US2405427A

US2405427A - Heater

Info

Publication number: US2405427A
Application number: US409190A
Authority: US
Inventors: Harry B Holthouse
Original assignee: Galvin Manufacturing Corp
Current assignee: Galvin Manufacturing Corp
Priority date: 1941-09-02
Filing date: 1941-09-02
Publication date: 1946-08-06
Anticipated expiration: 1963-08-06

Description

Aug? 1946. I H. B. HOLTHOUSE 2,405,427

HEATER Filed Sept. 2, 1941 2 Sheets-Sheet 1 Patented Aug. 6, 1946 AGSAZ? HEATER Harry B. Holthouse, Chicago, IlL, assignor to Galvin Manufacturing Corporation, Chicago, 111., a corporation of Illinois I Application September 2, 1941, Serial No. 409,190

16 Claims.

This invention relates generally to heating systems and in particular to a heating system of the internal combustion type operated in conjunction with an internal combustion engine.

It is an object of this invention to provide an improved heating system.

Another object of this invention is to provide an air heater of internal combustion type assembled as a portable unit with an internal combustion engine and utilizing such engine as the sole source of power supply.

A still further object of this invention is to provide a portable air heating unit comprised of a burner of internal combustion type operatively assembled with an internal combustion engine as a source of power, which is compact and simple in design, rugged in construction, light in weight, and easily transportable from place to place to provide heat wherever it is needed.

A particular feature of this invention is found in the provision of a heater of internal combustion type operated in conjunction with an internal combustion engine, in which the exhaust gases from the engine are burned in the heater together with a vaporous air and fuel mixture prepared by utilization of the heat, from such exhaust gases.

Further objects, features and advantages of this invention will become apparent from the following description when taken in connection with the accompanying drawings in which:

Fig. 1 is a view in perspective of the complete assembly of one form of this invention with parts thereof removed and other parts shown in section for the purpose of clarity;

Fig. 2 is a fragmentary sectional view showing the fuel vaporizing means for the heating system of Fig, 1; v

Fig. 3 is a transverse sectional View as seen along the line 3--3 in Fig. 2;

Fig. 4 is a fragmentary sectional view taken along the line 4-4 in Fig. 1 showing the construction of the heater combustion chamber; and

Fig. 5 is a fragmentary plan sectional view showing a modified form of th invention.

In practicing this invention there is provided as a portable unit, an air heater of internal combustion type and an internal combustion engine which produces all of the power for operating the heater. Liquid fuel used in the heater is introduced with air into a unit which conditions or prepares the fuel for burning, the heat from the engine exhaust gases being utilized to heat the conditioning unit and vaporize the fuel for mixing together with the air, thus vaporous mixture being admitted into the heater combustion chamber with the engine exhaust gases for burning therewith. The air to be heated is circulated in a heat transfer relation with the heater combustion chamber, the entire heating system being capable of mounting as a unit on a carriage or the like so as to be readily moved from place to place.

Referring to the drawings ther is shown in Fig. 1 one form of the invention which includes an internal combustion engine having an engine block l0, an air-cooled cylinder H cooled by a fan I2, an intake manifold l3, an exhaust conduit l4 and a crank shaft It. The engine operates an air heater or burner and is assembled therewith as a complete operating unit which is capable of being mounted on a carriage or the like (not shown) so as to be easily transported to furnish heated air wherever it is necessary, as for example to heat airplane engines to facilitate their starting, or to heat tents, barracks, cabins, or the like.

The heater includes a housing comprising a longitudinally extending cylindrical portion I1 and an integrally-formed L-shaped radially extending portion I8 at one end l9 thereoL-the end I9 being closed by a cover plate 2!. The cylindrical portion ll of the heater housing en closes a cylindrical combustion chamber 22 and an air chamber 23, while a fan compartment 24 is enclosed by the housing portion is and the cover plate 2!. The combustion chamber 22 is closed at one end by a cover plate 26 and at its opposite end by a cup-shaped member 2?, the bottom Zla of th cup being at the combustion chamber 22, and the open end of the member 21 being integrally formed with a radially extending annular flange 28 for assembly with the housing cover plate 2i, the air chamber 23 being formed within the cup-shaped member 21.

