JPH06140126A - Measuring device for blade tip gap - Google Patents

Abstract

PURPOSE:To measure blade tip gaps of respective blades by discharge technic. CONSTITUTION:This device is provided with a probe 1; a ball screw 5 and a stepping motor 7, etc., for moving the probe 1 to in a blade tip direction; a power source 8, for applying high-voltage; and a discharge judging apparatus 10, for judging discharge between the prove 1 and a blade tip 3. When the discharge by the probe 1 in the largest diameter part of a rotation blade 2 is judged by the discharge judging device 10, by a personal computer 12, control is made to measure a blade tip gap based on the moved distance of the probe 1, by more moving the probe 1 in the blade tip direction of the rotation blade 2 to be discharged between the probe 1 and the next nearest rotation blade 2, or, to measure a blade tip gap based on a discharge gap calculated from applied voltage by more increasing applied voltage to be discharged between the probe 1 and the next nearest rotation blade.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blade tip clearance measuring device, and is particularly suitable for measuring a clearance between a casing such as a turbine or a compressor and a moving blade tip by utilizing high voltage discharge. Wing tip clearance measuring device.

[0002]

2. Description of the Related Art Conventionally, in a device such as a turbine or a compressor for converting kinetic energy of fluid into mechanical rotational energy, how to improve the conversion efficiency has been one of the important issues. In this type of energy conversion, the reduction of rotational losses, for example in turbines, has a significant impact on the performance of the overall equipment in which it is used. Rotational losses in turbines are noticeable in jet engines. That is, in a jet engine, it is generally known that if the gap between the blade tip of the turbine and the casing is large, the efficiency of conversion into rotational energy is significantly reduced. Therefore, the improvement of the conversion efficiency in the jet engine is immediately related to the reduction of the fuel consumption, and therefore, it is one of the important improvement items particularly in the case of an aircraft flying a long distance.

On the other hand, not only the jet engine but also other various turbines and the like rotate at high speed in a high temperature atmosphere, and it is not easy to measure the clearance between the casing and the blade tip. . For this reason, research and development of contactless blade tip clearance measurement methods using discharge technology have recently been performed.

[0004]

However, at present, there is a problem that the technique for measuring the blade tip clearance of each blade in the rotating machine by using the above-mentioned discharge technique has not been put into practical use at present. .

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a blade tip clearance measuring device which is capable of improving the disadvantages of the prior art and measuring the blade tip clearance of each blade by an electric discharge technique.

[0006]

The present invention provides a blade tip clearance measuring device for measuring a clearance between a blade tip of a plurality of rotor blades and a casing arranged on the outer peripheral side of the rotor blades. A probe that is movably arranged in the blade tip direction and forms a discharge gap between the tip portion and the blade tip of the rotary blade, and a moving means that moves the probe in the blade tip direction of the rotary blade. When,
The discharge determining means includes: a power supply that applies a high voltage between the probe and the rotary blade; and a discharge determining means that determines the occurrence of discharge between the probe and the blade tip of the rotary blade. When it is determined that the probe has discharged in the maximum diameter portion of the rotary blade by means of the moving means, the moving means further moves the probe toward the blade tip direction of the rotary blade, thereby rotating the blade next to the probe. And the discharge control means is repeated to measure the blade tip clearance based on the moving distance of the probe, or the discharge determining means causes the probe to discharge at the maximum diameter portion of the rotary blade. When it is determined that the power supply voltage is further increased by the power supply, the control for discharging between the probe and the next-nearest rotor is repeated, and the blade tip clearance is calculated based on the discharge gap calculated from the applied voltage. Second measurement to measure It is obtained by a structure having a control means for executing the method.

