JPS60122328A - Investigating method of rotating speed-dependent oscillation of rotary machine - Google Patents

Abstract

PURPOSE:To obtain a more accurate test result by varying the rotating speed of a rotary machine stepwise while holding the load condition of the rotary machine constant, and calculating the attenuation ratio or permissible oscillation coefficient of the rotary machine from oscillation response data of every rotating speed. CONSTITUTION:While the load condition of the rotary machine is held constant, the rotating speed is increased to 1,000, 2,000, 3,000, and 4,000r.p.m. to perform stationary operation for a specific time at every rotating speed, and the oscillation frequency is varied gradually within a target range to measure oscillation response. Data on it are collected and analyzed to calculate the attenuation ratio xsi or permissible oscillation coefficient. Consequently, when the load condition is constant and the rotating speed is varied, the natural oscillation frequency, attenuation ratio, stability tolerance, and dangerous speed of the rotary machine are calculated and a more accurate test result is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for investigating rotational frequency dependent vibrations of rotating machines such as steam turbines, gas turbines, generators, combustion engines, blowers, pumps, etc. The unstable vibration that occurs in the high-speed range is an important problem that must be solved when building high-speed rotating machinery.

A typical example of such vibration is a vibration called oilwidth that occurs in rotating machines using sliding bearings. As shown in Figure 1, when the rotation speed is increased, large vibrations often occur suddenly, which impairs operation, so countermeasures must be taken to completely resolve the problem. However, since this type of vibration is not known until just before it occurs, this phenomenon becomes a problem only for the machine that generates the vibration, and data is accumulated, but even when the machine is operating at the very limit, no information can be obtained. If not, such vibrations may suddenly occur and cause trouble for the driver.

Therefore, if you can know how much stability margin there is in the machine that is actually being operated, you can prevent such troubles, and if there is little margin, you can take countermeasures in advance. That's why. However, until now there has been no research method that can safely obtain such information. Although it is possible to predict by calculation, there are few actual measurements, so the verification of calculation accuracy is insufficient.
In order to improve this accuracy, a method of obtaining data while the rotating machine is in operation is required.

On the other hand, in rotating machines where the gyro moment is effective, the critical speed is a function of the rotation speed. In such cases, there is also a need to confirm counting accuracy through experiments.

The present invention provides a method for investigating rotational speed-dependent vibrations of rotating machines, which can elucidate the characteristics of rotational speed-dependent low-frequency vibrations of rotating machines, and can provide a stability margin and critical speed for this type of vibration during operation. With the goal.

The present invention will be described above with reference to the drawings, but first the apparatus used to carry out the method of the present invention will be described.

This device generally includes a vibrator capable of applying an excitation force toward the center of a rotating shaft from a bearing portion of a rotating machine, a controller that controls the output of the vibrator, and a controller that controls the output of the vibrator, and a vibration detector for detecting a vibration response signal from the vibrator; a rotation speed controller capable of controlling the rotation speed of the rotating machine stepwise with a constant load condition; and a reference signal from the controller. A vibration analysis device that inputs the excitation force signal and the vibration response signal from the vibration detector and extracts the component that responds to the excitation force, and calculates the damping ratio or allowable excitation coefficient from these data. .

Figure 2 shows a specific example of this, where 1 is a test rotor that is directly connected to a load (not shown) and is the subject of the test, 2 is a bearing that supports the test rotor, and 3 is an inertial vibrator 4, for example. The jig 4 for fixing the bearing 2 to the bearing 2 is a direct-mounted type vibrator that does not require a reaction force support device, and is an inertial type vibrator that applies an excitation force of an arbitrary frequency to the bearing stand. 5 is an excitation force detector for measuring the magnitude and frequency of excitation force applied to the bearing 2 by the vibrator 4; 6 is a vibration detector for measuring the vibration of the test rotor 1; Various types are used, including non-contact displacement meters, contact vibration velocity meters, and accelerometers. Reference numeral 7 denotes an oscillator that generates vibration waves necessary for testing, and usually generates a sine wave of an arbitrary frequency. Reference numeral 8 denotes an energy source for supplying excitation energy, which is a hydraulic source when the exciter 4 is hydraulic, and a power amplifier when the exciter is electromagnetic. 9 is a device that controls the magnitude of the force generated from the vibrator, 1
θ is a signal for accurately giving the frequency of vibration, such as a sine wave, a rectangular wave, or a Norse wave. Reference numeral 11 denotes a signal indicating the excitation force, which is either the output of the excitation force detector 5 as it is or a signal whose amplitude has been adjusted. 12 is a signal from the vibration detector 6 indicating vibrations of the test rotor 1, bearing 2, etc. 13 inputs the reference signal 10, the excitation force signal 11, and the vibration response signal 12;
This is a vibration analysis device, such as a mechanical impedance measuring device, which has the function of extracting components corresponding to the excitation force, and analyzes transfer functions and modal characteristics (natural frequency, damping ratio, etc.) from these data.

