CA2142971A1 - Method and apparatus for generating high energy acoustic pulses - Google Patents

Abstract

A method and apparatus are disclosed for generating intense acoustic pulses by means of the water hammer effect. The method involves generating a water hammer in a conduit by suddenly interrupting a high velocity flow of fluid through the conduit. The kinetic energy of the fluid flowing in the conduit is converted into a high pressure pulse which propagates along the conduit away from the point where the fluid flow was interrupted. The high pressure pulse deforms the wall of the conduit so as to radiate acoustic energy away from the conduit into a fluid medium surrounding the conduit. The relative amount of energy dissipated in the form of mass flow in the surrounding fluid and acoustic energy in the surrounding fluid can be adjusted by changing the characteristics of the conduit wall. The direction in which acoustic energy is radiated into the fluid medium surrounding the conduit can be set by making the conduit wall asymmetrical or by bending the conduit.
Embodiments of the invention for acoustic cleaning, viscosity reduction in fluids and acoustic sedimentation are disclosed.

Description

~ W O 94/04944 2 1 ~ 2 9 7 1 PCT/CA93/0034s ~ . ~
.~ ~` ` ` , ` i ! :- -~ElEIO D ~ APPA~ JS FO R GE MER~ N G :~
EIXCaI ENE~C~Y ~C O USIIC P~nLSES

,, Field of the Invention .

` ~ This invention relates to a method and aMaratus for -' generating high inten~ity~ acoustic waves in a fluid and for directing t~e 10 acoustic waves so; generated: towàrd a workpiece or a~ volume of fluid to be ` treàted ` Backgroundofthelnvention~

It is known *at ~igh intensity acoustic pu!ses may~be produced by~ delib'eratély creating a "water hammer". A water harn~ner is ` ~ ; `; ` ~ "`,' the~high pressure pulse created~when~a rapidly flowing ~tream of fluid~in a~
conduit is'~sudde~bl~d.'~ ~en t s occurs,~for example by ~e~ sudden :`
d os'ng of a v~ve,~`~e~c energy of ~e`flow~g fl~d is conve~ed~to a `'20~ ,~gk pressure pulse,, g p~` re; se pr p at 9 ups r ?~ `the~valvé~ata'velo~which~is~a~;;~n~ionof;~es~edofso ndin~the~fluld~
, ", ~ `in t ,e pi~ a d ~e``dime~nsio~and elas~ci~ of ~ ~ ' ~.; A
" f ~ phenomènon resùlts~;in~a~'reduced~pressure p~se~ing~ propagated~
' do~,'srea away~f om~t e~v~ve.

Whe ~ ~ pres~ uré pulY arrive-~'at~a pomt in tl~ie~conduit~
upstre~of:~valve~,~e:flui ~,t at ` i~'s~sf g~ardthe~
è ~e~'nreaed~press eforces~ewa sof~econduitou~ardly~

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wo 94/04944 ~14 2 9 71 Pcr/cA93/oo34s~

closing of the valve until the pressure pulse reaches that point. The mathematics of water harnmer are discussed in various texts on fluid mechanics including Fluid Mechanics (7~ Edition) Victor L. Streeter and E.
Benjamin Wylie, McGraw-~Iill Book Company, 1979.
It is known that the water ha~uner effect can be used to generate acoustic pulses for use in marine seismic exploration. Baker et al., United States Patent No. 3,376,949, discloses an acoushc generator wl~ich ufflizes the water hammer effect to create acoustic pulses in a fluid. The acoustic generator comprises a high energy pump for providing a stream of rapidly flowing fluid, a downwardly extending pipe through which the fluid is pumped, and a valve at the lower end of the pipe. A zone in ;the pipe upstream from the valve is perforated and surrounded by a heavy rubber t~be.
::
The Baker et al. device is used by submersing the lower end of the downwardly extending pipe in a body o~ water and pumping fluid through the pipe at~high velocity. When an acoustic pulse~is desired, the valve is suddenly closed, thereby arresting the flow of fluid in ~e pipe and . .
20~ ~ cau~ing a water hammer within the pipe.

The water hammer pressure pulse created when the rapidly ;
;; ;; ~ flowing fluid is brought to a halt by the closed valve propagates up the , ~':' ~ : pipe toward the::p~mp~: ~Because ~e rubber: h~ is cornpliant~ the pressure :
pu!se forces ~e ~ub;ber tu~e outward as it travels up ~e pipe. The result is ~at the rubber tube displaces the surrounding water, thereby generating acoustic ~waves in ~e water surrounding the tube. A s~ngle short burst of acoustic waves is ~roduced each ~ne the~valve is closed.

; 30 ; ~ ~ ~nstey, Uruted 5tates Patent Nu: 3,536,157 dlscloæs an underwater acoustic~generator,~ also for use in~underwater~s2ismic SU~STI:~UTE S~EE:T

~ W094/04944 ~ l 4 2 9 1 PCr/CA93/00345 1;

exploration, which is designed to be towed behind a boat. The Anstey generator comprises a length of conduit with a velocity transforrner at each end and a normally-open valve near the trailing end of the conduit.~When the ~nstey device is towed through the water with the valve open, ~e ~ji 5 velocity~ transformers direct a high velocity stream of water ~rough the conduit. When the valve IS suddenly closed ~a water~ hammer is set up inside the conduit. Ihe water ha~er pressure pulse travels along the conduit away~ from~the~ valve. ~ The walls~ of the condult irl on embodiment of the Anstey ~device are par~àlly compliant so~ ~that the pressure pulse~
10~ causes acoustic energy to radiate from the conduit as~it~travels along the~
conduit.

Burg, Uruted States~ Patent No. 4,271,925 discloses ar~ther system for generating acoustic ~pulses ~for~use in seis~uc exploration ~by~
15~ ~ ~ delibèrately creating a water:ha~runer effect within a conduit. The~Burgsystem comprises;~a ~pressure~Yessel for providing~ a source of pressurized ; fluid, ~ an acoustically transparent conduit co~ted to the outlet~of the pressure ves~l, an upstrèam; valve be~n ~the ~ pressure ~ qessel `and co`d forco lin ~ w~o flud~o t ep~ssurevess Q ~ condùit and~ a downst èamv~ve~at~the~ t f~con it for~a p~
te ` nat gfl d~fl ~i ~con uit~

The Burg~device is ~ùsed to ~n~eratè ~acoustic pul ` steps of pressuri~ng ~fluid ~i~n thé prèss~e vessel, ~oper~ng:the 25 ~ju~team~v~veto;allow~ ;pressue;fluidtoflowi to~e~c waiting until the~fluid~in~the conduit~is flo~wing at a maximum v~, and ~è~su~s ~ . n ~do isclo~;awa har ~#i9~a dwi~ it:
The~ssu ~ pul is~back~dfor -~
;30~ ~ ~ùit ~ e~ ve~l~ and~ the~dowr~ea va ve.a~c ~ustis:~igrul pl~ls~ w~llh a characteris~dc l requency~

!`1`' WO 94/û494~ 2 1 ~ 2 9 7 1 PCr/CAg3/0034~ ~
l~
4 ~ 1;
~ependent upon the length of the conduit is radiated away from the conduit each time the valve is closed. ! :~

....;
Other references which dlsclose means for harnessing water h~nmer to generate acoustic waves in a fluld are Bricout, IJnited` St~tes patent No 3,369,519 and Davis, United States patent No. 3,690,403. :
Each of the references abo~e discloses the use :of a deli~eratelv create~
~: S water hanuner to produce a one-shot high amplitude burst of acoustic signals appropriate for geophvsical selsmic exploration. In each case, the acous~c signaIs are radiated fTom a circul~rly symrnetrical conduit~ ~one of the :: references abo~ e disclose: an acoustic source having means for rapidly c~clLng ~ a ~ alve open and closed to yield a senes of water ha~uner pulses in a con~uitto produce a contlnuous acoustic~signal with. a charactenstic frequencv:
: ~ dependant upon the rate o~ valve operatiorL :
Akimoff, German patent ~o.: 620,~83 discloses a siren in ~hich water hammer generated in a conduit i5 used to make noise in alr. Ihe siren has~a pump which pumps fluid through a clos d loop of pipe. .~ e in the plpe periodically interrupb~the flow of fluid through the ~pipe to cause water: ~
hammer in the pipe. The inte ior of the pipe is coupled to a ngld diaphragm which is: caused to :vibrate by water hammer Ln thel pipe. The vibrating diaphragm broadc~s:b sound ~nto~ the suITounding air. ;Akimoff does not harness: water hammer pu~sès~ to do work~ on: objec~s.
20~ coustdc cleaners u5~ng ;various ~piezoelec~ic ma~gnetostric~ve or ~oice coil :transducers a:re known in t~e~ pr.ior art For~ example, Japanese patent~No~
3318~93 dis~loses ~ clQthes washing machine~which uses so~ic energy ~to clfan:
clo~es. Th~ sonic energy is generated by means of a~voice coil which vibrates one;wall of a:~compartrnenlt~containin~: the ciothes.~
;ex~ple~ of :~e u~ of ~aso~c::waves for cle~g: items~is ~e:~
`~ ~o~ccIeaning~a~chis~cor ~us~d~i la~rat es~r;~e ng~
s~ iteins. Such ~ pnor: art ultrasoruc: clèr~ning baths~ o~rate ~t~

