FR2630213A1 - TEST DEVICE FOR VENTILATOR PALLETS VIBRATION - Google Patents

Abstract

The present invention relates to the field of vibration resistance testing of construction and equipment. The fan vane vibration resistance test device comprises an electric motor 1, the shaft of which carries the vane wheel 3 of a fan 4 to be tested. The input of the electric motor 1 is connected to the output of the control unit 8. On the pallet 9 of the fan 4, a strain gauge 10 is mounted, the output of which is connected to the input of a matching amplifier 12. On the output of the adaptation amplifier 12 is connected the input of a block 13 for detecting the resonant frequency of vibrations of the fan blade, the outputs of which are connected to the inputs of a block 14 of the fan. maintenance of the vibration resonant frequency of the fan vane. The output of the maintenance block 14 of the vibration resonant frequency of the fan vane is connected to the input of the control unit 8. The device is applicable in ventilation systems using axial and centrifugal fans in construction. mechanical, in aviation, etc.

Description

The present invention relates to the field of

  resistance to the vibrations of buildings and equipment

  ments, especially the test devices for

  naked to the vibrations of fan blades.

  The present invention will find its application in ventilation systems using axial and centrifugal fans in mechanical constructions,

  in aviation, in space technology, in the

  shipbuilding industry in the coal and oil industries

the.

  A device for program tests is well known

  pallets of a centrifugal fan which comprises a program block at the outputs of which are connected a dynamic load circuit of the fan blades and a static load circuit of the fan blades, each of these circuits having in series a comparison block , a block

  control and an electric motor. The shaft of the electric motor

  the static charge circuit carries the fan wheel

  to try. The electric motor of the load circuit dy-

  pallets is mechanically connected to the cylinder

  of an aerodynamic exciter introduced into the tubulu-

  re entry of the fan. On the pallet of the fan is an extensometric sensor whose output is connected, life a static component amplifier of stresses in the pallet, a dynamic component amplifier of stresses in the pallet and an amplifier of adaptation, on a block of comparison of the dynamic load circuit of

  pallets. The output of the amplifier of the dynamic component

  constraints in the pallet is connected to a

  second entry of an adder. The output of the addition-

  neur is connected, via the matching amplifier, to the

  block of comparison of the static charge circuit of the puck-

  The electric motor of the dynamic load circuit of the

  pallets puts the inner cylinder of the aerodynamic exciter

  in a given position imposed by the program block. The control unit of the static charging circuit acts on the electric motor on the shaft of which the fan blade wheel rotates with a determined number of revolutions per minute. On the extensometric sensor, a signal is taken carrying the information on the static and dynamic components of the stresses in the pallet, this signal is os05 compared with the setpoint and the differential signal acts

on the command block.

  This device requires a long duration of tests of

vibration resistance.

  The device does not give an opportunity to try

  the fan pallet at its resonance frequency, at-

  what the amplitude of oscillations of the fan blade and, consequently, the mechanical stresses occurring in

  the material of the pallet become maximum.

  The aim of the invention is to propose a device for testing vibration resistance of fan blades that makes it possible to test them at the resonant frequency of the pallet of the fan.

  fan, which improves the reliability of the puck-

the fan.

  The problem is solved by means of a

  test of resistance to vibration of ventilator pallets

  with an electric motor whose shaft carries the vane wheel of a fan to be tested and whose entry

  is connected to the output of a control block, and a

  strainer mounted on the fan pallet and

  whose output is connected to the input of a first ampli-

  adaptation adapter, characterized in that it comprises in

  be a block of detection of the resonance frequency of the

  fan, whose input is connected to the output

  of the first adaptation amplifier, and a block of

  the vibration resonance frequency of the pallet

  fan, whose inputs are connected to the outputs

  of the detection block of the resonance frequency of

  the fan blade and the exit on the

  control block, the resonance frequency detection block

  Oscillation of the fan blade

  in series, a two-wave rectifier

  the input is connected to the output of the first amplifier of

  adaptation, a smoothing filter, a differentiation block,

  a zero indicator and a first switching element.

