US2425630A

US2425630A - Internal-combustion airplane heater

Info

Publication number: US2425630A
Application number: US436090A
Authority: US
Inventors: Mccollum Thelma
Original assignee: Stewart Warner Corp
Current assignee: Stewart Warner Corp
Priority date: 1942-03-25
Filing date: 1942-03-25
Publication date: 1947-08-12
Anticipated expiration: 1964-08-12

Description

H. J. DE N. M COLLUM INTERNAL-COMBUSTION AIRPLANE HEATER Filed Mal ch 25, 1942 4 Sheets-Sheet 1 y l I 6 Aug. 12, 1947.

Aug. 12, 1947. H. J. DE N. M coLLuM INTERNAL-COMBUSTION AIRPLANE HEATER 4 Sheets-Sheet 2 Filed March 25, 1942 wzz zzzrcazzaa 4 Sheets-Sheet 3 Z JJ H. J. DE N. MOCOLLUM INTERNAL-COMBUSTION AIRPLANE HEATER Filed March 25, 1942 Aug. 12, 1947.

Aug Q12, 1947. v J. DE N. MpCOLLU 2,425,630

INTBRN AL-COIBUSTION AIRPLANE HEATER riled larch 25, 1942 lamas-sheet 4 Patented Aug. 12, 1947 IN TERNAL-COMBUSTION AIRPLANE HEATER Henry J. De N. McCollum, Chicago, Ill.; Thelma McCollum, executrix of said Henry J. De N. McCollum, deceased, assignor to Stewart-Warner Corporation, Chicago, 111., a corporation of Virginia Application March 25, 1942, Serial No. 436,090

8 Claims. 1

My invention relates generally to heating apparatus and more particularly to heating apparatus of the liquid fuel internal combustion type adapted for use in airplanes.

An object of my invention is to provide an improved internal combustion heater that burns vaporized liquid fuel in an enclosed space, that delivers an amount of heat adequate for large airplanes, that is simple in construction, light, in weight, safe and reliable in operation, and which requires a minimum of attention.

A further object of the present invention is to provide an internal combustion type airplane heater that is operable throughout a wide altitude range without supercharging means.

Still another object of the present invention is to provide an internal combustion heater using liquid fuel in which the combustible mixture is kept within a comparatively small zone, under all conditions, thus preventing burning of fuel elsewhere than in a combustion chamber provided specifically for this purpose.

Yet another object of the present invention is to provide an internal combustion heater of improved type in which a temporary failure of the fuel to ignite within the combustion chamber will not result in the heat exchanger becoming filled with a combustible mixture.

A further object is to provide an improved internal combustion heater for airplanes and the like which will deliver a large volume of air heated to a desired temperature under substantially all conditions of airplane operation.

Yet another object of the present invention is to provide a novel and improved arrangement for deicing the wings and control surfaces of aircraft.

Yet another object of the present invention is to provide a novel and improved internal combustion heater adapted for use in airplanes which accomplishes the above objectives and which requires no connection to an airplane engine induction system and no connection to other specific pressure producing means.

Still another object of the present invention is to provide an improved heater of the above type in which the air to be heated is maintained at a positive pressure above the pressure existing interiorly of the combustion chamber and related passages, thereby preventing the products of combustion from mixing with the air being heated in the event of leaks developing in the system.

Other objects will appear from the following description, reference being had to the accompanying drawings, in which a 1 Fig. 2 is a vertical transverse sectional view taken in the direction of the arrows substantially along the line 22 of Fig. 1;

Fig. 3 is a vertical transverse sectional view taken in the direction of the arrows substantially along the line 33 of Fig. 1;

Fig. 4 is a somewhat diagrammatic longitudinal sectional view of a portion of an alternative form of heater embodying the present invention;

Fig. 5 is a diagrammatic representation of the heater shown in Fig. 4 drawn to smaller scale and showing the disposition of the heater within an airplane Wing;

Fig. 6 is a vertical transverse sectional view taken in the direction of the arrows substantially along the line 66 of Fig. 4;

Fig. 7 is a plan view of an airplane wing with the leading edge portion thereof shown in section, illustrating a deicing system embodying features of the present invention;

Fig. 8 is a view similar to Fig. 7 but illustrating an alternative deicing system embodying features of the present invention;

Fig. 9 is a side view of an airplane empennage with a portion of the surface thereof broken away to show a deicing system embodying the present invention incorporated therein; and

Fig. 10 is a generally vertical sectional view taken in the direction of the arrows substantially.

along the line l0l0 of Fig. 9. I

Fig. 11 and Fig. .12 are diagrammaticvv views illustrating one type of aspirating means which may be considered as connected to the end of casing illustrated in Fig. 5.

