Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
778
This invention is generally concerned with a combustion
process and the novel means for achieving it and in particular
with a method and a fuel atomizing device for burning gaseous
and/or liquid fuels which are not considered as being useful
fuels, such as pitch and asphaltic compounds.
A burner assembly utilizing the novel fuel atomizing
device is described in Applicant's copending Application
filed
Burner assemblies heretofore used for the combustion
of liquid and gaseous fuels are numerous and each has a specific
application for which it is best suited.
Such present burner assemblies generally use mechanical
methods of atomizing the fuel. This requires high fuel pressure
in combination with very small openings which result in these
`~ openings readily becoming plugged and therefore require a con-
siderable amount of maintenance and steadily degrading efficiency.
~ Heretofore atomizers of the emulsion type and the ex-.`
ternal mixing type were used for all fuels even though the fuel
droplets were relatively large and therefore required an extended
dwell time in order to vaporize. These atomizers used air or
steam as the atomizing medium without any additional heat input.
In some cases the atomizing medium offered no additional advan-
tage and at times actually absorbed heat from the fuel.
This invention relates to a method for atomizing fuel
to promote efficient burning, comprising:
A. preheating a fluid atomizing medium;
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B. imparting a high velocity tangential motion to at
least a portion of the medium to create a vortex;
C. introducing said vortexual motion medium at a first
velocity and pressure upstream of a fuel entry
point;
D. introducing the fuel into a diffuser at a first
pressure;
E. atomizing the fuel within the diffuser by causing
the fuel and the medium to intimately mix in the
10diffuser area immediately adjacent the fuel intro-
duction point at substantially said first pressure,
' transferring heat from the medium to the fuel; and
-~ F. further decreasing the pressure of the mixed fluid
by controlled expansion while continuing to subject
the fuel to the tangential and shearing action of
, the introduced medium vortex.
: This invention also relates to a fuel atomizing device
~` for use in a burner assembly comprising: an atomizer head having
means for communication with a fuel source and means for communi-
20 cation with an atomizing medium source; :
A. said fuel source communication means defining a
conduit having an exit point within said atomizer
head;
B. said atomizing medium communication means defining
- a plenum upstream of said fuel conduit exit point,
a vortex cavity and an ejector nozzle surrounding :
said fuel conduit exit point;
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C. vortex generating means interposed between the
plenum and the vortex cavity so that a high ve-
locity vortex is imparted to the flow of the atom-
: izing medium which vortex acts on the fuel at and
, around the ejector nozzle; and means for diffusing
the atomized fuel downstream of said ejector nozzle.
The invention will now be described in reference to theaccompanying drawings, wherein:
Figure 1 is an elevational view showing in cross sec-
tion a burner assembly using an atomizer of the invention;
.:
Figure 2 is an elevational view shown in cross section
one embodiment of the atomizer;
Figure 2A is a sectional view of an alternate diffuser
providing for impingement of the flow; and
Figure 3 is a cross sectional view of another embodi-
ment of the atomizer head.
~ j
. Referring now to the drawings and particularly to
. Figure 1, there is illustrated an embodiment of a burner assembly
. for carrying out certain objects of this invention wherein is
20 shown a typical furnace floor 10, to which is attached a burner
support bracket 12, which carries burner assembly 14 having a
~ ceramic head and hot gas diffuser 16 extending through floor 10,
.~ the assembly comprising a heat exchanger 18 having spaced inner
and outer walls 20, 22 with a packing material 24 positioned
therebetween and retained by upper and lower packing retainers
26, 28, retainer 26 forming a communication means with upper
-~ manifold 30 which is connected to an atomizing medium supply
by port 320 Retainer 28 provides a communication means to lower
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manifold 34 and atomizing medium exit port 36, conduit 38 andconnecting tee 40, to which is connected conduit 42 to carry the
heated atomizing medium to the atomizer head 44. Conduit 42
surrounds fuel conduit 46 which also communicates with atomizer
head 44. Atomizer head 44 has an exit nozzle 48 and turbulator
50. A main gas fuel ring 52 having angled ports 54 is connected
to a fuel supply by conduit 56. A primary air register opening
58 is provided for the
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burner. The pilot igniter is shown at 60, and flame sensor
viewing tube and sensor at 62, 64 respectively.
The operation of the embodiment as illustrated in
Figure 1 under a typical condition to fulfill a specific re-
quirement can be described assuming that an atomizing medium
is connected to port 32, the main gas conduit 56 is connected
to a control valve and the liquid fuel conduit 46 is connected
to a preconditioned ~uel supply by way of a manual control
valve. The pilot ignitor 58 and the flame sensor 62 are not
a part of this disclosure and will not be discussed ~urther
other than to note that the pilot is lit and the flame is sensed
by the sensor which is connected to prescribed safety control
systems old in the artO
The atomizing medium is pressured into the port 32.
