JP2000028428A - Optical probe for measuring vibration of moving blade of turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical probe which can accurately measure the vibration of the moving blade of a turbine by constituting the probe in such a way that the probe can perpendicularly project incident light upon the front end face of the moving blade when the probe is perpendicularly attached to the external surface of a casing and the reflected light can surely return to the probe even if the front end face of the blade is slanted to a rotating shaft. SOLUTION: An optical probe is composed of a main body which is extended nearly perpendicularly to the rotating shaft of a gas turbine, a coaxial optical fiber 14 inserted into the main body from the outside along the axial line of the probe, and an optical system 16 provided between the inner end of the fiber 14 and the internal end face of the main body. The optical system 16 is composed of protective glass 17 provided near the internal end face of the main body, a condenser lens system 18 which is provided closely to the fiber 14 and condenses the laser light from an optical fiber for projection, and a prism 19 provided between the glass 17 and lens system 18. The prism 19 is constituted to perpendicularly refract the laser light from the optical fiber for projection to the front end face of the moving blade of the gas turbine and laser light reflected from the front end face in the direction of the axial line of the main body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical probe for monitoring a blade vibration of a running gas turbine engine in a non-contact manner.

[0002]

2. Description of the Related Art In order to evaluate the performance of a gas turbine, the vibration of a turbine rotor blade during operation may be measured. Conventionally,
In such a test, a strain gauge was attached to the moving blade itself, a deformation signal based on the vibration of the moving blade was detected, and a vibration state was measured from the deformation signal. However, this method cannot be applied to a gas turbine whose rotor blade is exposed to a high-temperature gas due to poor heat resistance of a strain gauge, and a large-scale device for extracting a deformation signal to the outside is required. was there. Therefore, the applicant of the present invention has previously proposed a measuring means for optically measuring the vibration of a turbine rotor blade (Japanese Patent Application No. Hei.
241505). This device provides a quartz glass lens at the tip of a light emitting optical fiber and a light receiving optical fiber arranged side by side, a quartz protective glass in front of the lens, and an outer cylinder on the outer periphery. An outer cylinder is mounted outside the casing of the rotor blade portion of the rotating machine so that the tip of the probe faces the rotor blade end, a cooling water passage is formed inside the outer cylinder, and the probe of the probe is provided in the casing. An air passage for flowing compressed air is formed at the tip. With such a device, the laser light emitted from the optical fiber for light projection is irradiated to the end of the moving blade through the lens and the protective glass, and reflected at the end of the moving blade, the protective glass,
The light passes through the lens and is returned to the optical fiber for receiving light. If the moving blade is vibrating, a slight displacement occurs between the light emitting laser beam and the light receiving laser beam. By analyzing the amount of change, the vibration of the moving blade can be measured.

[0003]

In order to measure the vibration of the turbine blade using the above-described optical probe, the laser light reflected on the tip surface (blade tip surface) of the blade is applied to an optical fiber for light reception. I need to go back. For this reason, in the conventional probe, the light emitting and receiving optical fibers are configured coaxially, and the probe is attached to the turbine casing so that the laser light is vertically irradiated on the blade tip surface and vertically reflected.

However, in a normal gas turbine, a flow path is generally expanded toward downstream in order to expand a working fluid (for example, combustion gas). As a result, the gas flow path and the flow path inner surface of the casing become outer surfaces of the casing. Are often not parallel to For this reason, the tip surface of the blade is also inclined with respect to the outer surface of the casing, and in order to make the light emitting and receiving direction of the probe perpendicular to the tip surface of the blade, it is necessary to mount the probe at an angle to the outer surface of the casing. . For this reason, the probe easily interferes with other adjacent devices, and there are cases where the probe can be mounted only perpendicularly to the outer surface of the casing due to restrictions around the probe mounting portion on the outer surface of the casing. However, in this case, since the light emitted from the probe hits the tip surface of the blade at an angle, the reflected light does not return to the optical fiber for light reception of the probe, and there is a problem that accurate measurement cannot be performed.