In the past, most efforts to heat airplane cabins usually consisted essentially of a simple heat exchanger in which heat was transferred from the engine exhaust to the air to be heated, or in some instances, the airplane engine exhaust has been used to produce steam, the steam in turn being used to heat the air in the cabin. It will be appreciated that the first of these systems has the inherentfdisadvantage that any failure of the heat exchanger will permit engine exhaust gases, including carbon monoxide, to leak into the cabin fresh air induction system and even though the presence of carbon monoxide within the cabin may not be sufficient to produce insensibility, it nevertheless greatly reduces the efficiency. of the airplane occupants. In all aircraft, and in milil tary aircraft especially, this danger is a, serious disadvantage since a moments inattention on the part of the crew may be disastrous.

The second of these prior used systems overcomes the above mentioned disadvantage, but is expensive to manufacture, requires complicated' and easily dislocated control mechanism, and is heavy, thus reducing the useful load of the airplane considerably. Both of these systems have I.

the inherent disadvantage that useful quantities of heat are produced only when the engines are operating at a comparatively high power output.

Thus, substantially no heat is produced while the airplane is gliding or otherwise maneuvering with the engine operating at a reduced throttle setting The airplane heater of thepresent invention supplies an adequate amount of pure air heated to the proper temperature, and the quantity and carbureter 38 fed from a fuel supply, not shown but from which the fuel passes to the carbureter 38 through a pipe Q9. The balanced carbureter has an outlet tube 42 located below the fuel surface which leads to an orifice or jet as within a Venturi throat 46, while a similar orifice 48 temperature is unaffected by the changes in the operation of the airplane engine; furthenthese factors are affected only to a minor degree by the airplane speed. It require no complicated controls, is extremely light in weight and the products of combustion'cannot leak into the cabin fresh air induction system, since the pressure maintained inthe combustion chamber and within the heatexchange system is less than that in the fresh air induction system, therefore, any leaks developing in the heat exchanger will result in fresh air leaking into the heat exchanger and mixing with the products of combustion, rather than in the products of combustion leaking outwardly into thefresh air system.

In Fig. 1 of the drawings, I have shown the leading edge portion of an airplane wing indicated generally by the numeral 20. The airplane heater is housed within this wing and comprises a heater induction pipe 22 having an opening 24, at the leading edge of the wing which faces the air stream. A ramming effect is, therefore, produced at the mouth of the pipe 22. This heater induction pipe extends inwardly a hort distance and then curves at right angles and extends generally parallel tothe leading edge of the, wing and is connected at its opposite end to a heat exchanger 26 having a plurality of heat exchange tubes 28. These tubes are equipped with heat radiating fins 30, and at their oppositeends are connected to an exhaust pipe 32 which extends rearwardly through the wing and opens therebeneath in a rearward direction, so that air moving past the opening produces an aspirating effect which maintain the pressure within the heat exchange tubes 28 below that of the surrounding atmosphere. 7 v

The heat exchange portion comprising the tubes 28 and fins 36 is located'within a fresh air induction pipe 34 which also has its open end at the leading edge of the wing facing in the direction of flight so that a ramming effect is produced. The fresh air pipe extends rearwardly and encloses the heat exchanger previously mentioned, and has its opposite end connected to the space to be heated in the cabin. Since the air within the cabin is maintained at substantially atmospheric pressure, or perhaps slightly thereabove, because of the ramming effect at the mouth of the tube 34, it will be appreciated that the heat exchange tubes 28 are surrounded by a pressure greater than that in the interior of these tubes. Thus any leakage developing in these tubes will be accompanied by a flow of air inwardly through the tube walls rather than outwardly. I

The heat producing portion of the apparatus,

indicated generally by the numeral 35, is located I somewhat smaller than the pipe '22 within which within the Venturi faces in the direction of the inflowing air and i connected to a tube 5!! which leads. to the. carbureter 38 and is connected to the bowl thereof above the liquid level therein.

