JPH10185538A - Method and equipment for ultrasonically measuring gap of a rotator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an easy noncontact measurement of the dimensions of a radial or axial gap of a metallic or nonmetallic rotator even in a dirty environment. SOLUTION: The inventive equipment comprises an ultrasonic sensor 3 for generating an ultrasonic pulse and receiving the reflected wave thereof fixed in the radial direction of a rotator or the direction of an axial gap thereof, and a sensor 5 for removing the effect of a resonance wave from the output signal of the ultrasonic sensor 3 upon excitation thereof and detecting the temperature in the gap. Sound velocity in the gap variable with the temperature is then calculated and then the dimensions of the gap are calculated based the time interval between transmission and reception of the ultrasonic pulse derived from the noise-free output signal, and the calculated sound speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring a gap size of a rotating body.

[0002]

2. Description of the Related Art There are eddy current type, discharge type, capacitance type, light reflection type, and X-ray transmission type as means for measuring the gap amount of a rotating body. In addition, there is an ultrasonic transmission / reception method as a means for measuring a distance much larger than the gap.

[0003]

The above-mentioned conventional gap measuring devices are of a type in which the rotating body must be made of a metal, such as an eddy current type, a discharge type, and a capacitance type, and a dirt such as a light reflection type. There are advantages and disadvantages such as a weak device and a device having a large device such as an X-ray transmission type, which has a problem in use. In addition, an ultrasonic type distance measuring device has a measuring range of several tens of meters or more, and is not suitable for measuring a gap (several tens of millimeters or less) between rotating bodies. The present invention has been made to solve this problem, and it is possible to easily measure the rotating radial gap or the axial gap of a metal or nonmetal in a non-contact and dirty environment. It is an object of the present invention to provide a measurement method and apparatus that can perform the measurement.

[0004]

SUMMARY OF THE INVENTION A gap measuring device for a rotating body according to the present invention is mounted in a gap in a radial or axial gap of the rotating body, generates an ultrasonic pulse and generates a reflected wave. An ultrasonic sensor for receiving,
Means for removing the influence of the resonance wave when exciting the ultrasonic sensor from the output signal of the ultrasonic sensor, a sensor for detecting the temperature of the gap, a means for calculating a sound speed from the detected temperature, A calculating device for calculating the gap amount from the time interval of transmission and reception of the sound pulse and the calculated sound speed.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS When an ultrasonic sensor is excited by a trigger pulse to generate an ultrasonic wave, the ultrasonic wave propagates at a sound speed in a gap space and is reflected on an object wall, and the reflected wave is received by the same ultrasonic sensor. Measured. The elapsed time T from the generation of the ultrasonic wave to the reception of the reflected wave is proportional to the gap dimension L and inversely proportional to the sound velocity V. Therefore, if the elapsed time and the sound speed are measured, the gap size is measured according to the relationship of L = TV / 2 ‥‥‥ (1) (1). The ultrasonic sensor has good environmental resistance and can operate without problems even in a high-temperature and dirty environment.

When this measuring method is applied to the measurement of the gap amount of the rotating body, there is a problem that the structure of the rotating body is not always uniform in the radial direction or the axial direction. If there are upper and lower irregularities, the gap between the opposing wall surface will change with rotation. Therefore, even if the gap amount is measured, whether it is the gap between the rotating body convex part and the wall surface, the gap between the specific part of the rotating body and the wall surface, or the temporal change between the rotating body and the wall surface The measurement method differs depending on whether a gap is determined. Further, the sound speed cannot always be treated as being constant, but changes depending on what medium the sound wave propagates (for example, air), and furthermore, the temperature and the density.
Therefore, the present invention is to calculate the sound speed corresponding to the environmental change and calculate the gap.

In the present invention, it is considered that a gap amount between an arbitrary specific point of the rotating body and a wall surface is obtained. The specific point is provided with a reference position sensor that determines a reference point on any of the rotating bodies and detects a signal when the reference point passes once per rotation.
By setting the trigger pulse with the signal with an appropriate delay, the rotational position of the rotating body can be specified. It is the positional relationship between the reference position sensor and the ultrasonic sensor,
It is determined by the rotation speed of the rotating body and this delay time. By changing the delay time, the gap at an appropriate position of the rotating body can be measured.

