MEASUREMENT OF PRESSURES IN EXPLOSIONS OF GASEOUS MIXTURES WITH A PIEZOELECTRIC SENSOR

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80-00809A000700260136-1
• Release Decision: RIPPUB
• Original Classification: U
• Document Page Count: 6
• Document Creation Date: December 22, 2016
• Document Release Date: July 15, 2011
• Sequence Number: 136
• Publication Date: November 28, 1956
• Content Type: REPORT

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STAT
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MEASUR WNT OF MUSURFB IN EXPLOSIONS OF GASEOUS MIXTURES
ITg ZOE
'
LEC
IIiIC 8E OR
Rrletallo Sf1 Vol 1, No 3
scow, 9 , pp 370-372
I. S. Zheludev and
V. M. Mskarov
(Numbers in parentheses refer to appended bibliography.
Introduction
The large lag characteristics of mechanical Pressure indicators do not
P -
Permit their use for measuring pressures of fast flowin explosions of gas
eous mixtures sines Aatttdan is In s,nx a- -
dted
at thepiezoelectricCentralmethodScientific Research Institute of FFiirewPrevention we chose the
for measuring the pressures developed in the explosion
process of certain gaseous mixtures; there are a great number o
methods of measuring such short-duration pressurea(l). f existing
The piezoelectric method is widely used for recording and measuring
pressures in internal-combustion engines(2). There is, however, some dif-
ference between the explosion of gaseous mixtures and the e
combustible mixtures (for example, in internal-combustion engines). of other
view of this, we have, to a certain extent, developed a method for measuring
pressures, for recording, for calibration, etc. Moreover, the adaptation of
ceramic barium titanate for use as a piezoelement, which was used by us in
earlier works(3,4), permitted, to a great extent, the simplification of the
device for registering pressures during the explosion of a gaseous mixture.
Device for Re sterin Pressures In Ex losion Process
The complete unit consists of a piezoelectric transducer (see Figure 1,
below), a DC amplifier and an MPO-
Litanate disk 22 mm 2 loop oscillograph. A ceramic barium
in diameter and 2 mm thick was used as the piezoelement
in the transducer. Electrodes were attached to the side surfaces of the disk
by means of silver fusion. After the electrodes were attached the barium
titanate was polarized for one hour by a DC electric field of 20 kv/cm
Potential.
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Figure I. Piezoelectric Transducer.
1, case; 2, socket; 3, lock
screw; h, gasket
; 5, washer;
6, packing; 7, conical washer;
8, cover; 9, oluo: 10 4,._.., _
tact plate; 13 crystal; -, 14, \
rin;,; 15, ; .
base; 16, bearing.
The explosion wave pressure, acting on the piezoelement of the transducer,
results in the polarization of the barium titanate, The resulting difference
in potential between the grounded and the insulated electrodes, due to the
polarization, is proportional to the pressure. The great capacitance of the
barium titanate piezoelement, which is 1,800 micromicrofarads in this case,
makes it possible to develop a fairly high time constant for the instrument
when the simple DC amplifier, previously described by us (5), is used.
time constant of our instrument was-?p,5 seconds
which, Increases the duration of the explosion process. The The a amplifier is to made delu,
enters one of the tubes the When the signal al from m the cr
output cnront which amplifier balance is disrupted; thus theiamplifier
l
of the oscillo, results from the unbalanced condition, deflects the loop
Srah
The piezoelectric transducer and amplifier are shown in Figure 2.
-: 3
Figure 2. Over-all View of the Piezoelectric Transducer and DC
Amplifier. 1, transducer; 2, amplifier
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Calibration of Transducer
To convert the current impulses recorded on the oscillogram into units
of pressure, the transducer was
Dynamic calibration previously calibrated with a special device.
with compressed air and a calibrating temperature equal
to the transducer operating temperature were selected and maintained in order
to bring the calibrated range closer to the actual operating range.
