JPH0449895B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention detects torsional vibration of a rotating shaft system as a torsional vibration angular velocity, and after modal decomposition and integration, monitor point stress waveforms are synthesized to detect each part of the rotating shaft system. This invention relates to a rotating shaft system torsional vibration monitoring device for monitoring fatigue life.

(Prior Art) A conventional rotating shaft system torsional vibration monitoring device for a turbine generator shaft system will be explained with reference to FIGS. 4 and 5.
As shown in FIG. 4, a high pressure turbine 01, a low pressure turbine 02, a generator 03, and a shaft 04 connecting these
A gear 05 is installed on a rotating shaft constituted by. Also, on the stationary side facing gear 05,
An electromagnetic pickup 06 is installed, and its output is input to a torsional vibration angular velocity variation meter 07. Further, the output of the same angular velocity variation meter 07 is input to band pass filters 08a and 08b installed as many as the number of natural vibration modes, and this output is passed through integrators 09a and 09b to stress calculators 010 installed as many as the number of monitoring points.
It is input to a to 010d. Stress calculator 010a
The output of ~010d is input to the fatigue life calculator 011.

Figure 5 is an example of torsional vibration mode. In the case of a rotating shaft system consisting of three rotors as shown in Figure 4, the modes of the main shaft system in which the shaft is twisted are mainly primary mode A and secondary mode. It appears as B. If a grid fault occurs in the power transmission system due to a lightning strike while the turbine generator is in operation, a shock is applied to the generator 03.
Torsional vibration occurs in the rotating shaft system. The torsional vibration of the rotating shaft system appears as minute rotational speed unevenness on the rotating shaft surface, so the rotational pulse is generated by the gear 05 installed on the rotating shaft system and the stationary electromagnetic pick-up 06 installed opposite the gear 05. The torsional vibration is detected by accurately measuring rotational speed unevenness using a torsional vibration angular velocity meter 07. In addition, the detected torsional vibration angular velocity at this time is filtered through a bandpass filter 0 whose center frequency is adjusted to the torsional natural frequency.
By passing it through 8a and 08b, it is separated into each mode. Further, since the torsional vibration stress is proportional to the torsional vibration angular displacement, the torsional vibration angular velocity is passed through integrators 09a and 09b to convert it into a torsional vibration angular displacement. The torsional vibration modes shown in Figure 5 A and B are determined in advance through actual measurements and calculations, and several points with severe stress are selected as monitoring points a to d, and the integrator 0
When the waveform of each eigenmode converted into an angular displacement by 9a and 09b is multiplied by the eigenmode ratio of the detection point p and the monitoring points a to d, the angular displacement of each of the monitoring points a to d is obtained. This is done for each monitoring point a~ by the number of eigenmodes.
By adding and combining with d, the torsional vibration angular displacement of each monitoring point a to d is obtained. Since this torsional vibration angular displacement is proportional to the torsional vibration stress, it can be converted into stress by multiplying it by a stress conversion coefficient. These processes are performed by stress calculators 010a to 010d for each monitoring point. Further, the fatigue life calculator 011 estimates and integrates the fatigue life for each monitoring point using the known range pair method.

(Problems to be Solved by the Invention) In the conventional rotating shaft system torsional vibration monitoring device shown in FIGS. 4 and 5, when integrating a continuous long-time angular velocity signal and converting it into an angular displacement signal, When detected as an analog quantity and subjected to analog integration, low frequency components unrelated to the eigenmode are greatly expanded due to the zero point drift and S/N characteristics of the analog system. Furthermore, when converting to a digital quantity and performing numerical integration, there is a problem that divergence occurs due to the effect of truncation error of the least significant bit, making it difficult to perform complete integration using an integrator.