[0007]

According to the blade tip clearance measuring apparatus of the present invention, first, a predetermined high voltage is applied between the probe and the rotary blade, and then the probe is moved by the moving means to the blade tip of the rotary blade. When the discharge determining means determines that the probe has discharged at the maximum diameter portion of the rotary blade, the control means further moves the probe toward the blade tip of the rotary blade to move the probe to the tip of the rotary blade. Next, a discharge is generated between the rotor and the next rotor. This is done for all rotor blades. Then, the blade tip clearance in each rotor is measured based on the distance moved by the probe. Alternatively, when the discharge determining means determines that the probe has discharged in the maximum diameter portion of the rotary blade, the control means further increases the applied voltage to cause discharge between the probe and the next rotating blade. This is done for all rotor blades. Then, the blade tip clearance in each rotor is measured based on the discharge gap calculated from the applied voltage. Therefore, the blade tip clearance in each rotor can be measured with extremely high accuracy.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment to which the blade tip clearance measuring device of the present invention is applied will be described below with reference to the drawings.

First, the principle of discharge type blade tip clearance measurement in the blade tip clearance measurement device of this embodiment will be described. As shown in FIG. 3, a predetermined voltage (minimum spark discharge voltage) is applied between the probe 1 and the rotor blade. When the probe 1 is gradually approached to the blade tip side of the rotor blade with the above voltage applied, electric discharge is generated at the maximum diameter portion of the rotor blade (the numbers shown in FIG. 3 are for five rotor blades). Wing number). The voltage generated in the resistance R of the power supply circuit at the time of the discharge is in an impulse state synchronized with the rotation speed of the rotary blade, as shown in FIG. In this case, assuming that discharge has occurred in all of the five rotor blades, the generated voltage in the impulse state should be observed on the time axis divided by the number of rotor blades, as shown by the dotted line in FIG. .

In view of this, in this embodiment, after the electric discharge is generated at the maximum diameter portion of the rotor blade which the probe 1 is closest to, the following measuring method 1 or measuring method 2 is performed to Discharge between the rotor and the rotor near
The blade length of each blade is measured by detecting the feed of the blade, or the blade tip clearance of each rotor is measured based on the discharge gap calculated from the applied voltage. In this case, both the measurement method 1 and the measurement method 2 are on condition that the applied voltage and the discharge gap have a constant relationship.

(1) In the measuring method 1 of the present embodiment, as shown in FIG. 6, after the discharge is generated between the probe 1 and the maximum diameter portion of the rotary blade (the probe 1 and the rotary blade are separated from each other). The discharge gap between them is dE), and this is a measurement method in which electric discharge is generated between the probe 1 and the rotor next to the rotor by sending the probe 1 in the direction of the rotor blade by a further minute distance Δd. The measurement method 1 has an advantage that the characteristics of the applied voltage and the discharge gap change depending on the humidity, but are not affected by the humidity. In this case, measurement method 1
If the environmental conditions and applied voltage are the same, the probe 1
Since the discharge gap between the rotor and the blade does not change, the feed amount of the probe 1 corresponds to the difference from the maximum diameter portion of the rotor.

(2) In the measuring method 2 of the present embodiment, as shown in FIG. 7, after the discharge is generated between the probe 1 and the maximum diameter portion of the rotary blade, the probe 1 and the rotary blade are separated from each other. This is a measurement method in which the applied voltage E between the probe 1 and the rotary blade next to the probe blade 1 is increased by further increasing the voltage ΔE. The measurement method 2 has an advantage that there is no risk of bringing the probe 1 into contact with the rotor blade and the signal is stable.

Here, the length conversion in the measuring method 2 will be described. The spark voltage Vs in the uniform electric field is the atmospheric pressure P from Paschen's law under the gas temperature T = constant.
It can be expressed by the following equation by the function of the product Pd of the gap length d and the gap length d. Vs = B (Pd) / {InA-InIn (1 + 1 / γ) + In (Pd)} A and B in the above formula are given by an empirical formula for the ionization coefficient α by α / p = Ae ^{−B / E / P.} (E: electric field), and γ in the above equation is a secondary ionization constant. The applicable range of the above formula is the atmospheric pressure P = 0.01 to 2400.
[MmHg], gap length d = 0.005 to 200 [m
m] and temperature T = −15 to 860 [degrees C], and a uniform electric field and a quasi-uniform electric field.