A partition member 29 (Figs. 1 and 4) of substantially cross-shape is positioned within and axially of the combustion chamber 22 and is of a construction to divide the chamber into four axially extending but connected passages 3la,3ld. The bottom or base portion 27a of the member 21 is formed with openings in communication with the passages 31a and 3m to provide an inlet 32 and an outlet 33 for the connected passages and hence for the combustion chamber. The wall of the combustion chamber 22 is integrally constructed with alternately arranged peripheral portions 34 and radially extending fins 36. The fins 36 are bent double with their inner ends 3] opening into the combustion passages 3M- 3ld. The partition member 29 is positioned within the open inner ends 31 of certain of the fins 3B and is retained in a fixed relative position within the combustion chamber 22 as by welding. The housing portion l1 extends about the outer ends 38 of the fins 35 to form an annular passage 33 about the combustion chamber 22, the end M of the housing portion I! extending outwardly of the combustion chamber 22 and being of funnel shape to provide a discharge or outlet opening 42 for the air passage 39.

As is evident from Fig. 1, the fins 35 are coextensive in length With th combustion chamber 22, with the air passage 39 being extended to the housing cover plate 2| by the cup-shaped mem-- ber 21. The air passage 39 is in communication with the fan compartment 24 through a passage 43, the fan 44 located in the compartment 24 being mounted on the end 45 of the engine crank shaft l5, which extends through and is rotatably supported by a bearing 41 in the housing cover plate 21. The bearing 4? is of a construction to seal the opening at the cover plate 2| for the crank shaft i6. An air inlet 48 for the fan 44 is provided in the housing portion IS. The air to be heated is thus drawn by the fan 44 through the inlet 48 passed through the passage 39 in heat exchange relation with the fins 35 and discharged from the heater through the outlet 42.

The air chamber 23, within the member 21, is connected with the fan compartment 24 by a passage 49 which is separated from the air circulating passage e3 by a bailie i integrally formed with the member 21 and extending to the periphcry of the fan 44. The bafile 5i divides the air delivered by the fan 44 for discharge into the passage 35 and the air chamber 23. Th air in the chamber 23 is used for burning with fuel in the combustion chamber 22 so that the fan 44 operates to supply both air for combustion and air to be heated. It is understood, of course, that the chamber 23 is'sealed from the combustion chamber 22 and the air passage 39 and is in communication With the fan compartment only through the passage 49.

From Figs. 1 and 2 it is seen that a portion 52 of the engine exhaust conduit !4 is inserted into the air chamber 23 through the housing cover plate 2! in a position axially of the combustion chamber inlet 32. The discharge outlet 53 for the engine exhaust gases at the end of the conduit portion 52 stops short of the combustion chamber inlet 32 and opens into a Venturi portion 54 fitted within the inlet 32 and integrally formed at one end of a sleeve member 56. The opposite end portion 51 of the sleeve member 55 is of a cylindrical shape and radially spaced about the conduit portion 52. It is seen, therefore, that the engine exhaust gases from the outlet 53 of the conduit portion 52 are discharged through the Venturi portion 54 of the sleeve member 56 and into the combustion chamber 22.

The fuel to be burned in thecornbustion chamber 22 together with the engine exhaust gases discharged from the outlet 53 is delivered by a pump 59 into fuel conditioning means designated generally as iii and comprising an air and fuel receiver or mixer 52 and a heat exchange unit 63 including the sleeve member 55. The pump 59, is illustrated as being of reciprocating type and is. operated from the engine crank shaft l6 through cam means 64. Connection of the pump with the enginefuel tank (not shown) but generally located in the base of the en ineblock I9, is made through pipe 65, the fuel from thepump being delivered through pipe 61 to the air and fuel mixing device 62 which is mounted on the cylindrical end portion 51 of the sleeve 55.