(Means for Solving the Problems) The present invention addresses the above problems by detecting torsional vibration of a rotating shaft system as a torsional vibration angular velocity,
In a rotating shaft system torsional vibration monitoring device that monitors the fatigue life of each part of a rotating shaft system by synthesizing monitoring point stress waveforms after modal decomposition and integration, multiplication is performed to multiply the swing vibration angular velocity signal by the function from the trigonometric function generator. an adder that adds the output of the multiplier and the output of the subtracter described later; a divider that divides the output of the adder by a constant; a subtracter that calculates the difference between the output of the adder and the output of the divider; two Fourier transform systems each having a multiplier/divider that multiplies the value obtained by dividing the output of the multiplier by a constant by a function from the trigonometric function generator; and a subtractive synthesizer that calculates the difference between the outputs of the respective systems. The purpose of the present invention is to prevent problems such as expansion of low frequency components due to analog integration and divergence due to digital numerical integration. Another object of the present invention is to provide a rotating shaft-related torsional vibration monitoring device that can detect torsional vibration as an angular velocity, and further synthesize a waveform after modal decomposition and integration as monitoring point stress.

(Function) The rotating shaft system torsional vibration monitoring device of the present invention is configured as described above, and multiplies the torsional vibration angular velocity signal by the function from the trigonometric function generator, and adds this multiplication result and the subtracter output. Then, this addition result is divided by a constant, the difference between the result and the addition result is obtained by the subtracter, and the function from the trigonometric function generator is added to the value obtained by dividing the division result by the set frequency ω. Fourier transform for multiplication is performed in two systems. To find the difference between the outputs of each system, Fourier transform is performed using a subtractive synthesizer.

(Example) Next, the rotating shaft system torsional vibration monitoring device of the present invention was
To explain with one embodiment shown in the figure, 20 is input data, 21 is a timer, 22 is a trigonometric function generator, 23a, 23b is a multiplier that multiplies the swing vibration angular velocity signal and the function from the trigonometric function generator 22;
24a and 24b are adders that add the outputs of the multipliers 23a and 23b and the outputs of the subtracters 26a and 26b described later, and 25a and 25b are the adders 24a and 24.
A divider 26a, 26b which divides the output of b by a constant is the same divider 25 as the output of the adders 24a, 24b.
a subtracter for calculating the difference between the outputs of a and 25b, 27
a and 27b are multipliers and dividers that multiply the value obtained by dividing the outputs of the dividers 25a and 25b by a constant by the function from the trigonometric function generator 22, and 28 is the difference between the outputs of the same multipliers and dividers 27a and 27b. A subtractive synthesizer that finds
29 is the output from the subtractive synthesizer 28.

Next, the operation of the rotating shaft system torsional vibration monitoring device shown in FIG. 1 will be specifically explained. A multiplier 23a uses a cosine function from a trigonometric function generator 22 controlled by a timer 21 and input data x20, and a multiplier 23b uses a sine function from a function generator 22 controlled by a timer 21 and input data x20. ,
Multiply each. The outputs of the multipliers 23a, 23b are input to adders 24a, 24b, and added to the outputs of the subtracters 26a, 26b. Further, the outputs of the adders 24a and 24b are the same as those of the subtracters 26a and 2
6b, and the dividers 25a, 25
b, and is divided by a constant N by dividers 25a and 25b. The outputs of the dividers 25a and 25b are input to subtracters 26a and 26b, and the difference between the outputs and the outputs of the adders 24a and 24b is calculated, and this is used as the adder input at the next timing.
a, 24b, and the multiplier/divider 27
It is also input to a and 27b. Multiplier 27a, 2
In 7b, after dividing by the focused frequency ω, multiplying by the previous sine and cosine functions, and applying the result to the subtraction synthesizer 2
After combining in step 8, the output data is output as output data X29.

Finite interval T sampled at time interval Δt
The Fourier transform of a single frequency ω component of is given by the following equation.

Here, if we replace section T with load section NΔt, we get
A continuous Fourier transformation of the load interval is made possible by the following equation.

Real part X _R ω(t)=2.Xγω(t)/N In addition, the inverse _{Fourier transform} is _:・sinωt＝X _Iω (t)／
It is expressed as ω・cosωt...

