SU771477A1 - Method of measuring oscillatory speed of turbomachine working blades - Google Patents

Description

(54) METHOD OF MEASUREMENT OF THE VIBRATION SPEED OF THE WORKING BLADE OF TURBO MOBILE

The invention relates to vibration measuring technology and can be used to measure the vibrational speed of turbomachine blades.

There is a known method for measuring the oscillatory speed of turbomachine blades, which consists in taking two pulse contactless sensors, placing them on the body of the turbomachine in the circumferential direction at a certain distance from each other in the plane of rotation of the impeller, measuring the time interval between the sensor signals, at the passage of the blades past them and on the measured time interval is calculated analytically the oscillatory velocity of the working blades of the turbomachines 1.

The disadvantage of this method is low measurement accuracy, since it measures the value inversely proportional to the square of the circumferential velocity.

The closest to the technical essence of the invention is a method for measuring the oscillatory speed of turbomachine blades, which consists in measuring the circumferential distance between two contactless impulse sensors of the position set around the circumference in the plane of rotation of the impeller of the turbo wrinkle, measuring the time intervals between pulses sensors at the moments of passage of each blade and analytically calculate the oscillatory velocities of the working blades 2.

The disadvantage of this method is that it has a low accuracy and reliability of measuring oscillatory

to speed, because its value is one to two orders of magnitude less than peripheral speed. In addition, the speed value is determined as a result of a calculation that does not allow receiving the signal necessary for use in the alarm mode of the Turbo15 machine.

The aim of the invention is to improve the accuracy and reliability of measurements.

The goal is achieved by filling the time interval between sensor pulses, pulses with a frequency proportional to the frequency of the impeller blades, determining the difference between the number of sensor pulses corresponding to the oscillatory and non-oscillating modes of operation of the impeller blades, converting a certain number difference pulses in the auxiliary interval by multiplying this difference by a constant period determined by a given measurement accuracy, fill the auxiliary Pulse spacing with a frequency proportional to the blade repetition frequency is measured by the number of pulses obtained and the oscillatory speed of the blades of the impeller of the turbomachine is calculated analytically using the formula:

(.

where V is the oscillatory speed of the blades; N is the number of pulses; That is a constant period defined by

specified measurement accuracy; D is the diameter of the impeller; Z is the number of impeller blades; K is the proportionality factor of the frequency of filling the time interval between the pulses of the sensors and the frequency of filling the blades; l- constant coefficient; L-circumference between sensors.

The drawing shows a block diagram of a device implementing the method.

The block diagram contains the impeller 1 of the turbomachine, the impeller blade 2, pulse proximity sensors 3, 4 positions, the unit 5 for measuring the time interval and highlighting the difference between the numbers of pulses corresponding to the oscillatory and non-oscillating modes of the impeller blades, the unit 6 for storing the difference and generating the auxiliary interval, unit 7 converts the auxiliary time interval into the number of pulses, proportional to the oscillatory speed, unit 8, frequency, proportional to the frequency of the follow. current, unit 9 of a generator of a sequence of pulses with a constant period, unit 10 controlling the sequence of the execution of measurement methods. The outputs of the pulse proximity sensors are connected to the inputs of blocks 5 and 8. The output of block 5 is connected to one of the inputs of block 6, and the output of the latter is connected to the input of block 7. The output of block 9 is connected to the second input of block 6. Blocks 5, 6 and 7 are connected with block 10. A method for measuring the oscillatory speed is to install sensors 3 and 4 in the circumferential direction, in the plane of rotation of the impeller 1. The circumferential distance L between the sensors is measured. The time interval between the pulse signals of the two sensors at the time when the blade 2 of the impeller 1 oscillates is equal to

  OrTuoITnloF

where and is the circumferential speed of the blade; A is the amplitude of the blade oscillation; 0) is the frequency of oscillation of the blade.

The time interval between the signals of sensors 3 and 4, when the blade does not oscillate, is equal to

Atcp -.

The signal from sensor 4 is fed to the input of block 8 frequency, the output of which receive a sequence of pulses with a frequency

where o is the frequency of rotation of the turbomachine rotor;

Z is the number of blades of the impeller of the turbomachine;

K - coefficient of proportionality of the frequency of filling the time interval between the pulses of the sensors and the frequency of the blades. The output of block 5 receive the number of pulses, defined by the formula

AN - (-) foZK, -Y-

  jtB u-v. where V Aoosintoi;

D-impeller diameter;

The number of pulses AN is fed to the input of block 6, to another input of which signals are sent from block 9. At the output of block 6, an auxiliary time interval equal to

- LZK Vt „jfD u-v о

The time interval t is fed to the input

block 7, to another input of which a signal is sent from block 8. At the output of the block, the number of pulses is received, equal to N -M- - / vr ToUZK LToC) X

0 where nDfo and. V

Since the value "1, then

N LTo (§ -) “V.

Then, the obtained number of pulses is measured and the oscillating speed of the blades of the impeller of the turbo-base is calculated analytically using the formula:

V

I T „V 7k

LTo Z K

V is the oscillatory speed of the blades;

N is the number of pulses; TO is the constant period defined by

specified measurement accuracy; D-impeller diameter; Z-number of impeller blades; k is the proportionality factor of the frequency of filling the time interval between the pulses of the sensors and the frequency of filling the blades; l-constant coefficient; L is the distance between the sensors.

The use of the described method of measuring vibrational speeds provides, in comparison with the existing ones, higher accuracy and reliability of measurements and the possibility of using the results of measurements of vibrational speeds in alarm systems of dangerous voltages of turbomachine blades, in systems of automatic processing of measurement results and control of the operating mode of the turbine machine, as well as in the process of refining the impellers of turbomachines.

Claims (2)

Invention Formula The method of measuring the oscillatory velocity of the working blades of turbomachines, which consists in measuring the circumferential distance between two contactless pulse position sensors installed circumferentially in the plane of rotation of the impeller of the turbomachine, measures the time intervals between the pulses of the sensors at the moments of passage of each blade and analytically calculating oscillatory speeds of working blades, characterized in that, in order to increase the accuracy and reliability of measurements, the time interval between the impu sensors, pulses with a frequency proportional to the frequency of the impeller blades, determine the difference between the number of pulses of sensors corresponding to the oscillatory and non-oscillatory modes of operation of the impeller blades, convert a certain difference in the number of pulses into an auxiliary interval by multiplying this difference by a constant period, defined given by the specified measurement accuracy. the auxiliary interval is filled with pulses with a frequency proportional to the blade repetition frequency, the obtained number of pulses is measured, and the oscillatory speed of the blades of the impeller of the turbomachine is calculated analytically using the formula: v -ftv () where V is the oscillatory speed of the blades; N is the number of pulses; TO-constant period defined by specified measurement accuracy; D-impeller diameter; Z is the number of impeller blades; K is the proportionality factor of the frequency of filling the time interval between the pulses of the sensors and the frequency of filling the blades; l-constant coefficient; L-circumference between sensors. Sources of information taken into account during the examination 1. Zablotsky I. Ye., Korostelev Yu. A. and Shipov R. A. Contactless measurements of oscillations of turbine blades. M., “Mechanical Engineering, 1977, p. 35 2. USSR author's certificate No. 236827, cl. G 01 H 11/00, 1967 (prototype).