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Патент USA US2404676

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July 23, 1946.
' Filed Oct. 8, 1942
Patented July 23, lhd?
2,404,67 6
Lynn A. Williams, J12, North?eld, 111., assignor
to Stewart-Warner Corporation, Chicago, 111.,
a corporation of Virginia
Application October 8, 1942, Serial No.*461,‘261
1 Claim. (Cl. 126—116)
My invention relates to heating apparatus and
is more particularly ‘concerned with, but ‘is not
limited to, heaters of the internal combustion type
The heating apparatus ‘illustrated in the draw
ing is an internal combustion type ‘of heater in
corporating a typical embodiment of my inven
especially adapted for use in aircraft.
tion. This heater has a combustion chamber ll]
In heaters of the internal combustion type, it 5 located in ‘one end of a ‘tubular heat transfer
is ‘common to provide ?nned transfer means for
means or heat exchanger l2 and supplying hot
transferring heat ‘from ‘the products of combus
products of combustion to this heat exchanger.
tion to ventilating air directed over the heat
A carburetor M has an open end 'I 6 receiving com
transfer means by a ram ‘or blower or other suit
busti'on air from the heater inlet 13, which is
able air circulating means. The heated products 10 adapted to be connected to a ram, blower, or other
of combustion are originally directed against the
air circulating ‘means. The air entering the car
?ns at one end of the heat transfer means.
buretor M is mixed with fuel supplied through a
Where the hot products of combustion ?rst come
pipe ‘2% having outlet openings 22 located ‘at the
in contact-with these ?ns, they are raised to a
throat '24 of the carburetor Iii. The combustible
temperature which is much in excess of the tema
mixture formed in the carburetor I4 is delivered
peratures of other portions of the ?ns and par
to the combustion chamber l9 through a burner
ticularly of that portion adjacent the outlet end
tube '28 which is designed to give the combusti
of the heater. There is a practical limit to the
ble mixture 2. whirling motion as it enters the
temperature to which the ?ns can be heated and
combustion chamber.
since the hottest portions of the ?ns can not be 20 The combustion chamber H] is provided with
operated above this temperature limit, the total
one or more electrical igniters 28 for initially ig
heat output of the heater is materially reduced
niting the combustible mixture supplied to this
where large portions of these ?ns are operated at
chamber. It will be understood by those skilled
a temperature materially below the practical
in the art that the igniters ‘28 are connected to a
25 suitable source of electrical energy through a
An object of my invention is to provide heating
thermostatic switch which is responsive to the
apparatus of the internal combustion type in
temperature of the heater and serves to discon
which local hot spots are eliminated and the heat
neat these igniters from their source of current
transfer means is heated to substantially uniform
when the heater attains normal operating tem
temperature throughout its length.
30 perature. A re-igniter 30 is provided to insure
Another object of my invention is to provide
continued burning of the combustible mixture
heating-apparatus wherein the temperature range
supplied to the combustion chamber after the
between different parts ‘of the heat transfer
igniters 2?. have ceased to function.
means is reduced to a minimum and stresses and
The tubular heat exchanger i2 is made of thin
strains caused by great variations in the temper
sheet metal, such, for example, as stainless steel,
ature of different portions of the heat transfer
and has hollow ?ns 32 extending longitudinally
means are avoided.
thereof. The ends of the ?ns are sealed and the
Another object of my invention is to increase
interiors of these hollow ?ns constitute gas pas
the efficiency of the heating apparatus by main
sages 3i for the hot products of combustion sup
taining all portions of the heat transfer means 40 plied by the combustion chamber ll! to the inlet
at substantially the practical temperature limit.
ends of these passages adjacent the combustion
Another object of my invention is to provide
chamber. The hollow ?ns 32 are provided with
new and improved heating apparatus which is
bases .35 and portions of these bases surround
extremely light in weight and ‘compact and has a
and closely engage the sheet metal shell 38 of a
high heat output.
45 muliler it which is ?lled with sound absorbing
Another object of my invention is to provide
such as glass wool or stainless steel
new and improved heat transfer means.
wool. The shell 38 is provided with a plurality
Other object and advantages will become ap
of openings ‘M which form ~acoustic couplings be
parent as the description proceeds.
tween the interior of the mulller shell and the gas
In the drawing:
passages 34, whereby sound may enter the mu?ler
Fig. l is a view showing a longitudinal section
shell and be absorbed by the glass wool or other
through heating apparatus embodying my inven
tion; and
material therein.
The mu?‘ler 40 has a tapered end 46 which is
Fig. 2 is a transverse, sectional view taken on
covered by a rounded cap or nose 48 located ad
the line 2-2 of Fig. 1 and showing part of my 55 jacent the combustion chamber ID. A space 50
novel heat transfer means in enlarged section.
located between the cap ‘48 and the adjacent end
ing has a cylindrical part which closely ' sur-
of the muffler shell serves as a heat insulator
rounds the heat exchanger [2 and cooperates
therewith to form ventilating air passages be
to protect the sound absorbing material from the
more intense heat created in the combustion
chamber. The cap 48 is preferably of heat re
tween and around the hollow ?ns 32. The ven
tilating air ?owing through these passages ab
sisting metal and is welded or otherwise attached
to the end of the muffler shell.
