JP2678647B2 - Measuring method of clearance between turbine blades - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention reduces vibration during rotor blade rotation by mutual contact of projections provided on turbine rotor blades such as steam turbines and gas turbines. The present invention relates to a so-called snubber type turbine moving blade, and more particularly to a gap measuring method between turbine moving blades for measuring and adjusting a snubber gap of the turbine moving blade.

(Prior art) The low-pressure final stage of a recent large-capacity steam turbine and the moving blades in front of it are extremely long as a result of pursuing turbine efficiency, and the effective blade length is almost limited due to the centrifugal force. Has reached. By the way, the force acting on the rotating blade is
Centrifugal force due to rotation, bending force due to steam flow, vibrational force generated due to turbulence of steam flow, imbalance of rotating body, etc., and centrifugal force acting on rotor blades and steam bending force are almost accurately predicted by theoretical analysis Although it is possible, the current value is that the exact value of the vibration force cannot be calculated. Therefore, various vibration damping structures have been devised and applied in order to reduce the vibration of the moving blade.

An example of the above-described vibration damping structure is shown in FIG. 6 as a snubber vibration damping structure. This vibration damping structure is provided with a protrusion (snubber) 1 at the middle or tip of the blade effective portion, and the snubbers 1 of each blade contact each other. It has a structure to reduce vibration by mutual contact, and is widely used from steam turbines to gas turbines. In particular, a torsion blade, which is often used for a long blade of a steam turbine, has a small amount of twist due to centrifugal force when rotated. This phenomenon is called twist back (untwist). That is, as shown in FIG. 6, the rotor blade 2 is deformed in the torsion return direction a, and the snubber on the rotor blade leading edge side of the rotor blade 2 is deformed.
The 1a and the snubber 1b on the trailing edge side of the moving blade are brought into contact with each other and pressed against each other, whereby a frictional force is generated between them and vibration is damped.

(Problems to be Solved by the Invention) However, in the snubber vibration damping structure shown in FIG. 6, each blade snubber suppresses deformation due to twisting back of the blade during high-speed rotation, so that the snubber contact portion and the effective portion are prevented. High stress is generated near the snubber mounting part. In order to reduce the occurrence of high stress due to this phenomenon, the snubber gap between the moving blades should be controlled so that high stress does not occur in the moving blades at the rated rotation and there is sufficient vibration damping effect. Must be set to. By the way, if the snubber gap is too large, the snubbers do not come into contact with each other, or even if they come into contact with each other, sufficient vibration damping cannot be obtained. On the contrary, if the snubber gap is small, there is a risk that excessive stress will be generated in the snubber itself and in the vicinity of the snubber mounting portion to crack the moving blade, or in the worst case, a flying blade scattering accident may occur.

Therefore, for a relatively large-sized snubber blade, it is necessary to measure the snubber gap with high accuracy during normal blade assembly and adjust the gap so that the snubber is in an appropriate contact state during rated rotation. However, the clearance measurement value when the turbine rotor blade is assembled, that is, when the turbine is stationary includes the backlash at the blade implant part, and cannot be said to be an accurate clearance measurement part. Is dangerous to manage. Therefore, even if the gap is adjusted based on this measured value, it is difficult to bring the snubber into an appropriate contact state at the rated rotation.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to obtain a clearance measurement method between turbine rotor blades that eliminates rattling of a rotor blade implantation portion and can measure a clearance between rotor blades.

[Configuration of the invention]

(Means for Solving the Problems) In order to solve the above-mentioned problems, the method for measuring the clearance between turbine rotor blades according to the present invention is such that the centrifugal force acting on the rotor blades installed in the turbine rotor is the weight of the rotor blades. The rotating means for rotating the turbine rotor at a rotational speed exceeding the rotational speed of the turbine rotor, and the gap between the snubbers provided at least at the tip of the rotor blade in synchronization with the timing of the rotation signal of the turbine rotor. A stroboscopic light emitting body that illuminates the entire circumference, and a photographing means for photographing the snubber gap between the moving blades obtained by illuminating with this stroboscopic luminous body, the snubber facing between the adjacent moving blades, While drawing a measurement reference line parallel to the snubber contact surface with a predetermined distance from the snubber contact surface, set a reference line for setting the reference length parallel to the measurement reference line on at least one of the snubbers. Is drawn, and the snubber gap is measured by calculating the ratio between the reference length dimension and the dimension between both measurement reference lines from the image obtained by the photographing means.