2 t 4 29 7 1 PCI/CA93/00345 j~

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high frequencies, typically above 20,000 Hz, and at acoustic intensities which are typically much lower than the acoustic power levels developed by the present inven~on. The acoustic signals in ultrasonic cleaning baths are typically developed by means of piezoelectric or rnagneto-strictive 5 transducers. These prior art ultrasonic ~transducers are essentiàlly pistons which can be reciprocated very rapidly to generate an acousbc signal.
When such prior art ultrasonic transducers are operated at high intensities cavitation can occur in the fluid near the ultrasonic transducer duling the retraction phase of ~e piston. The cavitation bubbles interfere wit~ the 10 propagation of the ultràsonic beam. It is therefore~difflcult to generate high intensity acoustic signals using such transducers. ~ ~

A further disadvantage of prior art ultrasonic trans~ucers in applications where an object or body~ of fluid is to be treated at a distance 15 ~ from~ the tran~ducer is~ ~at the attenuation of high frequeDsy acoustic~ waves in typical fluids is~ much greater ~an the attenuabon of lower fre~uency acoustic waves in the same fluids. Therefore, high intensity compressional _ pulses delivered at compara'dvely low frequency~ can be more effective for;
t reating ~materials at~ long~distances from a transducer than high frec~uency, 20 ~ ~relativelylowintens~:;ultrasonicwaves.
The disadvantages of ~prior~;art ~ansducers is compo~ ded in some àpplkatio;ns by~di~rsion effècts.~ }n~ense, ~igh frequency acoustic wave~travel~ n ~a fluid, ~adjacé`nt~ pressure; ea~ n ~e wave tend to spread out~mergè~w~ i~ each other.~s ef c c~se pa ar problems at ultrasonic frequencies~ because at such frequencies ~he ~
avelengt~is s~iort and adiacent pressùre~peaks are close toge~er.~ The effectiveness of ~ acousffc ~r ~ ' g~o ~r o r ~ic ` ~c ; be reduced ~ ;s~ead~g of ~e~ acous~ pressure:pe~s ~ ~e~ wave. ~ Thèse~
dis~rsi ~couI ~ uce ~b ~ ea ng~ dis~ ~ t ;;`30~ ~pressure ea in~;~ e~acous~c~wave-(i.e~bylowe~g~e~uenqof~
acoustic wave).~ Uowever, lowenng the ~frequency of a~ ginusoidal aCOUs~iC~

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WO 94/04944 PCI'/C~93/003~ ~:

wave, which is the type of acoustic wave mos~ commonly produced by prior art transducers, while holding the intensity of the wave constant has the effect of increasing the rise tirne for each of the pressure pulses in the acoustic wave. This, in turn, may retuce the effectiveness of the acoustic 5 wave for cleanis~g or for other applications. Ideally, a generator of acousticwa~ves for cleaning OI' other material treatment applications would be capable of producing distinct pressure pulses, with very fast rise times, separated by a selected interval~
, :
Water hammer~ has been used for cleaning the inside of pressure vessels and tubes. For example, Canadian patent No. 837971 discloses a method for cleaning a heat exchanger tube. The method . -comprises the steps of passing fluid through the heat exchanger tube, heating the fluid to near its boiling point and suddenly and repeatedly 15 i nterrupting the aOw of the fluid at the tube inlet. Interrupting ~e fluid flow causes low pressure pul;es to propagate through the tube. The low pressure pulses clean ~the mner surface of the tube by eausing the fluid to boil~at the tube's inner surface. Karpovichj United States patent No.

3,409j470 discloses a similar method.~ These references do not disclose the ., 20~ ~ use of water hammer for cleaning' obje~ts in a medium external to the t~be in which the'wakr:ha~uner~is generated.

Acoustic~fields have`also been u~d~for removing setiment from fluids. For example, Uruted'Kingdom patent No. 2098498 discloses a ~
system for removing sediment from a flowing fluid which comprises a pair~ .' of opposed ultrasonic transducers for generating~a drifting standing wave ';
across the direction of fluid flow.: The standing wave sets up pressure gràdients in *le~fluid which collect pa~cles of sediment. As ~e standing wavè dnfts, the~collffted particle- of sedi~nent are swept into a collection S~l3ES~l~Tl~ T~ S hEL~T -:

4~ 2 1~ 2 9 7 1 PCI/CA93/û034~ ~;
:, ', A problem with the prior art water hammer acous~c generators discussed above is that they are designed to produce single bursts of acoustic waves for seismic exploration. A one-shot acoustic generator is not optimal for acoustic cleaNng, acoustic sedimentation or ¦ -~
sirx~ilar uses where a substantially continuous acousbc signal is desirable to minimize processing times.

A further disadvantage of the prior art water hammer acoustic generators described above is that these generators emit acoustic waves in a pattern which is syrrunetrical about the axis of the conduit in which water hanuner is created. An axially symmetric radiation field ls useful in seismic e~cplora~on but is wasteful of acoustic energy in situations where it is desired to concentrate aco~stic waves to treat a volume of fluid or a ` workpiece.

Summar~ of the Invention :~.
This invention pro~ides a me~od and apparatus for producing conffnuous high intensity acoustic waves in a fluid.
The inuention~provides an acoustic generator comprismg: a source of prffstarized~ fluid; a conduit comrnurucahng with ~e source for carrying a~flow~of fluid from ~,e source, a ~alve capable of ~interrupting the~
~ ~ flow of~fluid;in the conduit at a locat~on spaced from~the source; ~d means ; ~ 25 for closing ~e valve while the fluid is flowing wi~in ~e conduit to produce a water hanuner wi~in the conduit The conduit has a longitudinal axis and an outer~wal} enclosing a ho~low interior. ~e compliance of a po~tion of ~e wali of the conduit:~aries àccording to the angular position around ~e longitudinal axis.~ r-The mvention fu*her ~pr~ides an acoustic generator :` Sfi~ TlJT~ S~ T

wo 94/04944 Pcl`/C~g3/0034; ~ ~, `~ 7;~4~,~71 -8- . I ~

con~prising: a source of press~ri~ed working fluid; a conduit corrununicating with the source; a valve at a location spaced from the source; and control means for repeatedly closing and opening the valve at a frequency greater than 3 Hz to produce a water hammer within said conduil each time the valve is closed. The conduit carries a flc)w of working fluid fron~ the source within the conduit. The valve is capable of interrupting the flow of working fluid out of the conduit.

The invention further provides an acoustic cleaner for cleaning a workpiece in a cleaning fluid. The cleaner comprises: a source of pressurized working fluid and a conduit;communicating with the source.
Thç conduit has a wall for confining a flow of working fluid from the source within the conduit~ At least a portion of the wall is in contact with the cleaning fluid. The cleaner further comprises a valve connected to the ~: 15 conduit at its end away fro~ the source. The yalve is capable of blocking the flow of working fluid out of the conduit. The cleaner further comprises : ~ ~
control means for repeatedly closing and opening ~e valve to produce a ~ :
water hammer within the~conduit each time the valve is closed.

. ~ ~
The invention fur~er provides apparatus for lowering the viscosity of a viscous fluid. The apparatus comprises: a chamber containirlg the viscous fluid, the: chamber having an inlet and an outlet; a source of pressurized working fluid; a conduit conununicating with~the source, the ;
conduit ca~ying a ~flow: of working fluid ~from tl:~e source within said :
conduit; a valve capable of blocking the flow of the working fluid in the conduit; and control means for repeatedly closing and opening ~e valve to produce a water barluner wlWF;the conduit ea~h time the valve ~s dosed. .