When the gap is measured by the ultrasonic transmission / reception method, the actual vibration of the ultrasonic sensor 3 for receiving the reflected wave is not limited to the reception of the reflected wave but also the ultrasonic sensor based on the excitation at the time of transmission. The own resonance wave is superimposed. When measuring long distances, the arrival time of the reflected wave becomes longer and the excitation resonance wave is sufficiently attenuated, so superposition of this resonance wave did not matter much, but when the gap to be measured was narrow Since the arrival time of the reflected wave is short, there is a problem that it is difficult to distinguish the reflected wave from the excited resonance wave and to determine the accurate reception timing of the reflected wave because the excitation resonance wave is less attenuated. Therefore, according to the present invention, the attenuation waveform characteristic of the excitation resonance wave is stored in advance, and this is subtracted from the output signal of the ultrasonic sensor 3 to remove the influence of the excitation resonance wave. If the gap is infinite, no reflected wave is received, and the output of the ultrasonic sensor can be simply regarded as corresponding to the excitation resonance wave. It can be obtained as measurement data of the ultrasonic sensor 3 at the time. The present invention removes the influence of the excitation resonance wave in this way to accurately determine the reception timing of the reflected wave and to easily calculate the elapsed time from the trigger pulse to the reflected wave.

[0009]

Embodiment 1 FIG. 1 is a block diagram showing an embodiment of the present invention, in which a gap between a rotor blade end of a compressor or a turbine and a casing is measured. In FIG. 1, 1 is a rotor, 2 is a casing, 3 is an ultrasonic sensor, 4 is a reference position sensor, 5 is a temperature sensor, 6 is an amplifier, 7 is an arithmetic unit, and is a microprocessor, an AD converter and a DA. It is composed of a converter, and performs delay (variable) of a trigger signal, measurement of elapsed time, calculation of a sound speed corresponding to a temperature change, and a process of removing the influence of an excited resonance wave to calculate a gap size.

Next, the operation will be described. The reference position in the rotation direction of the rotating body is detected by a reference position sensor 4 (for example, a magnetic sensor that attaches a magnet to one of the rotor blades and detects passage thereof). The signal is a signal as shown in FIG. 2A. The signal is converted into a digital pulse signal as shown in FIG. 2B via an AD converter 8 (for example, a one-shot multivibrator responding to a signal having a certain threshold or more). , Is delayed (τ) in the arithmetic unit 7 as shown in FIG. 2C. The delayed signal is converted to an analog signal having an ultrasonic vibration frequency with a pulse width as shown in FIG. 2D via a DA converter 9 (for example, an analog oscillator that outputs a gate only when the signal is high), and the ultrasonic sensor 3 Trigger pulse.
The ultrasonic sensor 3 is excited by this pulse, and an ultrasonic wave having the same shape as D is emitted, and the ultrasonic wave directed to the rotary wing 1 is reflected at the blade tip. The reflected wave is detected by the same ultrasonic sensor 3 (FIG. 2)
A signal like E) is input to the amplifier 6 and amplified. However, the actual vibration of the ultrasonic sensor 3 is not only a result of receiving the reflected wave but also a resonance wave of the ultrasonic sensor itself based on excitation at the time of transmission, and an electric signal corresponding thereto (FIG. 2F). Is A through the amplifier 6
The data is sent to the D converter 10 and is converted into a digital value. It is difficult to distinguish the reflected wave from this excitation resonance wave and to determine the accurate reception timing of the reflected wave. Therefore, the attenuation waveform characteristic of the excitation resonance wave (measurement data of the ultrasonic sensor 3 when the gap is infinite) as shown in FIG. 2G is stored in the arithmetic unit 7, and this is obtained from the output signal of the ultrasonic sensor 3. By subtracting, the effect of the excitation resonance wave can be removed,
A signal as shown in FIG. 2H corresponding to the reception of the reflected wave of E can be obtained. The timing of reading the attenuation waveform of the excitation resonance wave from the memory is synchronized with the excitation resonance signal superimposed on the output of the AD converter 10, and is subtracted by the subtractor. Eliminating the influence of the excitation resonance wave in this manner facilitates calculation of the elapsed time from the trigger pulse to the reflected wave.