TheVenturi throat 45 is formed within a heater induction tube 52, which at its outlet end is closed by a generally conical plug 54. This plug tends to cause the air flowing through the tube to move radially outwardly through radial ports 5'6 formed by punching veins 58 inwardly from the side walls of the tube, as may best be seen in Fig. 3. The combustible mixture flowing through these ports, therefore, has a swirling motion. as it passes outwardly into a surrounding cylindrical combustion chamber 60. r

The combustion chamber in diameter is some? what greater than the induction tube 52, but

made from a high-chromium nickel alloy, such I as Inconel, for instance. 7

The fuel passing into the combustion chamber 60 is adapted to be ignited by an electrical resistance wire igniter BB suitably secured in an igniter housing 68 threaded into the side wall of the combustion chamber. The igniter and housing are preferably of the construction more fully disclosed and claimed, in my prior Patent No. 2,191,178. This igniter is controlled by a bulb type thermostatlfl having its bulb located in a position between the combustion chamber 66 and the heat exchanger 25, the thermostat being connected in a circuit including a source of electrical energy 12 and an on and off switch hi, Thus when the switch M is closed,'the resistance wire of the igniter will be energizedproviding the bulb i0 is cool. After the combustible mixture has been ignited, and an operating temperature has been reached, the thermostat 10 will open the circuit tothe igniter, thus deenergizing the latter.

Since the claim within the combustion chamber may become extinguished, a re-igniter i6 is provided for re-igniting the combustible mixture, thus making it unnecessary for the system to cool sufficiently to bring the thermostat. it! into operation to reenergize the igniter resistance wire 66. This re-igniter, maybe of the type shown in my copending application Serial N 0. 410,039, filed September 8, l94l, for Liquid fuel combustion apparatusand' is comprised of a spirally coiled sheet 18, preferablyof a nickel chromium "alloy, such as Inconel or Nichrome-V, for instance, either of which is highly resistant'to the. deteriorating effects of gth e hot produc,ts of combustion present in the combustion chamber. The spirally coiled sheet 18 is located in a central position within the combustion chamber (HI and maybe attached; directly to the end of the induction tube 52 by welding its outer coil thereto. During combustion within the combustion chamber, the re-igniter coil is heated to a high temperature, and in the event that the flame becomes extinguished, combustible mixture passing into the spirally shaped pocket between the convolutions of the coil will become heated sufficiently to re-ignite the mixture. The convolutions of the coil 18 should be so oriented relativeto the swirling effect produced upon the combustible mixture by theradial ports 56 that the inertia of the rotating gases will tend to carry them inwardly between the convolutions of the coil.

Although it is not critical, the annular space between the outer walls of the combustion chamber and the heater air induction pipe 22 is of such size that approximately twice as much air flows through this annular space as flows-through the combustion chamber. With this arrangement, the combustible mixture or products of combustion passing from the combustion chamber will be quickly mixed with the fresh air flowing through the annular space 62. Any combustible mixture is, therefore, diluted below the lower critical limit at which it will burn. Therefore, combustion is impossible outside of the combustion chamber regardless of whether or not combustion takes place within the combustion chamber. One important result brought about by this feature is that if the combustible mixture within the combustion chamber should not become immediately ignited, or if combustion should fail for some reason, the unburned combustible mixture passing from the combustion chamber will have sufficient additional air added thereto, so that subsequent ignition of the combustible mixture within the combustion chamber will not cause an explosionor burning in the heat exchanger or exhaust pipe 32. The arrangement, therefore, provides an inherent safety factor which makes it impossible for burning to take place anywhere outside of the combustion chamber.

An additional advantage of this construction is that the hot products of combustion from the combustion chamber are quickly diluted with additional cool air, thus reducing the temperature and increasing the volume of hot gases passing through the heat exchanger. The fact that the gases passing through the heat exchanger are thereby considerably tempered, makes it possible to make the heat exchanger of lighter metals than would otherwise be possible. It also makes it possible to form the heat exchanger of thinner metals since the tempered and diluted products of combustion have less corrosive effect upon the heat exchanger than would more concentrated products of combustion at a higher temperature.