~e mvention fur~r.provides app~ratus for loweAng the ~ '.
3 0 viscosity of a viscous fluid. The apparatus comprisès: means for ~ ;
pressurizing the viscous fluid; a~condwt conDnunica~ng with the ~

. ~
: SU:B:S~iTUTE;~:~SHEET

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~, W0 94/04~44 ~1 ~ 2 9 71 Pcr/c~93/no34s pressurizing means, the conduit being capable of carrying a flow of viscous fluid from the pressuriz~ing means within the conduit; a valve capable of ¦`
interrupting the flow of the viscous fluid in the conduit; and control~means ¦ ~
for repeatedly closing and, opening the valve to produce a water hammer !` `
S within the conduit when the valve is closed.
, The invention further provides an acous;bc radiator driven by ~'~
a flow of pressuriæd fluid from a source of pressurized fluid for generating !,~,, acousffc pulses in a fluid. The acoustic radiator cornprises: a mandrel having a channel in communicabon with the source for delivering the i:
pressurized fluid to a first point on the surface of the mandreli an elastic ~, sleeve stretched over a first region of the surface of the mandrel, the fjirst region including the first point; a groove in the first region for c~rrying a ~J
flow of the pressuFized fluid frorn the fi,rst point to a second point in the `^
first region, the groove having a narrow opening; and a~ v~ve in ~ f~
communication with the second pvint for suddenly interrupting the flow of the fluid in the groove. _ The invention iur~er provides a method for producing work .
20 at a point in a fluid by means of acoustic signals. T he method comprises the steps of: (a) coruu~cting a source of a pressurizsd working fluid to the inlet of a conduit having an inlet and an outlet; ~ ~b) allowing the worlcing ~ , . , ; ~ fl~id to flow through the conduit; (c) suddenly blocking the flow of ~
working fluid at said outlet to cause acoustic signals to be radiated from ~e ~ ~¦
25 conduit to the point; ~d) waiting ~or an interval; (e) removing ~e blockage of the working fluld from t~e ou~et; and (f) continuously repeating steps (b~, (c), (d~ and (e) at a frequen~ sufficient to carry out the work. The work may be acoustic~ cleaning, viscosi~ reduction, removal of suspended particles from a volume of fluid or some other form of wvrk which can be ~-` 30 done by a series of acous~ic pulses in a fluid.~ ~

:
SUB~ST~ T~ Si~ T

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WO 94/04944 PCI/CA93/003~
?~47,971 ``

The invention further provides a method for cleaning an object. The method comprises the steps of placing the object in a fluid medium and creating a low frequency series of high energy acoustic pulses in the~ fluid medium.
Brief Description of the Drawin~ - ~ ~

~; An embodiment of the invention will: now ~be described by way of example wi$h reference to the following~:drawings in which: ~ :
10~ ~ , Figure I is a~ schèmatic diagram of an acoustic generator according to the invention;:

Figure 2 is a schematic diagram of a means for isolahng the 15 pump shown Figure: 1 fronn pressure pulses generated by the invention; ~

Figures 3A;through 3F are a series ~of graphs illustrating the : ~ ;
dispersion of adjacent pressure pulses in an acoustic:wave as the acoustic ;wave travels i~rough~a fluid;
.

Figures~ 4B, 4C and 4D~ are secffons through~ onP
;`embodimentof~a~radia~ng~cond:uit~accordingto~e:invention. Thée ~ : ; ::
Figures depict ~the ~:sequencé of ~events ~hat occur when a water harruner pulse propagates through a radiating conduit;
- ~ 2~," ;~
Figure~5 iS a section through an alterna~ve embodiment of a radia~ng~c~uit accord~g to ~ inven~on; ~

Figure 6 is a ~hematic~diagram showmg m embodiment of 30 ~ ~e invention :a~ted~for acoustic clèanirlg; ~

S~ SU~ rlTu:~E~ S~E~ET

~, W094/04944 ~1 ~ 2 9 71 Pcr/cAg3/0034s :~iigure 7 is a schematic diagram showing an alternative embodiment of the invention a~apted for acousffc cleaning which provides a pulsating jet of fluid which may be directed at a workpiece; ~ ;

S Figure 8 is a schematic diagram of an acoustic gen2rator according to the invention adapted to promote the sedimentation of sus-pended particles in a fluid;

~igure 9 is a schematic diagram of an alternative embodiment of an acoustlc generator adapted to promote the sedimentation of sus-pended particles in a fluid wherein the fluid containing the suspended parhcles is used to drive the acoustic generator;

Figure 10 is a schematic diagram of an acoustic generator adapted to reduce the viscosity of a fluid; :

Figure 11 is a schematic ~iew of an alternahve embodiment of an acoustic generator having a compliant radiator in fluid connection with the interior of a rigid conduit;
Figure 12 is a section through an embodiment of the acoustic : generator shown in Figure I adapted for washing clothes; :

Figures 13A and 13B are sec~ons ~rough the radiator in the ; ~ 25 acoustic generator of Figure 12;

Pigure 14 is a section through a compliant radiator which may be used for genèrating acous~c waves according to the illvention;

~ ~, ~Figure 15: is :a sec~on through a solenoid ac~vated valve which may be used in ~e acoustic generator of Flgure 1;

SlJl~STITUTlE~ SH~EET

wO 94tO49M PCT/CA93/003~
2l~29 11 . .
Figure 16 is a section ~rough a flow operated valve which may be used in the acoustic generator of Figure 1, and Figure 17 is a section through a cam operated ~alve 5 which may be used in the acoustic generator of Figure` 1.
: ~ ; :
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Detailed~ Description of the Preferred Embodiment ~ Figure 1 is a schematic diagram of an acoustic generator according to the invention. The acoustic generator provides a hydraulic circuit comprising fluid storage tanl~ 1 containing working fluid 2, pump 3, flui.d delivery conduit 4, r~diating conduit S, valve 7~ and fluid retum ;
conduit 9. ~ Pump 3; draws working~ ~fluid 2 from fluid storage tanlc 1 and forces it to flow at high velocity through fluid delivery conduit 4 into radiaffng conduit 5. It shvuld be understood tha~ pump 3 may be replaced with a pressuri~ed reservoir, or any oth~r source~ of high pressure fluid without departing~from ~the scope of ~ the inven'don.

20~ It is desi~able to maximize~the velocit~ of flow of working ; ;fluid 2~ wl~in ;radiating. conduit: 5.: Ta lthis end, ~luid: delivery conduit 4 may be constrùcted wi~: a grèater cross sectional area ~an radiajdng ~
conduit 5 ~and~ a velocity~trans~er 6 may be provided between conduit 4 `a~ d radlat;ng conduit~S.~Velocity trà~form~r 6 may~ a ~pered sec~on of~
25 conduit having a gradually reducing cross sectional~area.; ;

Upon~exiting radiating~cond~uit 5,~working fluid 2 passes through~v`alve;7,~which is~norrnally~ope~~ fter exi~ng valve ~ working fluid 2~is re~ed~to fl~d ~storage ~ 1 t~ough fl:uid re~ conduit 9.

tic;waYes ~e~genera~d:~by~sud~y~clos~g~v~ve 7;to~

` W094/0494~ 2971 PCT/C~93/00345 cause a water hamrner pressure pulse to propagate upstream ~rough radiating cond~it 5. Valve 7 need not be completely closed to create a satisfactory water hammer effec~ It has been shown ~Walter, United States patent No. 4,830,122) that an adequate water ha~uner effect may be created 5 as long as ~e cross sectional area of the flow passage of valve 7 in its "closed" position observes the following relationship: :

A, s Ao ~ (i) where: :
AO-area of valve 7 open to flow of working fluid 2 when valve 7 is fully open;
~=area of valve 7 open to flow of fluid at full res~iction of valve 7 (i.e. when valve 7 is in its "closed" position);
Wc=velocity of a sound wave in working flu;d 2;
W=velocity of working fluid 2 ~rough conduit 5 upstre~n ~rom valve 7;
p-specific mass of working fluid 2, (i.e. ~e density of working fluid ;~
2 divided by the acceleration of gravity); and H0=~e pressure head across valve 7 when valve 7 is open.
::
;~ ~ ; 20 Th~ intensity of the water hammer pulses produced wi~
:radia~g cond~ut 5 increases wi~ ~e velocity of working fluid 2 wi~in J
~ radiating conduit 5 at the moment valve 7 is closed. A3 noted above, it is :: therefore desirable to maximiz;e the flow veloci~ of working fluid 2 within ~e ~ ~ radiating conduit 5. Radiating conduit 5 should not be so large in cross :` : 25 section~l area that pump 3 cannot deliver enough flow of working fluid 2 at ~e rated output pressure of pump 3~ to mainf~in a maximum velocity f low L
~; of workingfluid~2~within:radia~ngconduit5. ~ : .

