JP6450196B2 - Steam turbine droplet measuring apparatus and steam turbine - Google Patents

Description

  The present invention relates to a droplet measuring device that measures droplets generated in a steam turbine and a steam turbine including the droplet measuring device.

  When the steam condition is operated in a saturated region, as in the low pressure stage of the steam turbine, a large amount of droplets are generated inside the steam turbine. Under such wet steam flow conditions, if some of the small droplets generated by condensate impact adhere to the stationary blade surface, a water film flows on the blade surface and is sprayed again from the trailing edge of the stationary blade. The

  In the wake of the stationary blade, there are a mixture of micro droplets with a droplet diameter of 1 μm or less to several hundred μm coarse droplets. It cannot get on the flow and collides with the moving blade at a speed almost equal to the peripheral speed, which causes the blade to be eroded. In particular, in recent years, the last stage of the steam turbine has become longer, and the peripheral speed of the tip of the rotor blade has increased. Therefore, the influence of droplets on blade erosion tends to increase. Therefore, from the viewpoint of reliability, it is required to elucidate the flow characteristics of droplets by measuring the diameter and velocity of the droplets generated in the turbine, and to accurately evaluate the impact and take effective measures. .

  As a technique for measuring the flow velocity of liquid droplets as described above, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2010-243197) discloses that laser light oscillated from a laser light oscillation unit is converted into a sheet-shaped laser sheet light. A laser sheet light forming unit that converts and irradiates the fluid to be measured, a borescope that observes an irradiated object image that appears in the fluid to be measured by the laser sheet light irradiated from the laser sheet light forming unit, and a borescope Discloses a fluid velocity measurement system including an image capturing unit that captures an image of an irradiated object observed by the above and converts it into irradiated object image data.

  In addition, as another example relating to the droplet flow velocity measurement technique, Patent Document 2 (Japanese Patent Application Laid-Open No. 2013-029423) discloses a first method for measuring a flow velocity of a first phase related to a working fluid flowing in a measurement object. The second measuring device for measuring the flow velocity of the second phase related to the particles in the working fluid flowing through the measurement object, the first measuring device, and the second measuring device measured by the second measuring device. From the flow rate of the first phase and the flow rate of the second phase, a correlation equation established between the flow rate of the first phase, the flow rate of the second phase, and the particle size of the particles was obtained in advance, and the correlation equation was measured. A flow rate and particle size measurement system is disclosed in which the flow velocity of the first phase and the flow velocity of the second phase are introduced to calculate the particle size of particles flowing in the measurement object.

JP 2010-243197 A JP 2013-029423 A

  However, the above prior art has the following problems.

  That is, the technique described in Patent Document 1 uses a laser beam and a high-speed camera to quantitatively measure the flow velocity of microparticles based on a particle image velocity measurement method (PIV: Particle Image Velocimetry). Because there is a condition that it is desirable that the variation in the particle size to be measured is as small as possible, measurement is required when droplets having a wide range of droplet diameters that occur in the low pressure stage of a steam turbine are to be measured. The accuracy is significantly reduced. In addition, in order to image a droplet, the flight direction of the droplet needs to coincide with the laser sheet plane, but the flight direction of the droplet generated in the steam turbine is not constant and is difficult to predict. Speed information cannot be calculated. Furthermore, the particle size is not subject to measurement.

  Although the technique described in Patent Document 2 can measure the particle size, a correlation equation established between the flow velocity of the working fluid, the flow velocity of the particles, and the particle size of the particles is obtained in advance by a wind tunnel test or the like. Many processes are necessary in advance. In addition, it is necessary to measure the flow rate of the working fluid and the particle flow rate that are introduced into the correlation equation in order to calculate the particle size of the particles, but it is necessary to measure the flow rate of the particles inside the steam turbine that is isolated from the outside. It is very difficult.

  The present invention has been made in view of the above, and a droplet measuring device for a steam turbine capable of more easily and accurately measuring the diameter and velocity of droplets generated inside a steam turbine, and a steam turbine using the same The purpose is to provide.

  To achieve the above object, the present invention provides a hollow tubular member that penetrates a casing of a steam turbine and is disposed so as to extend a flow path of a working fluid inside the steam turbine inward and outward, and the tubular A laser beam oscillation part that is provided outside the casing of the member and oscillates laser light, and a laser beam that is provided inside the casing of the tubular member and is oscillated from the laser beam oscillation part and passes through the tubular member A laser sheet light forming unit that converts the laser beam light into a sheet-shaped laser sheet light and irradiates the working fluid from the droplets in the working fluid by irradiation of the laser sheet light from the laser sheet light forming unit A borescope for transmitting the obtained reflected light and internally refracted light to the outside of the casing via the tubular member, and the droplet obtained via the borescope By capturing the reflected light and the internal refraction light et assumed that an image capturing unit that generates an interference fringe image based on the phase difference.