Flow is established through port 32 into the manifold 30,
through the heat exchanger packing 24 into the bottom manifold
34 by way of the retainer 26, the heat exchanger 18 and the
packing support 28. The atomizing medium leaves the manifold
34 by way of the passageway 36 and flows into the atomizer tee
20 40 by way of the conduit 38~ The atomizing medium flows to the
atomizer head by way of the conduit 42~ The ~low of the atom-
izer medium is around the fuel conduit 46 as it flows toward
the head 44. The atomizing medium ~lows through its respective
passageways in the head 44 and establishes a vacuum within the
liquid fuel tube 46.
The medium exhausts from the nozzle 48 and into ~e
combustor by way of the turbulator 50. When the atomizing flow
; has been established the main gas valve is opened and ignition
is immediate by way of the pilot flameO As the main flame
heats the combustor wall 20 the heat is transferred into the
atomizing medium flowing in the heat exchanger 18 by the effect
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of the packing 24, This pac~ing is of a conductive material
such as ceramic or metallic balls or any shape that would r,love
the heat from the combustor wall and place it into better con-
tact with the flowing atomizing medium. This unique construc-
tion has a definite advantage in increasing the heat transfer
resulting from the turbulence generated in the heat exchanger
by non-lineal ~low and the elimination of the film coefficient
on the heated surface by conduction. The temperature of the
atomizing medium continues to increase until a heat balance has
been reached. Proper design establishes the final temperature
by dictating those areas and velocities required based on the
heat radiator and the receiver at a given point or operating
condition. Water may be inJected to generate steam to serve as
an atomizing medium.
When the atomizing medium has reached the proper tem-
perature, the preconditioned liquid fuel is admitted into the
conduit 46. The fuel, sub~ected to the vacuum generated in fuel
conduit 46 by the discharge of the surrounding atomizing medium
in conduit 42, also receives heat by transfer from the surround-
ing heated atomizing medium. The lowered pressure resultantfrom the atomizing medium discharge from the circular e~ector,
lowers the boiling point of the fuel, thus permitting the light
ends in the fuel to boil off at a lower temperature and increas-
ing the efficacy of the heat transfer. As the liquid fuel dis-
charges from the conduit 46 it is subjected to the low pressure
resultant therefrom and then to the so~ic velocity tangential
flowO This causes a shearing effect on the molecules of fuel
while the delta pressures of the angled sonic shock waves form-
ing around and immediately downstream of the exit of conduit 46
and the multiple flow directions existing in the high velocity
tangential atomizing medium aid in atomizing and mixingO In
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778addition, the effect of the density transition as the heavy fuel
is ce~trifically forced toward the outer parameter of the tan-
gential flow, causes additional shearing of the liquid. The
turbulence generated when the sonic flow changes to subsonic
flow also provides additional atomization to produce micron drop-
lets of fuel that greatly reduces the dwell time required for
the transition from liquid to a vapor state.
A novel feature of this unique method of atomizing is
the direction of the tangential flow of the atomizing medium,
The normal vortex direction north of the equator is counter-
clockwise and south of the equator the normal flow is clockwiseO
Better atomization is obtained when the vortex is forced in a
direction opposite to that of normal flow. This does not sug-
gest or indicate the flow could not be the same direction as
the normal flow.
Another important factor and novel feature of the
unique method of atomizing liquid fuel is the use of the heated
atomizing medium, the high velocity gained by it through heating
and the ability of transferring this heat into the fuel.
It will be noted that the combustor is devoid of the
usual combustor block. Exhaustive tests have established the
fact that such a block is not required with the present novel
embodiment. This does not mean that a ceramic could not be used
within the combustor if the effect on the heat transfer can be
tolerated. It will also be noted that an excess air register is
not illustrated. Although the register is necessary in most ap-
plications, its usefulness in describing the basic operation of
the inventive device is not necessary.
