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Патент USA US2122929

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July 5, 1938.
Filed April 27, 1934
524mm Al. W‘
Patented‘ July 5, 1938
William Douglas Carter, Caldwell, N. J.
Application April 27, 1934, Serial No. ‘722,646
,2 Claims. (01. 158-—1)
This invention relates primarily to jet or injec
tor means for recirculating the hot gases in a
nected with the same air-pressure means-one
for mixing air directly with the oil spray, and the
fire-box or combustion chamber, so as more thor- ' other as a source of agitation for promoting the
oughly to- mix the gases and bring about com
Cl plete combustion with a minimum of excess air.
The process of combustion, like many other
chemical reactions, is best accomplished by thor
oughly agitating or stirring the proper quantities
of the constituent elements, and not through the
10 addition "of an excessive amount of one of the
elements; nevertheless it is a common practice
with many types of oil-burners to create turbu
lence and mixing of the gases by means of a blast
- of excess air forced or drawn. into the ?re-box.
,, As a matter of fact, in most furnaces, Whether oil,
gas, or even solid fuels are used, a large excess of
air is usually supplied to insure safety and com
plete combustion of the fuel. This results in
noisy combustion and impaired ef?ciency gener
ally recognized in the art.
With my invention, a minimum quantity of
excess air is admitted to the ?re-box (except dur
ing the short ignition period hereinafter de
scribed). Some of the necessary amount of air is
conducted under pressure to the nozzle of an in
[0 Di jector. The injector is so positioned as to in
duce a re-circulation of the hot combustion gases
which would otherwise escape to the stack after
substantially one passage through the ?re-box.
These recirculated gases mingle with the pre
heated jet of air issuing from the injector nozzle
inside ofqa refractory or ?re-resisting draft-tube,
wherein the gases are further pre-heated and
then discharged into the freshly supplied com
bustible gases and air. This operation serves to
re-heat, agitate, and dilute the unburned gases
so as to spread the ?ame throughout the ?re-box
and promote slower, quieter, and more complete
combustion before the ?nal products pass out
as o through the stack. Of course the extent of dilu
tion, and the rapidity of combustion are subject
to wide adjustment depending upon service con
While other fuels such as alcohol ‘ may be
burned, the apparatus will be described primarily
in its oil-burning application.
The general object of this invention therefore,
is to recirculate the air and fuel gases in the com
bustion chamber so as to promote thorough mix
ture and combustion before allowing the result
ant gases to pass up the stack.
Another object is to provide a gentle blast of
hot recirculated gases directed so as to mix with
the incoming fuel gases and air.
Another object is to provide an injector tube
of heat resisting material in the path of the
flame, through which the hot gases are recircu
lated and. blown into the newly supplied combus
tible mixture.
Another object is to provide two nozzles con
mixture of all the hot gases in the ?re-box or
combustion chamber.
Another object is to preheat the compressed air
before it reaches the jet in the recirculating tube,
so as to increase the volume of said air and there
by to minimize the amount of air required.
Another object is to increase gradually the air 10
pressure on the fuel atomizing nozzle, as the tem
perature of the fire-box rises, and thereby to im
prove the ignition and starting characteristics
of the oil burner.
Another object is to provide a refractory tar 15
get against which both the new fuel supply and
the recirculated gases are directed so as to pro- '
mote the mixing thereof.
Another object is to recirculate the chilled and
partly burned gases which lie adjacent to the 20
heat-absorbing walls of the combustion space.‘
Another object is to prevent the sound from
the air compressor from emanating through the
Another object is to insure safety by supplying
excess air during the short ignition period only. 25
The preferred constructions through which
the above objects are attained, are hereinafter
fully described and claimed, having reference to
the accompanying drawing in which:
Figure 1 is a vertical side elevation of my oil 30
burning mechanism, partly in section, wherein a
vertically disposed recirculation tube of conical
shape is directed toward a target formed on the
?oor of the ?re-box.
Figure 2 is a diagrammatic elevation showing 35
a modi?ed arrangement employing a curved or
horn-shaped recirculation tube bent to discharge
against one side of a target, while the incoming
fuel is directed against the opposite side of the
Figure 3 is a diagram of a third arrangement
wherein the recirculated hot gases and the fuel
spray are both directed horizontally toward each
Figure 4 is another side elevation, mostly in
section, illustrating another adaptation of my in
vention to a conventional type of pressure-atom
izing oil burner wherein the oil is atomized by oil
pressure means, and all of the air is supplied by '
means of a blower.
