TCCICH
L U2t\J% NThU?V1 VOOR DE K1J(MACHTe'd. ripp ten -cstr.ie
st t. tatuty
st
.owtie iati
in
ter fl&tag owvitti
(Issledo'ranie intensivnoti
kuticheskik
ii.achenii ypotoke voJ.y pri
kavitatsii)L. 8. UY&f
ENek&OMASIINOSTRONIE, 1958, (9), 23-27
The psr de.cx1bss the ..riasnta1 method. ed aM the result.
taime4 ing the tnvestipti
of
ultr..sio re4iatitres a
sptø-.triaties oesillat in hy1ro'iiic th.la
aM
med.luitii.
resulta iMiost. the pesMblUty of uaia,g the aheracteriatic ultrsaesio spectres to inve.tijst. o.vitaties in drsulio thstaflati.,C&vitatios in t.r flow i. '-fNI.)asisd by aoouatio radistios (mois.)
a wide range
of
hiaM low trsqei.s
ii i.s to th.ribratiosa
of
bl.. awing their powth, c.ri.saiosaM
Maqçesramoe
in th, liquid flø..All the.. sa are fairly Intan.. aM
b.det.ct.4 with the obj.ot
of
ob..rvin.g the mas cC oevitattowdees]it.
?requsn smeljsiaof
the noise spectres aseociat.d with oswitatiesin
liqaids he. bees oriod sut at thV.1. T4i Polytis Imetitut. at
t.v. The.. .xpsrimest. . merri.d ut is the diffuser
of
ao-dynaiic sl
of
r.cts*gelar orces .stiwith 41
4jj
of
31 z 31 .ltng e enge. tostrioties esciUsteraM in
droturbtn.s. &coua tic radiatice pidred by pissoal.otri.
d.tectors aM overt.d into electric osoilltiess 'ii after suitabl
1ifiosties, . tod to an lMiostimg iaatzest to a .athoi. ray
osciuloçsp.
koohelle salt, qes.rta aM bailes tit.nate e used sa piszoslsctric eles.nta in different e xpuri..ata.P4sUtI11a7
Esr1rrt.
Pr..li.ienry .srita ver carried sut im the diffuser itthe
dro4uio thm] Sn
dar to thtsin tntentiom cosoerniag theof
th. total cevitat tow ... iectr Saj a rsa r.usuiier, with a widebeM alifter
eM
a special3y.sr.
Us ix a het erodyn resuiver aysteswith rrow beM intermediate
fr.qu.
lifiosties
itpathl. t.
.t.ct rr.qi.aci.s fro. th. vary lat
to hi# fr.quies of
of 5
s.
noise 1.101 dt the o.tire fr.qosnay .p.etr
a
al..
assaur.d ovar
s specific shortti
interval.
The peli4".'y
..rits pv, the
foflo'u'ingr..u]ts:-Osvitat io. ast.. pos...' practiosily a lias .p.otra
with
avary vUe
fr.quo.cy rang. fros 1fr.quo.oies t1w
altmso.ic fr.qusnat.s up
topcyoL..
Tb. inteasity d.or.sses with increase in fr-.qus,
tI"(
prsotioslly to isro at o.. megacycle.In the ultr.so.io ro. it i. possibis to isolst a r.gto.
fro. 100 to 300 ko. fros ,hith with suitable a1ificstio.
it
in
po.sib], to s]w). noise dus te nearby
o.ohiary.It thervf'.
appeared ri.iug
to carry cat futher
iav.stigatioa of the ultrsso.io osvitatica noi... s. .ip.z1ta indioat.d that a oevitat io. noIse analyseriat possess
the f oUing properties:
Ability to asae the
intensity of the
.otic
rediatica over a vil. oo.tiaa ap.otrus tro.1.. fr.qu.ncl*. up
to ultraso.io fr.quenoi.sdt the oeder dt
megacycle.
Ability to isolat. a sufficiently asrrca
fr.-qnoncy
bsai
doca to 1000 ayo].. aMto asarw
th. nois l.v.l of the.. bszidiAbility to bift this
narro.
froqusaqy baaialcag the ol.t.
.p.etrus withinthe liait.
of
ioh noia, lavai as...
ts are required.