The fuel conditioning means 6! is carried by the conduit portion 52 and is located entirely within the air chamber 23. Referring to Figs. 2 and 3 the heat exchanger unit 63 is seen to in clude a plurality of longitudinally extending fins 5i! annularly spaced about the conduit portion 52 and in heat transfer relation therewith so as to be heated by the heat from the exhaust gases of the engine. The fins 60 are located within the annular space formed between the conduit portion 52 and the sleeve end portion 51. An inwardly projecting annular flange 65 integral with the sleeve 56 at its end portion 5'! is in sealed engagement about the conduit discharge end portion 52, so that the passages 69 formed between adjacent fins 60 are substantially closed at one end by the flange 65 and open at their opposite ends I! at the engine exhaust outlet 53. As best shown in Fig. 2, these ends H of the passages 69 are thus substantially within the end 68 of the venturi 54 so as to be positioned between such Venturi end and the outlet 53. Connection between the passages 69 in the heat exchanger unit 63- is provided by apertures 12 spacedlongitudinally of each fin 60, and an annular space 10 common to the passages 69 and provided adjacent the flange 65. An inlet 13 (Figs. 2 and 3) to the space 10 and hence to the passages 69 is formed in the periphery of the sleeve end portion 57, with the air and fuel receiver or mixer unit 62 being mounted on the sleeve at such inlet.

As best shown in Fig, 3, the. unit 62 includes a Venturi portion 14 having peripherally extending air openings 16 near one end thereof which are in communication with the air chamber 23. The air entering the ports 76 and the fuel from the fuel line 6'! are introduced together into the Venturi portion 14 for discharge therefrom into the annular passage 19 of the heat exchanger unit 63. Since the air in the chamber 23 is maintained under pressure by the fan 44 it is evident that an initial velocity is imparted to the air entering the venturi 14 through the ports 16 so that the body of fuel entering the Venturiportion 14 is partially broken up by the air prior to its passage into the heat exchanger unit 63. Additional air for mixing with the fuel in the fuel conditioning unit BI is introduced into the space 10 from the air chamber 23 through openings 75 formed in the sleeve 55 about the. inlet '13.

It is contemplated that the exhaust conduit portion 52, fins 6B and sleeve member 56 be composed of a high heat-conductingmaterial, such as copper Or the like, to provide for a high transfer of heat from the engine exhaust gases to such parts. During the operation of the heater, therefore, the temperature of these parts is substantially equal to the temperature of the exhaust gases in the conduit portion 52. The transfer of heat from the exhaust gases to the heat exchanger 63 is aided by impeding the flow of the gases through the conduit portion 52 as by a perforated plug 50 inserted in the outlet 53 thereof. As will now be explained, this engine waste heat is utilized to prepare the fuel from the receiver unit- 62 for an efficient burning in the combustion chamber 22.