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WO 94/049M ~ PCI~/CA93/0034s ~, .`~
2~ 9rl ~ - 14 - ;
If pump 3 is of a type which could be darnaged or impaired in its operation by pressure pulses propagating upstream from valve 7 through fluid delivery conduit 4 then an air gap may be provided be^tween the outlet of pump 3 and the inlet of fluid delivery conduit 4. As shown in 5 Figure 2, working fluid ~2 is expelled from the outlet of pump 3 through noæzle 8 in the forrn of a jet 10. Jet 10 shoots into the inlet of conc1uit 4 `-`
: ` . through air gap 12. Pressure pulses reaching air gap i2 are dissipated and do not affect the operation of pump 3. Fluid leaking from air gap 12 falls into sump 1~:from where it can be recycled. ; ~:
.

Radiating conduit 5 is either submersed or parffally submersed in a fluid 11. As described below with reference to Figures 4 and 5, radiating conduit 5 is designed to radiate energy from pressure pulses nside radiating conduit 5 into fluid ll in the form of acoustic pulses. A
: 15 continuous train of acoustic pulses may be radiated into fluid medium 11 .
by rapidly closing and re-opening valve 7. :

The characteristics of the acousbc signal radiated in~o fluid medium 11 from radiabng conduit 5 depend~ upon the frèquency ~at which 20 ~ `valve 7 is closed and opened, dle~pro~ortion` of eàch cycle du~ing which .va1ve 7:is open and:closed,~the~characteristics of~radia~ conduit~5, the ; `
characteristics of ~working flùid 2, the veloclty of flow of working fluid 2 inside; radlating conduit S: and~ the characteristics of fluid ll.

When valve 7 is closed, working fluid 2 iIIunediately upstream ~ 7 from valve 7 is brought to rèst.: When valve:~7:is~reopened, the worldng fluid 2~upstream from valve:~7 begins to flow thrDugh valve 7. lt~:takes~
some ~e~ after valve 7 is reopened for the~:wor~g fluid 2 immediately upstream from valve 7~to be -ccelerated to its~maximum velocity To ~maxi~ the amount of acoùsffc~;energy bansmitted ~int Sl~l:B~~ T7~TE~ S~ ET~

,~W094/04944 2l~2971 PCr/C~93/00345 ~"

fluid medium l1, valve 7 should be closed as soon as the fluid within radiating conduit 5 has been accelerated to a significant proportion of its maximum velocity. Valve 7 should then be reo~ened before the pres~ure pulse created by the closure of valve 7 reaches the upstream end of i `
5 radiating conduit 5. In some applications it may be desirable to hold valve 7 open for an additional interval in each cycle to increase ~e separation between pulses.

Figures 3A through 3F illustrate the advantage which may~ be 10 obtained by increasing the separation between adjacent pulses in an acoustic signal. Figure 3A shows a pair of pulses in an acoustic wave separated by a distance L.l as the pulses appear at a distance Dl from the transducer (not shown) where the pulses were generated. Figures 3B and 3C show the same pair of pulses after the acoustic wave has propagated 15 awày from the transducer to distances D2 and D3 from the transducer respectively. As shown in Figure 3A, the pulses are initially well formed but, as shown in Figures 3B and 3C, the; pulses disperse as the acoustic wave propagates away from the transducer. As shown in Figure 3C, when the acoustic wave has propagated ~o point~ D3 the~pulses have spread so ~ .
20 ~ n uch that they have merged and are no longer dis~nguishable from one another.

Figures 3D through 3F show a pair of pulses which are ;;
identical to the pulses shown in Figures 3A through 3C except that their .
` 25 crests are separated by a distance L2 which is greater ~an the distance Iq.
Figures 3D, 3E and 3F show the pulses at distances Dl, D2, and D3 respe~ vely. The~pulses shown in FIgures 3D~rough 3F broaden as;they ~ ~ `
; ~ propagate in t~e same way as ~the pulses shown in Figures 3A through 3C.
However, because ~e~:pulses shown in Fi~es 3D through 3F are more ~ -30` ~ widely ~eparated than the pulses shown:in fîgures 3A ~ugh 3C, the pulses remain dis~nct even ;after t~ey~ have propagated through distance D3 TUT~ ~H!E:ET

WO 94/04944 PCl'/CA93/003d~

:. '; ! `
2~4~9~ - 16-Therefore, a train of pulses separated from each other by ~ greater distance L2, as shown in Figures 3D through 3F, may be more effective than a ~ain of more closely spaced pulses in applications where an acoustic generator is located far from an item or a volume of ~luid to be treated.
S ''' The frequency of operatio~ of valve 7 should therefore be on the order of the frequency glven by thè~ equa'don:

f= I L : :(2j ~ ;
` ~+td~--W
C

:
Where: ~ ~
f is the frequency of operation of valve 7;
L is the distance to the upstream end of radiating conduit 5 from valve 7; ; ~
; ~ 5 ~ WC i8 the speed at ~hich pressure~pulses propagate along radia~dng conduit 5 in working fluid t~is the time~required for working fluid 2 in conduit 5 to be~
accelerated~ to` a significarlt proportion of its maxim~Lm velocity ~ after valve 7 `
is reopened; ~and ~
: td: is a delay~time~to~increase l~e sèparation between pulses as desired in a particular app}ication.

Valve ~7 must ~e of a ~type which can b~ o~ened ~d~closed~ at the desired~ ~re~uency.~ ~Por example, valve 7 may be a solenoid a~vated 25 ~ ~dle v~ve as s~wn in Figure 15 ~d des~bed below, a self-ac~at~g v ~ve~o~rated by~e flow~of wor~ing ~uid 2 as shown ~ Figure 16 and ; de~ bed ~hlo~ or a cam-operated` valve~ as shown ;n~ Figure 17~ and S~UBSTI~TUi~E SH;~ET ~

WO 94/04944 2 I '1 2 9 71 PCI /CA93/00345 ~ `

The pattern of sound radiated by radiating conduit 5 de~ends on the construction and configuration of radiating conduit 5. Radia~ng conduit 5 may be ~ent, for example into a spiral, to direct sound radiated by racliating conduit 5 preferentially into a selected volume of fluid.
5 Radiating conduit 5 may also be bent to fit a longer length of radiating conduit 5 into a volume of fluid. As noted above, a long radia~ng conduit -5 can be optimally operated at a lower frequency, in some cases, than a shorter radiating conduit 5.

17he sound radiated by radiating conduit 5 may also be made directioxlal by constructing the wall of racliating conduit 5 so thiat one or more of its characteristics, such as modulus of elasticity, densi~, or wall thiclcness, vary over the surface of radiating conduit 5. ~ -:
Figures 4A through 4D are cross-sec~ons thu~ugh a first embodiment of radiating conduit according to the imention. ~he radiating conduit of Figures 4A through 4D is designed to radiate an acoustic signal _ into a fluid 11 surrounding radiating conduit 5 in such a way that the acoustic signal is accompanied by a significant mass flow in fluid 11. ~s shown in Fig-tre 4~, the wall of radiating conduit S is depressed inwardly along a longitudinal area 21 in its outer surface. Longitudinal area 21 is :' more compliant than other areas on the surface of radiating conduit 5.
~stead of being indented, longitudinal aréa 21 may be~constructed of a~
different material from the rest of conduit S or may ~ thinner ~an other ~ i~
poI tions of the surface of conduit 5. As descr~bed below, acous~c waves~ ~ ;
are emitted more stron~ly from longitudinal area 21 of radia~ng conduit 5 than from o~er areas on thie surface~of radiatinig conduit S. Thi9 makes it ~ ~:
possible to concentrate ~e energy of the acousbc field en~iitted by radiating conduit 5 in a pa~ticular direc~on.
When a water hanuner pressure ~pulse propagates ~rough :Sl~BSTITU~TI~ SH~ET