£ special an..lya.r as.
ostriat.d to ast the..
requizassnts.(1)
'Tb. noise .nmly.sr ass
eo.atrted by L 3. Lso.er
sai
V.V 3j
-'r
s dtz.ctio. oC LV. P.d.rav.
lois. Iatity Ks.arnts
Tb. socuatie siVkt.
r piok.d
by a special probe nuing s pissoslectriccrystal
to ov.rt the
n1osl vibratia into electricctUatis.
Thia o.ist.d of s. quarts pitt. cut p.rsll.l to the a9tiosl axis in suob a wy that its wide planes wer. cut psrp.diau1sr tothe electrical
axis. In arder to slji,ist. resnc. .tf.ata, tb. thi*ns.s of the quarta plat. was auth that its natural frequency lay farabo,. the
observed
oavitat iou frequencies.Fig.re i sh. the ostruotten
of the probe.It oiats of a dsltuin rod
ioh is screwed, into the wallof
the krodynio
tb.wi.l
ioâ.l tuxtne end the probe bo otsinisg the qnarts piste whith ta f ir.iy pressed agei-t the rodby
of a spring. £ rod tr.'-4 t. the sooa.ttc vibratiasi to the qeerts crystal and
the
resultant .l.otrio oscillstime are fed directlyto
the vaiwe otained is the probe houin.g 'ioh sots e.0 a vid, bend a1ifisrer the rang. fras 20 zyel.s to 1
.5 los.
object
of
placing the first lifi*r directly inside the probe housing was to el44n*t.
oapscitative .ff.t. du. to the saurizg systand the oeoting osbiss,
analyser desiM
as
the basisof
the s,bo, .entios.d requi&uitsis sho .htis.li,y tu Ptiire 2. The electrical o.eillsti. tras the prob. are fed to a niser 'ubith also reasive. a voltage frs. the hi
frequ.r
b.t.r.n. asoillat (Q884).
The
xsr
ztput is ted t.the
first
11fi.r
ted to s freqiasney .1 2.83 $ sad t to s. uusdamar stag. r. it is .mad with the output tras a eo het.r.aie
oscillator tas.d to 2,3 loe.
Tb. vutyut of the
.so niar is f.4 toth. ..o narras! bead
.pl4fisr
td to 100 ko.
Th. 100 kas sigeal ist fed to s detectar stag.
sad f
4ly to the indicator inatzent.
The ssieotiasof
a hiwi int.ra.diat. fr,qiaenr forthe
first liti.r osans that asly s narras freqeenay bendis
passed whith,as -4 'ing with
the h.t.ri&dyse fr.qusn by ei or differenc. gives s freqasnayof
2.83
.
The ]yasr i. fed tras a voltage
stabilised
rectifier,The arr.'''t described p.rndtt.d the osyitat
tos nadee intity to
b. esasur.d
o'er the frequos rang. fros 50 kas to I Mos.A pointer eioro.tar was used to
ssur'. the
cavitaticm nois. intensity. Sinos theaoc.tic r..d.isti
&e
to ca'vitati is wstab1s at all frequencies the thstrent pointer was subject to f uatti sadin order
tool44v&t. the.. fluotuatics
theinatrsnt was
ahtmtsd by aocmdanser so as to increase the 1nstrent
tiesoc*st&nt to &
valueof
fras 8 to 10 s.oda.
As aresult the assswes.nt value obtsinsd was
the asan valus &
the inteosity .t th.obsrwed
frequency.The r.oarding of the
o1ete notas sp.otrta for a givesoavitatim
regles took aroztte1y 4. t. 5 ainitea.
This sppsratua was uasd to
inreltipt. as'vitatie. noise in this
aboye. ( djffusqr
in esêel
droturbias.
the
oavitati stand.In the ens.
of
the diffuser the probe was bettedalose
to thens.rrst oro.s .ecties. When invest ipting node]. turbinas the probe
was boated inside the turbins, sonsuhat
diaplaas4relative
to the axisof rotatioe of the
blade.in
the dir.etton of f1ø and was therefore situated fau-by
closeto
ther.gins uhoes the o.,itatiet spp.sr.d to b.
nest jutasse. Theveriaties in
the intensityof
oavttatic estas I.et.ise
1 rdr.tw%iess was investigated by this esano.The osvitatien noia.s speCtres thtained in
the diffa.r is hin
gure 3.