By virtue of the above-described construction of the heat exchanger unit 63, thefuel admitted thereto at the inlet. 73. is directed. through the passages .l' 2! and 6 9 and .into. contactwith the conduitportion 52, the fins 60 and the sleeve member 56. Because of the heating of these passages and parts by the engine exhaust gases the fuel i heated sufficiently to become vaporized, this vaporizing of the fuel preparing the same for a thorough mixing together with the air to provide for a substantially complete vaporous mixture passing from 'the heat exchanger unit 63 at the outlets ll of the passages 59. As was previously described; theoutlets 'H' are arranged between the engine exhaust discharge outlet 53 and the Venturi end 98; Because of this arrangement the flow of the exhaust gases through the outlet 53 of the conduit'porticn 52 coacts with the venturi 54 to provide an ejector action for drawing the vaporous mixture from the outlets i into the combustion chamber 22 for burning with the exhaust gases. This burning of the exhaust gases and vaporous mixture is initiated by a spark plug 11 arrangedin the passage am. The plug 11 is electrically connected by a cable 18 (Fig. 1) to a coil (not shown) mounted on the engine and energized by the magneto (not shown) associated therewith. Combustion proceeds through the passages 3la3ld, with the products of combustion being exhausted from the combustion chamber 22 through the outlet 33, the flow of gases through the passages in the combustion chamber being indicated by the arrow in Fig. 1. To facilitate combustion, supplementary air from the air chamber 23 may be admitted into the combustion chamber for mixing with the intermingled vaporou mixture and exhaust gases through apertures or ports 89 formed in the base portion 2la'of the cup member-2l and arranged concentrically about the venturi 54. Y 1 Y 1 As shown in Fig. 1 the combustion chamber outlet 33 is provided with a tail pipe 19 which pr jects outwardly therefrom into the air chamber 23. A second tail pipe 8| of larger diameter than the tail pipe 19 is inserted through the heater housing cover plate 2! into the air chamber 23, concentric with the tail pipe 39 but spaced therefrom.- The adjacent ends of thetail pipes 19 and 8| are thus both open to the air chamber 23. pressure by the fan 33, airtherefrom flows out wardly through the tail pipe .8l to provide an ejector action on the exhaust gases flowing in the tail pipe l3. Thi ejector action serves to reduce the back pressure in the combustion passages 3la-3id and facilitate the flow and combustion of the gases therein, the gases being discharged from the heater through the tail pipe, 8 I. On starting of the heater, or at times during its operation, it may happen that some raw fuel might form or find its way into the combustion chamber 22.- Should this occur the raw fuel is collected in the cavities 82 (Fig. 4) in the fins 35 through the openings 31 therein, the heat in the fins vaporizing thi fuel fortlaterburning. All of the fuel supplied to the heater is thus substantially completely vaporized so that burning thereof proceeds efficiently and uniformly atall times of heater operation. The fan 44 supplies both the air for combustion and circulates the air to be heated, the air being circulated through the passage 39 imultaneously with the starting of heater operation since the heater start concurrently with the starting of the engine.

The modified form of the invention shown in Fig. 5 is similar in all respects to the form of the invention in Fig. 1 except for the relational assembly of the fuel conditioning means 6|, the exhaust conduit portion 52 and the combustion chamber 22.. Similar numerals of reference shall However, since the air chamber 23 is under body portion 91.

be rinsed, therefore, to designatecorresponding par s.

' In Fig. 5 the conduit portion- 52 is shown as being of substantially goose-necked shape, with the sections 9| and 92 thereof extending in a direction axially of the combustion chamber 22 and connected by a section 93. Section 9| is inserted through the housing cover plate 2! and the section 92 is fitted within the combustion chamber inlet 32 so that the connecting section 93 is entirely within the air chamber 23. The engine exhaust gases in the conduit portion 52 are thus discharged directly into the combustion chamber passage 31a through the outlet 95 at the end of the section 92.

The fuel conditioning means 6! is carried by Q the section 93 and extends longitudinally of the sections 9|, 25 and 92, the air and fuel receiver or mixer unit 62 being located outside of the conduit portion'52' with the Venturi portion M thereof positioned within the air chamber 23, and its end portion 96 extended through the housing cover plate 2|. The heat exchanger unit 93' includes a-body member 91 of substantially cylindrical shape positioned axially of and within the conduit section .92. The body member 91is composed of copper or like material and is provided with an axial passage 98 having an inlet 99 communicating with the Venturi portion M and an outlet IOI open to the conduit section 92. The periphery of the body member 98 is formed with fins I92 to facilitate the heating of the body member by the engine exhaust gases passing through the conduit portion 52'. The transfer of heat from the exhaust gases to the body member 97 is aided by inserting an apertured plug I93 into the outlet 95, the plug acting to impede the flow of the exhaust gase about the member 9?.

