Note: Descriptions are shown in the official language in which they were submitted.
wo gs/24274 21 8 51 ~ 3 PCTlDKssl0001s
Title: Method and nozzle for proYiding a flow with separated gas and liquid
portions subjected to an acoustic field.
.
Technical Field
The present invention relates to a method and a nozle for providing a gas/liquid5 jet having finely atomised liquid droplets and is especially but not exclusively
directed towards the field of fire-fighting and can be used in relation to both
portable fire ~ h ~ and stationary fire-fighting systems.
Backvround Art
It is known from "Physical and Chemical bases of the d~ and extin-
10 guishing of fires", 1980, pp. 182-187 by E.M. Abduraimov and Yu. V. Govorov
that the efficiency of fire-fighting increases essentially in c ~ IA 1;~-111 with the use
of solid jets of frre-fighting liquid or jeoe with large droplets when feeding frnely
atomized fire r~ liquid to the fire centre. The increase in fire-fighting
efficiency is due to the heat exchange processes between the small liquid droplets
15 and the fire centre being intensified. This results in a t~ ,ld~ulc decrease in the
fire centre to the L.. l.~J.. ~.. c of flame extinction and in decreased
of fire; , ' ~ liquid.
Thus, to increase the fire-fighting efficiency it is necessary to provide ~urrlC;C,l,ly
high degree of liquid
20 Various methods of atomising fire r~ v liquid are known as well as
apparatus for carrying out said methods. One of the most efficient methods of
atomising liquid is feeding of a gas/liquid mixture (in the following called GLM)
through a spray nozzle as disclosed in USSR Inventor's Certificate No. 1353444,
published in the Bulletin of the Inventions No. 43, 1987. In this case, under equal
25 pressure, the GLM leaves the no771e at a higher speed than a pure liquid flow.
WO 95/24274 PCT/D1~9S/0001~ --
21 ~51 ~3
It is known from "Atomizers of liquids. - M., Chemistry, 1979, by D.G. Pazhi
and V.S. Galustov that an increase of vhe speed of the liquid outflow improves the
~i..",;, li.". thereof. The method of liquid ~ ,,.l;~-';-l.l used in the fire extin-
guisher is a typical example tbereof as disclosed by USSR Inventor's Certificate5 No. 1225585, published in the Bulletin of the Inventions No. 15, 1986. Due to
the high gas/liquid ratio and the high gas pressure, a higher speed of liquid
outflow is provided.
USSR Inventor's Certificate N. 1316713, published in the Bulletin of the Inven-
tions No. 22, 1987 - Method's Prototype, discloses vhat an even higher degree of
10 ' ~ may be achieved by ~u~ vai~ acoustic vibrations on the outflowing
GLM. Two flows are provided in this devise, viz. the GLM flow and the gas
flow. The gas flowing out of the Laval nozzle is directed to a specially installed
Hartman generator which generates a powerful ultrasonic field. This field acts on
the outflowing GLM providing a secondary ~ of liquid droplets.
15 However, such a device is complex in ~,V.~LIu~,Livl~ and requires separate feeding
of fluid and liquid.
The method of fire-fighting by a GLM according to USSR Inventor's Certificate
No. 1316713, published in the Bulletin of the Inventions No. 22, 1987 - Method'sPrototype, is considered the closest prior art of the method according to the
20 present invention.
One of the basic elements of any fire-fighting means is the nozzle and the quality
of ' .,..;, ~ .. of any fire ~ L liquid including a GLM depends on the
cv~uul,Livu thereof.
USSR Inventor's Certificate No. 1553151. published in vhe Bulletin of vhe Inven-
25 tions No. 12, 1990, discloses a device by means of which a gas-liquid, mist-like
spray is formed from a GLM. The device comprises a housmg having a water
W09~124274 2 1 8 5 1 4 3 PCT/DK9~/0001~
inlet and an air inlet, a movable rod spring-loading a deflector arranged on an end
thereof adjacent an outlet and blocking the outlet, as well as a mixing chamber
~.. , .. ;~-:;.. ~ with the outlet and with the water and air inlet. The mixing
chamber ~..... "~ with the water through a ring chamber with the outlet
5 ports to the mixing chamber, said ports being blocked by means of conical valve
members rigidly corlnected with the rod and having spiral grooves on their
surface. The air rnlet ~ with the mixing chamber through a central
channel and radial holes in the rod. Liquid from the ring chamber flows as
separate jets to the mixing chamber. Also, ~Idlla~ a~ly directed, cu~ aa~d gas
10 jets enter the mixing chamber and GLM is formed in the chamber. Under the
influence of the pressure in the mixing chamber, the deflector plate of the rod is
displaced from the openmg, and the GLM sprayed out in a mist-like state.
