SU1315826A2 - Device for determining frequencies of resonance vibrations of rotating shaft - Google Patents

Abstract

This invention relates to a measurement technique. It is an improvement of the known device according to A. .№ 1101686. The purpose of the invention is to improve the accuracy of determining the critical frequency of rotation of the shaft by correcting the dynamic measurement error introduced by the frequency-code converter. The signal from the vibration sensor 1 is fed to the input of the frequency detector 2, which separates the vibration component of the rotational frequency rotor. This signal is converted by an analog-to-digital converter 5 to a code and fed to a resonance indicator 4. The frequency detector 2 is controlled by the signal from the rotational speed sensor 3, ensuring that it is tuned synchronously with the change in the rotational speed of the rotor under study. The signal from the speed sensor 3 also goes to the frequency converter 6 — the code whose output is connected to the control unit 11 and the resonance indicator 4. In comparison diagram 8, the codes from the analog-to-digital converter 5 and the buffer register 7 are compared, the corresponding codes being the current vibration value and measured on the previous clock cycle. The operation of the buffer register 7 or the comparison circuit 8 is clocked by the control unit 11. At the moment of passing the maximum frequency response, the resonance indicator 4 fixes the critical frequency of rotation and the amplitude of vibration of the rotor. Achievement of the maximum is recorded by the AND circuit 10 by the trigger signals 9 and the code comparison circuit 8. At the same time, the correction indicator 13 fixes the number of revolutions by which the readings of the resonance indicator 4 must be corrected. The source of information for the correction indicator 13 is the Dynamic Corrector 12, associated with the output of the frequency converter - code. 1 il. (L with 01 00 GCHE O5 gh

Description

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The invention relates to a measuring technique, can be used mainly in a power system to determine the frequencies of resonant, oscillations of a rotating shaft, for example, the critical frequency of rotation of a rotor of a turbomachine, and is an improvement of the known device according to ed. No. 1101686.

The aim of the invention is to improve the accuracy of determining the critical frequency of rotation of the shaft due to the correction of the dynamic measurement error introduced by the frequency-code converter.

The drawing shows the block diagram of the device.

The device contains placed on a controlled shaft (not shown) vibration sensor 1, frequency detector 2 connected to it, speed sensor 3 connected to the control input of detector 2, digital resonance indicator 4, analog-digital converter 5 connected between the output of frequency detector 2 and the first input of the resonance indicator 4, the frequency converter 6 is a code connected between the rotation speed sensor 3 and the second input of the indicator 4 connected in parallel to the output of the analog-digital converter 5 is galvanically connected Buffer register 7 and code comparison circuit 8, connected to the last trigger 9, AND circuit 10 connected to it, the second input of which is connected to the TpeTbCNry output of the circuit 8 of comparison, and ltod - to the input of the 4 resonance indicator, control block 11, connected separate outputs to the inputs of the buffer register 7 and the code comparison circuit 8, and the input to the output of the frequency converter 6 is the code. The output of the latter is connected to a dynamic equalizer 12, the output of which is connected to the information input of the correction indicator 13, the control input of which is connected to the output of the AND 10 circuit,

The device works as follows.

The polyharmonic signal from the output of the vibration sensor 1 is fed to the first input of the frequency detector 2, which outputs the vibration component of the reversible frequency rotor. This signal is converted by the analog-to-digital converter 5 to a digital code.

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which is fed to one of the inputs of the digital display 4 of resonance. The signal from the output of the 3 turn sensor goes to the second (control) input

frequency detector 2, ensuring its reorganization synchronously with the change of rotation frequency, as well as a frequency to the input of converter 6 — a code, the signal from which is fed to block 11

control and 4 resonance indicator. The digital code from the output of the analog-digital converter 5 is fed to the input of the buffer register 7 and to one of the inputs of the code comparison circuit 8.

A code from the output of buffer register 7 is applied to the second input of circuit 8. The operation of the buffer register 7 and the comparison circuit 8 is clocked by the control unit 11. TS clock pulse

a comparison is made of the code of the current value of the vibration received by the comparison circuit 8 from the output of the analog-digital converter 5 with the code characterized in the buffer

register 7. TI2 clock pulse - the code of the current vibration value is written to the buffer register 7.

The TI1 clock pulses are generated by the control unit 1.1 according to the code value of the current frequency UJ | rotation The interval between pulses TI is a variable and depends on

turbomachine speed is determined by the duration of the time interval during which the increment of the rotation frequency will be a predetermined (fixed) value ds,

Clock pulses TI2 are formed by the control unit 1 1 on the back of the pulses TI1.

Depending on the value of the codes at the inputs of the comparison circuit 8, one of the conditions is formed at the outputs of the latter.

and) -4 uj j. + dw Lz ,. Ats + jyj,

where is A1. - the value of the vibration at the moment when the rotor reaches the frequency of rotation), -

W + Liu is the vibration value at the moment when the rotor reaches the rotation frequency ()).

The analysis of the conditions is carried out by the logic circuit And 10. At achieving equality A.j. A.-do) We stipulated that in the previous measurement cycle condition A and) was fulfilled; A-Lee) which is memorized by trigger 9, circuit 10 permits the triggering of indicator 4, which fixes the rotation frequency at the moment of passage of the maximum frequency characteristic; the critical frequency of rotation, as well as the amplitude of vibration of the rotor, corresponding to a given critical speed.

With a decrease in the number of revolutions of the turbomachine below the minimum frequency response, the rotation frequency is not indicated, since the condition AuJi AUJ; .U is not fulfilled.

At the same time, the digital correction indicator 13 fixes the number of revolutions by which the readings of the digital indicator -4 resonance need to be corrected, and the sign of the correction. When the turbomachine accelerates, the sign of correction is +, when braking -.

Dynamic corrector works as follows. The input of the dynamic equalizer 12 from the converter 6 frequency - code receives the code N | current frequency (l). rotation, which varies at regular intervals of time T (quantization time of frequency converter 6 — code). How. all integrator, converter

6 {. Code N; averaged over time T ,, the value of the current chaot of the compiler J.Petrakovsky Editor O.Yurkovetska Tehred N.Gluschenko Proofreader M.Sharoshi

---- .. - -.-. -., - -. - - - "..----- -. - ". .-

Order 2677 Circulation 499 Subscription

VNIIPI USSR State Committee for Inventions and Discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, Projecto st., 4

scheni oi; . This code differs from the true code corresponding to the instantaneous value of w, at the time of the end of time T, by the value

4N

Ni - N; -4

where N is the last code value

rotational speed; N - previous code value

rotational speed; 4N is half the increment of the code value, which is proportional to the rate of the set (decrease) of turns.

Therefore, the dynamic corrector determines the value of JN as half the difference between two adjacent values of the rotation frequency codes with the corresponding sign.

Claims (1)

Invention Formula A device for determining the frequencies of resonant oscillations of a rotating shaft according to the author No. 1101686, characterized in that, in order to improve the accuracy of determining the critical frequency of rotation of the shaft, it is equipped with a dynamic equalizer, an input connected to the output of the frequency converter - a code, and a correction indicator, whose information input is connected to the output of the dynamic corrector, and the control input - with the release of the scheme I.