. In the operation of this form of the invention the air and fuel introduced into the receiver unit 62 passes through the passage 98 in the Since the unit 63' is at substantially the heat of the exhaust gases passing through the conduit portion 52, the heat therein is sufficient to vaporize the fuel flowing in the passage 98 to provide for its mixing together with the air. A substantially complete vaporous mixture is thus discharged from the heat exchanger unit 63' at the outlet IOI thereof. From Fig. 5 it is evident that the mass of the body member 9'! is relatively large with respect to the passage 9950 that its overall temperature remains practically unchanged due to the cooling effects of the fuel vaporizing in the passage. Also since the body member 91 is coaxial with the conduit section 92 it may be extended longitudinally to any length required to provide a passage 98 which is long enough to completely vaporize the fuel flowing therethrough, By virtue of the heat exchanger outlet l0! being open to the conduit portion 52' and with the mixture flowing through the passage 98 in the direction of the exhaust flow in such conduit portion, the flow of the mixture through the passage 98 is aided by the ejector action produced" at the outlet l0l by the exhaust flow. This vaporous mixtureis intermingled with the exhaust gases, and. the resulting mixture burned in the combustion chamber 22, ignition being initiated by the spark plug 11. Additional air for burning in the combustion chamber 22 is introduced from the air chamber 23 into the exhaust conduit portion 52 through ports l05 formed in the conduit section 92, and intothe combustion passagef3la through 7 ports I06 provided in the base portion 21a aboutthe combustion chamber inlet 32.

From a consideration of the drawings and above description, it is seen that the invention provides for a unit heater of portable type which is operated in conjunction with an internal combustion engine, and which utilizes the power from such engine as the sole source of power supply. The exhaust heat from the engine is used in the operation of the heater to vaporize fuel used therein for mixing together with air prior to the burning thereof. This mixture is intermingled with the exhaust gases with the resultant mixture being introduced into the combustion chamber and burned. The substantially complete vaporization of the fuel to be burned in the heater assures its complete combustion with a maximum production of heat and a practical elimination of objectionable odors and visible exhaust; The engine and heater are assembled together in a compact unit which may be readily moved about to provide heated air wherever it is needed. The unit is thus readily applicable for use in an airport to heat airplane engines for starting purposes, or to heat cabins, small workshops, and the like. The entire unit is simple in design and of a rugged construction so as to withstand any rough handling thereof during its movement from place to place, without impairing its efiicient operation.

Although the invention has been described with specific reference to several preferred forms thereof, it is to be understood/that changes can be made therein which are within the full intended scope of the invention as defined by the appended claims.

I claim: 7

1. In an air heater of internal combustion type operated in conjunction with an internal combustion engine having an exhaust gas conduit, a combustion chamber means for said heater having an inlet at one end, an air chamber means at said one end separated from said combustion chamber means, passage means about said combustion chamber means for the air to be heated, air supply means, means proportioning the air from said air supply means to said air chamber means and air passage means, a Venturi portion positioned in the inlet of said combustionchamber means, said exhaust conduit having an end portion thereof positioned in said air chamber means with a discharge outlet at said Venturi portion, means preparing a combustible mixture for burning in said combustion chamber means including heat exchanger means mounted on said conduit end portion, said heat exchanger means being adapted to receive air and fuel and having an outlet at said Venturi portion, means admitting air into said heat exchanger from said air chamber means, means supplying fuel to said heat exchanger means, said fuel being heated in said heat exchanger means and vaporized for mixing together with said air, with the flow of the engine exhaust gases from said conduit through said Venturi portion providing an ejector action for drawing the vaporous air and fuel mixture from said heat exchanger outlet into said combustion chamber means for burning therein with said exhaust gases.