The noia, intensity was ala.
.s.s.r.d foe' eodelawith type LP
sed I
iars in the
I kydrodynios isboestoryfor type 1%8
-IL. 63 rs in
the
kydruturbtee laboratory at the L.siagradtl
Wora,
The araatoriatioeof the noise
spestra tsiest with ditterestoavltatis regine., possessing different values ef the avitaties
ooettteient Q" , ars
ta Pipw. ., ièsre
the tzeqummr is plotted
sleng the abseissa. asia end the Intemsity alesg the oedinets s1i.
ob oureu gives the noise
intsity
at different frequencies foe t
gives esvitatir. Tb. rss.lta obtained lend t. the tollawI.ag
_- noise spectra obtained both in th. diffuser and in the model
tmbinss imdioa.t. the pr..o.
of
herp r4-and
i sners1 ws14 .
e
t. the .p.atrsl oeryse obta.tn.d in the pr.l
44 iiry
.psrinta.
Thesr
of
r4 obtained .iiff.r. with diff.rwnt flos oiti both inthe oas of the diffuser and of the models. ¿. 'rl-. say b. due to the ertti
of
transient acoustic radiation by the oa'vitatlon babb1.s w*ic'z was partteu]ar int.m. at the time & r.00rding.t
8is the bubbles diff sr in au, their fr.qu. spectra and
iat.nsttiss ist also b. ditfsrent, transient pulses result in a lin'
a-Tb.
ri
oavltaticn noise intensity was obser,d overt
relativ.:1.ynsrros frequency baal extending approximately f roe 100 to 250 kns. Th noise intensity dec:rss.sM with inca-ease in f requena,,
b..4ng practically
¡ero at a fr.qiy of I cs.
The resulta obtained represented the nean values over a given tim.
int.ri*l sal the .p.ctr oharacterised the acoustic r.Aiatien for a given regimi during a given finit, bui mot very large tim. later,'.].. Sino. the vibrational charact.r of the otyitation proc... is wiatab1., it
b.00nes
necessary to obtain these spectrafor instantaneous fis eiti (
at l...t during the .ht..t possible tine) taza permitting
t
"e sconTate and dstailsd investigation of their struotn-e end rslati.h1p with thecavitation pa-coses.
Por this reason the seriaental sathod vea verted and a .ç*cial ultrasonic noia. analyser developed which enabled the mois. spectra to be recorded practically instantaneously ca the sca-sen of a oat
rey tub., The spectra ware permineat].y recorded by pbotogrs.
method of investigating the intensity
of
ultrasonic radiation by sp.ctronphotography.
The aoous tic raitiatico was detected by the semi typeof
probe (see Figure i).The noise intensity -. sgsred by feeding a voltage proportional to the intensity to the vertical aveop plates of a cathode ray tubs, Thu
wee grat.d by & b.ri
titanate piesoeleotria ele.ent with an&ttntl freqoy
of
the ord.rof
1.5 io.. Lt the same tise a voltageprcçortiwal to
the frequency of the seaaured radiatien sea fed to th. borisental eseep plat.. of the cathod.rey
tube.A beterodyn. sy.tes
with hi
speed vs.riati of the heterodyns frequency was ilay.d in order to obtain the cclete sp.ctr in a very short periodof ti...
By aean.a at this rrangseent narr re.diatibends were auoo.ssively passed througi the analyser,
over
the entire rsn of the ultrenanic r.4iati over any desired r.gi of theultra-sic epectr, during e. very aht time interval
of
th. order of e or afew hzmdredths of a seccsd. spectrum 'sea photographed tiring the .e short ti.. interval. ¶ oorreapoeding frequency spec tr was then abose
o.
the s cathode ray s'.sn ath ses photographed. The two nega t ive s war. then superposed and the frequency saale sea transferred to tb_s intensity speotr which enabled the intensity to be determined for sr given frequency. In this respect it should be noted that thefrequency seal. within the li.it.