(Operation) In the method for measuring the clearance between turbine rotor blades according to the present invention, the rotational speed of the turbine rotor on the rotating means is set so that the centrifugal force acting per rotor blade exceeds the dead weight of the rotor blades. As a result, a force in the turbine radial direction acts on each rotor blade, and it is possible to avoid rattling of the rotor blade implantation portion. In this state, I tried to shoot the snubber gap between the moving blades,
The snubber gap can be accurately measured.

Based on the snubber gap measurement value between moving blades that does not include rattling in the blade implantation portion, if the snubber gap is narrow, change the blade arrangement or adjust the moving blade to an appropriate snubber gap. On the other hand, if the snubber gap is too wide, it is possible to adjust the snubber gap to an appropriate value by changing the arrangement of the blades, so the contact of the snubber of the blade during turbine rated rotation has a sufficient vibration damping effect. Moreover, the state in which excessive stress is not generated in the moving blade is achieved.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

Note that the same or corresponding portions as those of the conventional configuration will be described using the same reference numerals.

FIG. 1 and FIG. 2 show an embodiment of a clearance measuring device for carrying out the clearance measuring method between turbine moving blades according to the present invention.
In this embodiment, the moving blades 2 are planted in a steam turbine rotor 4 mounted on a rotation test device (not shown) as a rotating means such as a low speed balance device or a high speed balance device. In the radial direction of the outer circumference of the turbine rotor 4, a high-speed camera, a video camera, and a position where the moving blade 2 can be monitored,
A camera device 5 as a photographing means such as a still camera is provided.

The camera device 5 is for photographing the snubber gap in each rotor blade 2, and its optical axis direction is accurately adjusted so as to face the rotation center axis of the steam turbine rotor 4, and the snubber gap during rotation of the turbine rotor 4 is accurately adjusted. By taking a picture from directly in front, the occurrence of measurement error is suppressed. The image signal of the snubber gap captured by the camera device 5 is output to the image recording device 19, the image of the snubber gap is recorded by the image recording device 19, and the image recording signal is sent to the image observation device. Is displayed on the monitor screen 20 and is monitored.

On the other hand, the stroboscopic light emitting body 6 that illuminates the snubber gap portion of the moving blade 2 photographed by the camera device 5 is installed at an arbitrary position where a shadow that hinders the measurement of the snubber gap is not generated, and the steam turbine rotor 4 or the rotation test device described above is installed. The rotation signal output obtained by the rotation detector 21 provided in the above is sent to the strobe control device 18 to emit light in synchronization with the rotation cycle of the turbine rotor 4. Further, since the light emission time of the stroboscopic light emitting body 6 is, for example, 1 to 5 × 10 ⁻⁶ seconds, it is observed that the moving blade 2 and the snubber gap illuminated by the stroboscopic light emission are stationary. Strobe control device 18
To generate the strobe light from the strobe light emitter 6 and the rotation detector 21.
By synchronizing and adjusting the timing with the rotation signal obtained in step 1, all snubber gaps during the rotation of the turbine rotor 4 can be observed, and the still image of the snubber gap obtained by the strobe generation is displayed by the camera device 5. The snubber gap can be measured by taking an image and analyzing this camera image (record).

In this snubber clearance measurement, the rotation speed of the steam turbine rotor 4 on the rotation test device is set so that the centrifugal force acting on one of the moving blades 2 exceeds the dead weight of the moving blades 2. The number of rotations of the device is set. By performing the snubber clearance measurement at this required number of revolutions, it is possible to accurately measure the snubber clearance that is not affected by rattling of the blade-implanted portion.

 Next, the operation of the present embodiment will be described.

The steam turbine rotor 4 mounted on the rotation test device is rotated at a constant speed such that the centrifugal force acting on each moving blade 2 exceeds the own weight of the moving blade 2, and the moving blade 2 is rotated at a constant speed. Illumination is performed by the stroboscopic light emitting body 6 adjusted to emit light in synchronization with the rotation cycle of. The snubber gap of the moving blade 2 illuminated by the strobe light emitter 6 is photographed by the camera device 5 and the recorded image is analyzed to measure the snubber gap.

