JP2004077163A - Air type non-contact oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable an efficient test to be performed by amplifying an exciting force and to allow a fatigue test of a component of a high strength member to be performed with a relatively small device, in fatigue test by an air type non-contact oscillator. <P>SOLUTION: The air type non-contact oscillator is provided with an oscillating nozzle 4 for spraying air to an object and a pulse wave generator 6 which is connected to an air source 8 and generates pulse-like air of a predetermined frequency N, for determining fatigue strength of the object by spraying the continuously injecting pulse-like air. The oscillating nozzle is set to have a length where the pulse-like air passing through the inside oscillates gas-columnarly. The frequency of the pulse wave is made to coincide with the natural frequency of the object, and the oscillating nozzle preferably has a telescopic mechanism for telescoping the full length of it. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an air-type non-contact vibration device, and more specifically, an air-type non-contact vibration device used for a high cycle fatigue test performed by vibrating air by continuously blowing air to a turbine blade or the like. Related to a vibration device.
[0002]
[Prior art]
For example, gas turbine blades that obtain rotational power by converting the kinetic energy of fluid into rotational motion are subjected to stresses and moments in various directions during operation of the gas turbine. Various strength tests are performed to confirm the above.
Fracture of moving metal parts is often due to fatigue of the material, so fatigue tests, which are performed by continuously and repeatedly exciting the turbine blades as test specimens, are the most important in ensuring the reliability of gas turbines. This is one of the strength tests.
[0003]
A general method for performing a fatigue test is a reciprocating type in which an object is cantilevered and attached to a fatigue test machine that performs reciprocating movements up and down, and this is vertically vibrated at the natural frequency of the object. In addition to the vibration method, there is an air-type non-contact vibration method in which pulsed air (shock wave) is continuously blown onto an object fixed to a holder on the ground to vibrate the object.
[0004]
FIG. 4 shows a simplified configuration of an air-type non-contact vibration device for performing a fatigue test of an object by the above-mentioned air-type non-contact vibration method.
The air-type non-contact vibration device 40 receives a rotation from a vibration shaft 45 for blowing air to the object 2 fixed to the holding portion 3 and a first shaft 41 extending from a motor (not shown) and multiplies the vibration approximately 10 times. A speed-up gear 43, a pulse wave generator 47 for sending a pulsed air to a vibrating nozzle 45 by receiving a rotational force from the speed-up gear, and supplying compressed air to the pulse wave generator 47. And an air source (not shown).
[0005]
A second shaft 49 extends from the speed increaser 43 into the pulse wave generator. In the pulse wave generator 47, a large number (several tens) of through-holes 51 are circumferentially arranged at radially outer positions. The rotating disk 53 is attached to the tip of the second shaft 49 in a flange shape. Separately from this, a fixed disk 55 having the same shape as the rotating disk is arranged in a state fixed in the pulse wave generator.
[0006]
The rotating disk 53 slides and rotates with its axis aligned with the fixed disk 55, and sends compressed air to the vibrating nozzle in a range where the through hole of the rotating disk and the through hole of the fixed disk overlap. In a range where the respective through holes do not overlap with each other, the air is jetted in a pulse shape by blocking the flow of the compressed air. In other words, the through-hole of the rotating disk and the through-hole of the fixed disk function as an on-off valve to generate a pulse wave (shock wave) of air.
Each part is sealed to prevent the compressed air from leaking out of the part other than the through hole. In addition, the vibrating nozzle 45 has a flow path cross section that is gradually reduced at the tip end thereof, so that the flow velocity of the compressed air passing through the inside becomes higher as going downstream.
[0007]
In the high-cycle fatigue test performed using such an apparatus, the object 2 was firmly fixed to the holder 3 in a cantilever manner, and was installed in advance on the ground near the vibration nozzle 45, and was determined in advance. This is performed by blowing a pulse wave having the same frequency as the natural frequency of the target object 2 near the tip of the target object to cause the target object to resonate at a high cycle.
[0008]
[Problems to be solved by the invention]
However, in the conventional air-type non-contact vibrating apparatus described above, it is difficult to efficiently vibrate an object with a sufficient vibrating force to perform a fatigue test, and particularly to a part made of a high-strength member. In order to confirm the fatigue strength, a very large-scale apparatus for performing the vibration was required.