The angled gas ports as illustrated in Figure 1 at 54
perform major functions. The angle has an effect on the turbu-
lence generated in the combustor to hold the gas generated flame
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front at a specific point within the combustorO Also the angle
of these ports greatly e~fects the mixing of the alr and fuel
and controls the type of flame entering the furnace when operat-
ing on gas only. Likewise, the kinetlc energy of these multiple
ports inspirates primary air into the combustorO Additional
primary air is inspirated by the kinetic energy of the atomized
fuelO The amount of primary air is controlled by the position
of the register 58 as it blocks or restricts the flow of air
through the port 660
It is also feasible to provide for an alternate loca-
tion for maln gas ln~ection at the top of the assembly. This
may be accomplished by installing multiple tubes angled at a
point where they terminate in the combustor so that they pass
through the ceramic head and have their inlet on the external
surface of the burner shellO Multiple gas nozzles are piped to
these inspirator tubes and positioned so that the gas flow from
; the nozzles will enter the tube and inspirate airO The multiple
pipes supplying the nozzles terminate in a suitable manifoldO
Valving is made available so that the assembly can be started
and heated with the fuel ringO When the liquid fuel is ignited
. the gas is transferred to the top in~ection point and uses the
radiant heat of the oil flame to keep the atomizing medium hot.
When the embodiment is used without the atomizer head
it is necessary by proper valving or repiping to direct the flow
; of main gas through the heat exchanger~ Care should be exercised
; to insure that the temperature does not reach the cracking tem-
perature of the fuel in useO
Likewise, liquified petroleum gas can be directed
through the heat exchanger so that it may serve as a vaporizer
for the LPG~ Liquid propane and butane have been tested and
documented with excellent resultsO
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Referrin~ to Figure 2 there is illustrated an embodi-
ment of an atomizer head wherein 46 is the liquid fuel conduit
centrally located within the atomizing medium conduit 42, 44 is
the atomizer head, 48 is the exit nozzle, 68 is the atomizing
medium plenum, 70 is the impingement nozzle annulus, 72 illus-
trates the typical multiple impingement openings, 74 is the dif-
fuser, 76 is the atomized fuel, 78 is the circular nozzle throat,
80 is the primary atomizing, low pressure, and expansion zone,
82 is the tangential generating slot directed to cause the gen-
eration of a vortex opposite to the natural vortex, 84 is thevortex generating plate and 46 A illustrates an alternate loca-
tion for the fuel conduitO
In operation the atomizing medium is flowing through
conduit 42 and fuel is flowing down conduit 46. This method
insures adequate tracing for specific applicationsO The flow of
the atomizing medium enters the plenum 68 and the flow is divid-
ed into the number of flow paths, on an area ratio basis, that
is required for the specific head design. One path is through
the annulus 70 where it communicates with the multiple impinge-
ment nozzles 72. These are terminated in the wall of the dif-
fuser 74, however, the sonic flowg although warped by the angled
exit, forms an impingement point within the diffuser. Another
path for the atomizing medium is through the tangential slot 82
that is located in the swirl plate 84. As the atomizing medium
exhausts from the tangential slot 82 a vortex or tangential flow
is generated within the cavity 86 having a swirl opposite in
direction to the normal ~low. As the transition section 88 of
vortex cavity 86 becomes smaller the vortex flow velocity is in-
creased until a critical pressure ratio is reached. At this
point the flow velocity is sonic, As the rotating atomizing
medium leaves the nozzle 78 formed by the fuel tube 46 and the
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head 44 sonic shocks are formed as the compressed atomizing me-
dium attempts to shock down to subsonlc velocities. These
shocks are circular and angled corresponding to the tangential
flow. Also at the center of this vortex the pressure is below
atmosphere. Likewise, the manner of placing the fuel tube 46
in the center of the opening of head 44 to form an annular nozzle
90 creates in essence a circular ejector. The combination of
these phenomena provides an ideal low pressure primary area 80
into which the liquid fuel is deposited. In essence this lowers
the boiling point of the fuel depending upon the vapor pressure
of those elements that make up the fuel in use, In this primary
zone 80 the liquid fuel is subjected to sonic conditions and
severe pressure changes that tend to shear the fuel molecules,
` while the density variations within the atomizing medium and the
liquid fuel causes it to be moved toward the outer edge of the
vortex where it is subjected to the sonic shocks that continue
to cause molecular shear. As the diffuser 74 accomplishes a form
of controlled expansion and begins to convert some of the total
` pressure to static pressure, the atomized fuel is forced into
sonic impingement by the multiple flows from the angled nozzles
; 72 within the diffuser body 74. Any rotational fl~w is immedi-
ately stopped and the mixture is again sub~ected to the violent
action of the impinging sonic jets. As the atomized fuel is ex-
hausted from the atomizer head through exit nozzle 48 the fuel
droplets are in the micron size and quickly convert from liquid
to vapor for immediate and trou~le free combustion.