In Figs. 4, 5 and 6, I have shown a modification of the heater illustrated in Fig. 1. This alternative form is extremely simple to construct and extremely light in weight. Its longitudinal dimension is somewhat greater than the embodiment shown in Fig. 1, but in installations where a sufficiently long space is available, it is generally to be preferred over the arrangement shown in Fig. 1, because of its greater lightness and simplicity.

The combustion apparatus may be identical with that shown in Fig. 1 and, therefore, no additional description of this mechanism is needed here. The combustion apparatus is surrounded by a pipe 80 imilar to the heater air induction pipe 22. This pipe is of considerable length and may be made of comparatively light gauge aluminum tubing. The major portion of this tubing beyond the exit end of the combustion chamber is provided with longitudinally extending creases or corrugations 82, thus providing considerable heat exchange surface in an extremely simple manner. These corrugations also greatly stiffen the tube and, therefore, have a structural advantage. The heat exchange tube, the length and size of which will be determined very largely by the heating capacity of the heater, extends a considerable distance from the combustion chamber, and at its outer end is connected to an aspirating vent 83 which may, if desired, be located at the under surface of the wing near its trailing edge. As in the embodiment shown in Fig. 1, this aspirating vent should preferably maintain the interior of the heat exchange tube below atmospheric pressure.

An air intake pipe 84 has its inlet end at an opening 86 at the leading edge of the wing or other forwardly facing aircraft surface, so as to provide a ramming efiect within the pipe 84. This pipe axially surrounds the tube including the heat exchange corrugations 82 for substantially the entire length of the corrugations. Near the outlet end of the corrugated portion the pipe 84 is closed around the corrugations and is connected to a hot air pipe 88 leading to the aircraft fuselage.

In this device, the ramming effect at the opening 86 forces air thereinto somewhat above atmospheric pressure. This air is divided so that approximately twice as much flows around the combustion chamber 60 inside the pipe 80 as flows through the induction tube 52. The gas mixture, therefore, passing into the corrugated heat exchange portion is too lean to burn, regardless of whether or not combustion has taken place within the combustion chamber 60. The annular space between the pipe 84 and the pipe 80 is such that approximately four and one-half times as much air flows through this annular space as flows through the interior of the tube 89, including that which flows through the induction tube 52. The above proportions are given as examples only, it being understood that they are not critical.

It will be seen that the alternative heater shown in. Figs. 4, 5 and 6 is in general similar to that shown in Fig. 1. The heat exchanger however is different, and only one air intake openingis used instead of two. It will be seen further that the arrangement shown in Figs. 4, 5 and 6 is extremely simple to fabricate and can be extremely light in weight inasmuch as, with the exception of the burner, it can be constructed almost entirely of comparatively thin walled aluminum tubing. Like the apparatus shown in Fig. 1, the embodiment shown in Figs. 4, 5 and 6 is inherently incapable of supplying a combustible mixture beyond the end of the combustion chamber, thus preventing burning within the corrugated tube 82. It will be appreciated further that with the exception of the carbureter 38 and the thermostat l0, neither of these heaters requires any moving parts. Although in the interest of simplicity of illustration it is not shown in Fig. 4, the carbureter and jet arrangement and the thermostatically controlled heater energizing circuit shown in Fig. 1 will normally be used with the apparatus shown in Figs. 4, 5 and 6.

In modern high flying aircraft, particularly military. aircraft, great difficulty is experienced tube.

with mechanism located within the wings'becatise of the extremely low temperatures encountered. At these low temperatures machine guns and other apparatus having moving mechanism usually refuse to operate unless heated. For this reason electric heaters are frequently included where heat is needed within the wings. However, with a heater embodying the present invention, branch pipes can be connected to the main hot air pipe so as to divert a portion of the hot air to the machine guns and other mechanisgn that should desirably be heated. These branch pipes will add extremely little to the weight of the aircraft and in some instances will involve nothing more than the formation of a small opening in the side wall of the main heater pipe opposite the device to be heated.