FIG. 8 shows a gas constant A = 15 [1 / cm.m].
mHg], gas constant B = 365 [V / cm · mmHg]
(However, E / P = 100 to 800 [V / cm / mmH
g]), calculated using the secondary ionization coefficient γ = 0.01,
It is a curve (Paschen curve) of the above equation at atmospheric pressure P = 760 [mmHg] and temperature T = room temperature, which coincides with the actual measurement in air. In the region R2 used in this experiment,
The relationship between the spark discharge voltage Vs and the gap d is Vs = kd (where k is a constant that changes depending on temperature and pressure). In the atmosphere, the relationship between the spark discharge voltage Vs and the gap d during rotation with the rotor of the gap as the cathode is known to approach the Paschen curve by irradiating with ultraviolet light. The above formula is used for conversion.

Next, the structure of the blade tip clearance measuring device of this embodiment will be described with reference to FIG. Probe 1 used in this embodiment
Has a diameter of 1 mm and is made of brass, for example, and its tip is rounded. Further, the rotating body (sample) to be the gap measurement target in the present embodiment has, for example, a diameter of 10
0 [mm], rotation speed 2650 [r. p. m], number of blades 5
It is a micro fan whose blades are made of iron.

The probe 1 forms a discharge gap between the probe 1 and a blade tip 3 of a rotary blade 2 which constitutes a rotary body, and is fixed to a ball screw 5 as a moving means via a mounting member 4. The ball screw 5 is connected via a reduction gear 6 to an output shaft of a stepping motor 7, which is a moving unit. The feed rate of the probe 1 per step of the stepping motor 7 is 0.5 [μm / step]. Further, a jet portion 1a for jetting argon gas is provided at the tip of the probe 1, and the argon gas is supplied to the jet portion 1a from a supply portion (not shown).

When the probe tip 1 is fed toward the blade tip of the rotating body when the blade tip clearance is measured by the blade tip clearance measuring device, the stepping motor 7 is driven and the stepping to the ball screw 5 via the reduction gear 6 is performed. By transmitting the rotational force of the motor 7 and operating the ball screw 5 downward in FIG. 1, the probe 1 is fed to the blade tip 3 side of the rotary blade 2. In this case, in this embodiment, ultraviolet rays are irradiated between the probe 1 and the blade tip 3 of the rotary blade 2 at the time of discharge.

On the other hand, a power source 8 is connected between the probe 1 and the rotary blade 2 for applying a voltage of at least the minimum spark voltage between them, and the plus terminal side of the power source 8 is connected to the probe 1.
, And the negative terminal side is connected to the rotor 2. Further, the resistor 9 is connected to both ends of the resistor 9 of the power supply circuit.
A discharge determination device 10 (see FIG. 2) for determining the occurrence of discharge based on the voltage generated at the is connected. In this case, since the probe 1 discharges in the maximum diameter portion of the rotor blade that is closest to the rotor blade, the number of rotations of the rotor can be calculated from the discharge pulse signal and the probe passage time per rotor blade can be calculated. Can be calculated. Therefore, if the probe passage time is synchronized with the gate signal, it is possible to detect the discharge pulse of the blade tip of the rotary blade with respect to each gate.
The discharge determination device 10 is for performing the control as described above.

Further, the discharge determination device 10 is connected to a personal computer 12, which is a control means including a display / printer (not shown), through an I / O board 11, and the discharge generation voltage or the like is connected to the display. Is displayed, and the measurement data and the like are printed out from the printer. Furthermore, the personal computer 12
A control board 13 as a control means is connected to the stepping motor 7, and a stepping motor 7 and a stepping motor power supply 14 for supplying electric power to the stepping motor 7 are connected to the control board 13.