USSR Inventor's Certificate No. 1426643, published in the Bulletin of the
Inventions No. 36, 1988, Apparatus prototype, which is considered the closest
15 prior art to the nozzle of the present invention discloses a gas/liquid no~zle
C~.,.ll..;: " a chamber of changing sections into which a GLM is mtroduced.
Liquid and gas passed separately to a first chamber part through a gas and an air
rnlet and mixed in said first chamber part. From the first chamber part, the GLMis passed mto a cone-shaped chamber part and ~ ly into a ll~ lC
20 chamber part provided with outlet openings for allowing the mixture to flow into
the d~ ua,ul~c. As the GLM leaves through the holes, a blow-like expansion of
the c( ~ air tdkes place breaking the liquid film mto mist-like droplets.
The described nozzle is m-~r~ lly ~~ ,' ' ' as to the formation of the
mixture of liquid and gas.
25 Disclosure of the Invention
The object of the present inYention is to provide a highly efficient method of
providmg an atomised spray with very fine droplets using GLM, said method
w095/24274 2~1 85 1 43 pcrlDK9sloo~l5
being ~la~ ,uldlly efficient in fire-fighting.
According to tbe invention, this object is obtained by a method of providing a
gas/liquid jet having finely atomised liquid droplets comprising the steps of
feedmg a mixture of gas and liquid mto a tube provided with at least one outlet
5 nozzle having an outlet opening and being 1~ 7 by the features of the
g part of claim 1.
In order to understand the principles of the method according to the invention,
various GLM flows through a pipe-line provided with a nozle are considered.
In case of small amounts of gas, i.e. when its mass (~onf~nr~rion in the GLM
lO does not exceed 0,4 weight %, a so-called bubble mode of gas/liquid flow is
formed, i.e. gas bubbles (G) are more or less equally distributed in the liquid
flow (L), confer Fig. 1. In this case, a stationary (without pulsation) GLM
outflow is observed.
In case of very high amounts of gas in the order of 6 weight %, a pseudo emul-
15 sion mode is obtained, where liquid droplets (L) are more or less equally distribu-
ted in the gas flow (G), confer Fig. 2. In this case a stationary GLM outflow isalso observed.
Finally, an UIU~ ' mode, a so-called portion or plug mode of the mixture
flow, is formed, confer Fig. 3, at certain GLM ..., ~ , in particular when
20 the volume of gas and liquid is close to each other and at certain GLM flow
modes (speed, pressure, pipe-line diameter). In this case, separate flows of liquid
and gas portions along the pipe-line are provided, said portions being formed bythe liquid surface tension forces causing single liquid droplets to merge, confer
USSR Inventor's Certificate No. 1184567, published in the Bulletin of the
25 Inventions No. 38, 1985.
wo 95/24274 2 1 8 5 1 4 3 PcTIDKg5loool~
When utili_ing such a mode, the GLM outflow of the nozzle has a pulsating
character due to the essential differences rn the liquid and gas densities. The
frequency of such a pulsation depends on the l-Yalue and outflow V, confer Fig.
3.
S In the method according to the invention, such a GLM flow is formed and flows
out of the nozzle.
Further, on flowing out of the nozzle the GLM plug flow is subjected to an
acoustic filed providing a resonance ~,l,...., ,. ".., For this purpose, a frequency
of the generated acoustic field close to the pulsation frequency of the outflowing
10 GLM plug flow or being a multiple thereof is chosen. Thereby, the gas portions
influence on liquid portions abruptly increase resulting in a more efficient disper-
sion or A~ illll of the liquid.
AS mentioned above, the formation of a plug flow can be made in various ways,
for example by selecting an ~ l u~ gas ~ in the GLM. Formation
15 of the acoustic field under resonance conditions with the pulsing GLM flowing out
may be provided by means of the nozzle according to the invention or may be
provided by other means, e.g. by an acoustic field formed by a separate source,
such as an acoustic-electric transducer or a Hartman generator as described in
USSR Inventor's Certiflcate No. 1316713.