In Fig. 7, I have shown an aircraft wing deicer embodying features of the present invention. This deicer comprises a tube 90 which extends substantiall the length of the wing in a position closely adjacent to the leading edge. This tube may be tapered as Shown so that its diameter adjacent the fuselage is somewhat greater than its diameter at the wing tip. At the wing tip the end of this tube is closed, while the side wall of the tube facing th leading edge of the wing is provided with a plurality of perforations 92, so arranged that air flowing into the tube 90 will be forced out through these perforations against the inside leading edge portion of the wing. The inner end of the tube 90 is connected to a forwardly facing opening 94 in the leading edge of the wing so that a ramming effect will be produced at this opening to force air into the Air, therefore, flows into the opening 94, into the tube 90, out of the openings 92 against the leading edge of the wing, and thence rearwardly within the wingand passes outwardly through a plurality of vents 96 located in the lower surface of the wing and pointed in a rearward direction so that an aspirating effect is I produced at these vents.

Closely adjacent the opening 94, the inner portion of the tube 90 is connected to the outlet end of an internal combustion heater burner 98, generally similar to the burner shown in Figs. 1 and 4. In general, the burner 98 includes a combustion chamber, an igniter in the side wall thereof, a re-igniter, an induction tube having fuel jets therein and a balanced carbureter, all of the type shown in Figs. 1 and 4. The inlet end of this heater can be connected to an air ram, or if preferred, it can be connected to the outlet end of a small blower I having an inlet opening I02 near the inner end of the leading edge of the wing.

The operation of this deicer is as follows:

When the aircraft enters an icing zone and the ice begins to collect upon the leading edge of the wings, the pilot energizes the igniter in the side wall of the heater and the motor which drives the blower I00. The blower forces air through the induction tube of the heater, thus forming a combustible mixture which burns within the combustion chamber. The hot products of combustion flow from the combustion chamber into the tube 90 near its inlet end and are quickly mixed with air flowing into the opening 94. They are thus considerably diluted and reduced in temperature and the warm mixture thus produced passes into the tube 90 and outwardly through the openings 92 into contact with the leading edge of the wing. It thus quickly raises the temperature of the a leading edge of the wing sufficiently to melt ice formed thereon, or alternatively it raises the temperature of the 'wing sufficiently so that ice cannot be formed thereon. The hot 'air after this is advisable will depend largely upon the fuel used and, therefore, the chemical composition of the products of combustion, and upon the interior structure of thewing and the mechanism located therein. Under those circumstances where it is not desirable toper'niit these products of combustion to circulate freely within the'i'nterior of the wing, the alternative structure shown in Fig. 8 may be used. This is essentially similar to the arrangement shownin Fig. 7, excepting that the tube '90 is not perforated and is placed in intimate heat transfer relation to the leading edge portion of the wing. It mayin fact serve as one of the wing leading edge structural members, if desired, The outer end of this tube is connected to a tail pipe I04 which extends rearwardly and exhausts the products of combustion directly to the atmosphere.- With this arrangement the products of combustion heat the tube which transfers its heat directly to the leading edge of the wing, while the products of combustion flow outwardly to the atmosphere without coming into contact with the interior structure of the wing. I 1

Although not specifically shown in the drawings, it will be appreciated that instead of using an inlet opening94 leading to the tube 90 and a separate inlet opening I02 and blower I00 for supplying air to the heater, the arrangement shown in Figs. 1 and 4; may be used, that is, a single ramming opening can be used for supplying air to the tube 90; and the heater can belocated within the tube 90 so as to receive a portion of the air passing inwardly through the opening 94.

Figs. 9 and '10 illustrate the invention shown in Figs. 7 and 8 adapted for use in deicing the tail surfaces of the aircraft. In this arrangement the vertical stabilizer I06 of the aircraft has an opening I08 near its upper extremity facing in a forwardly direction, which acts as an air ram. Air flowing into the opening I08 passes downwardly through a tube 0 located adjacent the leading edge of the wing and provided with forwardly faced perforations II 2, similar to those shown in Fig. 7. These perforations cause air flowing into the opening I08 to be forced against the leading edge of the vertical stabilizer. The lower end of the pipe H2 is connected to a transversely extending pipe II 4 which is located within the horizontal stabilizer H6 in a position closely adjacent its leading edge. The tube II4 likewise is provided with perforations II8 which force air into contact with the leading edge 0 the horizontal stabilizer, I