2. In a heater of internal combustion type operated in conjunction with an internal combustion engine having an exhaust gas conduit, a combustion chamber means for said heater havan inlet, said exhaust conduit havlngthe discharge opening thereof arranged to discharge the exhaust gases from said engine into the inlet of said combustion chamber means, means preparing an air and fuel mixture for burning in said combustion chamber means including heat exchanger means having a plurality of radially extending apertured fins angularly spaced about said conduit to receive heat therefrom, a housing extended about said fins to form passages therebetween, and having an inlet and an outlet, with said outlet being in communication with said conduit discharge opening, with said passages being fiuid connected by the apertures in said fins, and means introducing air and fuel into the inlet of said heat exchanger means, with said fuel in passing through said heat exchanger means being heated and vaporized for mixing together with said air, said vaporous air and feed mixture being mingled with the exhaust gases from said conduit for passage therewith into said combustion chamber mean to be burned.

3. A heater of internal combustion type operated in conjunction with an internal combustion engine having an exhaust gas conduit, a combustion chamber means for said heater having an inlet, said conduit having the discharge end thereof positioned in said inlet to discharge the engine exhaust gases into said combustion chamber means, means preparing a combustible mixture for burning in said combustion chamber means, carried by said conduit and including heat exchanger means positioned within said conduit, said heat exchanger means having an inlet at the outside .of said conduit and an outlet near said conduit discharge end, and means introducing air and fuel intosaid heat exchanger means at the inlet thereof, said fuel on passing through said heat exchanger means being vaporized and mixed together with said air, with said vaporous mixture being admitted into the exhaust gases at said conduit discharge end for passage therewith into said combustion chamber means to be burned.

4. A heater of internal combustion type operated in conjunction with an internal combustion engine having an exhaust gas conduit, a combustion chamber means for said heater having an inlet, said conduit having the discharge end thereof positioned in said inlet to discharge the engine exhaust gases into said combustion chamber means, means preparing a combustible mixture for burning in said combustion chamber means, carried by said conduit and including a heat exchanger unit extended longitudinally of and within said conduit and radially spaced therefrom, said heat exchanger unit having heat receiving portions on the periphery thereof to receive heat from saidexhaust gases, longitudinal passage means in said heat exchanger unit having an inlet at the outside of said conduit and an outlet near said conduit discharge end, and means introducing air and fuel into said heat exchanger unit at said inlet, said fuel on passing through said passage means being vaporized and mixed together with said air, with said vaporous air and fuelmixture being admitted into the exhaust gases at said conduit discharge end for passage therewith into said combustion chamber means to be burned.

5. In combination with an engin which is provided with an exhaust outlet through which heated exhaust gases are discharged; an internal combustion heater provided with means defining a combustion chamber, a tubular member having a mouth opening into said combustion chamber, a fuel feed conduit, means comprising a fuel feed pum and a fan both driven by said engine for delivering a mixture of fuel from said conduit, and air through said tubular member to said combustion chamber, means for transmitting heated exhaust gases from said exhaust outlet through said tubular member into said combustion chamber, and a second heat conductive tubular member mounted within said first-named tubular member and having a mouth terminating short of the mouth of said first-named tubular member so that a mixing zone is provided within said first named member between the mouths of the two members within which the fuel, air and heated exhaust gases are mixed before entrance into said combustion chamber, said second tubular member functioning to separate the exhaust gases from the mixture of air and fuel prior to entry of the named elements of the combustible mixture into said mixing zone and having fins extending therefrom for transferring heat from the exhaust gases to the mixture of air and fuel.

6. In an internal combustion heater which is provided with means defining a combustion chamber, a tubular member provided with a discharge end opening into said chamber, a fuel and air. mixing device provided with means for discharging a mixture of fuel and air into said tubular member at a point along the wall thereof removed from said discharge end, a second tubular member disposed within said first-named tubular member, and extending beyond said point toward the discharge end of said first-named tubular member, radially spaced apart heat radiating fins extending axially of said two members between the walls thereof to support said second member within said first-named member and to transfer heat from within said second member to a mixture of air and fuel delivered to said first-named member from said mixing device, and means for providing a heated medium within said second tubular member.