[0009]
The present invention has been made in view of the above problems, and when performing a fatigue test by a pneumatic non-contact vibration method, enables efficient fatigue test by amplifying the excitation force, It is an object of the present invention to provide a pneumatic non-contact vibrating apparatus capable of performing a fatigue test of a component of a high-strength member with a relatively small apparatus.
[0010]
[Means for Solving the Problems]
The present invention that achieves the above object is an air-type non-contact vibrating apparatus for vibrating an object (2) by spraying air that is continuously ejected in a pulsed manner and determining the fatigue strength thereof. The air-type non-contact vibration device (10) includes a vibration nozzle (4) formed of a hollow tube for blowing air to the object, and a predetermined frequency connected to the air source (8) and directed toward the vibration nozzle. (N) a pulse wave generator (6) for generating pulsed air, wherein the vibrating nozzle is set to a length at which the pulsed air passing through the air column vibrates. Provided is a pneumatic non-contact vibration device characterized by the following.
[0011]
In the present invention, the length of the vibrating nozzle of the air-type non-contact vibrating device that blows the air ejected in a pulse shape as a shock wave (pulse wave) to the object is set to the length at which the air passing through the air nozzle vibrates in the air column. By setting, the exciting force to the object is amplified. This makes it possible to carry out efficient fatigue tests, and eliminates the need for a large-scale air source that supplies high-pressure compressed air for exciting high-strength components and equipment for handling high-pressure air. Is achieved.
[0012]
Here, it is preferable that the predetermined frequency (N) is set to a natural frequency of the object (2).
[0013]
In this way, the frequency of the pulse wave is made to coincide with the natural frequency of the object and sprayed on the object, causing the object to resonate. Further efficiency is achieved.
[0014]
Preferably, the vibration nozzle (4) is provided with a telescopic mechanism (14) for adjusting the total length thereof.
[0015]
Since a pulse wave of the same frequency as the natural frequency of the test object is caused to vibrate in the air column within the vibration nozzle, a fatigue test can be performed by replacing the vibration nozzle with a vibration nozzle of a length suitable for that frequency. If a vibration nozzle is provided with an expansion / contraction mechanism for adjusting the overall length, the trouble of replacing the nozzle can be eliminated and the test can be easily performed.
In addition, the natural frequency of each part is slightly different even for the same kind of parts, so the nozzle length is optimized by finely adjusting the total length of the nozzle according to each part, and the air column vibration is easily placed inside the nozzle. Can be generated.
[0016]
The vibrating nozzle (4) has a first hollow pipe (4a) having one end connected to the pulse generator and having a threaded portion (12a) formed at the other end, and a threaded engagement with the threaded portion at one end. And a second hollow pipe (4b) formed with a threaded portion (12b) for blowing air from the other end. The expansion / contraction mechanism (14) tightens or loosens the male screw and the female screw. It is preferable that the first hollow tube and the second hollow tube are moved in the axial direction with their central axes aligned so that the vibration nozzle is expanded and contracted.
[0017]
The length of the vibrating nozzle can be adjusted steplessly within a certain range by a screw-type expansion / contraction mechanism provided on the vibrating nozzle, eliminating the need to replace nozzles and quickly changing to various pulse wave frequencies. Correspondingly, the nozzle can be adjusted to an optimal length for generating air column vibration.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an air-type non-contact vibration device of the present invention will be described with reference to the drawings. In the drawings, common parts are denoted by the same reference numerals, and redundant description is omitted. Also, the parts used in the conventional example are used for the parts basically common to the conventional example.
[0019]
FIG. 1 is a side view showing an internal structure of a pneumatic non-contact vibration device for a high cycle fatigue test of a turbine blade of a gas turbine. This air-type non-contact vibration device 10 continuously blows pulsed air (shock waves) on an object 2 (blade) fixed to a holder 3 on the ground, as described in the related art. It is a device for exciting. The amount of deflection of the blade is always detected by an optical displacement meter (not shown).
[0020]
The air-type non-contact vibration device 10 includes a vibration nozzle 4 for blowing air to an object, and a pulse wave generator 6 for sending pulsed air to the vibration nozzle 4. Is supplied with compressed air from an air source (not shown). Each part of the apparatus employs a seal structure (not shown) so that the compressed air does not leak.