The trailing edge of the horizontal stabilizer I I6 and the trailing edge of the vertical stabilizer I06 are provided with a plurality of vents I20 which have an aspirating effect, and permit the air flowing into the interior of the stabilizers to be exhausted to the atmosphere. An internal combustion heater I22 of the type shown in Figs. 1 and 4 is located within the pipe IIO in .a position slightly below the opening I08. Thus air flowing into the opening "38 passes downwardly through the heater, thus producing a combustible mixture which burns within the combustion chamber, while a portion of the cool air flows around the heater and dilutes the products of combustion before the gases pass downwardly and out of the openings I I2 and l I8.

Preferably, a battle 324 extends inside the vertical stabilizer from a position at the top thereof, downwardly behind the tube Hi] to a position below the heater I22, and thence forwardly to the leading edge of the stabilizer. Just above the portion of the baflle in contact with the leading edge of the stabilizer, the tube H9 is provided with an opening I26 somewhat larger than the perforations H2. Thus a portion of the heated air will pass outwardly through the opening I25 and will flow upwardly to the top of the vertical stabilizer and out of an aspi'rating'opening I28 at the upper end of the vertical stabilizer. The reason for providing the bafile I24 and openings I25 and I28 is that this arrangement insures hot air circulating upwardly, so as to heat the portion of the fin above the heater I22, thus maintaining the entire fin in an ice-free condition.

If desired, the arrangement shown in Figs. 9 and 10 can be modified in the same manner-that the arrangement shown in Fig. '7 is modified in the alternative embodiment shown in Fig. 8. That is, the tubes H and I M can be provided without perforations and can be placed directly in heat transfer relation with the leading edge surfaces of the vertical and horizontal stabilizers. In. the event that this arrangement is used, the ends of the tube H4 located within the horizontal stabilizer should be connected to the atmosphere.

All of the heaters and defroste-rs I have shown and described depend for their normal operation upon movement of the aircraft, but if ground heating is desired, this can be accomplished by connecting the outlet of a blower to the ram openings, thus providing the necessary air movement through the several systems.

While I have shown and described particular forms of my invention, it will be apparent to those skilled in the art that numerous modifications and variations may be made in the particular constructions disclosed without departing from the underlying principles of the invention, I, therefore, desire by the following claims to include within the scope of my invention all such variations and modifications by which substantially the results of my invention may be obtained by the use of substantially the same or equivalent means.

I claim:

1. An internal combustion airplane heater comprising a conduit, a casing within said conduit in spaced relation to the wall thereof, means comprising an air ram to produce a pressure differential within said conduit and casing to cause a flow of air through said casing andbetween the casing and said conduit, means in said casing forming a combustion chamber spaced from the walls of said casing and opening into a mixing chamber, an induction tube connected to said combustion chamber, means to produce a pressure differential through said induction tube and combustion chamber, said combustion chamber having an outlet for products of combustion. emptying into said mixing chamber, means to produce a combustible mixture for induction into said combustion chamben means to ignite said mixture within said combustion chamber, said mixing chamber adapted to receive air flowing 10 through said casin and products of combustion from said combustion chamber, and the air flow through said casing being discharged into said mixing chamber in sufiicient quantity to dilute any combustible mixture flowing from said combustion chamber sufilciently to prevent subsequent combustion thereof.

2. The combination set forth in claim 1, in which the heater is located in the wing of the airplane, and in which the pressure differential producing means comprises a ram in the air stream at the leading edge of the wing and connected to an inlet opening in said casing, and an aspirating means in the air stream at the trailing edge of the wing and connected to an outlet opening of said casing.