At that time, the rotation speed of the steam turbine rotor 4 is set to 1 of the rotor blade 2.
Since the centrifugal force acting on the main contact is set to a rotational speed that exceeds the own weight of the moving blade 2, a force in the turbine radial direction acts on each moving blade 2, and rattling of the implanting portion of the moving blade 2 is eliminated. It Since the snubber gap of the moving blade 2 is measured in this state, the accurate snubber gap can be accurately measured.

FIG. 3 shows an example of another gap measuring device for carrying out the method for measuring the gap between turbine rotor blades according to the present invention. The same members as those in the first embodiment are designated by the same reference numerals and described. To do.

Generally, when the rotational peripheral speed of the turbine rotor 4 exceeds 25 m / sec, the rotation test device is obliged by law to install a protective wall around it. In this embodiment, the snubber gap measurement is performed through the protective wall 14, and two holes are formed in the protective wall 14 arranged around the rotation test device, and mounting flanges 17, 17 are formed in the holes. It is fixed, and the mounting flanges 17, 17 are provided with a viewing window 15 for the camera device 5 and an illumination window 16 for the stroboscopic light emitting body 6. According to the present embodiment, it is possible to apply even a rotation test device that rotates the turbine rotor 4 so that the rotational peripheral speed thereof exceeds 25 m / sec. The rest of the configuration and operation are the same as in the first embodiment, so a description thereof will be omitted.

FIG. 4 illustrates a specific measuring method for measuring the snubber gap by using the gap measuring device between turbine blades shown in each embodiment.

The monitor screen which image | photographed the snubber gap when a video camera is used for the camera device 5 of a gap measuring device is shown. In FIG. 4, since the corner portion formed by the snubber outer peripheral surface 10 and the snubber contact surface 8 is usually chamfered or rounded, a clear image cannot be obtained, and the snubber gap (distance between the snubber contact surfaces) is not obtained. Cannot be measured directly.

Therefore, the snubber contact surface 8 is previously attached to the snubber outer peripheral surface 10.
Mark the measurement reference lines 11 and 12 that are parallel to the line with a mark or the like. Since these two reference lines 11 and 12 substitute for the snubber contact surface 8 in the method of the present embodiment, it is necessary to draw them in parallel with each other at a precisely defined dimension (known as a predetermined dimension) from the snubber contact surface 8. Further, in order to show the known reference length on the outer peripheral surface 10 of the snubber, the set reference line 13 is drawn in parallel with the measurement reference line 11 by the reference length and accurately separated.

In this snubber gap measuring method, the distances L _B and L _C between the snubber contact surface 8 and the measurement reference line 11 and the measurement reference line 12 on the snubber outer peripheral surface 10 are known to be 3.0 mm, respectively, and the set reference line is set.
When the distance (reference length) L _AB between 13 and the measurement reference line 11 is known to be 7.0 mm, the dimension between the setting reference line 13 and the measurement reference line 11 (reference length dimension) l on the monitor screen 20 is known. _ab is 35.0 mm, dimension l _bc between measurement reference line 11 and measurement reference line 12 on monitor screen 20
Is 32.8 mm, the snubber gap of this embodiment can be obtained by the following equation by calculating the ratio between the reference length dimension and the dimension between both measurement reference lines. That is, Actually, when the measurement is performed as in the present embodiment, the measurement reference lines 11 and 12 and the setting reference line 13 on the image of the monitor screen 20 may be displayed thick depending on how the strobe light from the stroboscopic light emitting body 6 hits. Therefore, if the dimension between the measurement reference lines and the reference length dimension are directly measured on the screen 20, an error may occur during measurement. Therefore, measurement error can be prevented by measuring the measurement reference line dimension and the reference length dimension after the measurement reference line is thinned by the image processing device for image analysis. Further, by combining the above-mentioned image processing device and dedicated analysis software, it is possible to automatically measure the gap between the moving blades.