[0021]
The pulse wave generator 6 has a motor 5 for a high-speed spindle with a rotation speed of 2,000 to 40,000 rpm incorporated therein, and a radial direction mounted on a tip of a shaft 7 of the motor 5 in a flange shape. A rotating disk 55 having a large number (eight in this embodiment (see FIG. 2) of through-holes) 51 formed in the outer position and a fixed disk 53 fixed in the same shape as the rotating disk 55 are included. Have been. Since the vibration device 10 uses a motor for a high-speed spindle, a speed-increasing device is not mounted unlike the conventional example. The number of rotations of the motor is controlled by a control device (not shown).
[0022]
As shown in FIG. 2, the rotating disk 55 (broken line) slides and rotates with its axis aligned with the fixed disk 53 (solid line), and the through-hole 51a of the rotating disk 55 and the through-hole of the fixed disk 53. In the range where 51b overlaps, compressed air is sent to the vibrating nozzle 4, and in the range where each through-hole does not overlap, the flow of compressed air is cut off to generate pulsed air. Here, the through-hole 51a of the rotating disk 55 and the through-hole 51b of the fixed disk 53 gradually overlap with each other in the order of (a) to (d) of FIG. Is repeated to repeat the cycle of no overlap, thereby generating a substantially sinusoidal pulse wave.
[0023]
As shown in FIG. 1, the vibration nozzle 4 is formed by a hollow circular tube disposed downstream of the fixed disk 55 and passing all the pulse waves ejected from the through holes 51 b of the fixed disk 55 through the inside thereof. I have. Reference numeral 11 denotes a pressure sensor.
[0024]
The vibrating nozzle 4 has one end connected to the pulse generator 6, the cross section of the flow passage inside thereof is gradually reduced within a certain range from a portion where the pulse wave generator 6 is attached, and a thread portion ( A first hollow tube 4a having a thread (thread) formed therein, and a threaded portion (screw groove) to be screwed into the first hollow tube 4a at an inner periphery of one end, and a second portion for injecting air from the other end. The two components of the two hollow tubes 4b are screwed together with their central axes aligned. That is, the vibration nozzle 4 has the expansion mechanism 14 which can expand and contract by tightening or loosening the screw thread and the screw groove.
[0025]
According to the air-type non-contact vibration device 10 having the above configuration, first, (1) the use of a motor for a high-speed spindle eliminates the need for a speed-increasing device, thereby making it possible to reduce the size of the device. The speed of the motor is controlled by increasing the number of through-holes in the rotating disk and fixed disk from about several tens to about ten without increasing the number of rotations by the speed machine. When the frequency of the motor is adjusted to the natural frequency (N) of the object (turbine blade), the error of the rotation speed of the motor is not extended to several tens of times, and (3) the vibration nozzle can be extended and contracted. As a result, air column vibration of air can be easily generated in the interior, and as a result, the excitation force on the object can be amplified and an efficient fatigue test can be performed. By tapering the inner diameter of the vibration nozzle (5) Large-scale air for supplying high-pressure compressed air to enable efficient testing with relatively low-pressure compressed air by increasing the flow rate of compressed air Measures for handling the source and high-pressure air can be eliminated.
[0026]
FIG. 3 shows the results of an experiment conducted to prove that the exciting force is amplified when air column vibration occurs inside the nozzle.
In this experiment, for the sake of convenience, the length of the vibrating nozzle was fixed at 118 mm, and the number of rotations of the motor was variously changed, that is, the frequency of the pulse wave was variously changed. (Shock wave) pressure fluctuation was measured.
Here, the horizontal axis represents the frequency (Hz) of the pulse wave, and the vertical axis represents the pressure of the air blown to the object when the pressure of the compressed air supplied from the air source is set to 1.
[0027]
In this experiment, the motor for the high-speed spindle incorporated in the pulse wave generator was rotated at a rotation speed in the range of 2,000 to 40,000 rpm, and 266.6 Hz (2,000 (rpm) × 8 (through hole) (Number) / 60 (seconds)) to 5,333.3 Hz (40,000 (rpm) × 8 (number of through holes) / 60 (seconds)) to generate a pulse wave to blow air to the object. The pressure (psi) was measured.