WO 94/04944 PCr/C~93/003~ ;~
9 ~ 1 , radiating conduit 5 the fluid inside radiating conduit 5 becomes pressuriæd, as is indicated by the arrows in Pigure 4B. As longitudinal area 21 is initially more compliant than o~er parts of the walls of ~radiating conduit 5, the water hammer pressure pulse forces iongitudinal area 21 5 outwardly until radiating conduit 5 is circular as shown in Figure 4C.
~uring this phase, longitudinal area 21 acts essentially like a diaphragm and pushes fluid 11 ahead of it as it:moves outwards. ~ This causes an :
acoustic wave 23~to be propagated away from longitudinal area 21 into fluid 11. Acoustic wave 23 is accompanied by :a~ sigruficant màss flow in 10 the region of fluid lI . adjacent to longltudinal area 21 as fluid 11 is pushed ahead of longit~dinal area 21~
:: :
: , `
After longitudinal area 21 has been forced outwardly until : radiating conduit S~ is circular, as shown~in Figure~ 4C, the compliance of IS ~ longitudinal area 21 is:not::significantly different~from the compliance ofother portions of ~the~surface of radiating~ conduit S. If the fluid flowing~
within radiating conduit S~ has: not compIetely :ceased to flow at this point, then thè walls of radiaffng~conduit S will be expanded outwardly as the kinetic ~energy~ of ~the~ still~ flowing~working: fluid 2~ is converted into :, 20~ increasedpressure:wit~n~radiating~conduit;5. Thes ddenexpa sionof radiating~ conduit ~5~ is~indicated ~ by dashed~ 1ine 25 ~ Fi~re 4D.: The expansion of ràdiating~conduit S~caùses:~àn acoustic-compressional:wave~
f ont~ ~ ~to ~: radiat~ed .::into f uid~ ~y~ from ~radiat~g conduit S. ~ ~the~
w~l :of radia~. conduit S~ i$~ acoustic~1y ~ansparent acous~tic; :
25~; ~ compressional wave front Z7 is accompa ie~d b very little mass iiow In acoùstic wa~véform~generated in fluid ll~by~a series of ;water~:hammer~wi~radia~c``~nduit5`is~a~a- ~of~p 30 :~ is~eated~ each.~e :~:7 is~cled ~om~o~n to clo~d.~ ~Each:;
a~modera~;~sùdden~onset,~w~ch~co~espon~s to aco s~ ~w ~ Sul~TiTUTt ~sil5ET ~

WO 94/04944 ~ 2 9 71 PCT/CA93/0034~ ~, -19- ' ! : ' 23, followed by a sudden sharp pressure spike, which corresponds to acoustic wave 27.

The relative proportion of t~e energy radiated from radiating 'i `' 5 concluit 5 in the form of mass ~low in fluid Tnedium 11, acoustic waves 23 and acoustic waves 27 may be controlled by altering the construction of radiating conduit 5. If longltudinal area 1 is compliant,~rough only a small range of motion then most of the energy radiated from radiating conduit 5 will be in the form of compressional~acoustic waves 27 with very 10 little mass flow in fluid medlum 11. In applications such as sonically driving sediment out of fluid medium 11, mass flow in fluid medium 11 is not desirable. In such applica~dons, radiating conduit~5 does not need a ~' longitudinal region 21 or else longitudinal region 21 should have a very linuted range of motion through which it has increased compliance so ~at 15, very~ le mass~flow is generated in fluid 11 by water hammer wi1~in ~ ' radiating conduit 5. In o~er~ applicati'ons, such as washing clothes, a signiRcant mass flow in fluid medium 11 is desirable. For such applications, the outer wall of radiating conduit S should be compliant ~
through a larger range of rnotion. :' Figure~5 is a section through an alternative embodiment:of a direcl:ional-radia,ting~conduit 30 according to the invention. Radiating conduit 30 compr~ses~ ;a flattened tube~ 31 lying within~ the cha~el of a rigid ;
U-shaped bar 33. ~ The bottom surface 35 of tube 31 ~and~t~e end regions 37, ;25 ~9 of tube 31 are~ supported by U-shaped bar 33. The, result is a radiati,ngconduit 30 in which onîy the top sur~ace 41 of tube 31 is able to move in response to pressure pulses in interior 47-of conduit 30. ~ The cross sectional ; shape~of flattened ~ e 31 provides a radiating conduit 30 with a smal1 cross~se~tional area, which is desirable, ~as noted above, and~ a reasonably ~ r ' , 30~ 1arge s~face area. '; ~

SU~B~TIT~UTE~ SH'~:T

WOg4/04944 : PCr/CA93/003'1~ ~
2~3~9~1 ~o When a water ha~uner pulse travels through radiating conduit 30, as described above with reference to rad;ating condui~ 5 in Figure 2, th expansion of radiating conduit 30 occurs almost entirely on top side 41 of `
tube 31. The result is that acousbc energy is emitted preferentially from top 5 side 41 of tube 31 and very little acoustic energy is radiated; from bottom surface 35 Ol end regions 37, 39 of tube 3:1. Projecting sides 43, 45 of U-shap~d bar 33 may serve to further shape the sound pulse emitted by radiating conduit 30.
,.
~Figure 6 is a schematic diagram~`showing an embodlment~of the invention adapted~for acousbc clèaning.~In this embodiment, radiating conduit 5 lies within vat 51 which is filled with clearuing fluid 53. An`item to be cleaned 55 is inunersed in cleaning fluid 53 adjacent to radiating conduit S. Acoustic energy;is generated at radiating conduit 5 by crea~ng a 15 ~ ~ water~ hammer in working fluid 2 within radiating conduit 5 as is descri~ed~
above with reference to Figure l. ~ In the embodiment of Pigure 6, working ;fluid 2 is isolat~d from ~cleaI~ing fluid S3. Radiating conduit 5 is arranged so as to direct acoustic energy~ preferen~ally~ toward~item to be cleaned~55.
Ràdiating conduit:5~may~be;cù~ed to simultaneously irradiate different 20 ~ hces~ of item to be cleanèd SS. ~ The mass~ ~flow which is~ created in` clea~ g uid 53 by the expansion~and;contraction of radiating conduit 5~aides~e ; ciea~ng~ process. ;;:; ~

Figure;7 is a~hematic~diagram~of an alternative~embodiment 25 ~ of the invention adapted~for acous'dc cleamng. In the embodiment of Fi~re 7, clear~ing fluid~53 i9 used as a working fl~d. P~p 3 draws clearung fluid~S3 ~y~ ~om vat ~51 (ra~ ~n draw- wor ng ~ id 2 from tank 1 as shown in~the~emb~odiment~of~FIgure 6). T~us embod~ent;~o~ 3 ;the~invention is a~tageous~ause it~lows~t e water~ha~n~ Ises~
30~ opag~g ~down :~eam` ~o :va ~7 ~ ~ ~d t i~m ~ ed ``55. T~sis~done~by*~ fluid~exi~ng~m~va 7~d:~i~m-to ~W O 94/04944 2 t ~ 2 9 71 PCr/CA93/00345 .~

be cleaned 55 through hose 56 and nozzle 57. The pulsahng jet of cleaning ¦ ~:
flui~ 53 emerging Ifrom nozzle 57 and the acoustic pulses emanating from no~zle 57 contribute to better cleaning of item to be cleaned 55.

Because acoustic cleaning apparatus according to this invention is capable of providing acoustic pulses of high inter~sity, the rate of cleaning is greater than that of acoustic cleaning systems which provide lower intensity acoustic pulses. This permits cleaning using solvents which :
have desirable properties, such as the property of being biodegradable, but which are unsuitable for use in prior art acoustic cleaners~ because the rate of cleaning in such solvents is unacceptably slow at the lower acousffc ~`^
intensities provided by commonly available prior art acoustic cleaners.
: ;:
Figure 8 is a schematic diagram of an acoustic generator ~ -according to the invenffon adapted to promote the sedimentation of sus- ` `
pended particles in a fluid. In the embodiment of Figure 8, radiating conduit S is immersed in a dirty fluid 60 contain~ng suspended particles 62._ Fhe acti~on of the acousffc fièld generated at radiating conduit 5 on suspended particles 62 causes suspended par~cles 62 to be precipita:ted out ;20 ~ a~ dirty fluid 60 fluid onto ~e bottom of vat 63. Suspended particles 62 which sinlc to the bottom of vat 63 are removed by conveyor 64.
:
Apparatus similar to that shown ~in 1iigure 8 may be used for large scale sedimentation, for example, it may be used to increae the rate of sedimentation in a lake. In such large scale ues, r~dia~dng conduit 5 could be suspended from a raft floating in the lake near to the su}face of ;:
the lalce and oriented to direct acousffc puIses downward. ~ The~equipment ` fo~ driving radiating conduit 5 could ~ mounted on ~e raft ; Figure 9 is a schemaffc view of an altemative embodiment of a i-system for~ separating suspended ~particles ~from a~ dir~y flu~d 60 in which SlJ:BsTlTurE~s~l~~ET ~

wO ~4/04944 ~ P~r/CA93~003$~ ~
~ 1_ 4 ~ I `

dirty fluid 60 is used to generate the acousffc field used to increase the rate of sedimentation. In the embodiment of Figure 9, dir~ fluid 6Q containing ` ``
suspended particles 62 is pumped by pump 3 into radiating conduit 5~
Radiating conduit 5 lies within chamber~ 68~ Water harnmer pulses are generated inside radiating conduit S by`repeatedly closing and r~opening ` `"
; valve 7 as desc~ibed above with reference to Figure ~1. Radiating conduit 5 ; ``
is preferably oriented so that ~e acoustic energy derived fr the water hamrner pulses within radiating conduit 5 is directed`primarily downward.