20 The no771e according to the invention comprising a housrng forming a cavity and
having an inlet opening and at least two outlet openmgs is ..l.,.,,, ~ by the
.1,~.,.... ;-: ,~ features of clarm 3.
AdVGIIL~ U~ J~ t` of the nozzle according to the invention are disclosed
in claims 4 to 6.
25 Nozzles of srrnilar basic ~U~ U11iUlh, are known, (confer p. 90 of "Atomi_ers of
wo 95/24274 PCT/DK95/00015
21 ~51 43
liquids. - M., Chemistry, 1979, by D.G. Pazhi and V.S. Galustov), but they have
only been used for atomising liquids and not for GLM. The nozzle accordimg to
tbe invention is mtended for atomismg a GLM in the plug mode. A very high
degree of ^~nmi7:--inn of gas/liquid flow is provided due to a reson;mce cavity or
5 chamber being formed between the bottom wall of the small cylinder amd a radial
plane through the outlet hole(s) in said small cylinder. This provides the following
mPrh ~ m of droplet ~ when the GLM flows out of the outlet holes.
On the one hand, droplets (' O due to their collision (like jets collisions)
and on the other hand liquid droplets add;Liv. ~lly .l;~ under the influence
10 of the oscillation of the GLM gas component takmg place in the closed resonance
cavity formed between the end wall of the small cylinder and a radial plane
through the outlet hole(s) in said small cylinder.
The principle of the nozzle according to the invention is as follows:
- A GLM plug flow is formed;
lS - The flow is divided into two flows;
- One flow is passed through a first nozzle outlet hole;
- The second flow is directed to a resonance chamber prior to leaving the
nozzle through a second nozzle outlet hole;
- In vhe resonance chamber, the GLM gas component energy is converted
into the energy of acoustic radiation (acoustic energy);
- The generated acoustic radiation acts on the GLM flow and breaks the
liquid droplets.
As the pulsation frequency of the outflowing GLM plug flow and the frequency
of vhe acoustic radiation obtained by means of the energy from the O~as component
~5 of the GLM flow equals one another, an effective breaking of the liquid droplets
is obtained.
In the known acoustic noz_les, acoustic waves increasmg the frequency of the
wo 95/24274 2 1 8 5 1 4 3 PCT/DKg5/OOOlS
surface oscillations of the liquid ~ the liquid jets and improve the
Cul~uu~llLly, tne acoustic waves are provided in a gas medium
separated from the GI~ under tbe influence of oscillations of special emitters,
and the liquid film flowing out of the nozzle output is broken under the influence
5 of the acoustic oscillations of this gas flow, (confer USSR Inventor's Certificate
No. 1316713). In the present invention, the source of acoustic oscillations is the
GLM gas component and the acoustic oscillations take place in the closed cavity
of the nozzle in a self-excitation mode and are superposed on gas/liquid flows in
the zone of their collision.
10 Brief Description of the Drawin,es
The invention is described in greater detail in the following with reference to the
particularly preferred r~ and dCCu~ llyill~ drawings, in which
Fig. 1 is a .l;..c"~ illustration of the bubble mode of a GLM flow,
Fig. 2 is a ," ~ illustration of the pseudo emulsion mode,
15 Fig.3 is a ~ illustration of the portion or plug mode,
Fig.4 is a .l; .rl.ll.l-~;. illustration of the apparatus for carrying out the method
according to the invention,
Fig. 5 is an illustration of a first ~ udilll~ of the nozzle according to the
invention,
20 Fig. 6 is an illustration of a second rll~ of the nozzle according to the
invention, in which the end wall of the resonance cavity is modified,
Fig. 7 is a .l,..,,"."..,-:;. view of tbe relation of efficiency of fire-fighting
WO 9~/24274 PCT/DK9~10001~ --
21851~3
using the present inventions.
Best Mode for carrYin~ out vhe Invention
The apparatus in Fig. 4 for carrying out the method according to the invention
comprises a tube 2 having an end extending into the liquid in the vessel 1. The
5 other end of the tube is comnected to a mixing device or chamber 3 for mixing
liquid and gas. Gas is supplied to the mixing device 3 from a gas vessel 4 con-
taining a gas via a tube 20 provided with a valve 7 for regulation of the gas flow
to the mixing device 3. Further, the apparatus comprises an outlet tube 5 connec-
ted at one end to the mixing device 3 and provided with a nozzle 6 at the other
10 end. Finally, the liquid vessel 1 is connected to the gas vessel 4 by means of a
tube 21 provided with a valve 8 for regulating the flow of gas to the liquid vessel.