of
0 and 250 ko. i. practically linear. Th. analyser cyst is chose schematically in Figure 5. The pulses Cros the probe are fed to & sixer valve which also reoeivee a betero4n. voltage so that a certain frequency e is fed to an lifier tuned to1,.65 kos. After detecticai, the aigeal i. fed to the vertical sweep plates
of
the cathode ray tube The heterodyne frequency is capacitativel.y tuned averthe range Cran
5J45 to 765 ko. during a periodof
fran 0.1 to 0.01 secid by seamsof
& special relay. Thus th, intensity sp.ctrum between the lits Cros 70 to 300 ko. can be recordedan
the catheray
screen during the s time int.rval. The spindle of the heteronevariable condenser is rigidly oo.nected to the spindle of a potentiose ter the voltage Cran 'which is fed to the boriztai sweep pistes of the cathode ray tube which are thus .ynábronia.d with the vert io.] sweep frequency. The harisontal sweep length is oantrolled by a special rheostat.
The schene provided for the possibility of switching in & frequency
marking generator in place
of
the prob. using for this purpose a st.'i.rd eisal generator. In addition provision was aleo sede for6.
contro1liJ1 the amplificati of the applied to the vertical sweep plates and tar regulating the ti reqtdr.d for analysis.
The ayste we.a supplied fran an electrc*i and i stabilised rectifier with a high frequency input filter.
The spectra appearing an the cathode ray screen were photographed
with a 'Zen1t" oara.
In
order to utilisa the full trame diiiena ians,the focal length could be adjusted by aeans of a special ring. During photograpby the camera was located at a distance of 200 tras the cathode ray screen.
The appe.ratus described was used to inestigae the acoustic r.4isti of cavitatiou generated by a aaetostriction oscillator at a frequency of
7 kas in
the diffuser at a bydroc'namic channel and with a 250 diaiter .odel of a typePL.577
kydroturbine. Tb. .xperi.entawere carried out in the hyth-cxtynmzatca laboratory of the The typ. of spectrogram obtain.d is shown in Figure
6.
A rauher of spectrograms were obtained with different elitudes of vibraticai of the aaseto-strictios oscillator, thus COrrespOEldin.g to different intensities ofcavi tat tas.
The piotograpb.
obtained
establish the following propertie, of ultraaasic cavitation noise as produced by magnetastriotirsi.(i) A typical characteristic of all the .pectrogra obtained is
their line structure and the relatively narrow frequen' bend in the region of 100 to 130 kas where the ultrasonic radiation possesses aaiirau intensity for all te magnet astriction vibration amplitudes investigated.
(2) ith increase in the mgnetostriction vibration anplitude, i.e.
with increase in the cavi tat ion intensity, the ultrasonic radiation intensity increases over a narrow frequency range;
in
..iitiou the intensity also increases at other frequencies up to values of the order of 175 kas; it ebould be notedhowever that the intensity within the abcre-ent toned limita always greater than at other frequencies.
(3)
The spectra obtained are fairly twifcrm in character thus indicating the unit ority of the veri ous cavitation procesase in all the case. investigated. Figure 7 shows a spectrogre.e which indicates the intensity and frequency of the radiation produced in the diffuser of a hydrodynamic channel during the early stages of oavitatica developsent.!xamina tion of the speotrogree of the radia t ion in the diffuser lead
to
th. f ollowin ccneluai:(i) In the absence of cavitation, the intensity of the ultras onlo radiation is very low. achines in operation produce no
isarked rtd tion
end do not
affect the igr4tude of the cavitat ion radiation.With the &rrangenent used, line apeotra re obtained. The a&xi radiation intensity was observed at a narrow frec,uency band in the re gicm of 150 kcs.
Le the cavitation oontthues to develop, the axi.a intensity
rin at the sa
frequency region but & general increase in intensity also oocurs at other frequencies, chiefly at lower frequenci.s.By way of exarple Figuree 8 aM 9 show spectrograi reccuded at the cavitation te et s taM during the invee t
igati on
of a 250 Ma.ieter od.1PL. 577 runner far the eanc operating
conditions but
different cavitationr. glees. These tes t e lead to the following conclusions:
-(i) High frequency noise i. practically absent during operation
of
a aodal turbine without cavitation. Noiseof
u4.partantintensity is recorded at only a few isolated frequencies. This fully agrees with
spectrogra
of diffuser noise
recardd in the absence of cavitation. This confirms that thenoise
due to zeachine operation possessesno
noticeable hi frequency(
) L.. the ariginat ionend
develoçnt of the cavitation proceeds,the
nois,
intensity also inases. Th. nois spectra extend 8.9
P.T.S. No. 10g2
still further both into the low.r
and jsr fr.qucy regi.