The present invention has been made to solve the above-mentioned problems. In other words, an object of the present invention is to provide a probe accurately mounted on the casing outer surface even when the blade tip surface of the rotor blade is inclined with respect to the rotation axis and the casing inner surface is not parallel to the casing outer surface. An object of the present invention is to provide an optical probe for measuring the vibration of a turbine rotor blade capable of performing various measurements. Another object of the present invention is to
An optical probe for measuring vibration of turbine blades that can irradiate incident light vertically to the blade tip surface inclined with respect to the rotation axis from a probe mounted perpendicular to the outer surface of the casing, and reliably return the reflected light to the probe Is to provide.

[0006]

According to the present invention, there is provided an optical probe for measuring vibration of a turbine rotor blade having a blade tip surface inclined with respect to a rotation axis, wherein the optical probe is spaced apart from the blade tip surface. A probe body having opposed inner end surfaces and extending substantially perpendicular to the rotation axis, a coaxial optical fiber inserted into the probe body from a radially outward direction along the probe axis, and an inner end of the coaxial optical fiber And an optical system provided between the inner end surface of the probe body and the coaxial optical fiber, wherein the coaxial optical fiber is a light emitting optical fiber for introducing a laser beam from the outside to the center, and a reflected laser coaxially disposed therearound. The optical system is composed of a light-receiving optical fiber for extracting light to the outside, and the optical system is provided with a protective glass provided near the inner end surface of the probe main body and a light-transmitting light provided near the coaxial optical fiber. A condensing lens system for condensing the laser light from the fiber, and a laser beam provided between the condensing lens system and the protective glass, which refracts the laser beam in the axial direction of the probe body in the direction perpendicular to the wing tip surface and the wing tip surface An optical probe for measuring vibration of a turbine rotor blade, comprising: a prism for refracting laser light vertically reflected from the probe body in the axial direction of the probe main body.

According to the configuration of the present invention, the prism is disposed near the tip of the probe vertically mounted on the outer surface of the casing, and the light that has passed through the condenser lens system from the tip of the optical fiber is bent by the prism to be measured by the prism. Since the light impinges perpendicularly on the blade tip surface of a certain turbine blade, the laser light that is reflected perpendicularly from the impeller can also be returned to the light receiving optical fiber through the same path with little loss. Therefore, the use of the prism makes it possible to easily and accurately measure the vibration of the rotor blade having an angle at the blade tip surface by using a prism having an appropriate angle regardless of the situation inside and outside the casing. .

According to a preferred embodiment of the present invention, the probe main body includes a cooling gas flow path extending from the outside to the vicinity of the inner end face, and a cooling gas injected from the cooling gas flow path to the surface facing the blade of the protective glass. And a flow path area of the plurality of nozzles is set to be sufficiently smaller than the cooling gas flow path so that the pressure of the cooling gas flow path can be maintained substantially constant. With this configuration, the pressure in the cooling gas flow path is maintained substantially constant, and the cooling gas (for example, compressed air) is injected from the plurality of nozzles to the blade-facing surface of the protective glass,
It is possible to prevent the combustion gas from coming into direct contact with the protective glass, thereby preventing contamination and overheating.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In addition, the same reference numerals are given to the common parts in the respective drawings, and the duplicate description will be omitted. FIG. 1 is an overall perspective view of a turbine rotor blade vibration measuring device using the optical probe of the present invention. As shown in this figure, the optical probe 10 of the present invention is attached to a plurality of locations outside the casing 1 of a gas turbine. Each probe 10 is connected to a laser system 3 via a coaxial optical fiber 14 composed of an optical fiber for projecting and receiving light, and this laser system 3 is further connected to a photoelectric converter 5 by an optical fiber 4. It is connected to an analyzer 7 by a cable 6. In this figure, reference numeral 8 denotes a power supply. The laser light emitted by the laser system 3 is applied to the blade tip surface of the turbine rotor blade rotating in the casing 1 via the central fiber of the coaxial optical fiber 14 and the probe 10, and the reflected light is combined with the pulsed laser light. As a result, the light reaches the photoelectric converter 5 via the outer peripheral fiber of the coaxial optical fiber 14, where it is converted into an electric signal and input to the analyzer 7. When the rotor blade is vibrating, the blade deformation due to the vibration causes a slight shift in the tamping of the pulsed laser light reflected from the blade tip surface,
By analyzing the amount of change, vibration measurement of the moving blade can be performed.