The vibrator 4 may be of any type as long as it is capable of applying an excitation force toward the center of the rotating shaft from the bearing portion of the rotating machine and can be vibrated with a sine wave or a pulse wave.

The excitation conditions of the above vibrator 4 are: ■ Sweep excitation in the frequency range of interest; ■ Interruption after excitation at the resonant frequency; ■ Intermittent excitation in an arm-pulse manner; ■ Random excitation. good.

Next, the mechanical impedance measuring device described above will be explained with reference to FIG. In FIG. 3, 21 is the subject (
22 is an exciter (corresponds to 4 in FIG. 2), 23 is a power amplifier, 24 is an oscillator, 25
is a cage attached to the object 21 to measure the excitation force F;
26 is a plurality of accelerometers that measure the response acceleration of each part of the subject 1, 27 is a multi-channel amplifier, 28 is a multi-channel vector filter that extracts excitation frequency components from the force signal and acceleration signal, and 29 is an analog/digital conversion vessel, 3
o is a pulse counter for counting the excitation frequency, 31
is a digital computer that calculates mechanical impedance from acquired data, and includes a data acquisition program 32, a calibration calculation program 33, and an impedance calculation program 34.
It consists of

35 is a plotter that outputs the calculated mechanical impedance as a graph, 36 is a printer, 37 is an external storage device for data storage, and 38 is a range signal.

In such a device, a sinusoidal voltage from an oscillator 34 enters the exciter 22 via a power amplifier 33;
excites the subject 21, but since the oscillator 24 is an automatic sweeping sine wave oscillator whose frequency changes over time, it is swept and excited in an arbitrary frequency range.

The card gauge 25 measures the force applied to the subject 21 by the vibrator 22, the accelerometer 26 measures the response acceleration of each part of the subject 21, and the cardano 25 and accelerometer 26 measure the measured force and acceleration, respectively. A proportional voltage is generated, and this voltage signal is amplified by a multichannel amplifier 7.

The signals measured by the vehicle gauge 25 and the accelerometer 26 contain components other than the excitation frequency due to the nonlinear characteristics of the object 21 and noise, so in this device, the multi-channel vector filter 28 is used. The excitation frequency component is extracted from the measured voltage signal.

The excitation frequency components of the force signal and acceleration signal output from the multi-channel vector filter 28 are digitized by an analog/digital converter 29 and input to the digital computer 3.

At this time, the output of the oscillator 4 is input to a nof counter 30 to measure the excitation frequency, and the measured value of this excitation frequency is input to the digital computer 31.

In the digital computer 3, first, the data acquisition program 32 acquires the force and acceleration digital signals from the analog/digital converter 29 and the measurement value of the excitation frequency from the pulse counter 30, and then the calibration calculation program 3
3 converts the voltage value into a physical quantity, and further, the impedance calculation program 34 integrates the acceleration A and converts it into velocity V, and divides the force F by the velocity V to calculate the mechanical impedance 2. There is. In other words, A (integral) jω Z=F/V (divide@) However, A: Acceleration (complex number) V: Velocity (complex number) ω: Excitation frequency (real number) z: Mechanical impedance (complex number) It measures mechanical impedance.

Next, the method of the present invention will be explained. The method of the present invention is applicable to a rotating machine that is capable of applying an excitation force from the bearing part of the rotating machine toward the center of the rotating shaft. The present invention is characterized in that the damping ratio or permissible excitation coefficient of the rotary machine is determined from the vibration response data for each rotation speed by changing the number in steps.

Examples of the method of the present invention will be described below.

The rotating machine is operated at a steady rotation speed (load condition -5 constant) as shown in FIG. 4, and the low speed rotation state is maintained for a predetermined period of time, and in this state, a low speed rotation vibration test is performed. In this vibration test, the vibration frequency is gradually changed in the range of interest and the vibration response is measured. This data is collected and analyzed to calculate the damping ratio ξ or the allowable excitation coefficient K as described later.

Next, the load condition of the rotating machine is kept constant, and the rotation speed is set to 1000.
．． 2000, 3000, 400 Or, p, m, steady operation is performed for a predetermined time at each rotation speed, the frequency is gradually changed in the range of interest, and the imaging response is measured. This data is acquired and analyzed to calculate the damping ratio ξ or the allowable excitation coefficient K as described later.

As a method for determining the above-mentioned damping ratio, there are, for example, a method (half power method) from a frequency response curve (Date diagram or Nyquist diagram) or a free damping method which will be described later. The former method focuses on the resonance part of the vibration response curve, and calculates the natural frequency ω that shows the maximum amplitude of the mode component and the rotational speed ω1 that shows about 70% of the maximum amplitude. Read ω2. This is the date diagram in Figure 5,
Combine it with the Nyquist diagram in the figure. Then, calculate the damping ratio ξ from the following equation: ω2+ω1 The following relationship exists between the damping ratio ξ and the allowable excitation coefficient.

K=2mωξ Here m: 6 in modal mass.

The allowable excitation coefficient K was determined for each load state from the above formula and is plotted in FIG. 7. For example, the following can be said from FIG.