Like numerals ‘refer to similar parts in the
several ?gures.
Referring to Fig. 1 in particular, I is the cy
lindrical wall of a, ?re-box having a circular top
2, elevated floor 3 and bottom 4. Formed in the
wall l between the ?oor 3 and bottom 4 is the
secondary air inlet opening 5 which communi
cates through square ports 6 in ?oor 3 with
the ?re-box or combustion chamber. An addi 60
2 .
tional excess air inlet opening 1 is shown in wall
I and is provided with a door 8 hinged at 9 to
wall I. An arm II is ?xedly attached to the
shaft of the control motor it. The link 12 is
UK pivotally attached at one end to the outer end
of arm‘ ll and at the other end to door 8 so
as to open and close the excess air opening ‘I
automatically during the ignition period.
The floor 3 is covered with refractory lining
10 l3 forming a target, and the lower face of wall
I is lined with ?re bricks l4—certain onesof
which bricks are leaned across ports 6 as in
dicated in Fig. l to form ba?les l5 around which
the secondary air from ports 6 may enter the
15 ?re—box. One or more exit or ?ue openings are
formed in the top wall 2 and surrounded by the
inwardly projecting nipples I6. Other ports ‘are
‘formed in ‘the wall I for the entrance of the air
pressure conduit l1 and the fuel conduit I8. The
air conduit I1 communicates through a heater
section I!) with the air-nozzle 2B which is .attached
to and supports the gas recirculation ‘tube 2|.
This tube contains one or more inlet ‘openings
and the communicating nozzle 20 to form the
air-jet which is blown downward through the
recirculation tube 2|; and the other stream con
tinuing through conduit I8 and the‘ nozzle 29
Where it is discharged into the ?re-box as in
Simultaneously it will be assumed that
the fuel oil pump 3i which is connected to a
suitable source of oil supply not shown, is op 10
erating to deliver oil under pressure through the
control valve 32 and pipe 33 into the air conduit
28, ‘at a point where the air-stream will conveythe
oil through I8 to the fuel nozzle 29 from which it
is sprayed into the ?re-box. Suitable gas or elec
tric ignition means, not shown but of conven
tional type, is provided to ignite the spray of
fuel as it enters the ?re-box. It is important
that no oil be allowed to accumulate in the'muf-‘
22 formed at or near one end, and a main dis
?er receiver 21 to'be blown suddenly through‘
nozzle 29 when the burner is started; and the
drain hole 30 is provided to drain the receiver
when the burner stops operating.
It‘willybe‘evident that the proportions ‘of air
charge opening 23 at the other end thereof.
?owing through each of the nozzles, will depend 25
Other discharge openings such as 24 may also
upon the relative frictional resistance encoun
be provided.
tered in the two parallel streams. Assuming that
'The air compressor 25 (see Fig. 1) discharges
through the discharge pipe 26 into the upper
:30 part of the mu?ler receiver 21 which in turn
the amount of oil delivered through conduit 18 is
constant, and therefore that the friction of the
air encountered from the oil passing with the air 30
communicates at its‘lower end with conduit 28.
The latter communicates with air conduit l1 and
through I8 and nozzle 20, does not vary, then a
de?nite proportion of air will flow through‘ each
with the elbow shaped fuel conduit I8 at the
.end of which is connected the fuel spray nozzle
29. The drain hole '30 in pipe 26 communicates
with the lower end of mui?er receiver 21. Oil
nozzle depending upon the relative physical pro
portions of the two lines, including the nozzles.
Such will be the condition the instant before ig
nition takes place.
After the ?re is established,‘ the air passing
‘supply pump 3!, which is supported by bracket
Slat attached to compressor 25, discharges
through control valve 32 in pipe 33 into conduit
‘The modi?cation shown in Figure 4 contains
the additional flue pipe manifold 34, and the rec
through the pre-heating coil or section [9 ex
pands with the heat imparted to it, so that its
volumeis greatly increased while the frictional 40
resistance of its conduit and nozzle 25} is not
' changed materially. Hence the amount or weight
tangular refractory target 35. This arrangement
of the air ?owing through nozzle‘ 20 will mate
utilizes what is conventionally termed a pressure
rially decrease, while the proportion discharged
through the fuel nozzle 29"will increase.