  The diameter and speed of the droplet generated inside the steam turbine can be measured more easily and accurately.

It is a figure which shows typically the structure of the droplet measuring apparatus between the steam turbine low-pressure stage stages which concerns on one embodiment. It is a figure which shows schematically the structure of the probe in a droplet measuring device. It is a figure explaining the basic principle of droplet measurement. It is a figure which shows roughly about the relationship with the basic principle of the droplet measurement which concerns on a droplet measurement apparatus. It is a figure which shows typically an example of the image containing the several particle image obtained by the droplet measurement of a droplet measuring apparatus, and is a figure which shows the image in a certain time. It is a figure which shows typically an example of the image containing the several particle image obtained by the droplet measurement of a droplet measuring device, and each shows the image at the time when fixed time passed from a certain time. It is sectional drawing which shows typically an example of the behavior of the droplet which generate | occur | produces in the low pressure stage of a steam turbine. It is sectional drawing which shows typically an example of the behavior of the droplet which generate | occur | produces in the low pressure stage of a steam turbine. It is a figure which shows typically the structure of the droplet measuring device of the steam turbine which concerns on the modification of one Embodiment.

  An embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram schematically showing a configuration of a droplet measuring apparatus for a steam turbine according to the present embodiment.

  In FIG. 1, a steam turbine 100 includes a turbine rotor 104 penetrating a casing 101, a plurality of moving blades 103 provided on the outer periphery of the turbine rotor 104, and a turbine rotor 104 surrounded by a casing 101. The outer diaphragm 102a and the outer diaphragm ring 102a that are arranged coaxially with each other, a plurality of stationary blades 102 fixed in the circumferential direction between the outer diaphragm ring 102a and the inner diaphragm ring 102b, and the steam flowing in the steam turbine 100 It is schematically configured from a droplet measuring device 1 that measures a droplet 31 (see FIG. 7 and the like later). In FIG. 1, only the stationary blade 102 and the moving blade 103 at the final stage of the low-pressure turbine constituted by a plurality of stages are illustrated, and the exhaust chamber and the like are also omitted.

  The droplet measuring apparatus 1 includes a laser interference imaging method (ILIDS) inserted through the casing 101 on the downstream side (right side in FIG. 1) of the steam main flow 105 of the moving blade 103 in the final stage inside the casing 101. Sizing) probe 2 (hereinafter simply referred to as probe 2) and a control device 3 for controlling the operation of the droplet measuring device 1.

  In the present embodiment, the probe 2 is disposed on the downstream side in the flow of the working fluid (steam) of the moving blade 103 in the final stage, and a laser sheet light 8 to be described later is irradiated on the upstream side. A case where a drop is measured will be described as an example.

  FIG. 2 is a diagram schematically showing the configuration of the probe in the droplet measuring apparatus.

  In FIG. 2, the probe 2 is disposed so as to extend inward and outward through the casing 101, and a hollow tubular member 20 provided so as to be rotatable around an axis with respect to the casing 101, and a tubular member A laser beam oscillation unit 4 that oscillates the laser beam 4a, a laser adjustment optical system 5 that adjusts the laser beam 4a oscillated from the laser beam oscillation unit 4 to collimated light, and a laser beam. The laser beam reflecting mirror 6 that changes the traveling direction of 4a and the laser beam 4a that is provided inside the casing 101 of the tubular member 20 and is oscillated from the laser beam oscillator 4 and reflected by the laser beam reflecting mirror 6 is formed into a sheet shape. The laser sheet light forming unit 7 that converts the laser sheet light 8 formed in the laser beam 8 and irradiates the working fluid with the laser sheet light 8, and the irradiation of the laser sheet light 8 from the laser sheet light forming unit 7 The borescope 10 that transmits the reflected light and internal refracted light obtained from the droplet 31 in the working fluid to the outside of the casing 101 via the tubular member 20, and the reflection from the droplet 31 obtained via the borescope 10. An image capturing unit 21 that captures the light 32 and the (internal) refracted light 33 is provided.