  In addition, it is advantageous that the block of

  maintenance of the vibration resonance frequency of the pa-

  the fan includes, in series, an air flow pressure sensor mounted on the fan blade, a second matching amplifier, a first rectangular pulse generator, a phase difference detector whose output is connected to the first input of a

  comparison circuit and, by a second commu-

  the control input of which is connected to the output of the zero indicator of the detection block of the oscillation resonance frequency of the fan pallet, on

  the input of a memory block whose output is connected

  on the second input of the comparison circuit, and

  the output of the comparison circuit is connected, by a third

  sth switching element, whose command input is

  connected to the output of the zero indicator of the detection block

  tion of the resonant frequency of oscillations of the

  the fan on the first input of an integrator whose second input is connected to the output of the first switching element of the oscillator resonance frequency detection block of the fan pallet and

  the output, on the input of the control block, said block of

  maintenance of the resonance frequency, which also includes one

  twelfth rectangular pulse trainer whose input

  is connected to the output of the first amplifier

  and the output, on the second input of the

phase difference.

  The use of the present invention will increase the reliability of the fan blades, especially

  their resistance to vibrations and the stability of their behavior

  in the presence of vibrations, thanks to the puck tests.

  fan speeds at vibration resonance regimes and automatic maintenance of vibration resonance

  pallets with high precision ..

  The invention will emerge from the description which follows

  a concrete example of the test device for resistance to

  fan pallet bursts schematized on the

  in which: - Figure 1 shows an overview of an electric motor with, fixed on its shaft, a vane fan wheel, according to the invention;

  FIG. 2 represents the block diagram of a

positive according to the invention.

  The fan blade vibration withstand test device comprises an electric motor 1 (FIG.

  1) whose shaft 2 carries a paddle wheel 3 of a fan

  axial tester 4 to be tested. The entrance opening 5 of the shirt

  6 of the ventilator 4 houses an aerodynamic exciter 7

  read in the form of a flat disc with slots.

  In the test variant of a centrifugal fan

  fuge, it is possible to realize the aerodynamic exciter

  in the form of a cylinder with berries.

  The input terminals of the electric motor 1 are connected to the output of a control block 8. The control block 8 is produced according to a known mode ("Guide to the conversion technique" ("Spravochnik po preobrazonvatelnoi tekhnike") by Chizhenko IM, 1978, "Tekhnika" / Kiev /, pp.

377 to 389).

  A pallet 9 of the fan 4 carries an extensometric sensor 10 and an air flow pressure sensor 11. The output of the strain sensor 10 is connected to the input of a first matching amplifier 12 (FIG 2). The output of the first matching amplifier: 12 is connected to the input of a detection block 13 of the

  oscillation resonance frequency of the pallet of the

  tilateur. The device also includes a block 14 of

  maintaining the oscillation resonance frequency of the fan pallet, the duiblo14 inputs being connected to the outputs of the block 13 for detecting the oscillator resonance frequency of the fan pallet and the output on the input of the fan. control block 8,

  The block 13 for detecting the resonance frequency

  this of the fan pallet includes, in series, a re-

  trainer with two half-waves 15, whose input is connected to the output of the first matching amplifier 12, a smoothing filter 16, a differentiation block 17, a zero indicator 18 and a first switching element 19, the block 14 of maintenance of the oscillator resonance frequency of the fan blade comprises, put in series, an air flow pressure sensor 11, a second

  amplifier 20, a first trainer 21 of im-

  rectangular pulses 21, a phase difference detector

  se 22, whose output is connected to the first input of a

  comparison circuit 23 and on the first control input

  of a second switching element 24. The second control input of the second switching element 24 is connected to the output of the zero indicator 18 of the block 13. The output

  of the second switching element 24 is connected to the

  of a memory block 25. The output of the memory block

  25 is connected to the second input of the comparison circuit 23. The output of the comparison circuit 23 is connected to the first control input of a third switching element 26. The second control input

  third switching element 26 is connected to the output

  of the zero indicator 18 in block 13, the output of the third

  the second switching element 26 is connected to the first

  entry of an integrator 27. The second entry of the integra-

  27 is connected to the output of the first switching element

  19 of block 13, the output of integrator 27 is

  on the entry of the control block 8. Block 14 of

  the vibration resonance frequency of the puck-

  The fan assembly also includes a second rectangular pulse generator 28 whose input is connected to the output of the first matching amplifier 12 and the output to the second input of the phase difference detector 22. vibration resistance test of

  Fan palettes work as follows.