atomizing type of oil burner having a centrifu
gal blo'wer't? and the communicating wind-pipe
31. The by-pass opening 38 provides a discharge
from'the wind-pipe‘31 to the heater section 19
Air also passes through nozzle
43 to the ?re-box. The highpressureoil spray
.150 nozzle ‘39'is connected to the end of oil pressure
‘conduit Ml—the last leading from an ‘oil pres
~ and nozzle 20.
sure means analogous to‘ 3| but not shown ‘in
‘Figure Ll. In fact the centrifugal blower ‘36 ‘may
be considered analogous to the air compressor
25 in Fig. 1 since both constitute air pressure
means; wind pipe 37 is analogous to pipe 26, by
pass opening (33 to 23, nozzle “39 to fuel ‘spray
nozzl‘e'29, and conduit EMl‘ to fuel conduit I8,
although different numerals are given in Figure
4 for identification purposes. With the arrange
ment shown in Fig. 4 a conventional type of cir
cular shutter M, to which is attached the ac
tuating arm 42; is pivotally linked by means of
lc: Ci
receiver 2‘! is divided into two streams, one pass
ing upward through pipe l1, heater section I9,
link l2 to the arm H of the control motor l0. .
The operation of my oil burning apparatus is
as follows: Referring first to Figure 1, the com
pressor 25 is assumed to be delivering air through
the discharge pipe 26 into the mu?ier receiver
'21, ‘where the sudden volumetric enlargement
Several advantages are gained by this arrange
ment: In the ?rst place, quieter and more re
liable ignition is obtained with the low initial
pressure prevailing at the fuel nozzle 29 before
section l9 becomes heated, while the gradual in 50
crease in pressure at nozzle 29, as the ?re-box
becomes hot, greatly improves the atomization
and turbulence required for the ‘best combustion.
The pre-heated air in the jet issuing from noz
zle 20 prevents-cooling the gases which are sucked
in through ports 22 and‘discharged downward
through the recirculation tube ,2 l. Furthermore,
the preheating of the air effects a material econ
omy in the total amount of air‘required to operate
the burner.
It will be apparent that‘ a very small quantity
'of ‘high pressure‘ air discharged from nozzle 20
will 'cause' the recirculation of a relatively large
amount of hot gases in the ?re-box. These hot
gases are taken preferably from a point near
the ?ue or exit end of the fire‘ box and carried
through the recirculation tube in which they are
reheated and discharged at the part of the ?re
box at which the incoming oil is sprayed, so as
to mix'with the freshly supplied oil gases, and
with the secondary air also admitted at this point.
The hot recirculated gases serve to heat the in
andireversal of direction of ?ow serve to cushion
any pulsations and thereby minimize the sound
"which otherwise Would be carried on with the coming secondary air and to vaporize any stray
air stream and emanate as an objectionable noise particles of oil, and by increasing the turbulence
from the ‘nozzles. The airiileaving-ithe muf?er " of all ofithe gases produces-a uniform combustible 75
mixture and an efficient ?re. Simultaneously with
the above action, additional secondary air is con
tinually being drawn into the ?re-box from the
cavity behind the leaning bricks or ba?ies l5
which cavity is in communication with the air
port 5 through the square ports 6. Owing to the
recirculation of the hot gases within the ?re-box
a minimum quantity of secondary air is required
but in order to assure an ample supply of air
10 when starting, and before the chimney draft
has reached its full running intensity, the ex~
cess air inlet 1 is opened automatically by means
of the control motor I0, arm H and connecting
link l2. In about one minute, or when ignition
15 is established, the control motor lowers the door
8 and closes inlet 1 in an obvious manner. This
arrangement insures an adequate amount of air
for starting and still permits a minimum but
e?icient setting of the air supply through 5 dur20 ing the ensuing operating conditions when the
?re-box is hot and the draft normal. The air
port 5 may be throttled by any obvious means to
obtain the proper setting above referred to, after
which no further adjustment is usually required.
The walls I and the top 2 of the ?re-box trans
fer heat from the hot gases to the ?uid medium
in contact with their outside surfaces. This trans
fer of heat tends to cool the gases within the ?re
box adjacent to the walls, and sometimes pre
30 vents complete combustion of the gases close to
the walls. For this reason the inlet openings 22
are advantageously located close to the wall and
top of the ?re-box as indicated in Figure 2 so as
to recirculate these slightly chilled gases and
thereby promote complete combustion before the
gases ?nally pass through nipples IE to the stack.