  The laser sheet light forming unit 7 is provided with an irradiation angle adjusting unit 7 a that adjusts the irradiation angle of the laser sheet light 8. In addition, an imaging window 9 for taking the reflected light from the droplet 31 and the internal refracted light is provided at an end (hereinafter referred to as an incident end) inside the casing 101 of the borescope 10. The imaging window 9 is provided with an imaging angle adjustment unit 9a that adjusts the imaging angle.

  The image capturing unit 21 collects the light transmitted from the borescope 10 and irradiated from the end opposite to the image capturing window 9 (in other words, the end on the outer side of the casing 101; hereinafter referred to as the irradiation end). An objective lens 12, a cylindrical lens 14 that adjusts the light collected by the objective lens 12 to parallel light, a camera 15 that captures the light through the cylindrical lens 14 and sends it to the control unit 3, and expands and contracts in the optical axis direction A second imaging distance adjusting unit 11 that adjusts the distance in the optical axis direction between the irradiation end of the borescope 10 and the objective lens 12; and an objective lens 12 and a cylindrical lens that are extendable in the optical axis direction. And a first imaging distance adjustment unit 13 that adjusts the distance in the optical axis direction with respect to 14.

  The control device 3 includes a storage unit 3b for storing droplet measurement condition settings and measurement results in the droplet measurement device, a display unit 3a for displaying condition setting screens and measurement results, and various information input and operations. And an input unit 3c to perform.

  Next, the principle of droplet measurement by the droplet measuring apparatus 1 of the steam turbine 100 according to the present embodiment will be described.

  FIG. 3 is a diagram for explaining the basic principle of droplet measurement according to the present embodiment.

  As shown in FIG. 3, the droplet measurement of the present embodiment is based on laser interference imaging (ILIDS), and spherical particles 331 in a sheet-like parallel laser sheet light 308. The scattered light 337 is captured from a particle image 36 that is out of focus in an appropriate angle θ (for example, 20 ° <θ <80 °) (that is, an out-of-focus image of the particle), and interference fringes are obtained for the spherical particle 331. The particle image 36 in which the pattern 36a appears is acquired. Then, the diameter of the spherical particle 331 is calculated based on the proportional relationship between the number of interference fringes 36 a in the particle image 36 and the diameter of the spherical particle 331. Further, the particle position is specified from the center of the particle image 331, and the particle velocity is calculated from the moving distance of the particle position per unit time.

  Specifically, the objective lens 312 is arranged so that the angle (scattering angle) formed by the scattered light from the laser sheet light 308 and the spherical particles 331 is θ, and the angle at which the spherical particles 331 look at the objective lens 312 (condensing light). The distance L2 between the objective lens 312 and the spherical particle 331 is adjusted so that (angle) becomes α. In this case, the outer diameter and shape of the particle image 36 of the spherical particle 331 obtained on the imaging surface 335 are the same as the size of the objective lens 312, the imaging surface 335, and the image surface 334 regardless of the actual size of the spherical particle 331. Depends on the distance L1. For example, when the outer diameter shape of the objective lens 312 is circular, the particle image 36 of the spherical particle 331 is circular. Then, using the number N of interference fringes 36 a formed in the obtained particle image 36, the angle (condensing angle) α at which the spherical particle 331 looks at the objective lens 312, the scattering angle θ, and the like, The diameter d is obtained by the following (formula 1).

  Here, d is the diameter of the spherical particle 331, λ is the wavelength of the laser sheet light 308, N is the number of interference fringes 36a in the particle image 36 (particle defocused image), and m is the refractive index of the spherical particle 331 (specifically Is the refractive index of the droplet in the working fluid), α is the collection angle, and θ is the scattering angle.

  FIG. 4 is a diagram schematically showing the relationship with the basic principle of droplet measurement according to the droplet measuring apparatus of the present embodiment.

  In FIG. 4, the laser sheet light 8 and the objective lens 12 correspond to the laser sheet light 308 and the objective lens 312 in FIG. 3. Also, the angle θ formed by the laser sheet light 8 in FIG. 4 and the optical axis in the light collecting window 9 corresponds to the scattering angle θ in FIG. In the droplet measurement in the droplet measuring apparatus 1, the angle θ (the angle θ (the angle between the laser sheet light 8 and the optical axis of the imaging window 9) between the reflected light 32 and the refracted light 33 from the droplet 31 in the laser sheet light 8. For example, a particle image 36 that is out of focus in the direction of 20 ° <θ <80 °) (that is, an out-of-focus image of the particle) is captured, and a particle image 36 in which the pattern of the interference fringe 36a appears on the droplet 31 is obtained. get. Then, the diameter of the droplet 31 is calculated based on the proportional relationship between the number of interference fringes 36 a in the particle image 36 and the diameter of the droplet 31. Further, the particle position is specified from the center of the particle image 36, and the particle velocity is calculated from the moving distance of the particle position per unit time.