'7; In an internal combustion heater which is provided with means defining a combustion chamber, a tubular member provided with a discharge end opening into said chamber, a fuel and air mixing device provided with means for discharging a mixture of fuel and air into said tubular member at a point along the wall thereof removed from said discharge end, a second tubular member disposed within said first-named tubular member, and extending beyond said point toward the discharge end of said firstnamed tubular member, radially spaced apart heat radiating fins extending axially of said two members between the walls thereof to support said second member within said first-named member, to divide the space between said members into a plurality of chambers which extend axially of said members and to transfer heat from within said second member to a mixture of air and fuel delivered to said first-named member from said mixing device, said fins being provided with openings therethrough which extend between adjacent ones of said plurality of chambers, and means for providing a heated medium within said second tubular member.

8. In an internal combustion heater which includes means defining a combustion chamber, a tubular member provided with a discharge end communicating with said chamber, means for discharging a heated gaseous medium into said chamber through said tubular member, an elongated heat transfer body disposed within said tubular member and provided with an elongated passage therethrough, said body having walls occupying a volume substantially greater than the volume of said passage, thereby to minimize fluctuations in the temperature at the surfaces of said walls defining said passage which tend to result from fluctuations in the temperature of said heated gases, and means for injecting a mixture of fuel and air into said chamber over a path which includes said elongated passage, the discharge end of said body terminating short of the discharge end of said tubular member, thereby to provide a mixing zone for the mixing of the air, fuel and gaseous medium prior to entry of the named constituents into said combustion chamber.

9. In an internal combustion heating system which includes an engine provided with an exhaust and a heater provided with means defining a combustion chamber having an inlet, means defining an air chamber at said one end of said combustion chamber, air moving means for delivering air to said air chamber, a fuel conditioning unit disposed at said inlet within said chamber comprising a pair of tubular members opening into said combustion chamber and disposed one within the other to provide two spaces which are separated by the walls of the inner member, means connected with one of said members at a point outside of said combustion chamber for delivering fuel to one of said spaces, said one space being fluid connected with said air chamber to receive air therefrom for mixing with said fuel, said inner member having a mouth terminating short of the mouth of the outer member so that a mixing zone is provided within the outer member between the mouths of said two members, and means for transmitting heated exhaust gases through the other of said spaces for mixing with the fuel and air in said mixing zone prior to entry of the named constituents into said combustion chamber.

10. In an internal combustion heating system which includes an engine provided with an exhaust and a heater provided with means defining a combustion chamber having an inlet, means defining an air chamber at said one end of said combustion chamber, air moving means for delivering air to said chamber, a fuel conditioning unit disposed at said inlet within said air chamber and comprising a pair of tubular members opening into said combustion chamber and disposed one within the other to provide two spaces which are separated by the walls of the inner member, means connected with one of said members at a point outside of said combustion chamber for delivering fuel to one of said spaces, said one space being fiuid connected with said air chamber to receive air therefrom for mixing with said fuel, said inner member having a mouth terminating short of the mouth of the outer member so that a mixing zone is provided within the outer member between the mouths of said two members, means for transmitting heated exhaust gases through the other of said spaces for mixing with the fuel and air in said mixing zone prior to entry of the named constituents into said combustion chamber, and a perforated wall partially closing the mouthiof one of said members to impede gaseous flow therethrough and thus enhance the transfer of heat from said exhaust gases to said fuel and air.

11. In an internal combustion heating system which includes an engine provided with an exhaust and a heater provided with means defining a combustion chamber having an inlet, means defining an air chamber at said one end of said combustion chamber, air moving means for delivering air to said chamber, a fuel conditioning unit disposed at said inlet within said chamber and comprising a pair of tubular members opening into said combustion chamber and disposed one within the other to provide two spaces which are separated by the walls of the inner member, means connected with one of said members at a point outside of said combustion chamber for delivering fuel to one of said spaces, said one space being fluid connected with said air chamber to receive air therefrom for mixing with said fuel, said inner member having a mouth terminating short of the mouth of the outer member so that a mixing zone is provided within the outer member between the mouths of said two members, means for transmitting heated exhaust gases through the other of said spaces for mixing with the fuel and air in said mixing zone prior to entry of the named constituents into said combustion chamber, and heat transfer fins extending outward from said inner tubular member, thereby to enhance the transfer of heat from said exhaust gases to said fuel and air,