,The hot products of combustion formed in the
combustion chamber 18 flow from the open left
sorbs heat from the hollow ?ns 32 and the aux
iliary ?ns 54 and the heated ventilating air is
discharged from the lefthand end of the casing
66 into the air craft cabin, or other space to be
hand end of this chamber around the tapered end
of the mu?ier and into the gas passages 34 in the 10 heated, or into a system of ducts for conducting
this heated air to variously located outlets.
hollow ?ns. The annular wall 52 of the combus
When the heater is in operation, the auxiliary
tion chamber is illustrated as being spaced from
?ns 54 conduct heat away from the adjacent por
the bases of the ?ns and this arrangement and
tions of the bases 36 of the hollow ?ns with su?i
the tapered end of the mu?ier permit these gases
to ?rst contact the heat exchanger l2 over an
cient rapidity to maintain these portions of the '
appreciable portion of its length. By thus creat
bases at substantially the same temperature as
other portions of the heat exchanger. In other
words, the entire heat exchanger is maintained
at substantially the same temperature during
heater operation. Since this temperature may be
the practical temperature limit at which the heat
exchanger can be maintained, the heat output
of my novel heater may be'the maximum pos
sible for the materials used. This provides a light
r and compact heater of high output and wherein
ing a relatively large area over which the hot
products of combustion ?rst establish contact
with the heat exchanger, the creation of intense
v1y heated local hot spots in the heat exchanger,
and more particularly inthe bases of the hollow
‘?ns, is avoided. Even with this arrangement,
.however, those portions of the ?n bases with
which the hot products of combustion ?rst come
in contact, would be heated to a higher ‘temper
ature than the rest of the heat exchanger, un
durability and long life are insured by the ab
sence of stresses and strainsresulting from sub
stantial temperature variations in the heat ex
‘ less special means is provided to carry off more
rapidly heat from these portions of the ?nned
bases. My invention lies in the provision of such
special means.
changer. Such a heater isrparti'cularly adapted
for, but not limited to, use in aircraft.
My novel means for reducing the temperature ‘
'While my novel heat exchanger with its auxil
iary ?ns at one end thereof is particularly adapt;
of these portions of the ?n bases which are ?rst
contacted by the hot products of combustion is
ed for use in a heater of the internal combustion
best illustrated in Fig, 2. This means comprises
type, this heat exchanger is not limited to such]
the provision of auxiliary fins‘ 5!! located‘ between
the hollow ?ns 32 and extending only through
Under some circumstances, ‘my new and
improved heat exchanger is particularly advan
"out that portion of the heat exchanger which is
?rst contacted by the hot products of combustion
from the combustion chamber It. The auxiliary
?ns 54 are illustrated as being formed of sheet .
metal and as being of T-shape in cross section.
The heads 55 of the ?ns 54 extend lengthwise
tageous in connection with exhaust heaters where .
the hot exhaust gases are delivered to one end
of the heat exchanger. and tend to raise the tem
perature of the ?n bases adjacent this end above
the temperature of other portions of the heat ex
changer. My invention is also not limited to the
details herein shown and described, but may as
. of the bases 35 of the hollow ?ns and are se
. curedlthereto by welding,rsilver soldering, or in.
surnenumerous other forms and my invention is
any other suitable manner so that theheads 55 i, -to be construed as including all variations and
are in intimate, heat-conducting contact with
modi?cations falling within the scope of the ap
these bases 36. Large quantities of heat absorbed
pended claim.
* by the bases 36 of the hollow ?ns are transmitted
to the auxiliary ?ns 54, which dissipate this heat
to the ventilating air and thus reduce the operat- ,
A heating ‘apparatus of the class described,
comprising in combination a heat exchange mem
. ing temperature of the ?n bases where these
Ibases are ?rst contacted by the hot products of
combustion. The auxiliary ?ns 513 may be made
‘of any suitable length, but I have found that en-_
ber formed of thin sheet metal and having deep
‘ longitudinally extending corrugations in its w .1
providing outwardly projecting hollow ?ns In
spaced relation to each other about said member,
Vmeans forming a combustion chamber at the rear
end of said heat exchange member adapted to
supply hot gases to the interior of said member
and said ?ns, a backwardly tapered mui?er in
said heat exchange member serving to close the
inner faces of the ?ns through a substantial por
tion of their length at their forward portions,
tirely satisfactory results are obtained where '
these auxiliary ?ns are substantially co-extensive
with that portion of the heat exchanger which is
?rst contacted by the hot products of combus
The lefthand end of the heat exchanger [2 is
closed by a plate 58 supporting an outlet ?tting
50. The hot products of combustion give up their
outwardly projecting auxiliary ?ns in the form
:heat to the heat exchanger 12, as they ?ow
Solid metal plates secured in position in the.
lengthwise of the passages 34 in the hollow ?ns,.
and the cooled gases then flow from the lefthand 65 spaces between said ?ns by means of ?ange por
tions turned at an angle to the ?ns and in snug
ends of the passages 34 into an outlet chamber
engagement with the outer faces of the wall por
62 ‘formed between the plate 58 andthe adja
tions between said ?rst named ?ns and extending
cent‘ end of the muffler 40. These gases are dis
charged through the outlet ?tting 60 and pass
‘longitudinally adjacent the tapered portion of
to atmosphere through any suitable exhaust pipe 70 said muffler, and means for feeding ventilating air
attached to the threaded end 64 of the'outlet
through the spaces between said ?ns for heating
said ventilating air and for protecting the ?ns
- The heat transfer means l2, carburetor I4, and
‘ adjacent parts are enclosed within a sheet metal
casing 66 connected to the air inlet I8. The cas
from burning out.
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