  Specifically, when the droplet 31 in the working fluid in the steam turbine 100 passes through the laser sheet 8, the reflected light 32 and the refracted light 33 (corresponding to the scattered light 337 in FIG. 3) are generated. The reflected light 32 and the refracted light 33 from the droplet 31 in the laser sheet light 8 are condensed by the light collecting window 9 in the direction in which the angle between the laser sheet light 8 and the optical axis of the light collecting window 9 is θ, It is transmitted by the borescope 10. The objective lens 12 is disposed at a distance L2 in the optical axis direction from the irradiation end of the borescope 10, and the cylindrical lens 11 is disposed at a distance L1 in the optical axis direction from the objective lens 12, thereby allowing the imaging surface 335 in FIG. Light corresponding to the particle image 36 can be guided to the camera 9, and the camera 9 can acquire an out-of-focus particle image 36 in which the pattern of the interference fringe 36 a appears for the droplet 31. The particle image 36 acquired by the camera 9 is sent to the control unit 3.

  5 and 6 are diagrams schematically showing an example of an image including a plurality of particle images obtained by droplet measurement of the droplet measuring device. FIG. 5 shows an image at a certain time t1, and FIG. The images at the time when a certain time Δt has elapsed from a certain time are respectively shown.

  5 and 6 exemplify images 37 and 38 in which particle images 361 to 364 regarding four droplets are obtained. The size of the outer diameter of the particle images 361 to 364 in which the four droplets 31 of the images 37 and 38 are out of focus is not the actual size of the droplet 31, but the actual size of the droplet 31 is the particle size. The number N of the interference fringes 361a to 364a of each of the images 361 to 364 is determined and obtained by substituting them into the above (Equation 1).

  Further, when the imaged particle images 361 to 364 of the droplet 31 are circular, the position of the droplet 31 can be defined by obtaining the center thereof, so two images captured at a known minute time interval Δt. That is, by calculating the change (movement distance) of the position of the particle images 361 to 364 in the image 37 (FIG. 5) captured at the time t1 and the image 38 (FIG. 6) captured at the time t1 + Δt, each liquid is calculated. Two velocity components in the plane of the drop can be determined. For example, the liquid corresponding to the particle image 361 at time Δt is determined from the distance between the center (see FIG. 5) of the particle image 361 at time t1 (ie, FIG. 5) and the center (see FIG. 6) of the particle image 361 at time t1 + Δt. The moving distance of the droplet 31, that is, the velocity of the droplet 31 can be obtained.

  7 and 8 are diagrams schematically showing an example of the behavior of droplets generated in the low pressure stage of the steam turbine. FIG. 7 is a circumferential view of the stationary blade and the moving blade, and FIG. 8 is a blade of the stationary blade. It is the figure seen from the height direction, respectively.

  As shown in FIGS. 7 and 8, in the low pressure stage of the steam turbine, when a part of minute droplets generated by the condensate impact or the like adheres to the blade surface of the stationary blade 102, the water film flow 30 on the blade surface. Then, it is sprayed again as the droplet 31 from the trailing edge of the stationary blade 102. That is, since the behavior of the droplet 31 is three-dimensional as shown in FIGS. 7 and 8, it is very difficult to predict the flight direction of the droplet 31 in advance.

  In the droplet measuring apparatus 1 of the present embodiment, the angle θ formed by the laser sheet light 8 and the optical axis of the light collection window 9 is changed by adjusting the irradiation angle adjusting unit 7a and the imaging angle adjusting unit 9a. Is possible. Moreover, the condensing angle α can be changed by adjusting the distance L2 in the optical axis direction between the irradiation end of the borescope 10 and the objective lens 12 by the second imaging distance adjusting unit 11. Furthermore, the irradiation direction of the laser sheet 8 can be changed by rotating the tubular member 20 of the probe 2 around the axis with respect to the casing 101. Therefore, the droplet measuring apparatus 1 of the present embodiment can measure droplets for droplets in any flight direction.

  The effect in this Embodiment comprised as mentioned above is demonstrated.