3. In. an internal combustion airplane heater locatedin the airplane wing, a ram constituted by an opening in the leading edge of said wing, a conduit connected to said ram and to the space to be heated, a long narrow casing located within said conduit and having its inlet opening facing in the direction of said ram, aspirating means connected to the opposite end of said casing, said aspirating means being constituted by an opening in the trailing edge of the wing, said casing near its inlet end providing a housing for a combustion chamber, a combustion chamber having inlet and outlet openings located within said housing and spaced from the walls thereof, a portion of said casing adjacent the outlet opening of said combustion chamber providing a mixing Chamber and substantially the entire remaining portion of said casing providing a heat exchange surface, .means to supply a combustible mixture to said combustion chamber, means to ignite said combustible mixture in said combustionchamber, said conduit being so proportioned in size and shape relative to said casing that the major portion of 'the air entering said ram flows between said conduit and said casing, said combustion chamber and said casing being so proportioned in size and shape that a portion of the air passing through said casing bypasses said combustion chamber in sufficient quantity to dilute any combustible mixture flowing from said combustion chamber enough to prevent subsequent combustion thereof and that under dynamic conditions the pressure within said casing is less than the pressure between said casing and said conduit.

4. The combination set forth in claim 3, in which the casing comprises a length of tubing of substantially full diameter throughout the portion forming the housing for the combustion chamber and the mixing chamber and in which the heat exchange portion is corrugated longitudinally to increase its stiffness and, heat transfer area.

5. In an internal combustion airplane heater, a conduit connected at one end to the space to be heated and at its opposite end to an air pressure producing means, a long narrow casing located within said conduit and having its inlet opening facing in the direction of said pressure producin means, suction producing means connected to the opposite end of said casing, means for partially obstructing the inlet opening of said casing so that under dynamic conditions the pressure within said casing is less than the pressure between said casing and said conduit, means within said casing to burn a combustible mixture, means to dilute said combustible mixture adjacent said burning means and to pass said combustible mixture through the remaining portion of said casing, and a portion of said casing intween said casing and said conduit.

11 eluding heat exchange means-totransfer heat from the interionof said casing to the space he- .6.'The combination set forth in claim 5, in

which the pressure pro-ducing.means comprises .a ram in the aircstream connected'to the inlet 7. ,An internal combustion heater comprising a casing located in the wing of an airplane, means including an air ram at the leading edge of the wing and connected to an inlet opening in saidcasing to produce a pressure differential 12 from said combustion chamber and the lay-passed air, and said second. portion of air being discharged into-said'mixingchamber in suificient within said casing to cause a flow of air therethrough, a combustion chamber located within saidcasing, an induction tube connected to said combustion chamber, said induction tube having an inlet opening facing against the direction of air flow through said casing, said combustion cham er ha n an. outlet o p odu o comhustion located downstream from said induction tube in and fac g i h dire tion o air w thr u h said ca in means to rod e a com.-

tio chamb r, m ans to iezfi e'sai m u W t in aid combus ion chambe .said c mbustion chamberbei so oriented within ai asin and ofsuc si e rel ti e to the s e o a d as n t at a po tion f the ir flowin th ugh sai casin wi l b -d verted so; a to. l w in o sa d induct and ombustion hamber and hence b c 25 bustllole mixture for induction into said combus- I said easin wh le ars n p ion of the 1 quantity toolilute any combustible mixture flow from said eornbustion'charnber suflieiently to prevent subsequent r qmb tifln th a c sin having an outlet opening and suction producin means in the air stream connected to said outlet opening ofv said casing.

8, The combination. set forth in claim '7 and means forming an enclosure for said casing and means to pass air to. be heated through said enclosure inheat exchange relation to said casing.

.1]. D MQCOLLUM.

REFERENCES QI'ITED The following references are of record in the file of this patent:

V UNITED 'sTnT 's PATENTS Number Name Date 2,285,718 Isaacson June 9, 1942 2,295,177 King sept, a, 1942 1,349,668 Good Aug. 17, 1920 2,192,688 McCo1lum Mar. 5, 1940 1,938,625 Engels Dec. 12, 1933 617,482 Baetz Jan. 10, 1899 2,156,101 Willett et a1, Apr. 25, 1939 2,196,828 Hess Apr. 9, 1940 2,046,521 Mahafiey V V V July '7 1936 2,142,699 amen Jan. 3, 1939 2,187,506 Van Daam Jan. 16, 1940 2,225,775 Garrett 1; 24, 194 0 FQREIGN PATENTS Number Country Date' 261,232 7 Great Britain 'NOV. 18,1926