The apparatus operates in the following manmer:
By means of the pressurised gas in the gas vessel 4, fire-~ Iiquid is
dispensed from tbe vessel l and fed along vhe tube 2 to the mixing device 3,
15 where the liquid is mixed wivh the gas flowing through the tube 20. The gas/li-
quid mixture (GLM) flows along the outlet tube 5 and enters the nozle 6 as a
plug flow which is dispensed therefrom. The outflowing flow is subjected to an
acoustic field of a frequency cvllc*lul~dill~ to the frequency of the plug flow,whereby a jet of fine atomised droplets is formed. The nozzle 6 may be formed
20 so as to provide tbe acoustic field ad described blow.
The nozzle 6 (confer Fig. 5) comprises a cavity of two different sections formedby a large cylindrical portion 16 having a large cylmdrical bore 9 and small
cylmdrical portion 17 having a small cylindrical bore 10. The two portions 16,17are CUII.~ by means of an annular wall 19. The small cylindrical portion
25 17 is closed by means of an end wall 18, thereby formmg a small cavity 14. The
inner surface 13 of tbe end wall is plame. Axial outlet holes ll are formed m the
~ WO 95/24274 2 1 8 5 1 4 3 PCT/DK9S100015
annular wall 19 and radial outlet holes 12 are formed in the small cylindrical
portion 17. The radial outlet holes 12 are formed at such a distance h from the
end wall 18 so as to form a resonance chamber 14 Ih..cb.,~... In said resonan-
ce chamber, the energy of the GLM gas component is converted into the energy
S of acoustic radiation (acoustic energy) acting on the GLM flowrng out of the
outlet holes as described above.
A thread 15 is formed on the inner surface 9 of the nozzle for fastening the nozzle
6 on the outlet tube 5, and the outer surface of the large portion 16 is of a
hexagonal shape.
10 The holes 11 and 12 are arranged as pairs of holes having i,~ axes,
preferably situated in the same radial plane. In the ClllbOdull~ shown, six evenly
distributed pairs of holes are provided ~ u~l~L.cllLidlly.
It should be mentioned that the inner surface 13 of the wall 18 may be of another
shape than plane. In Fig. 5, the inner surface 13 of the end wall 18 is formed by
15 an end cutter, and in Fig. 6, the rnner surface is formed by an ordinary drill, for
which reason the end surface is conical. Tests have shown that the function of the
nozzle does not depend on the inner shape of the end wall 18, but entirely on the
existence of the cavity or resonance chdmber 14.
The gas/liquid nozzle of Fig. 5 operates as follows:
20 The GLM, in this case water mixed with carbonic acid, flows under pressure
along the outlet tube 5 to the nozzle and into the cavity of large cylindrical bore
9 as a plug flow. A portion of the plug flow leaves the nozzle through the axialholes 11 as a pulsating jet. At the same time, the small chamber 14 acts as a reso-
nance chamber, whereby a portion of the flow leaves the radial holes 12 as a
25 pulsating jet. As the axes of the outlet holes 11, 12 of each pair of holes are
arranged in the same plane, the gas/liquid jets of each pair collide, whereby
WO 95t24274 2 1 8 5 1 4 3 PCT/DK95/OOOIS
refned droplets are formed. At the $ame time, the acoustic filed formed by the
GLM gas component acts on the outflowmg jets in the collision zone of the jets
causing additional liquid droplets to break.
The standard conditions described in "~ethods of Evaluation of fire-flghting
5 ability of fire r~ h. I~" by O.M. Kurbatsky a.o. were used for testing the
method accordmg to the invention employing the nozzle design shown in Fig. 5.
A fre centre of a "131~" type was used as a fire centre comprising a round steeltray with a square of 0.41 m2 and containing a ~ il Ir. matter of 13 litres A-
76 petrol, confer pages 8-10, in particular.
10 The tests were carried out on an apparatus constructed according to the principles
of the apparatus shown in Fig. 4 and having a liquid vessel contents of 2001
(MIITP-200) and 2 1 (OBM-2), ~ ly . The gas . " r - ~ - . in the GLM
was regulated and nozzles with different depths h of the resonance cavity 14 were
used (confer Fig. 5).