  In the prior art, there is one that uses a laser beam and a high-speed camera to quantitatively measure the flow velocity of fine particles based on the particle image flow velocity measurement method, but the variation in the particle size to be measured is as small as possible Therefore, when measuring droplets having a wide range of droplet diameters that are generated in the low-pressure stage of the steam turbine, the measurement accuracy is significantly reduced. In addition, in order to image a droplet, the flight direction of the droplet needs to coincide with the laser sheet plane, but the flight direction of the droplet generated in the steam turbine is not constant and is difficult to predict. Speed information cannot be calculated. As another prior art, a correlation equation established between the flow velocity of the working fluid, the flow velocity of the particles, and the particle size of the particles is obtained in advance, and the flow velocity of the working fluid and the velocity of the particles are measured to obtain the correlation equation. There are some that calculate the particle size of the particles, but there are very many man-hours in advance, such as finding the correlation equation by wind tunnel test.In addition, the flow velocity of the working fluid and particles introduced in the correlation equation are isolated from the outside. There is a problem that it is necessary to measure under the condition of the inside of the steam turbine.

  On the other hand, in the present embodiment, a hollow tubular member 20 disposed so as to extend inward and outward through the casing 101, and provided outside the casing 101 of the tubular member 20, is provided with laser light. A laser beam oscillation unit 4 that oscillates 4a and a laser sheet that is provided inside the casing 101 of the tubular member 20 and that is oscillated from the laser beam oscillation unit 4 and forms the laser beam 4a via the tubular member 20 in a sheet shape. The laser sheet light forming unit 7 that converts the light 8 into the working fluid inside the casing 101 and irradiates the laser sheet light 8 from the laser sheet light forming unit 7 and the reflection obtained from the droplet 31 in the working fluid. A borescope 10 that transmits the light 32 and the internally refracted light 33 to the outside of the casing 101 via the tubular member 20, and a droplet obtained via the borescope 10 Since the image pickup unit for picking up the reflected light 32 and the internal refracted light 33 from 1 and picking up the interference fringe image based on the phase difference is provided, the diameter and velocity of the droplet generated inside the steam turbine can be made easier. And it can measure accurately.

  That is, in the present embodiment, it is possible to find optimum measurement conditions corresponding to various operation conditions and measurement objects by separately adjusting and combining setting parameters such as angles, and complicated in advance. It is possible to adjust parameters during steam turbine operation without the need for a verification test, and to measure any properties of droplets generated within the steam turbine.

  In addition, since the scattered light generated when the droplets pass through the laser sheet light is captured as an out-of-focus image, even if the distribution density of the droplets generated in the steam turbine differs depending on the measurement region and operating conditions It is possible to image. In addition, by providing a slit-like mechanism in front of the camera and using it together with the optical compression technique, it can be applied to a measurement region where droplets are generated at high density.

  In the above embodiment, the probe 2 is disposed on the downstream side in the flow of the working fluid (steam) of the moving blade 103 in the final stage, and the laser sheet light 8 described later is irradiated on the upstream side. However, the present invention is not limited to this. For example, like the steam turbine 100A of the modified example shown in FIG. 9, the probe 2 is placed between the stationary blade 102 and the moving blade 103 in the final stage, that is, It is arranged downstream of the flow of the working fluid (steam) of the stationary blade 102 and upstream of the moving blade 103, and by irradiating the laser sheet 8 upstream, the droplets in the steam are measured. It may be configured. Even in this case, the same effect as the present embodiment can be obtained.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. It is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment. For example, a part or all of the part that forms the laser beam may be attached to the steam turbine low-pressure stage instead of being housed in the ILIDS probe body.

DESCRIPTION OF SYMBOLS 1 Droplet measuring device 2 Laser interference imaging method probe 3 Control apparatus 4 Laser beam oscillation part 4a Laser beam 5 Laser adjustment optical system 6 Laser beam reflecting mirror 7 Laser sheet beam forming unit 7a Irradiation angle adjusting unit 8 Laser sheet beam 9 Imaging window 9a Imaging angle adjustment unit 10 Borescope 11 Second imaging distance adjustment unit 12 Objective lens 13 First imaging distance adjustment unit 14 Cylindrical lens 15 Camera 20 Tubular member 21 Image imaging unit 31 Droplet 100 Steam turbine 101 Casing 102 Stator blade 103 Motion Wings

Claims (5)