Next, the detailed configuration of the discharge determining device 10 will be described with reference to FIG. 2. The current-voltage converter 15 converts the current flowing through the resistor 9 into a voltage and supplies the voltage to the switching circuit 16. The switching circuit 16 supplies the output signal (voltage) of the current-voltage conversion unit 15 or the output signal of the test signal generator 17 that generates a test signal to the waveform shaping unit 18. The waveform shaping unit 18 waveform-shapes the output of the current-voltage conversion unit 15 or the test signal generator 17, and outputs the waveform-shaped signal to the first determination circuit 19, the second determination circuit 20, the third determination circuit 21, and the fourth determination circuit 21. It is adapted to be supplied to the judging circuit 22 and the fifth judging circuit 23, respectively.

The first determination circuit 19 for determining the discharge in the rotor blade of blade number 1 (see FIG. 6) of the rotor (microfan) supplies the determination start signal to the CPU (Z80CPU) 24, thereby The determination circuit 19 to the fifth determination circuit 23 are adapted to determine the discharge of each rotor blade. The first determination circuit 19 determines the presence or absence of discharge in the rotary blade of blade number 1 based on the output of the waveform shaping section 18, and displays the determination result on the first display section NO1 of the LED display device (not shown) with LED. Further, the second determination circuit 20 determines the presence or absence of discharge in the rotary blade of blade number 2 based on the output of the waveform shaping section 18, and the determination result is transferred to the second display section NO2.
The ED display is performed, and the third determination circuit 21 displays the waveform shaping section 1
Based on the output of 8, the presence or absence of discharge in the rotary blade of blade number 3 is determined, and the determination result is LED-displayed on the third display portion NO3.

The fourth decision circuit 22 decides the presence or absence of discharge in the rotary blade of the blade number 4 based on the output of the waveform shaping section 18, displays the decision result in LED on the fourth display section NO4, and the fifth decision. The circuit 23 determines the presence or absence of discharge in the rotary blade of blade number 5 based on the output of the waveform shaping section 18, and displays the determination result on the fifth display section NO5 by LED. Further, the first determination circuit 19 to the fifth determination circuit 23
A drive signal is supplied to the LED driver 25 that drives and controls the above-described LED display device.

The 1 / n frequency divider 26 divides the basic clock (1 MHz) into 1 / n based on a command from the CPU 24, and the 3-second counter 27 measures the discharge time and the time measurement time. Which is output to the CPU 24,
The CPU 24 determines that there is a discharge when the discharge is continuous for, for example, 3 seconds (3 seconds in the present embodiment, but is not limited to this value). Further, the quinary counter 28 counts by “1” for every 5 pulses input from the 1 / n frequency divider 26, and supplies the count result to the decoder 30.

The comparator 29 is a CPU I / O (Z
80 CPU I / O) 31 output and 1 / n frequency divider 2
The output from 6 is compared, and if they match, the reset signal is supplied to the 1 / n frequency divider 26. The decoder 30 sequentially supplies the drive signal to the second determination circuit 20, the third determination circuit 21, the fourth determination circuit 22, and the fifth determination circuit 23, so that the second determination circuit 20 to the fifth determination circuit 23 are driven. It is designed to be driven sequentially. Furthermore, CP
The U 24 outputs to the frequency display unit of the LED display device via the CPU I / O 31 that the frequency (the rotation speed of the rotating body) is being measured.

Next, the blade tip clearance measuring process by the blade tip clearance measuring device of the present embodiment configured as described above will be described with reference to the general flow chart of FIG.

When the measurement of the blade tip clearance of the rotor (microfan) is started by the blade tip clearance measuring device, first, the reference point calibration for setting the ball screw 5, the probe 1, etc. to the initial position is performed ( In step S1), rotation of the rotating body is started. Then, it is determined whether or not the measurement of the rotation speed of the rotating body has been confirmed by the discharge determination device 10 (step S
2). If the measurement of the rotation speed is not confirmed, the stepping motor 7 is operated and the ball screw 5 is driven through the reduction gear 6 to lower the probe 1 to a predetermined position (step S3), and then the determination in step S2 is performed. Do it again.