Upon exiting from valve 7, dirty fluid 60 travels through diffuser 66 mto chamber 68~ Diffuser 66 slows the flow of dirty fluid 60 to ;`~
aid in sedimentation~ Chamber 68 has a cross-sectional area significantly ~
larger than that of radiating conduit S. The~refore, the velocity of dirty fluld` 15 ~ ~ 60 in ~chamber 68 is~ much lower than the velocity of dirty fluid 60 inradiating conduit S. Upper outlet 65 and lower out et 67 are at the end o f chambèr 68 away from diffuser 66. Dir~y ~fluid 60 flows through charnber ~
;68 past radiating conduit S~before it is drawn off from chamber 68 ~rough outlets~ 65, ~67.

Lowff ou~et 67 draws off fluid fIorn~ the lower poItion o~
chamber 68~ ànd ~upper~ oùtlet 65 draws off ~fluid from the up~per~portion~of ch~r 8. ~d~fluid 60 pass s by radia~g conduit~5, ~e acoùs~c~
p~l~s produced~ at radia~; conduit 5 d~ve sus~nded ~particles 62 25; downward into ~the !ower ~or~on~of ;ch~ ~. ~Th~ef lore, ~e flu~d~
3 ~ ~ drawn off at lower outlet 67 contains a higher propo~on of suspended ~
pà cles6~t an~the~fluidd`rawnoffatup o 5.~;~A~co yo ~ t `~ show~n~may ~p~d~to remove~d~pa~ s 6 w~ch;~s~` o F;~e;10 is~a~ m c diagram~ ~ a s~c ge - a~

S U~B~ST IT UTE; : S H~ E~ET ~

~, ~ 9 ~ ~ ~ 3 9 ~,i WO 94/0494~ 2 t 4 2 9 7 1 pcr/cA93/oo345 j~' ..:~:
- 23- ~, according to the invention adapted to reduce the viscosity of a viscous fluid -70 flowing in pipe 72. Acoustic pulses are produced at radiating conduit 5 as described with reference to ~igure 1 above. In this embodiment ofthe , invention, radiating conduit 5 lies within pipe 72. The high energy acoustic 5 pulses enutted from radiating conduit 5 interact with fluid 70 in the region of fluid 70 adjacent to radiating conduit 5 and reduce the viscosity of fluid ``~
70~ , .,.
, ." .
If radiaffng conduit 5 is positioned at the centre of pipe 72, as shown ;n Figure 8, then'radiating conduit 5 may be symmetrical about its , axis so that all of fluid 70 is equally treated. ~ ,, An apparatus similar to the apparatus of Figure 1 may also be used to reduce the viscosity of ~ a viscous fluid. The viscous fluid is used in `,' 15 place of working fluid 2 in the apparatus of Figure 1. As descri~ed above, ,pressure pulses are created wi~in radiating conduit 5 as valve 7 is cycled , `,between its open and closed states. The pressure pulses act on the viscous f1uid ;within radiating conduit 5 to reduce its viscosity.~ Of course, the . . .
apparatus of Figure 1 can~ be`used in ~is manner for viscosity reduction 20 , only if ~e viscosi~r of the ~iscous fluid is initiaDy low enough thiat it can be pumped through radiating conduit S by pump 3 at a signuhcant velocity.

Figure ll ls a~ schematic view of àn alternaffve embodiment of 25 thel in,vention adapted for cleaning ite~. In the embodiment of ,Figure 11, acoustic waves are generated by causing a water hammer within a rigid ~ ~, w~led conduit 80. ~coustic waves are radiated ~into~cleaning fluid 53 by means;of a compliar~t radiator;82 in fluid connection wi~h ~e working fluid 2 inside rigid conduit 80. ;This~ is in contrast to ~e ~embodiments of the ~, ' ~ '`
30~ inventiondescribed~aboveinwhich~water~hammffpressurepulsesact ~ ;"
against compbant w-lls of ~ radiating conduit which move to generate SUBSTlT~l~rE~ 50~1E~T:~

WO 94J04944 PCT/CA93/0034~

~ : 2 ~ 24 - I ;
,.. ..
acoustic waves in the fluid surrounding the radiating conduit.

. . .,-The device of Figllre 11 is similar to the device of Figure 6. It iS~;
provides a hydraulic circuit comprising ~luld storage tank 1 containing a ~
5 worlcing fluid 2, pump 3, rigid conduit S0, valve 7 and fluid return conduit 9. Pump 3 draws working fluid 2 from fluid storage tank 1: and forces it to .' ~;.
flow at high velocity through rigid conduit 80. Water hanuner pulses are : generated within rigid conduit 80 by closing valve 7~in the same manner as is described above with reference to Figure 1.

:: : A compliant radiator 82 is provided to :convert the water ` ~;~
haIIuner pressure pulses in rigid conduit 80 into acoustic pulses in cleaning fluid: 53. The interior of compliant radiator 82 is: in~fluid communication :wi~th~: the int~rior of rigid conduit 80 through conduit 84. Cunduit 84 joins 15 ~ rigid: conduit 80 at tee 86. ~ When ~a~ water hammer~ pressure~ pulse propagates along rigid conduit 80 past tee 86:~the sudden overpressure at~
`the:~operling of conduit 84 ~forces working fluid~ 2 to~ flow from the interior~of :
rlgid~ conduit :80 into co~ùit ~ ~thùs expanding compliant radiator 82.~ ~ The~
sudden:expansion of`comp~ant radiator~82 generates a:~mass:flow and:
20 ~ acoustic:waves~:inclear~ng:`fluid~53~surroundingcom~ant~radiator82.
Colnpliant~radiator 82~may~be:shaped *~:radiate; acous~c;~u1ses;into clèan~ng~;fluid~ 53 in a~:prefèrred direction.: Items to ~ leaned 55,~ for èxarnple clothes,~can~ submèrged in~clea~ ~d~53 to ~ acted on acous!dc waves arùl~owing~`:cle~ng~fluid 53. :
Figure l~2~is a sect~ion through an altemative~e ~mbodiment of~
t appaa~s f~figure11in~w ich leàn-ngfluid53isu~d:aswor ing~
uid :2. ` Items to ~be~:cIeaned~55~:are~ plàcéd; in eleaning: flu~d 53 inside ~b~90.
Cle uung~fluid 53~is dr ~ gh n~9 ~ co~uit~ ~ ~p 3 30:~ r ~ ~where~it is~ for ed ~u `dff ~ure~;into ~i~t~radia~r 96~i~ide~b~
90.~ Cornpliant _dlajor 96 carnprises mandrel 98 and~eIastic sleevt fO0 SU~IT~J T~ S H EET~

W094/04944 21~2971 PCI/CA93/0034 which fi~ over the outer surface` of mandrel 98. Mandrel 98 has a }arge diameter in upper por~don 99 of compliant radiator 96 and a narrow waist 1 :
101. Elastic sleeve 100 has a narrow portion at its lower end 106 v~hich , `:
holds elastic sleeve 100 in place over mandrel ~98. Pump 3 forces cleaning fluid 53 through central passage 103 of mandrel 98 into narrow slots 102. : :
Narrow slots 102 form cavities bounded by mandrel 98 on the inside and ` `
elastic sleeve 100 on the outside. Cleaning fluid 53 flows down through `:
vertical narrow slots 102 (which are also shown in ~Figure 13A) and out into tub 90 through a narrow annular region 104 ~which is also shown in Figure 13B) at the low~r end 106 of elastic sleeve 100 between :elastic sleeve 100 ~.
and mandrel 98.
, Annular region 104 acts as a valve to periodically int~rrupt the ~:
flow of cleaning fluid 53 out from narrow slots 102. As the velocity of flow : i :: .
of cleaning fluid 53 in annular region 104 increases, the p~ssure of cleaning: ~ :
fluid 53 in annular region 1~ is reduced by the Be:rnoulli effect. When dle velocity of cleaning fluid 53 within annular region~1~ reaches a critical value, the hydrostatic pressure of cleaning ;fluid 53 in tub 90 acting on the : `
:; ~` outside of elastic sleeve 100 in its:portion adjacent to annular region 104 ;
becomes sufficient to force elastic sieeve 100 a~ainst mandrel 98 in:annular r egion 1~j thereby shutting off the~flow;of fluid through annular region ach :tirne the flow; of ~cleaning fluid 53 through annular region 104 is : interrupted elastic sleeve 100 p:ulses outward as cIeaning fluid 53~ conbnues to be pumped into narrow slots:10æ The resultant agitation of cleaning flu~d 53 in tub 90 and acoustic waves: radiated from elastic sleeve 53 into , ;
tub 90 act on items to~be ckaned 55 in tub 90.