A hollow tubular member disposed through the casing of the steam turbine so as to extend the flow path of the working fluid in the steam turbine inward and outward;
A laser beam oscillation unit that is provided outside the casing of the tubular member and oscillates a laser beam;
Provided inside the casing of the tubular member, and oscillates from the laser light oscillating portion to convert the laser light through the tubular member into a laser sheet light formed into a sheet shape, and within the working fluid inside the casing A laser sheet light forming section for irradiating
A borescope for transmitting reflected light and internal refracted light obtained from droplets in the working fluid by irradiation of laser sheet light from the laser sheet light forming unit to the outside of the casing via the tubular member;
An image capturing unit that captures reflected light and internal refracted light from the droplet obtained through the borescope and generates an interference fringe image based on a phase difference ; and
A condensing angle adjusting unit that adjusts a condensing angle of a condensing unit that is provided at an end portion of the borescope on the inner side of the casing and collects reflected light and internal refracted light from the droplet. A droplet measuring device for a steam turbine, comprising: A hollow tubular member disposed through the casing of the steam turbine so as to extend the flow path of the working fluid in the steam turbine inward and outward;
A laser beam oscillation unit that is provided outside the casing of the tubular member and oscillates a laser beam;
Provided inside the casing of the tubular member, and oscillates from the laser light oscillating portion to convert the laser light through the tubular member into a laser sheet light formed into a sheet shape, and within the working fluid inside the casing A laser sheet light forming section for irradiating
A borescope for transmitting reflected light and internal refracted light obtained from droplets in the working fluid by irradiation of laser sheet light from the laser sheet light forming unit to the outside of the casing via the tubular member;
An image capturing unit that captures reflected light and internal refracted light from the droplet obtained through the borescope and generates an interference fringe image based on a phase difference ;
The image capturing unit includes:
An objective lens for collecting the light transmitted by the borescope;
A cylindrical lens for adjusting the light collected by the objective lens to parallel light;
A camera for imaging light through the cylindrical lens;
A second imaging distance adjustment unit for adjusting a distance in the optical axis direction between the borescope and the objective lens;
A steam turbine droplet measuring apparatus, comprising: a first imaging distance adjusting unit that adjusts a distance in an optical axis direction between the objective lens and the cylindrical lens . In the steam turbine droplet measuring device according to claim 1 or 2 ,
A droplet measuring apparatus for a steam turbine, comprising: an irradiation angle adjusting unit that adjusts an irradiation angle of the laser sheet light irradiated from the laser sheet light forming unit. A steam turbine casing;
A hollow tubular member disposed so as to penetrate the casing and extend the flow path of the working fluid in the casing inward and outward, and provided outside the casing of the tubular member, and oscillates laser light A laser beam oscillating unit that is provided inside the casing of the tubular member, and oscillates from the laser beam oscillating unit and converts the laser beam via the tubular member into a sheet-shaped laser sheet beam. A laser sheet light forming unit for irradiating the working fluid inside the casing, and the reflected light and internal refracted light obtained from the droplets in the working fluid by irradiation of the laser sheet light from the laser sheet light forming unit A borescope that transmits to the outside of the casing through a member, and images of reflected light and internal refracted light from the droplets obtained through the borescope; An image capturing unit that generates an interference fringe image based on phase difference, the provided on the end of the casing inner side of the borescope, the condensing of the condensing unit for condensing reflected light and the internal refracted light from the droplet A steam turbine, comprising: a droplet measuring device including a condensing angle adjusting unit that adjusts an angle . A steam turbine casing;
A hollow tubular member disposed so as to penetrate the casing and extend the flow path of the working fluid in the casing inward and outward, and provided outside the casing of the tubular member, and oscillates laser light A laser beam oscillating unit that is provided inside the casing of the tubular member, and oscillates from the laser beam oscillating unit and converts the laser beam via the tubular member into a sheet-shaped laser sheet beam. A laser sheet light forming unit for irradiating the working fluid inside the casing, and the reflected light and internal refracted light obtained from the droplets in the working fluid by irradiation of the laser sheet light from the laser sheet light forming unit a borescope for transmitting to the outside of the casing through a member, is condensed light transmitted by the borescope condensed to an objective lens, in the objective lens A cylindrical lens that adjusts light into parallel light, a camera that images light through the cylindrical lens, a second imaging distance adjustment unit that adjusts the distance in the optical axis direction between the borescope and the objective lens, and the objective lens and the cylindrical lens A first imaging distance adjustment unit that adjusts a distance in the optical axis direction from the lens, and images reflected light from the droplet and internal refracted light obtained through the borescope, and interference based on a phase difference A steam turbine comprising: a droplet measuring device including an image capturing unit that generates a fringe image.

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