Next, a method of adjusting the clearance between turbine blades using the clearance measurement value according to the present invention will be described. As a result of the snubber gap measurement obtained by the gap measuring devices of the first and second embodiments, adjustment is performed by changing (changing) the array position of the moving blades 2 that does not provide an appropriate snubber gap. If it is not possible to adjust even with this method, the arrangement position of the moving blades 2 is changed to eliminate the portion where the snubber gap is too wide. To the proper gap. According to this adjusting method, it is possible to obtain a moving blade having a snubber vibration damping structure that has a sufficient vibration damping capacity and does not cause an excessive stress in the moving blade 2.

Here, the appropriate snubber gap is obtained by measuring the change in the snubber gap during the snubber gap measurement and the rated rotation in advance by FEM (Finite).
Element Method: Finite element method) Determined by calculation.
At this time, the snubber gap at the rated rotation uses the value calculated under the condition that both centrifugal force and steam force are applied.

FIG. 5 shows another method of adjusting the clearance between turbine rotor blades using the clearance measurement value according to the present invention. This method aims to improve wear resistance at the contact portion between rotor blades between metals. Blades coated with wear resistant materials such as compounds, cemented carbides or ceramics are used. In FIG. 5, the snubber contact surface 8 on the outer peripheral surface 10 of the snubber before coating has a coating margin 23 indicated by a chain double-dashed line, so that the snubber gap 9 is wider than an appropriate gap. In this state, the snubber gap 9 is measured by using the gap measuring device between the moving blades of the first method, and the coating thickness at which each snubber gap becomes an appropriate gap is calculated. If the coating thickness becomes so thin that the effect of the coating cannot be expected, the snubber contact surface is trimmed by a correction process such as a grinder to adjust the coating thickness. The other methods are the same as those of the first method, and therefore their explanations are omitted. According to this adjusting method, the first
The same effect as the adjustment method of is obtained.

In addition, in each of the above-described embodiments, an example in which the present invention is applied to a moving blade of a steam turbine has been described.

〔The invention's effect〕

As described above, according to the gap measurement method between turbine rotor blades according to the present invention, it is possible to accurately measure the snubber gap between rotor blades, which does not include rattling in the implanted portion of the turbine rotor blade. it can.

Further, by adjusting the arrangement of the moving blades based on the measured value of the snubber clearance measured by the above-mentioned clearance measuring method, sufficient vibration damping action can be obtained at the turbine rated rotation, and the moving blades are excessively large. The effect that the reliability of the moving blade can be significantly improved without causing stress.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing an example of a gap measuring device for carrying out the method for measuring a gap between turbine rotor blades according to the present invention, FIG. 2 is a schematic front view of the device shown in FIG. 1, and FIG. A schematic plan view showing an arrangement state of a protective wall in another example of the gap measuring device for implementing the gap measuring method between turbine moving blades according to the invention,
FIG. 4 is an explanatory view showing a method of measuring a gap between moving blades from a monitor image taken by a gap measuring device, FIG. 5 is an explanatory diagram showing a monitor image taken by each example of the gap measuring device, and FIG. It is a schematic diagram showing a snubber of a general turbine rotor blade. 2 ... moving blade, 4 ... steam turbine rotor, 5 ... camera device (imaging means), 6 ... stroboscopic light emitter, 11, 12 ...
Measurement reference line, 13 ... Setting reference line.

Claims (1)

(57) [Claims] 1. A rotating means for rotating a turbine rotor at a rotational speed at which a centrifugal force acting on a moving blade planted in a turbine rotor exceeds the own weight of the moving blade, and in synchronization with a timing of a rotation signal of the turbine rotor. Between strobe light emitters that emit light and illuminate the gap between the snubbers provided at least at the tip of the moving blade over the entire circumference for each snubber gap, and between the moving blades obtained by illuminating with the strobe light emitters. Of the snubber gap, and draws a measurement reference line parallel to the snubber contact surface at a predetermined distance from the snubber contact surface on the snubber facing between the adjacent moving blades, while at least the snubber at least Draw a set reference line for setting the reference length on one side parallel to the measurement reference line, and calculate the ratio of the reference length dimension and the dimension between both measurement reference lines from the image obtained by the photographing means. Clearance measuring method between turbine blades, characterized in that to measure the snubbers gap treated.