: Figure l3A is a :section through up~er portion 99 of compliant r adiator g6:on plane~A-A~shown in Figure læ ~ Elastic sleeve 100 is closely`
: 30 ~ fitted over the outer surface: of mandrel 98.; ~Narrow slots 102 pass down i ~:
~rough upper portion 99 of man~rel 98 benea~ elastic sleeve 100 to ~o~

U B S~ TI T U T~ 5 pl E E T

WO ~4/049q4 PCr/CA93~00345~

2 1 '¦ ~ 9 7 26 channels for the flow of cleaning fluid 53. Narrow slots 102 have a small ~ ";
cross sectional area so that cleaning fluid 53 flows through narrow slots 102 at a high velocity for a given rate of flow of cleaning fluid 53~ ~axrow slots ~.
102 are narrow to prevent elastic sleeve 100 from being sucked into narrow l:~
slots 102 by the flow of cleaning fluid 53 within narrow slots 102~

Figure 13B is a section through compliant radiator 96 on plane B-B shown in Figure 12~ Plane B-B cuts through waist 101 of mandrel 98 and Figure 13B therefore shows annular region 104 between mandrel 98 and elastic sleeve 100~ The hydrostatic pressure of: clearung fluid 53 acting on the outside of elastic sleeve 100 is indicated by arrows.

Figure 14 is a section through a compliant radiator which may be used with apparahls similar to that shown in Figure 11. The compliant : 15 :radiator has a body 110 and an ~interior passage 112 penetrating through body :110~ Interior passage 112 is filled with a worlcing fluid 2 and is in fluid communication with a conduit (not shown) in which water hammer ; ~, pulses can be generated~
~;s'' : ~ :20 Outlet l14 Of interior passage ~112 is blocked by flexible i~
diaphra:gm 116. The outer side of flexible diaphragm 116 is in contact with ': ;.~;`
a;fluid ~medium 11 into which it i9 desired to:introduce acoustic pulses~
Flexible d;aphragm 116 is compliant so that pressure pulses transmitted :;
through inte~or passage: 112 ;are ~ansmitted through flexible di~phragm 116: into fluid medium 11.

Flexible diaphragm 116 is held in place over outlet 114~by; nut 118 which clamps ~e outer periphery of flexible diaphragm 116 between body 11~ and nut 118.: Nut 118 is provided with a~flange 120 which forms a cylindrical channel 127 concentric with ~e~a%is of flexible diaphragm 116~
~coustic pulses emitted from~flexible diaphragm:ll6 are guided along - 1!'.' S~)B~TiT~lJT~ :S~ ET ~ ~ `

WO 94/04944 2 1 ~ 2 9 7 1 rcr/cAs3/uo34; 1 ~

-27- ` :`
I ~
cha~nel 122 by flange 120 as indicated by the acoustic wave fronts ¦ -illustrated as dashed lines 1~

Figure 15 shows a solenoid operated valve 130 which may be 5 used to interrupt the flow of working fluid 2 in the invention. Valve 130 comprises valve body 132, fluid inlet 134 and ~luid ou~et 135. Whell valve 130 is open, fluid flows in through inlet 134, through orifice 138 and out through outlet 135. Valve 130 is normally cloæd by piston 136 which blocks orifice 138. Piston 136 is ~forced into orifice 138 by spring 140. Valve 130 is opened by means of solenoid 142 which~ draws piston 136 away from `
orifice ~38 against the force of spring 140. The rate at which valve 130 is .:
opened and shut depends upon the spring constant of spring 140 and upon .
the rate at which solenoid 142 is energized and d~energized.

Figure 16 is a section through a flow operated valve 150 which ` : may be used to rapidly inter~upt the flow of working fluid 2 in a conduit (not shownj. Valve 150~ cornprises a valve body 152, a fluid inlet 154, a ~ ;
fluid outlet 156 and a sliding piston l58. Fluid flows~ ~rough flùid inlet 154 . .. ~..
i nto cavit~r 160 inside valve~b~ody 152 an~ out through outlet~l56. Sliding 20 ~ piston 158 has a tapered plug 162`at its end toward outlet 156. Tapered plù$~ 162 engages valve~seat 166 and blocks t~e flow of fluid through valve 15~ when sliding piston 158 slides towards ou~et 156.

`~` ` ` In n~flow condihons, sliding piston 158 is~ biased away from 25 I oudet 156 ~y spring ~ 1eaving a ~restricted opening ~e~veen t~peredl plug 162 ~ and ~ valve seat ~166.~ When~ fluid is~forced ~into iTllet ~154, the fluid f~ows `
into central cavity 160, around tapered plug~l62,~ through the restricted op~ning`~etw~n;ta~red~plug~l62 and~valve;~at 166 ~d~ out ~ough outlet l;56. ~ Due~ to t jh~e~Bernoulli; effect, the pressure;~ of the~ rapidly flowirlg `; " 30 ~ fluid in~ the opening ~bétween tapered ~g 16~and: valve seat 166 is lower than~ the fluid~ pressure~in other; par~ of intenor~cavity l6~ e result is SU~S~TITUTE SHEEI

WO94/049~ PCI/CA93/0039~
2l l~29'~

i:
that tapered plug ~62 is sucked toward valve seat 166 agamst ~e action of spring 164 until valve 150 is closed. As soon as valve 150 is closed, the ~ -fluid flow around tapered plug 162 ceases and spring 164 draws tapered `:
phlig 162 away from valve seat 166 at which point Pne process repeats itself.
5 The rate of operation of valve 150 may be adj listed by varying the spring constant of spring 164, the mass of sliding piston 158, the shapes of tapered plug 162 and valve seat 166 and the fluid pressure at the inlet 154 of valve , 150.

Figure 17 is a sechon through a cam-drlven valve 170 which may be used to interrupt the flow of fluid in a conduit (not shown). Valve 170 has a valve body 172, a fluid inlet, 174 and a fluid outlet passage 176. `
Fluid flows into valve 170 through inlet 172 into chamber 178 frorn where it flows out through outlet passage 176. The~passage of fluid out from 15 chamber 178 through outlet passage 176 can be blocked by plug 180 which engages valve seat 182 at the inner end of outlet passage 176. Plug 180 is mounted at the end of reciprocating rod 184 which passes out of valve body 172 through seals 186. The end of reciprocating rod 184 is biased i~ :
: against cam 190 by spring 19~. :Cam 190 is rotated by a motor (not shown). :
:~ ~ As cam 190 rot~itesj reciprocating rod 184 re~iprocates as its end follows `
~e profile:of cam 190~ Valve 170 is alternately opened and closed as plug 180 moves into and out of contact with valve seat 182~
" ,.~
As will be apparent to those skilled in the art in ~e light of 25i~" !thie foregoing disclosure, many alterations and modifications are possible in . . .
~ie practice of thi~ invention without departing fromi the spirit or scope ~ ~:
thereof~ Accordingly, t~e scope of the: inven'don is to be construed in accor~
`: ` dance`withi the substance defined by ~ie following~daiims~ ~`

< ` ~ ~ !

SlJBSTlTUT~; Si~ T

Claims (29)

WHAT IS CLAIMED IS:

1. In an acoustic generator for radiating acoustic energy into a liquid (53), said acoustic generator comprising:
(a) a source (1,3,4) of pressurized fluid (2);
(b) an elongated conduit (5) communicating with said source (1,3,4) for carrying a flow of fluid (2) from said source, said conduit (5) having a longitudinal axis and an outer wall;
(c) a valve (7) at a location spaced from said source, said valve having an open position wherein said flow of fluid in said conduit (5) is substantially blocked and a closed position wherein said flow of fluid in said conduit (5) is substantially unimpeded; and (d) means to move said valve (7) from said closed position to said open position, retaining said valve member in said open position for a period sufficient to allow said fluid (2) to commence flowing through said conduit (5) and said valve (7) with sufficient velocity to produce a water hammer within said conduit (5) when said valve is moved to said closed position, and again moving said valve to said closed position to produce a continuous series of water hammer acoustic pulses within said conduit (5);
an improvement wherein said wall of said conduit (5) in non-rigid and is in direct contact with said liquid (53), said wall has acoustic properties such that acoustic energy from said water hammer is efficiently radiated into said liquid (53) along the length of said wall, and a compliance of said wall varies with angular position around said longitudinal axis.