Tb. frequency r.gic in which the hiest intensities are locatedlie betw.sa 80 sM 300 kos. Tb.
1
intensity is locatedin th. rs gton
fr
150 to 250 kas.(3)
The critical cavitation regias orespondln.g toT,
is a.rks4 by considerable intensity at a wberof
frequencies and althou no specific indications are .vident inthe
cavitation noise spectra, two or three frequencies in their oun region af the speotrta iniioate oonaid.reble alitudei.11th
furtherdav,loent of
cavitationthe
intity increases in as regions of the .pectrogre*. Tb.a. characteristics war. evident ta sil the experisents pert ord.The frequency s ctrt of the ul traseaio cavitation noise in a
nodal k'droturbine was oosidarably wider than that obtained by maetostriotion or in the diffuser
of
a ydrodynenloÑutrl.
This ii prssueably due to the fact thatthe flou
conditions it the cavitation stand e less honoen.ous.(5) The experinonts ahowad
that
it was possible to use a nsrros bandnoise aenauring
syiton
for th.investigation of
cavitation. A1. Probe with preamplifier. I - screcne4 cable; 2 - MIS
amplifier valve; 3 - iean; 4 - *obe hoizJ..g; 5 - IIINlItII.g
150buik. 6 - uxu ay*al. 7 - plug; 8 - bydxoChke chug.
.vsaaa..aa. s
100ssa'i ..sus.
50ka
100 200 300 400 500 600 70G1fi
40 30 20 10mi:
s....
s....
.t
.4.
lnLenhityga*ge (graduated scale) 200 Profile 100 20 300 400 500 U) 70Fil. 4. Radiadca thxe1ty .perwIn le w fer cav'tt*tkes by
a model PL. 634 rez: a - PL. 634 r:
410°; $
lO80; Qj - 770.
I9.165; fo
1.192; fl1.0.145.
b-PL.634rer:p = *2; a10; nj1O0; Q1360.
fVir
0.574; Vv -
0.998.10
Fi. 2.
Itock diagram of the a(x,ic
radia-tioe analysa.
i - k. f. au11fla: 2
ist m13- ist I.!. amplJlIa; 4- 2nd mIxer; 5-2M
t. f. amplifier; I - 4ctec; 7 - 2nd betaodyne;
8 - 1* heterodyne.
s
I
a....,
asasi
s.... i,
u...)
si... s
u.... s
u...,. i'
a...'
u.u. 61
.s..au aaaaauaua
Saul. sauau...s.a
sar am. usassi....
4I1 uuisau..iU
U
'iiuaus.aa.a
f
ayas. i
sa.aaua
va'au usasuus
'iaflas aasau
I 5Û 200 Probe location 300FIl. 3.
RadIation lnrealry spcftnmle waterfr cavitation ti the differ.ez of a hyo4yiamlc
ckane1.
400 f
ka
Fil. 5.
Slack diagram of u1tras.nc r4titkiianaiya with high spoed radtng.
i - h. f.
gcnera
sad ampU; ta - mixer; Zb - t.f.
amp1Lf; 2c dettr; 3
-4 - *sply
ix; Sa - and 5- e.f. amplifier;
6 - htetal swap generaerr; 7
- frtquancybase gencza; $ - czt
ray tóe.
R.T.5. No. 1002 40 30 20 10 o b)
10i
e.
.1,'-lic
?O k,
.te4,1, I IliC 150
Flj. 8,
Spectrogram of r4Iaiban bi wa from a mo1 typePL5TT nmner 0' 0.213.
e
t
I100 200 250ka
Fit. 9. SpecVokm of rid1a biw froni a model type
PL. 577 rmaa - 0.230.
li
200 k
1.
R.T.S. No. l0O
FIj. i
Spcctrogra.m of magncuisuctk rl41.' P1g. 7. Spscuovn of radiiUa ttizelty la walrz diarto the dll.rr vibraban dwing the developmz of