  Initially, the switching elements 19 (Fig. 2), 24 and 26 are open, With the arrival of a start signal

  P on the first control input, the switching elements

  19 and 24 are closed. The input of the integrator 27 receives a reference voltage U0O The electrical output signal

  of the integrator 27 acts, through the block of

  8 on the electric motor 1 (fig 1) while

  2. The stream of aerodynamic air produced by

  the fan 4 passes through the slots of the aerodynamic exciter

  7 and acts on the blades 9 causing their vibra-

  tions that are converted by the extensometric sensor.

  than 10 in an electrical signal. The air flow pressure sensor 11 converts the pressure into an electrical signal

  of the air stream acting on the pallet 9, the signal of the

  11, via the second matching amplifier 20 (FIG 2) of the vibration resonance frequency detection block 14 of the fan blade, to the input of the first rectangular pulse generator 21. The signal

  of the extensometric sensor 10 arrives, via the first amplifier

  adaptation adapter 12, to the two-wave rectifier of the block 13 for detecting the vibration resonance frequency of the fan blade. The corrected signal

  passes through the smoothing filter 16 oa are deleted the

  RF signal posers and attacks the differentiation block

17.

  At a vibration frequency of the vane 9 (FIG 1) of the ventilator 4 which is smaller than that of resonance, the output signal of the differentiation block 17 (FIG 2) is positive, whereas at the frequency increase of

  vibration of the pallet 9 (fig, 1) and the speed of rotation

  the fan 9, the forced vibration amplitude of the pallet 9 and the output signal of the smoothing filter 16 (FIG. 2) increases continuously, the output signal of the differentiation block 17 decreases,

  The output signal of the integrator 27 and the

  speed of rotation of the shaft 2 (FIG 1) of the electric motor 1 increases until the signal at the output of the differentiation block 17 (FIG 2) becomes zero, which takes place in

  presence of resonant oscillations of the pallet 9 (Fig. 1).

  In this case, the zero indicator 18 (FIG 2) is triggered and produces a signal which opens the switching element 19 (the reference voltage U is switched off), opens the element of O

  24 (the connection between blocks 22 and 25 is

  gate) and closes the switching element 26. The

  mutation 26 puts the comparison circuit 23 of the block 14 on the input of the integrator 27. The switching element 24 opens when the vibrations of the pallet 9 come into operation.

  resonance. Therefore, the memory storage block 25

  the value of the output signal Ur of the difference detector

  phase 22 that it provides in the event of oscillations of

  pallets 9 (fig 1) of the fan 4 and whose

  their is proportional to the phase difference between the output signals of the rectangular pulse waveforms

  21 and 28 (Figure 2) corresponding to the phase difference between

  the action of the aerodynamic current arriving through the slots of the aerodynamic exciter 7 (FIG 1) and the vibrations

  forced from the pallet 9 of the fan 4.

  At the moment of closure of the switching elements

  19, 24 and 26 (Figure 2), the output signal of the

  parison 23 is equal to zero because its entries are

  the signals of the phase difference detector 22 and the storage block 25 proportional to the resonance value of the phase difference between the

  output of rectangular pulse trainers 21 and 28.

  During the tests, the characteristics of rigidity

  This variation necessitates a continuous adjustment of the speed of rotation of the shaft 2 of the electric motor 1.

  that is to say, the frequency of the aerodynamic current acting

  on the pallet 9, to carry out the tests of the pallet-

  te 9 at the vibration resonance frequency The resonance value of the phase difference (the phase difference in the presence of resonance vibrations of the pallet 9) of the rectangular pulse trainer signals

2630? 13

  21 and 28 (FIG 2), which characterizes the given pallet 9 (FIG 1) of the fan 4 and does not depend substantially on the

  variation in stiffness and damping characteristics

  pallet 9 has been determined by block 13 (FIG.