A modification of the embodiment of Figure 2 is illus-
trated in Figure 2A. It depicts an alternate diffuser having an
action effecting the impingement flow whereby the impingement
area is larger, the static pressure is higher and the velocity
is greater than sonic. Like reference numbers denoting like
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parts, l~6 is the fuel tube, 24lL is the atomizer head, 248 is
the diffuser exhaust exit, 270 is the lmpingement nozzle inlet
annulus, 76 represents the atomized fuel, 78 is the nozzle
throat of vortex cavity 86, 292 is the impingement nozzle inlet
throat and 272 is the impingement nozzle diffuser section. The
atomizer operation is identical to that already described except
that the expansion of the sonic velocity flow downstream of the
throat 292 in the diffuser section 272 is controlled in such a
manner that the velocity pressure is converted into static
pressure and the velocity is increased above sonic. Although
the flow is warped due to the angled exit, the amount of atom-
izing efficiency is increased.
The atomlzer head as illustrated in Figure 3 is iden-
tical to the previous atomizers except it does not have any
impingement nozzles nor does it have a diffuser.
As illustrated in the figures at 46A is an alternate
method of admitting fuel to the atomizer head for specific fuel
applicationsO
The turbulator body 20 is no~ shown on any of the
atomizer heads of Figures 2, 2A, or 3~ It is a needed item but
is not considered a novel feature and will not be discussed
furtherO
The embodiments as disclosed and described herein
have been tested with excellent results on the following fuels
using air and again using steam as the atomizing mediumO These
were naphtha, kerosene, carbon black oil, 40 API crude, 24 API
crude, 19 API crude, Bunker "C" and Ten Pen AsphaltO The amount
of air or steam per pound of fuel required for the present ln-
vention was less than normally used in state of the art devices
and the preheat fuel temperatures were lowerO
From test data and observations the efficiencies dur-
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ing the static firing tests resulted in the following advan-
tages over present known devices: Less pollution, greater sta-
bllity, better turndown, and the ability to successfully use
those fuels that to date have not been considered as useful
fuels.
The abllity of the atomizer to form micron droplets
makesit very useful for application using fuels that presently
require ambient air temperatures~ HoweverJ the atomizing
method as disclosed herein requires less atomizing medium weight
flow per pound of fuel~ less fuel pressure and produces greater
combustion efficiencies that result in a greater heat release.
For some applications the atomizer will pump the fuel by the
action of the circular ejector. Tests indicate that it is pos-
sible to produce an emulsion with the water vapor and fuel oil
merely by the effect of the sonic energy within the atomizer.
A metered amount of water can be injected into the fuel for ad-
ditional emulsion water content.
Further studies provide an additional use for atomiz-
ing a coal dust slurry. The atom~zing feature can easily be
modified for oxygen injection for coal dust or other applica-
tions.
For specific applications the fuel is caused to flow
tangentially as it enters the atomizing head by use of a swirl
vane within the fuel tube.
As apparent, one of the principal ob~ectives of the
present invention is to provide an improved heat exchanger to
super heat the atomizing medium through the heat usually lost by
way of combustor wall radiation and to offer adequate cooling of
the combustor and at the same time to put the absorbed heat into
the fuel within the atomizer headin such a manner that the
atomization of the fuel is greatly improved.
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77~3
While the device as disclosed herein has been de-
scribed as a liquid fuel burner assembly, the device is useable
as a gaseous fueled assembly, a liquid fueled assembly or a com-
bination gaseous-liquid fuel assembly. Various tests have been
conducted using propane, butane or natural gas as a gaseous
fuel, and as a liquid fueled combustor device. Excellent re-
sults have been obtained using naphtha, kerosene, 40 API Crude
Oil, Bunker "C" and Ten Pen Asphalt. In the preferred embodi-
ment, the combustion air is inspirated into the combustor by
the kinetic energy of the gaseous fuel or the kinetic energy of
the atomized fuel. However~ positive air pressure may be di-
rected into the ccmbustor or around the combustor as secondary
air. The presently anticipated application for this device will
be as a heat source for furnace applications where suitable
draft is available to assist in the supplying of the required
combustion airO However, this does not suggest nor indicate
that the device as disclosed herein cannot be applicable to
other uses.
One test condition used saturated steam at 150 pounds
pressure (36~F.) at a demand of 130 pounds per hour for a Ten
Pen Asphalt flow of 660 pounds per hour at a temperature of
400F. The heat exchanger superheated the steam to 800F. or
an increase of 433F. The resulting flame of the aspha~tic
fuel was very efficient and smoke free. Other tests using
lower steam pressures and air pressures were documented with
similar results.
Although particular embodiments of the invention have
been illustrated and described, changes and modifications will
become apparent to those skilled in the art and it is intended
to cover in the appended claims all such changes and modifica-
tions as come within the true spirit and scope of the inven-
tion.
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