As is clear from these results, the pressure ratio of the pulse wave (shock wave) blown to the object is usually about 0.4 to 0.9, but the frequency of the pulse wave is 1,812 Hz and 3 Hz. , 500 Hz, the pressure ratio sharply rises to about 1.5 to 1.6. At this time, it is considered that the secondary mode and tertiary mode air column vibrations are generated inside the excitation nozzle.
[0028]
In this way, by generating air column vibration in the nozzle, the vibration force can be amplified, and the object can be efficiently vibrated even by compressed air of relatively constant pressure supplied from an air source. It turns out that it becomes possible.
[0029]
In the case where the air column vibration is generated in the excitation nozzle by fixing the frequency of the pulse wave, the opening end correction caused by the excitation nozzle and the object being arranged with a slight gap therebetween, Although it is necessary to determine the length in consideration of the influence of a portion where the cross section of the flow passage formed in the vibration nozzle gradually decreases as going downstream, the length can be easily adjusted by the expansion and contraction mechanism.
[0030]
Although the configuration and experimental results of the air-type non-contact vibration device of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it is needless to say that various changes can be made without departing from the gist of the present invention. . It is also desirable to vibrate the object more efficiently by changing the inner diameter of the vibrating nozzle in various ways.
[0031]
【The invention's effect】
As described above, according to the pneumatic non-contact vibration device of the present invention, when performing a fatigue test by the pneumatic non-contact vibration method, an air column vibration is generated in the vibration nozzle and the vibration force of the nozzle is increased. By amplifying the above, efficient fatigue tests can be performed, and the fatigue strength test of components of high-strength members can be performed by a small-sized device. Further, preferably, by providing the vibration nozzle with an expansion / contraction mechanism, the entire length of the nozzle can be expanded / contracted in accordance with the natural frequency of each object, and air column vibration can be easily generated inside the nozzle.
[Brief description of the drawings]
FIG. 1 is a side view showing an internal structure of a pneumatic non-contact vibration device of the present invention.
FIG. 2 is a diagram showing a state of a rotating disk that slides and rotates with respect to a fixed disk.
FIG. 3 is a table showing the relationship between the frequency of a pulse wave and pressure fluctuation (pressure ratio).
FIG. 4 is a configuration diagram of a conventional air-type non-contact vibration device.
[Explanation of symbols]
2 Object 3 Holder 4 Vibration nozzle 4a First hollow tube 4b Second hollow tube 5 Motor 6 Pulse wave generator 7 Shaft 8 Air source 10 Pneumatic non-contact vibration device 11 Pressure sensors 12a, 12b Screw section 14 Telescopic mechanism 40 Air-type non-contact vibration device 41 First shaft 43 Speed increasing device 45 Vibration nozzle 47 Pulse wave generator 49 Second shaft 51, 51a, 51b Through hole 53 Fixed disk 55 Rotating disk N Frequency

Claims (4)

An air-type non-contact vibrating apparatus for vibrating an object (2) by blowing air that is continuously jetted in a pulsed manner and for obtaining its fatigue strength,
The air-type non-contact vibration device (10) includes a vibration nozzle (4) composed of a hollow tube for blowing air to the object, and a predetermined frequency ( N) a pulse wave generator (6) for generating pulsed air,
The pneumatic non-contact vibrating device, wherein the vibrating nozzle is set to a length at which pulsed air passing through the vibrating air column vibrates. The air-type non-contact vibration device according to claim 1, wherein the predetermined frequency (N) is set to a natural frequency of the object (2). The pneumatic non-contact vibrating device according to claim 1, wherein the vibrating nozzle is provided with a telescopic mechanism for adjusting a total length thereof. The vibrating nozzle (4) has a first hollow tube (4a) having one end connected to the pulse generator and having a screw portion (12a) formed at the other end, and a screw screwed at one end with the screw portion. A second hollow pipe (4b) formed with a portion (12b) and ejecting air from the other end;
The expansion / contraction mechanism (14) moves the first hollow tube and the second hollow tube in the axial direction with their central axes aligned by tightening or loosening the screwed screw portion, and the vibration nozzle The air-type non-contact vibration device according to claim 3, wherein the non-contact vibration device expands and contracts.

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