12. In an internal combustion heating system which includes an engine provided with an exhaust and a heater provided with means defining a combustion chamber having an inlet, means defining an air chamber at said one end of said combustion chamber, air moving means for delivering air to said chamber, a fuel conditioning unit disposed at said inlet within said chamber and comprising a pair of tubular membersopening into said combustion chamber and disposed one within the other to provide two spaces which are separated by the walls of the inner member, means connected with one of said members at a point outside of said combustion chamber for delivering fuel to one of said spaces, said one space being fluid connected with said air chamber to receive air therefrom for mixing with said fuel, said inner member having a mouth terminating short of the mouth of the outer member so that a mixing zone is provided within the outer member between the mouths of said two members, means for transmitting heated exhaust gases through the other of said spaces for mixing with the fuel and air in said mixing zone prior to entry of the named constituents into said combustion chamber, heat transfer fins extending outward from said inner tubular member, thereby to enhance the transfer of heat from said exhaust gases to said fuel and air, and a perforated wall partially closing the mouth of one of said members to impede gaseous flow therethrough and thus further enhance the transfer of heat from said exhaust gases to said fuel and air.

13. In an internal combustion heater which includes means defining a combustion chamber, a tubular member provided with a discharge end communicating with said chamber, means for discharging a heated gaseous medium into said chamber through said tubular member, an elongated heat transfer body disposed within said tubular member and provided with an elongated passage therethrough, said body having walls occupying a volume substantially greater than the volume of said passage, whereby the heat retentivity of said walls, minimizes fluctuations in the temperature at the surfaces of said walls defining said passage which tend to result from fluctuations in the temperature of said heated ases, and means for injecting a mixture of fuel and air into said chamber over apath which includes said elongated passage.

14. In an'internal combustion heater, combustion chamber, means providing a source of combustible mixture, conduit means connecting said source to said combustion chamber, an aspirator in said conduit means adjacent said combustion chamber, said aspirator being so positioned that the passage of fluid through said aspirator will produce a low pressure zone insaid conduit, an internal combustion engine, conduit means connecting the exhaust side of said internal combustion engine to said aspirator, a heat exchanger means, aircirculatin means arranged to be driven by said engine, means connecting said combustion chamber t said heat exchanger means, and means connecting said air circulating means to said heat exchanger means so that air moved by said air circulating means passes in heat exchange relation to the products of combustion issuing from said engine and said combustion chamber.

15. In an internal combustion heating system which includes an engine provided with an exhaust and a heater provided with means defining a combustion chamber, an aspirator for delivering a'combustible mixture to said combustion chamber, passage means for delivering a combustible mixture to said aspirator, mean for transmitting gases from said engine exhaust through said aspirator, thereby to produce a low pressure zone insaid passage means, and means including a fan driven by said engine for moving air to be heated in heat exchange relationship with said combustion chamber.

16. In combination with an engine which is provided with an exhaust outlet through which heated exhaust gases are discharged; an internal combustion'heater provided with means defining a combustion chamber, a tubular member having a mouth opening into said combustion chamber, means for delivering a combustible mixture of fuel and air through said tubular member into said combustion chamber, means including a second tubular member mounted within said first tubular member for transmitting heated exhaust gases from said exhaust outlet through said firstnamed tubular member into said combustion chamber, said second tubular member having a mouth terminating short of the mouth of said first-named tubular member so that a mixing zone is provided within said first-named member between the mouths of the two members within which the combustible mixture and heated exhaust gases are mixed before entrance into said combustion chamber, heat exchange means re ceiving heat from said combustion chamber, and air circulating means driven by said engine for circulating air over the heat exchange means.

HARRY B. HOLTHOUSE.