On the other hand, when the measurement of the rotation speed is confirmed,
The discharge determination device 10 confirms the occurrence of discharge in the rotor blade having the maximum diameter of the rotating body, and when the discharge is generated, measures the frequency f (the number of rotations of the rotating body) based on the output of the 3-second counter 27. At the same time, the process of measuring the gap between the rotor 1 having the maximum diameter of the rotor and the probe 1 (output 1 process)
Is executed (step S4). After that, it is determined whether or not the measurement of the rotational speed is in the released state (step S5). It is determined whether there is a next output corresponding to the wing (step S6).

If there is no next output, the above-mentioned measurement method 1
Control for lowering the probe 1 by the length Δd toward the blade tip 3 side of the rotor 2, or control for increasing the applied voltage E between the probe 1 and the rotor 2 by ΔE based on the measurement method 2 described above. After the electric discharge is generated by the rotor blade smaller than the rotor blade having the maximum diameter of the rotor (step S
7) Then, the process returns to the step S6 to re-determine whether or not there is the next output.

On the other hand, if there is the next output, a process (next output process) for measuring the gap between the probe 1 and the rotor next smaller than the rotor having the maximum diameter of the rotor is executed (step S8). . The above output processing is performed until the rotor blade having the minimum diameter of the rotor is reached. Then, it is determined whether or not the output processing has been completed for all five rotor blades of the rotating body (step S9). If not completed, the determination in step S6 is performed again, while if completed, the measurement is performed. After performing various kinds of processing such as calculation and tabulation of data (step S1
0), the measurement data is printed out from the printer attached to the personal computer 12 (step S1).
1). The above is the general flow chart of the experimental procedure.

The measurement results of the above experiment are shown in FIGS. The horizontal axis in each figure represents the blade number of the five rotor blades that make up the rotor (test piece) used in the experiment. The rotor blade with the largest diameter is blade number 1, and the rotor blades are shown in a bar graph. It represents. The vertical axis in each figure is the difference [m from the rotor having the maximum diameter]
m] is shown. In this case, the bar graph shows the average value and the range of ± 2 × σ (σ: standard deviation). Figure 10
In any of the cases shown in FIGS. 13A to 13C, irradiation of ultraviolet rays was performed between the probe and the blade tip of the rotary blade before the start of discharge.

FIG. 10 shows the measurement results when the measurement method 1 is adopted. In the case of the rotating body (test piece) used in the experiment,
Electric discharges were generated in all five rotor blades at an applied voltage of 1800 [V], but a total of 5 at an applied voltage of 1800 [V] or less.
No electric discharge was generated on one of the rotor blades. The larger the difference from the rotor having the maximum diameter, the higher the applied voltage, and the greater the variation in the measured values.

FIG. 11 shows the measurement results when the measurement method 2 was adopted. After the probe was brought close to the blade tip of the rotor with an applied voltage of 400 [V], after discharging at the maximum diameter portion of the rotor, The applied voltage was raised to 1400 [V].

FIG. 12 shows the measurement results when the measurement method 2 was adopted. After the probe was brought close to the blade tip of the rotor with an applied voltage of 600 [V], the probe was discharged at the maximum diameter portion of the rotor. The applied voltage was raised to 1450 [V].
11 and 12, there is no difference due to the difference in the first applied voltage.

FIG. 13 shows the measurement results when the measurement method 2 is adopted. After the argon gas is ejected from the tip of the probe and the probe is brought close to the tip of the rotor with an applied voltage of 400 [V]. , The maximum voltage of the rotor blade was discharged, and then the applied voltage was increased to 760 [V]. In the case of the measurement results of FIG. 13, when an applied voltage of 760 [V] or higher was applied, discharge was generated in all five rotor blades.