On the other hand, the temperature is measured by a temperature sensor 5 installed in the vicinity of the gap to be measured, digitized via an AD converter 11, and the sound velocity corresponding to the temperature is determined using the known physical property values of the working fluid. Is calculated. By the way, when the sound velocity V in the air is considered, it is given by: V = 332 m / sec + 0.61t (2), which varies depending on the temperature t regardless of the pressure or the density. Calculate the sound velocity V. Since the elapsed time corresponds to the reciprocation of the gap, the gap L to be measured is calculated by T
(Elapsed time) × V (sound speed) ÷ 2.

By changing the delay time (τ) of the trigger pulse, the tip clearance of an arbitrary rotor can be measured. Further, if the delay time is adjusted so that a trigger pulse is output when there is no rotor, the above-described attenuation waveform characteristics of the excitation resonance wave (measurement data of the ultrasonic sensor 3 when the gap is infinite)
Can be measured, and this data may be stored in the RAM in advance.

[0013]

According to the present invention, the distance measurement method of the ultrasonic transmission / reception method can be adapted to the gap measurement, and the gap size in the radial direction or the gap size in the axial direction of the metallic or non-metallic rotating body can be measured in a non-contact manner. This is a measurement device that can easily measure even in dirty environments, measuring the tip clearance during operation of aviation gas turbine engines, industrial gas turbines, steam turbines, etc., and axial displacement of the rotating shaft Measurement, etc. This makes it possible to improve the performance and safety of these engines.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing operation waveforms in one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Turbine rotor blade 2 Turbine casing 3 Ultrasonic sensor (Transceiver) 4 Reference position sensor 5 Temperature sensor 6 Amplifier 7 Arithmetic unit

Claims (4)

[Claims] 1. A method for measuring a gap with a rotating body as an arrival time interval by transmitting and receiving an ultrasonic wave, wherein a sound velocity that changes with temperature is calculated, and an excitation resonance wave superimposed on an output of an ultrasonic sensor. By removing the effect of, an accurate reflected waveform is obtained, and an accurate propagation time is obtained.
A method of measuring a gap of a rotating body, comprising calculating a gap size from the propagation time and the calculated sound velocity. 2. An ultrasonic sensor mounted in a gap in a radial direction or an axial direction of a rotating body and configured to generate an ultrasonic pulse based on a trigger pulse and receive a reflected wave, and the ultrasonic sensor. Means for removing the effect of the resonance wave when the ultrasonic sensor is excited from the output signal of the ultrasonic sensor, a sensor for detecting the temperature of the gap, a means for calculating the speed of sound in the gap from the detected temperature, A gap calculating device for calculating the gap dimension from a time interval of pulse transmission and reception and the calculated sound velocity. 3. A member for indicating a reference position is provided on a part of the rotating body, and a reference position detection sensor for detecting passage of the member at a position apart from the ultrasonic sensor by a certain rotation angle is provided. Means for delaying the output of the sensor, detecting a signal when the reference point passes once per rotation, and providing the signal with an appropriate delay as a trigger pulse, thereby obtaining a rotating body to be measured. The gap measuring device for a rotating body according to claim 2, wherein the rotating portion of the rotating body can be specified. 4. An arithmetic unit comprising a storage means for storing the output of the ultrasonic sensor and a subtraction means, and a part having a sufficiently large gap with the rotating body is specified by giving an appropriate delay time, and the ultrasonic pulse is generated. 4. The gap of the rotating body according to claim 3, wherein an output signal of the ultrasonic sensor when the vibration is generated is stored, and the effect of the resonance wave when the ultrasonic sensor is excited is subtracted from the output of the ultrasonic sensor. Measuring device.