FIG. 2 is a partial structural view showing the optical probe of the present invention. As shown in this figure, the turbine blade vibration measuring optical probe 10 of the present invention is an optical probe for measuring the vibration of the turbine blade 9 having a blade tip surface 9a inclined with respect to the rotation axis Z. In addition, the optical probe 10 is mounted perpendicularly to the outer surface of the casing (that is, to the rotation axis Z) due to restrictions around the probe mounting portion on the outer surface of the casing. In this figure,
Reference numeral 1a denotes an inner surface of the flow passage of the casing facing the blade tip surface at an interval.

As shown in FIG. 2, an optical probe 10 for measuring vibration of a turbine blade according to the present invention comprises a probe main body 12, a coaxial optical fiber 14, and an optical system 16. In this embodiment, the probe main body 12 includes a substantially hollow cylindrical outer cylinder 12a directly attached to the turbine casing 1, an almost hollow cylindrical inner cylinder 12b inserted inside the outer cylinder 12a, and the outer cylinder 12a. Inner cylinder 12
b, and an inner end member 13 attached to the inner end of b.
That is, the probe main body 12 has an inner end member 13 having an inner end surface 13a opposed to the wing tip surface 1a at an interval.
And an outer cylinder 12a and an inner cylinder 12b extending substantially perpendicular to the rotation axis Z. The coaxial optical fiber 14 is inserted into the inner cylinder 12b of the probe main body 12 from the outside in the radial direction along the probe axis, and the inner end thereof is fixed in the inner cylinder 12b. As described above, the coaxial optical fiber 14 is composed of a light projecting optical fiber 14a for introducing a laser beam from the outside to the center, and a light receiving optical fiber 14b coaxially arranged therearound for extracting the reflected laser beam to the outside.

The optical system 16 is provided between the inner end of the coaxial optical fiber 14 and the inner end surface 13a of the probe body 12. The optical system 16 includes a protective glass 17, a condenser lens system 18, and a prism 19. Protective glass 17
Is mounted near the inner end face 13a of the probe body 12 (that is, the inner end member 13). This protective glass 1
Numeral 7 is preferably a flat quartz glass, which is hermetically attached by a sealing member (for example, an O-ring) so as not to affect the laser light passing therethrough and to prevent the condenser lens system 18 from being directly exposed to a combustion gas or the like. I have. Further, the probe body 12 has a cooling gas flow path 21 extending from the outside to the vicinity of the inner end face, and a plurality of nozzles 22 for jetting the cooling gas from the cooling gas flow path 21 to the surface of the protection glass 17 facing the blade. . The overall flow path area of the plurality of nozzles 22 is:
The cooling gas passage 21 is set to be sufficiently smaller than the cooling gas passage so that the pressure of the cooling gas passage 21 can be maintained substantially constant. This prevents the combustion gas from coming into direct contact with the protective glass, thereby preventing its contamination and overheating. Further, as shown in FIG. 1, the inner cylinder 12b is provided with at least two sealed cooling water flow paths 23 extending from the outside to the periphery of the prism 19. The cooling water flow paths 23 communicate with each other via a ring-shaped groove 24 surrounding the prism 19.
The probe body 12 can be cooled by circulating cooling water and flowing cooling water.

In FIG. 2, a condenser lens system 18 includes a small-diameter lens 18 provided close to the coaxial optical fiber 14.
a and a large-diameter lens 18b provided adjacent to the small-diameter lens 18a. With this combination, the condensing lens system 18 condenses the laser light from the light projecting optical fiber 14a at the center of the coaxial optical fiber 14 onto the blade tip surface 9a of the moving blade 9.

The prism 19 is provided between the condenser lens system 18 and the protective glass, and refracts the laser beam in the axial direction of the probe body 12 in a direction perpendicular to the wing tip surface 9a and perpendicularly from the wing tip surface 9a. The reflected laser light is refracted in the axial direction of the probe main body.