  2), stored by the storage block 25 and is automatically

  maintained by block 14. For example, in the

  where, under the action on the test regime of factors de-

  stabilizers, the frequency of vibration of the pallet 9 (FIG 1) decreases U =, r 'the rotation speed of the shaft 2 of the electric motor 1 increases automatically due to the rise in the level of the output signal of the integrator 27 (FIG 2) as a result of the appearance at the output of the circuit

  for comparing 23 a signal of positive polarity. AC-

  phase-frequency characteristic of the pallet 9 (FIG.

  fan 4 has a continuous uniform character,

  the variation of the vibration frequency of the

  9, the phase difference between the output signals of the rectangular pulse formers 21 and 28 (FIG 2) is smaller than the phase difference between these signals at the resonance frequency) = br of the pallet 9 (FIG. 1) of the

  This is why the output signal of the

  phase difference converter 22 (FIG 2) becomes less than

  the value U and the output of the comparison circuit 23 degenerate

r

  a signal of positive polarity, which leads to the increase

  tation of the output levels of the integrator 27

  and the control block 8 and the elevation of the speed of rotation

  2. The speed of rotation of the shaft 2 of the electric motor 1 then increases until the phase difference between the output signals of the shapers 21 and 28 (FIG 2). of rectangular pulses reaches its resonance value and the output signal of the phase difference detector 22 reaches the value Ur, in which case the output signal of the comparison circuit 23 becomes zero and the output signals of

  the integrator 27 and the control block 8 cease to vary.

  Thus, block 14 ensures automatic maintenance of the frequency

  vibration resonance of the fan blade

high precision.

  The pallet vibrations of the fan wheel

  being at the resonant frequency, the holding tests

  vibrations are made to the maximum mechanical stresses

  in the material of the pallet, which reduces

the duration of the tests.

  The use of the device makes it possible to increase the life of the fan,

Claims (3)

  1, device for vibration resistance testing of fan blades comprising an electric motor (1),   whose shaft (2) carries the vane wheel (3) of a ventilator   (4) to try and whose input is connected to the   of a control block (8), and an extensometric sensor (10) mounted on a pallet (9) of the fan (4) and whose output is connected to the input of a first adaptation amplifier (12). ), characterized in that it further comprises   a block (13) for detecting the resonance frequency of   bends the fan blade, the input of which is connected to the output of the first matching amplifier   (12), and a block (14) for maintaining the resonance frequency   this oscillations of the fan blade, which   are connected to the outputs of the sensor block (13).   the vibration resonance frequency of the fan blade and the output on the input of the control block (8).   2. Device according to claim 1, characterized   in that the block (13) for detecting the frequency of resetting   The vibration signal of the fan blade includes, in series, a two-wave rectifier (15) whose input is connected to the output of the first matching amplifier (12), a smoothing filter (16), a indicator   zero (18) and a first switching element (19).   3. Device according to claim 1, characterized   in that the maintenance frequency block (14) of the frequency   vibration sensor of the fan pallet comprises, in series, an air flow pressure sensor (11) installed on the pallet (9) of the fan (4), a second   amplifier (20), a first trainer of im-   rectangular pulses - (21), a difference detector of   phase (22) whose output is connected to the first   of a comparison circuit (23) and, by a second switching element (24), whose control input is connected to the output of the zero indicator (18) of the block   (13) for detecting the resonance frequency of the puck   fan, is connected to the input of a memory block.   (25) whose output is connected to the second input of the comparison circuit (23), while the output of the comparison circuit (23) is connected by a third switching element (26), the input of which control is connected to the output of the zero indicator (18) of the vibration resonance frequency detection block (13)   of the fan pallet, at the first entry of an in-   a tegulator (27) whose second input is connected to the output of the first switching element (19) of the oscillator resonance frequency detection block (13) of the fan blade and the output at the input of the control block (8), and that said block (14) also comprises a second rectangular pulse generator (28) whose input is connected to the output of the first matching amplifier (12) and the output, on the second entry of the   phase difference detector (22).