15 The efficiency of fire-fighting E can be u,uallliLdLi~ly estimated as a ratio of fire
centre square S to water mass M used for its r - l; l lv. . ;~l l; . ~v, e.g. E= SIM (m2/kg. )
The result of the performed tests for MIlTP-200 and OBM-2 are given in Table
I and Table 2 l ~ h,.,ly, where the efficiency of fire-fighting E and the time
t used for ~.1;"~ ;,* are stated depending on the gas ~ ;.... r in the
20 GLM and the depth h of the resonance cavity or chamber 1~.
The results stated in the tables show that optimum ranges of gas ....,...1l.,.l;.,.. r
in the GLM and an optimum depth h exist at which an ~ . ;~lc increase in E
and decrease in t are obtained.
W095l24274 2 i 8 5 1 4 3 PCTIDK9S/000l5
11
Table 1
Fire-fighting efficiency, m2/kg; sec
NResonance Gas c.",~ ;.", %
cavity depth
(h), mm 0.4 2.0 4.0 5.0
3.0 0.12; 9.0 0.20; 5.0 0.25; 5.0 0.28; 4.0
S 2 5.0 0.11; 10.0 0.22; 5.0 0.24; 5.0 0.25; 5.0
38.0 0.11; 11.0 0.40; 3.0 0.38; 3.0 0.36; 3.0
410.0 0.10; 11.0 0.25; 5.0 0.28; 4.0 0.28; 4.0
Fire-fighting efficiency, m2/kg; sec
10 N Resonance Gas ~ %
cavity
depth 0.4 2.0 4.0 5.0
(h), mm
1.0 not extin. 0.25; 16.0 0.26; 15.0 0.28; 14.0
2 2.0 not extin. 0.40; 10.0 0.38; 11.0 0.36; 12.0
3 4.0 0.22; 18.0 0.42; 9.0 0.40; 10.0 0.38; 11.0
4 6.0 not extin. 0.26; 15.0 0.26; 15.0 0.25; 16.0
lS For MIlTP-200 the optrmum gas ~ range is about 2-35 amd the op-
trmum value is h = 8 mm and for OBM-2 the same gas ~.--.. ~1.. ~1;.~. range, but at h values of about 2-3 mm.
The mentioned gas ~..,., ...1.,-l;.~l..~ correspond to a plug flow of the GLM flowing
into the nozzle, wbich was shown by of the vibrations of the outlet tube feeding20 the GLM to the nozzle. As the diameters of the outlet tube of the MlITP-200 and
the OBM-2 differ from one another, the GLM plug flow flowing out is different
from one another. The g~r~m~trir:ll parameters of the resonance cavities 14
WO 95~24274 2 l 8 5 1 4 3 PCT/DK95100015
12
providing resonance oscillations differ ~:u~lc~ol~d;ll~ly.
Analogous tests were carried out usrng an apparatus, OBM-10, having a water
contents of 101. The results of these tests are presented (confer Fig. 7) by means
of cunes showmg the fire ~ .g efficiency E as a function of the gas con-
S centration r in the GLM, the resorlance cavity depth h and the pressure p. It canbe seen that in the r range from 0.6 to 2.~ and h = 5 =m~m an increase in E
occurs, which is typical of the reson mce ~ .l l This is ~ u~ evident
m ~ with the curve plotted for h = 2 mm. In the latter case, such
resonance cavity depth does not provide a generation of oscillation resonance in10 relation to the frequency of GLM plug flow flowing into the nozzle and only auniform increase in the fire ~. I;l~,,..; l l,v efficiency E due to the gas component
in the GLM can be seen.
Thus, the tests carried out show the advantages obtained by the present invention
in relation to fire-fighting meams, and in particular, that a substantial increase (at
15 least 1.5 times) in efficiency may be obtained in ~v~ u.. with the known
means. The efficiency of fire-fighting with a powder fire-~ ,. (OM-lû)
is shown in Fig. .7 for Cu~ iaull.
The tests carried out using varying fire-fighting meaps differing from each other
marnly by the diameter of the GLM outlet tube and the GLM pressure show that
20 the plug mode of the GLM flowing out can be provided and that the dimensions
of the nozzle resonance cavity cam be selected so that the fire . .li.,~,.;~l.;,.~
liquid flowing out breaks mto very fine droplets due to the resonance phenome-
non. Thus, at additional tests, excellent results have been obtained with flow
velocities ranging from 3 mlsec to 10 m/sec rn the outlet tube 5 providrng a plug
25 flow with a frequency of 25 to 50 kHz.