2. The acoustic generator of claim 1 wherein said wall comprises a compliant strip (21) extending longitudinally along said wall, wherein said wall is more compliant in said strip (21) than it is outside said strip (21).

3. The acoustic generator of claim 2 wherein said conduit (30) comprises a flattened tube (31) having narrow sides (37, 39) and broad faces (35, 41), anda rigid member (33) supporting one face (35) of said tube (31) .

4. The acoustic generator of claim 2 wherein said strip (21) comprises a longitudinal indentation in said wall.

5. The acoustic generator of claim 2 wherein said conduit forms a spiral with said strip (21) facing radially inwardly.

6. The acoustic generator of claim I wherein said conduit comprises:
(a) a mandrel (98) having an outer surface;
(b) an elastic sleeve (100) stretched over a first region of the surface of said mandrel (98);
(c) a channel (103) in communication with said source (1,34) extending to a point on the surface of said mandrel (98) beneath said elastic sleeve;
(d) at least one slot (102) having a narrow opening beneath said elastic sleeve (100) on said surface of said mandrel (98) extending from said point; and (e) a valve (104) at a downstream end of said at least one slot (102) for suddenly interrupting the flow of said fluid in said at least one slot (102).

7. The acoustic generator of claim 6 wherein said valve (104) comprises a surface (101), a valve member (100) adjacent said surface (101), a volume (104) between said surface (101) and said valve member 9100) and bias means (100, 53) for biasing said valve member (100) toward said surface (101) wherein said valve member (100) is drawn toward said surface (101) when said fluid (53) flows through said volume (104).

8. The acoustic generator of claim 7 wherein said valve member (100) comprises a portion of said elastic sleeve (100).

9. The acoustic generator of claim 8 wherein said bias means comprises a hydrostatic pressure of a liquid (53) acting on an outer surface of said elasticsleeve (100).

10. The acoustic generator of claim 1 wherein said source (1,3,4) of pressurized fluid (2) comprises a pump (3) and an air gap (12) between the outlet of said pump (3) and the inlet of said conduit (5).

11. The acoustic generator of claim 1 wherein said source of pressurized fluid further comprises a delivery conduit (4) between said pump (3) and said conduit (5) and a velocity transformer (6) between said delivery conduit (4) and said conduit (5) wherein said delivery conduit (4) has a larger internal diameter than said conduit (5).

12. Apparatus for doing work at a point in a liquid (53), said apparatus comprising an acoustic generator for radiating acoustic energy into said liquid (53), said acoustic generator comprising:
(a) a source (1,3,4) of pressurized fluid (2);
(b) an elongated conduit (5) communicating with said source (1,3,4) for carrying a flow of fluid (2) from said source, said conduit (5) having an outer wall in direct contact with said liquid (53); and (c) a valve (7) at a location spaced from said source, said valve having a closed position wherein said flow of fluid in said conduit (5) is substantially blocked and an open position wherein said flow of fluid in said conduit (5) is substantially unimpeded, wherein said apparatus further comprises (d) means to repeatedly move said valve (7) from said closed position to said open position; retain said valve (7) in said open position for a period sufficient to allow said fluid (2) to; commence flowing through said conduit (5) and said valve with velocity sufficient to produce a water hammer within said conduit (5) when said valve (7) is moved to said closed: position; and move said valve to said closed position;
to produce a continuous series of water hammer acoustic pluses within said conduit (5); and (e) a vessel (51) containing said liquid (53), at least a section of said conduit (5) and said point.

13. The apparatus of claim 12 wherein said conduit (5) forms a spiral.

14. The apparatus of claim 12 wherein said conduit (5) comprises a flattened tube.

15. The apparatus of claim 12 further comprising a delivery conduit (4) between said source of pressurized working fluid and said conduit and a velocity transformer (6) between said delivery conduit (4) and said conduit (5) wherein said delivery conduit has a larger internal diameter than said conduit

16. The apparatus of claim 12, further comprising a tube (56) having a fixed end connected to the outlet of said valve and a free end (57), said free end (57) being directable toward a workpiece (55) for directing a jet of fluid (2) onto said workpiece.

17. The apparatus of claim 12 further comprising means to harness said acoustic generator to remove particles from a dirty fluid (60), said means comprising:
(a) a treatment chamber (68) surrounding said conduit;
(b) a dirty fluid inlet for introducing said dirty fluid (60) into said treatment chamber (68) and flowing said dirty fluid past said conduit (5) for irradiating said dirty fluid with acoustic waves from said conduit (5) and for driving said suspended particles (62) from said dirty fluid into a first region of said treatment chamber by means of said acoustic waves to produce a concentrated dirty fluid in said first region and a cleaned fluid in a second region;
(c) a first outlet (67) in said first region for removing said concentrated dirty fluid; and (d) a second outlet (65) in said second region for removing said cleaned fluid.

18. The apparatus of claim 17 wherein said fluid (2) comprises dirty fluid (60), said dirty fluid inlet is the outlet of said valve (7) and further comprising a diffuser (66) between the outlet of said valve (7) and the interior of said treatment chamber (68).

19. The apparatus of claim 12 wherein said liquid (53) and said working fluid (2) both comprise a cleaning fluid and said vessel (51) includes a space for placing a workpiece (55) near said conduit (5).

20. The apparatus of claim 12 further comprising means to harness said acoustic generator to reduce a viscosity of a viscous fluid (70), said means comprising a pipe (72) generally concentric with said conduit (5) and means for flowing said viscous fluid (70) past said conduit (5) in said pipe (72).

21. In an acoustic generator comprising:
(a) a source (1,3,4) of pressurized working fluid (2);
(b) a conduit (5) communicating with said source, said conduit carrying a flow of working fluid (2) from said source within said conduit;
(c) a valve (7) at a location spaced from said source, said valve capable of interrupting said flow of said working fluid (2) out of said conduit; and (9) control means for repeatedly closing and opening said valve at a frequency greater than 3 Hz to produce a water hammer within said conduit each time said valve is closed;
an improvement wherein said control means comprises a detector for deleting water hammer within said conduit (5) and for producing a control signal whenever water hammer is detected within said conduit and valve actuator means to open said valve (7) in response to said control signal.

22. In a method for producing work at a point in a liquid (53) by means of acoustic signals, an improvement wherein said acoustic signals are generated by the steps of:
(a) connecting a source (1,3,4) of a pressurized working fluid (2) to an inlet of a conduit (5) having an inlet and an outlet and a;
(b) placing said conduit (5) in said fluid medium (53) near said point;
(c) allowing said working fluid (2) to flow through said conduit (5);
(d) suddenly blocking the flow of said working fluid (2) at said outlet to cause acoustic signals to be radiated from said conduit (5) to said point;
(e) waiting for an interval;
(f) removing said blockage of said working fluid from said outlet; and (g) continuously repeating steps (b), (c), (d) and (e) at a frequency sufficient to carry out said work.

23. The method of claim 22 wherein said steps (b), (c), (d) and (e) are repeated at a frequency of between 5 Hz and 2000 Hz.

24. The method of claim 22 wherein said interval in step (d) is less than or equal to the time taken by a water hammer pulse to travel along said conduit from said outlet to said inlet.

25. The method of claim 22 comprising the further step of waiting for an interval between steps (b) and (c).

26. The method of claim 22 wherein said work is acoustic cleaning of an object (55).

27. The method of claim 22 wherein said work is the reduction of viscosity of a viscous fluid (70).

28. The method of claim 22 wherein said work is driving suspended particles (62) out of a volume of fluid (60).

29. In a method for transporting a viscous fluid (70), said method comprising the steps of:
(a) pressurizing said viscous fluid (70);
(b) causing a flow of said pressurized viscous fluid (70) to flow through a conduit (5);
an improvement comprising reducing the viscosity of said viscous fluid (70) by:
(c) repeatedly interrupting said flow of said viscous fluid (70) in said conduit (5) to produce a water hammer in said viscous fluid (70) within said conduit (5) each time said flow is interrupted.