Damping ratio ξ〈〇 - Completely unstable 0〈ξ(0,01 - Almost unstable 0.01(ξ(0,02 - Stable but with small margin 0
．． 02<:ξ(0,04-normal stability 002 ξ)
0.04 - Sufficiently Stable In this way, externally controllable excitation forces cause vibrations at the minimum necessary level, thereby providing valuable data on the stability of the actual machine. Note that the above excitation force does not cause any harm to actual operation.

According to the embodiments described above, it is possible to elucidate the characteristics of rotation speed-dependent low-frequency vibrations, and to know the stability margin and stability limit rotation speed for this type of vibration during operation. An example will be described. Similar to FIG. 4, the load condition of a rotating machine is kept constant, the rotational speed is arbitrarily changed in stages, and an excitation test is conducted under each rotational speed state. The same equipment as shown in Figure 2 is used for this test, but the vibration investigation method is different. That is, the excitation frequency is set to resonate at a constant excitation frequency as shown in FIG. 9 in accordance with the point of interest, and the excitation force is abruptly cut off.

Record the vibration response data in this state, apply a filter to the frequency of interest to this data, measure the free damping,
From the response waveform in Figure 10, the amplitude AI l A2 ) A3
Read r...An sequentially and calculate the logarithmic attenuation rate δ from the following equation.

δ=lnmu I or δ = engineering tn4 u n　Ama However, tn is a natural logarithm, and n is the number of peaks.

FIG. 10 shows the relationship between the logarithmic attenuation rate δ determined in this manner and the number of peaks. Fig. 11 shows the relationship between the damping ratio and the rotation speed, and Fig. 12 shows the relationship between the vibration frequency and the excitation response amplitude according to the actually measured excitation response data.
The following equation holds between the damping ratio ξ and the logarithmic damping rate δ.

δ ξ=−2π This embodiment also provides the same effect as the previous embodiment.

Although an inertial type vibrator was used as the vibrator in the above embodiment, it is not limited to this, and it is possible to apply a vibrating force from the bearing part of the rotating machine toward the center of the rotating shaft, such as a sine wave,・If it can be excited by a flat pulse wave, etc., it is a reaction force type (a vibrator is attached directly to the specimen, and it is supported by a reaction force support device via a pressure gauge on the opposite side of the vibrator). , Figure 13 (a
) Any of the non-contact electromagnetic exciters shown in s < b) may be used. This electromagnetic vibrator is capable of directly vibrating a rotating shaft 41 using an electromagnet 40. Therefore, the excitation force can be effectively transmitted to the test object, for example, the rotor, and the excitation force can be transmitted to the excitation force detector 4 attached to the base of the electromagnet 40.
It can be measured by 2. In addition, as shown in Figure 13(b), by installing 213 electromagnets 40 at right angles and adjusting the phase angle of the excitation force acting on both types of magnets to ±90°, this type of vibration is likely to occur. Vibrations can be made in the forward rotation direction (swinging in the same direction as the rotation direction) or in the opposite direction, making it possible to obtain more accurate test results.

According to the present invention described above, when the load condition is constant and the rotation speed is changed, the natural frequency, damping ratio, stability margin, and critical speed of the rotating machine can be determined.Rotation speed dependent vibration investigation of the rotating machine I can provide a method.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the relationship between rotation speed and amplitude in oil whip vibration of rotating machinery, Figure 2 (a) # (b)
3 is a partial front view and a schematic configuration diagram showing an example of the apparatus for carrying out the method of the present invention, FIG. 3 is a schematic configuration diagram showing an example of the vibration analysis apparatus of FIG. 1, and FIG. Flowcharts for explaining the embodiment, FIGS. 5 and 6
The figure is a diagram 1A for explaining the method of the same example.
- and Nyquist diagram; FIG. 7 is a diagram showing the relationship between load, damping ratio, and allowable excitation coefficient for explaining the same embodiment; FIG. 8 is a flowchart for explaining the embodiment of the method of the present invention. , FIGS. 9 to 12 are diagrams showing the relationship between time and vibration waveform, diagrams showing the relationship between the number of peaks and logarithmic damping ratio, and diagrams showing the relationship between load and damping ratio, respectively, for explaining the method of the same embodiment. Figure 13 (a
)s (b) is a sectional view and a schematic configuration diagram showing an example of a non-contact electromagnetic vibrator. 1... Test rotor, 2... Bearing, 4... Vibrator,
5... Excitation force detector, 6... Vibration detector, 7...
Oscillation a9...control device, 13...vibration analysis device. Applicant Sub-Agent Patent Attorney Takehiko Suzue 15-ku1-

Claims (1)

[Claims] In a rotating machine that is capable of applying an excitation force toward the center of the rotating shaft from the bearing part, the load condition of the rotating machine is kept constant and the number of revolutions is changed in stages, and the vibration at each number of revolutions is A rotation speed-dependent vibration investigation method of a rotating machine in which the damping ratio or allowable excitation coefficient of the rotating machine is determined from response data.