I(θ) expressed in absolute intensity (light energy density W/m ² ). That is, first, prior to measuring the vapor to be measured, a group of particles whose particle size distribution and particle density are known is irradiated with laser light to obtain the scattered light intensity distribution Im(θ).
Measure. On the other hand, the theoretical scattered light intensity distribution Ip (θ) by this particle group is calculated based on scattering theory, and the calibration coefficient K (θ) is calculated as follows: K (θ) = Ip (θ) / Im (θ) ...(3) ), then from the actual measured value Ir(θ), the absolute scattered light intensity distribution I(θ) can be calculated using the formula I(θ) = K(θ)・Ir(θ) (4) You can ask for it. Here, considering the attenuation of the incident light incident on the measurement area P, I(θ) is: I(θ)=∫ ^L ₀ {Iin exp[−xN ₀ ∫c(D)n _r (D)dD 〕・∫i
It can be expressed as (D, θ)·πB ² N ₀ n _r (D)dD}dx (5). However, L: scattering optical path length Iin; incident light intensity C(D); scattering cross section B: radius of the irradiation beam. Therefore, by substituting the value I(θ) converted using the above equation (4) into the right side of equation (5) and solving equation (5) for N ₀ , the particle density N ₀ can be found. Therefore, the absolute particle size distribution n(D) is also calculated by the formula n(D)=N ₀ ·nr(D) (6). Another method is to measure transmittance. That is, the measured transmittance E=Iout(θ)/Iin(θ) can be expressed as E=exp{−L∫c(D)N ₀ n _r (D)dD} (7). By solving equation (7) for N ₀ , the particle density can be found. The same applies below. Through the above calculations, the calculation device 16 calculates the particle size distribution n(D) and the particle density N ₀ and sends the results to, for example, a display device or a control device (not shown). Note that the steam humidity H of the steam turbine is expressed as H=Wl/Wb (8). Here, Wl: Weight of liquid in vapor Wb: Weight of total vapor. The pressure inside the turbine can be easily measured, and once the pressure is determined, the density of the gas and the density of the liquid can be determined from the saturated steam curve, and the weight of the total steam can be determined.
Find Wb. Since the particle size distribution n(D) is determined by the apparatus of this embodiment, the number of particles of each particle size is known, and eventually the weight Wl of the gas in the steam is determined. As described above, according to this embodiment, the particle size distribution and particle density of water droplets in the steam turbine 1 can be accurately measured, so that the turbine efficiency and the erosion state of the rotor blades can be constantly and quantitatively monitored. be able to. Moreover, in this case, only the probe 2 needs to be slightly inserted into the steam turbine 1 through one insertion port, and other equipment can be installed outside the steam turbine 1, so it is possible to install the probe 2 in a hot and humid environment such as inside the turbine. Measurement at the bottom becomes possible. Further, since large diameter fibers are used as the light receiving optical fibers 5 ₁ to 5n, there is no need for a condensing lens or the like, which contributes to miniaturization of the probe 2 . In addition, in this embodiment, the occurrence and influence of scattered light, which becomes a noise component in measurement, is effectively prevented by the matte coating applied to the opening 23 of the optical fiber housing tube 21, the optical shield 34, etc. This allows for highly reliable monitoring. In addition, since air purge is applied to the exit port of the collimator lens 27 and the entrance and exit ports of the optical shield 34, the micro-diameter openings, etc. are blocked by water droplets in the steam, disturbing the progress of the light. It is possible to prevent this from happening. In this way, according to this embodiment, extremely great effects can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a schematic configuration of a steam measuring device for a steam turbine according to an embodiment of the present invention, FIG. 2 is a sectional view showing details of a probe in the device, and FIG.
The figures are views showing the annular member in FIG. 2 in more detail, in which figure a is a perspective view, figure b is a sectional view, and figure c is a front view. 1...Steam turbine, 2 ...Probe, 3 ...
Device main body, 4... Optical fiber for irradiation, 5 ₁ to 5n
...Optical fiber for light reception, 6 ...Cable, 7, 8
...Air pipe, 13 ₁ to 13n... Interference filter, 14 ₁ to 13n... Detector, 21...
Optical fiber housing tube, 23... opening, 24... support arm, 25... light shielding pipe, 26, 35... support plate, 27... collimator lens, 29... annular member, 33... air outlet , 34... optical shield, P... measurement area.

Claims (1)

[Scope of Claims] 1. A laser light source installed outside the steam turbine, a probe to be inserted into the inside of the steam turbine at the tip, and a laser light source from the laser light source installed inside the steam turbine. An irradiating optical fiber that guides the irradiating light to the steam turbine, and a scattered light that is guided into the steam turbine through the irradiating optical fiber, irradiates the steam to be measured, and receives the scattered light at each scattering angle and guides it to the outside of the steam turbine. A cable consisting of a plurality of light-receiving optical fibers and the plurality of light-receiving optical fibers guide the scattered light for each scattering angle to the outside of the steam turbine, respectively, and output the received scattered light as a scattered light intensity distribution signal. and an arithmetic device that calculates the particle size distribution and particle density of the vapor to be measured from the scattered light intensity distribution signal output from the photodetector, and the probe The tip of the light irradiation fiber is bent in a U-shape so as to rotate the direction of travel of the laser light traveling therein by 180 degrees, and the light emitted from the tip of this irradiation optical fiber is shaped and 1. A steam monitoring device for a steam turbine, comprising: an optical system for irradiating steam to be measured; and a tip of the light-receiving optical fiber facing the optical system. 2. The optical system includes a collimator lens that shapes the laser beam emitted from the tip of the light irradiation fiber into a parallel beam, and an optical shield that has an opening that allows the light emitted from the collimator lens to pass through. A steam monitoring device for a steam turbine according to claim 1, characterized in that the device comprises: 3. Steam monitoring of a steam turbine according to claim 2, wherein the collimator lens and the optical shield are supported by a mechanism that can adjust their relative positions. Device. 4. The optical system has an opening through which the laser beam passes and is in contact with the steam to be measured, and this opening is air-purged with air introduced from outside the steam turbine. A steam monitoring device for a steam turbine according to claim 1, characterized in that: 5. The steam monitoring device for a steam turbine according to claim 1, wherein at least a tip of the light-receiving optical fiber is covered with a member having a black matte surface.