During calibration the transducer was connected to a cylinder through
a fast acting valve, the cylinder being filled with compressed air to a
desired pressure. The air pressure in the cylinder was measured by means
of a calibrating pressure gauge. On the application of pressure to the
actuating lever, the valve opened momentarily and the transducer was sub-
jected to the pressure of the compressed air, which simulated the explosive
force of a gaseous mixture. As a result of the error-compensating cali-
brations introduced by the pressure gauge and through the "dead space"
(the change in the volume of the cylinder chamber when the valve is open),
a calibrating graph was plotted (Figure 3).
68 MU 1416182U224i8283U
Pressure kg/cm2
Figure 3. Calibrating Graph for the
Piezoelectric Transducer.
The acting forces, in kg/cm2, were plotted along the abscissa of the graph,
while the amplitude of the current impulses, in mm, as recorded on the oscil,-
lograph film, were plotted along the ordinate axis. Repeated calibrations
were made for the sake of n,-..,+.,. .- .
pressure measurements up to 28 kg/cm2,_ ~~Y111~er output current and the
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e and Accurac of
Measurements e
l
v
to beOf the
ord
e press r5 es' which it was necessary to measure, were expected
designed so that atmospheres, The registering device ryas therefore
curate pressure measurements could be made Within the range
of 2 to 25 kg/cm To hold the measurement errors to a minimum the following
precautionary steps were taken: (1) calibration and measurements were
at the same surrounding temperature to eliminate the effect of t
tuations on the behavior (2) the rectified voltage was stabilized to eliminate the unit;
of an error by the DC amplifier due to the fluctuation in the line voltage; as
a result, during introduction
a varied t,0 ng a line voltage fluctuation of 4 7.5% the stabilized voltage
Vari ; and (3) the influence of the fluctuation of tube emission was
eliminated by means of preliminary tube adjustment under operating conditions.
Calculations show that the sum of all the errors under these conditions
amounts to approximately 2.5%.
Testing the Transducer
The transducer was tested on test explosion installations for
bl'drgen-
air and propane-air mixtures of various concentration ratios. Figure 40
Figure 4. Oscillogram of the Explosion Process of a Hydrogen.
Air Mixturemarks
time . 1, the oscillogram of the explosion;
2,
.
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having a 4 --'..eaaru oozalned from an explosion of a hydrogen-air mixture
hae rr3n hydrogen concentration at partial pressure; The direction of rrow. 25 cm/sec. Thertinesmarks thate
to Tof recording speed (the
frequency of the time marker was 50 hertzes The ex the on prose (the
recorded on a loop having a sensitivity factor of explosion The as
was recorded on photographic
during printing. process
film, after which the3osc11111oa The gram was enlarged
The resulting oscillogram permits the determeinastu
pressure developed by the explosion and allows th
tion or the maximeumof
the explosion. With the aid of the calibrating graph Fif the natur
unit conversion graph] It was determined tat the
by the explosion in this case was 26 kg/cm maximum Pressure developed
The work conducted demonstrates the complete applicability described for recording the explosion process of gase
measurement of of the apparatus
utilized for of ress rest thus developed Evidently, ly, us thee haprpar ea u and for the
s t also be
processes having analogous characteristics.
The authors are grateful to L. M. Dzhulardyan and I. B. Ogiyevich for their
assistance in this work.
b
3. I. S. Zheludev A S om ustion Engines , 19 5
BIBLIOGRAPRY
1. A. M. lurichin, Elektricheski Izmereni
(Electrical Measurement of Nonelectrical Yalueslektricheskikh Velichia
2. L. Volchok, , 195
S orani P ezoelektricgeski Indikator D1
(Piezoelectric Gages for Internal
Dvi tele Vnutrenne
electric Transducer for MeasurinI. Shteynberg, N. A. Calybin. "Piezo-
g Pressures, Zav. Lab,
4, B. I. Shteynber --~ ' 7' 852-855, 1953
Pressures in Indust ial Ptbin, Shein, I, S. Zheludev. "MesetaIng
ea
Pres s ses
30, 1953 , Ibfya_Pronyeh-an 4, 25-
5. I. S, Zheludev, I. B. Ogiyevich. "Mechanises of Intermittent Action Measuring
Trudy, Institute Krlstallografii, 12, 1956
Institute of Crystallography,
Academy of Sciences USSR; Submitted for publication y1956
on 24 February Institute of Fire Prevention i 1956