FIG. 1 shows a circuit configuration of the equations and. In the trigonometric function generator 22, the timing [t]
21 and the set frequency [ω], a cosine function [cosωt] and a sine function [sinωt] are determined. In the multipliers 23a and 23b, input data [x
(t)] 20 multiplied by the above cosine and sine functions, [x
(t)・cosωt] and [x(t)・sinωt]. In the adders 24a and 24b, multipliers 23a and 23b
, and the outputs of the subtractors 26a and 26b to obtain [Xγω(t)] and [Xiω(t)]. The dividers 25a and 25b divide the outputs of the adders 24a and 24b by a constant [N] to obtain [Xγω(t)/N] and [Xiω(t)/N].

In the subtracters 26a and 26b, adders 24a and 2
4b output and the dividers 25a and 25b, [Xγω(t)−Xγω(t)/N] and [Xiω(t)−Xiω
(t)/N] and the next timing (t-Δt)
It is output to the adders 24a and 24b as the adder output. On the other hand, the outputs of the dividers 25a and 25b [X _R
ω(t)/Z] and [X _I ω(t)/Z] are multiplier/divider 2
7a and 27b, and divides [X _R ω(t)/ω] and [X _I ω(t)/ω] and multiplies [sinωt] and [cosωt]. ,
The integrated waveform Xω(t) is synthesized by subtraction of [X _R ω(t)/ω·sinωt]−[Xiω(t)/ω·cosωt] and output 29.

Figures 2A, B, and C show analysis examples of transient response waveforms that include two natural frequencies.
is the original waveform, and FIG. 4B is the response waveform when an impact is applied at time t _0. FIG. I am doing it. Also the second
FIG. C shows an example in which the waveform is converted after being similarly integrated using a band-pass filter using the apparatus of the present invention. 3A and 3B show an example in which a bandpass filter is applied in the same way as in FIG. 2, but the input data is once stored and processed with the time elapsed direction reversed. A is the same original waveform as in FIG. 2, but the time axis is reversed and the time width is shortened, and FIG. 3B is an example of the bandpass filter. By doing so, the amplitude immediately after the transient can be determined more accurately.

(Effects of the Invention) The rotational time-based torsional vibration monitoring device of the present invention is configured as described above, and after converting the torsional vibration signal into the frequency domain by Fourier transform and integrating it in the frequency domain, Since it is converted into a modal displacement response for each mode, problems such as expansion of low frequency components caused by analog integration and divergence caused by digital numerical integration can be prevented. In addition, it separates frequency components with the same effect as an analog bandpass filter, and also performs complete integration of the separated waveform, so it is possible to detect the torsional vibration angular velocity, modally decompose it, and synthesize the integrated waveform as the monitoring point stress. There is an effect that can be done.

Although the present invention has been described above with reference to embodiments, it goes without saying that the present invention is not limited to such embodiments, and that various design modifications can be made without departing from the spirit of the present invention. .

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an embodiment of a rotating shaft system torsional vibration monitoring device according to the present invention, Figs. 2 and 3 are explanatory diagrams showing waveform examples, and Fig. 4 is a conventional rotating shaft system torsional vibration monitoring device. FIG. 5 is an explanatory diagram showing an example of the vibration mode. 22... Trigonometric function generator, 23a, 23b...
Multiplier, 24a, 24b... Adder, 26a, 2
6b...Subtractor, 25a, 25b...Divider, 2
7a, 27b...Multiplication/divider, 28...Subtraction synthesizer.

Claims (1)

[Claims] 1 In a rotating shaft system torsional vibration monitoring device that detects torsional vibration of a rotating shaft system as a torsional vibration angular velocity, and after modal decomposition and integration, monitors stress waveforms at monitoring points and monitors the fatigue life of each part of the rotating shaft system, torsional vibration A multiplier that multiplies the angular velocity signal and the function from the trigonometric function generator, an adder that adds the output of the multiplier and the output of the subtracter described later, a divider that divides the output of the adder by a constant, and the output of the adder. Two Fourier transforms each having a subtracter that calculates the difference from the output of the divider, and a multiplier/divider that multiplies the value obtained by dividing the output of the divider by a constant by the function from the trigonometric function generator. A system for monitoring torsional vibration of a rotating shaft system, comprising a system and a subtractive synthesizer for determining the difference between the outputs of each system.