FIG. 3 is an explanatory diagram schematically showing the optical system of FIG. When laser light is introduced from the laser system 3 into the optical probe 10 having the above-described configuration via the light projecting optical fiber 14a at the center of the coaxial optical fiber 14, the laser light is condensed by the small-diameter lens 18a and the large-diameter lens 18b, The light converges on a virtual point indicated by O 'in the figure. Next, this laser light is applied to the wing tip surface 9 by the prism 19.
It is refracted in the direction perpendicular to a and focuses on point O on the wing tip surface. When the blade tip is vibrating, the laser light reflected on the blade tip surface 9a is slightly deviated from the incident light due to a slight inclination of the blade tip surface, and is refracted by the prism 19 in the axial direction of the probe main body. Part of the light enters the light receiving optical fiber 14b around the coaxial optical fiber 14 through only the large diameter lens 18b. Therefore, the light receiving optical fiber 1
The reflected light incident on 4b is converted into an electric signal by the above-described photoelectric converter 5 and analyzed by the analyzer 7, whereby vibration of the moving blade can be measured.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the present invention.

[0017]

As described above, according to the optical probe for measuring vibration of a turbine rotor blade of the present invention, the blade tip surface 9a of the rotor blade 9 is inclined with respect to the rotation axis Z, and the inner surface of the flow passage of the casing 1 is formed. Even when 1a is not parallel to the casing outer surface, it is possible to irradiate the incident light perpendicularly to the blade tip surface 9a from the probe 10 mounted perpendicular to the casing outer surface, and to reliably return the reflected light to the probe. It has an excellent effect that accurate vibration measurement of the turbine blade can be performed.

[Brief description of the drawings]

FIG. 1 is an overall perspective view of a turbine rotor blade vibration measuring device using an optical probe of the present invention.

FIG. 2 is a partial configuration diagram showing an optical probe of the present invention.

FIG. 3 is an explanatory view schematically showing the optical system of FIG. 2;

[Explanation of symbols]

 Reference Signs List 1 turbine casing 1a flow path inner surface 3 laser system 4 optical fiber 5 photoelectric converter 6 cable 7 analyzer 8 power supply 9 rotor blade 9a blade tip surface 10 optical probe 12 probe body 12a outer cylinder 12b inner cylinder 13 inner end member 13a inner end face 14 Coaxial optical fiber 14a Light emitting optical fiber 14b Light receiving optical fiber 16 Optical system 17 Protective glass 18 Condensing lens system 18a Small diameter lens 18b Large diameter lens 19 Prism 21 Cooling gas flow path 22 Nozzle

Claims (2)

[Claims] 1. An optical probe for measuring vibration of a turbine rotor blade having a blade tip surface inclined with respect to a rotation axis, the optical probe having an inner end surface opposed to the blade tip surface at an interval and having a rotation axis. A probe body extending substantially perpendicular to the probe body, a coaxial optical fiber inserted into the probe body from the radial outside along the probe axis, and between an inner end of the coaxial optical fiber and an inner end face of the probe body. Provided optical system,
The coaxial optical fiber is composed of a light emitting optical fiber that introduces laser light from the outside to the center, and a light receiving optical fiber that is arranged coaxially therearound and takes out reflected laser light to the outside. A protective glass provided near the inner end surface of the probe body, a condensing lens system provided in close proximity to the coaxial optical fiber, for condensing laser light from the light emitting optical fiber, and a condensing lens system and the protective glass. A prism that is provided between the probe body and refracts the laser light in the axial direction of the probe body in the direction perpendicular to the blade tip surface, and refracts the laser light vertically reflected from the blade tip surface in the axis direction of the probe body. Characteristic optical probe for measuring turbine blade vibration. 2. The probe main body has a cooling gas flow path extending from the outside to the vicinity of the inner end face, and a plurality of nozzles for jetting the cooling gas from the cooling gas flow path to the surface facing the blade of the protective glass. The flow path area of the plurality of nozzles is set to be sufficiently smaller than the cooling gas flow path so that the pressure of the cooling gas flow path can be maintained substantially constant. Optical probe.