As is apparent from the measurement results shown in FIGS. 10 to 13, the same measurement results are obtained regardless of the difference in the measurement method, the difference in the applied voltage, and the difference in the type of gas ejected from the probe. I was able to get Therefore, it was found that the measurement accuracy of the blade tip clearance of each rotary blade by the blade tip clearance measuring device of this embodiment was extremely reliable.

As described above, according to the present embodiment, when the probe discharges at the maximum diameter portion of the rotary blade, the probe is further moved toward the blade tip of the rotary blade, and the rotary blade next to the probe is moved. By repeating the control for discharging between the probe and the blade, the blade tip clearance is measured based on the moving distance of the probe, or the applied voltage is further increased and the discharge is performed between the probe and the next rotating blade. By repeating the above procedure, the blade tip clearance is measured based on the discharge gap calculated from the applied voltage. Therefore, the blade tip clearance in each rotary blade can be measured with extremely high accuracy for the first time in the discharge method.

[0037]

As described above, according to the present invention,
When the probe discharges in the maximum diameter part of the rotor blade, by moving the probe further toward the tip of the rotor blade and repeating discharge control between the probe and the rotor blade next to it, The blade gap is calculated based on the discharge voltage by measuring the blade tip clearance based on the moving distance, or by repeating the control of further increasing the applied voltage and causing the discharge between the probe and the next rotating blade. Since the tip clearance is measured, it is possible to provide the blade tip clearance measuring device capable of measuring the blade tip clearance in each rotor blade with extremely high accuracy for the first time in the discharge method.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a blade tip clearance measuring device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a discharge generator according to the present embodiment.

FIG. 3 is a schematic diagram showing the principle of measurement of the blade tip clearance of the present embodiment.

FIG. 4 is a schematic diagram showing a generated voltage in this embodiment.

FIG. 5 is a schematic diagram showing a generated voltage in the present embodiment.

FIG. 6 is a schematic diagram showing a measurement method 1 of the present embodiment.

FIG. 7 is a schematic diagram showing a measurement method 2 of this embodiment.

FIG. 8 is a characteristic diagram of a Paschen curve in the air of this example.

FIG. 9 is a general flowchart of the experimental procedure of this example.

FIG. 10 is a bar graph showing the measurement results according to the measurement method 1 of this example.

FIG. 11 is a bar graph showing the measurement results according to the measurement method 2 of this example.

FIG. 12 is a bar graph showing the measurement results by the measurement method 2 of this example.

FIG. 13 is a bar graph showing the measurement results by the measurement method 2 of this example.

[Explanation of reference symbols] 1 probe 2 rotary blade 3 blade tip 5 ball screw 6 reduction gear 7 stepping motor 8 power supply 9 resistance 10 discharge determination device 11 I / O board 12 personal computer 13 control board

Claims (1)

[Claims] 1. A blade tip clearance measuring device for measuring a clearance between blade tips of a plurality of rotor blades and a casing arranged on the outer peripheral side of the rotor blades, wherein the blade tip gap measurement device is movable in a blade tip direction of the rotor blades. A probe forming a discharge gap between the tip of the rotary blade and the tip of the rotary blade; a moving means for moving the probe toward the tip of the rotary blade; A power source for applying a high voltage between the blade and a discharge determining means for determining the occurrence of discharge between the probe and the blade tip of the rotary blade, the probe by the discharge determining means When it is determined that discharge has occurred in the maximum diameter portion of the rotary blade, the probe is further moved in the blade tip direction of the rotary blade by the moving means to discharge between the probe and the next closest rotary blade. Repeat the control to measure the blade tip clearance based on the moving distance of the probe. No. 1 measurement method, or when the discharge determination means determines that the probe has discharged at the maximum diameter portion of the rotor blade, the applied voltage is further increased by the power supply to rotate the probe next closest to the probe. A blade tip clearance measuring device comprising: a control means for repeating a discharge control with the blade to execute a second measurement method for measuring the blade tip clearance based on the discharge gap calculated from the applied voltage. .