Nipples IE project into the interior of the ?re box
so as not to withdraw these partly burned gases
from the wall or top surfaces before they can be
The recirculation tube 2| may be made of any
heat resisting material, preferably a refractory
substance which becomes red or white hot, there
by aiding combustion and adding to the visual
45 attraction of the ?re.
Figure 2 also shows a curved type of recircula
tion tube 2! and a refractory target 35 positioned
so as to receive the impact of the hot recirculated
gases against one side and the fresh stream of
50 fuel against the other side thereof. The atomized
oil issuing from the nozzle .29 is usually vaporized
by the heat of the ?ame before reaching the tar
get, and the two streams of gas are thoroughly
mixed around the edges of the target; or through
55 openings or passages, such as M, which may be
provided through the target.
Figure 3 shows diagrammatically, a third ar
rangement wherein the hot gases are drawn from
the top wall of the ?re-box through opening 22
60 into the recirculating tube 2 I, and directed
through discharge opening 23 in a horizontal di
rection counter to the incoming atomized stream
of‘ fuel entering through nozzle 29.
In Figure 4 the recirculation tube 2| draws the
65 hot gases from. a point near the top of the ?re
box, between the outlet nipples l6, and directs it
through the curved passage in 2| against the tar
get 35. These gases may be diverted through var
ious other points of discharge as, for instance,
nozzle 39 from which it is sprayed into the ?re
box as indicated. Simultaneously air is blown
by means of the centrifugal blower indicated by
36, through wind pipe 31 and by-pass opening
38. Part of the air flows directly into the ?re
box with the oil spray, and the remainder is by
passed through the preheating conduit section
!9 to the nozzle 26 located inside of the recircu
lation tube w2|. In this arrangement all of the
air for combustion is supplied through the blower 10
36. The proportion of air entering the ?re-box
through the nozzle-like restriction 43 is here
again increased as the temperature and there
fore the volume of the air passing through the
preheater "conduit section l9 increases.
Various types of control devices and ignition
means, all well known in the art, may be em
ployed in connection with my apparatus; separate
high-pressure air-pumping means, such as 25 in
Fig. 3, may be employed for supplying air to the 20
nozzle in the recirculation tube; and still other
means for preparing fuel for combustion may be
used in combination with my recirculation equip
ment; all without departing from the spirit of my
Where the expression “spray-nozzle” is used in
the claims, it will be understood to mean the ter
minal part of a conduit having an ori?ce through
which, or by means of which, ?nely divided par
ticles of fuel are projected into the ?re-box. The 30
spray-nozzle mayor may not discharge another
fluid such as air simultaneously with the fuel.
The term “air-nozzle” differentiates from the
“spray-nozzle” primarily through the fact that
the former discharges no fuel but does discharge 35
a jet of air for creating turbulence in the ?re-box
or combustion chamber.
What I claim, and desire to secure by Letters
Patent, is:
1. In an oil—burning apparatus, the combina 40
tion of a ?re-box, a target against which imping
ing gases are mixed in the ?re-box, a liquid-fuel
spray-nozzle, means supplying liquid fuel to the
spray-nozzle, the spray-nozzle being directed to
ward the target, a gas recirculation tube, said 45
tube having openings formed therein communi
cating with the ?re»box, one of said openings be
ing directed toward the target, an air nozzle, and
means supplying air under pressure to the air
nozzle, the air-nozzle being so positioned as to 50
discharge a jet of air through the tube toward the
target whereby gases from the ?re-box are also
impelled through the tube against the target.
2. In an oil-burning apparatus, the combina
tion of a ?re-box, a target in the ?re-box, a liquid
fuel spray-nozzle, means supplying liquid fuel
to the spray-nozzle, the spray-nozzle being di
rected toward the target, a gas recirculation tube,
said tube having openings formed therein com
municating with the ?re-box, one of said open 60
ings being directed toward the target, an air
nozzle, so positioned as to discharge a jet of air
through the tube toward the target, an air-heat
ing conduit in the ?re-box communicating with
the air-nozzle, and means supplying air under 65
pressure to both the air-heating conduit and the
fuel spray-nozzle whereby hot air is delivered
through the air-nozzle and cooler air is delivered
simultaneously with the liquid fuel through the
70 through port 26 if desired. In this arrangement “liquid fuel spray-nozzle.
oil under high pressure is supplied (by oil-pres
sure means not shown) through conduit 40 to
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