Heater Apparatus With Controlled Air And Fuel Intake

Abstract

An engine pre-heater comprising a pair of concentric screens mounted in one end of a pear-shaped swirl chamber and forming a combustion chamber in which diesel fuel vapors are mixed with forced air delivered from a fan through the swirl chamber and from which oil residues are forced along a flow path extending to the other end of the swirl chamber to a drain.

Description

BACKGROUND AND SUMMARY OF INVENTION

This invention relates to an engine pre-heater for use with internal combustion liquid-cooled engines (diesel or gasoline), which are used by vehicles operating on the highways, off-the-road earth-moving and stationary equipment. The function of the heater is to pre-heat the engine coolant, making normal engine-starting possible in cold weather. The engine pre-heater also eliminates the need for conventional engine warm-up periods during which engine efficiency is quite low and thereby acts as an anti-pollution control as well as reducing fuel costs. Furthermore, the pre-heater itself is extremely clean burning and produces no substantial amounts of carbon or other residue. The invention involves improvements in heater apparatus of the type disclosed in U.S. Pats. No. 3,072,176 and No. 3,234,928, the disclosures of which are incorporated herein by reference.

While the pre-heater of the present invention may be used with other types of fuel (e.g., gasoline), one of the primary advantages of the present invention is the provision of engine pre-heater apparatus which is able to vaporize any grade of diesel fuel and burn vaporized diesel fuel containing substantial amounts (e.g., 20 percent) of oil ordinarily provided in commercial diesel fuels for lubrication of engine cylinder walls. It has been discovered that in order to successfully burn such diesel fuel, it is necessary to vaporize the liquid fuel and to separate and remove the oil. This oil, which those skilled in the art refer to as the "back-end," is heavier than the balance of the fuel and does not burn or vaporize. Therefore, means must be provided to separate and remove the oil to prevent accumulation in the heater apparatus in sufficient quantities to terminate combustion.

In order to more completely vaporize the liquid fuel, the burner apparatus is arranged to concentrate the heat of combustion in the fuel burning area and to create turbulence in the burning area by use of temperature differentials and shock waves and a high degree of molecular activity. As a result, in the burning area, there is explosion-like activity indicating high energy molecular movement which causes vaporization and complete burning of all but the distillation residue back-ends which collect as residue on the bottom of the combustion chamber and which are constantly removed therefrom jacket heater operation. jacket.

The pre-heater apparatus is associated with the engine cooling system in a new and improved manner providing a thermosiphon system for circulating the coolant through the engine water jacket. The heater apparatus includes a vertically extending coolant jacket with a coolant outlet at the top of the jacket located somewhat lower (e.g., at least approximately one-half inch) than the engine block coolant inlet and with a coolant inlet at the bottom of the jacket. The system includes means to hold coolant in the coolant hacket to maximize heating of the coolant by delaying the circulation of the coolant through the coolant ja ket. In the preferred embodiment, the heater apparatus is formed as a self-contained portable unit which may be mounted closely adjacent the engine or spaced some distance therefrom.

The size, shape and position of the burner housing and combustion chamber apparatus is extremely important. The burner includes an elongated swirl chamber, having a somewhat pear-shape configuration in the presently preferred embodiment, to which combustion air is delivered under pressure and caused to move therewithin in a particular flow pattern. To this end, a new and improved air delivery system is provided by the present invention.

The burner housing includes a fuel pot having a relatively small size in which a relatively small amount of fuel is maintained as compared with prior art devices. For example, approximately 20 cc of fuel are kept in the heater fuel pot in the present invention, whereas fuel pots having a capacity of approximately 60 cc of fuel or more have been utilized in prior art devices. Furthermore, in the present invention, the fuel delivery system and the shut-off apparatus are arranged to maintain a full fuel pot both during and after heater operation. To this end, new and improved means of terminating heater operation are provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a somewhat schematic side elevational view of illustrative apparatus embodying the principles of the invention;

FIG. 2 is another side elevational view of a portion of the apparatus shown in FIG. 1;

FIG. 3 is still another side elevational view of a portion of the apparatus shown in FIG. 1;

FIG. 4 is an exploded view, partly in section, of a portion of the apparatus shown in FIG. 1;

FIG. 5 is a perspective view in cross section of a portion of the apparatus taken generally along the line 5--5 in FIG. 2; and

FIG. 6 is a plan view of the apparatus shown in FIG. 4 taken along the line 6--6.

DETAILED DESCRIPTION

Referring now to FIG. 1, in general, the pre-heater apparatus is shown to comprise electrical means 10, an air delivery system 11, burner apparatus 12, chimney-heat exchanger apparatus 13, coolant jacket apparatus 14, a fuel system 15, and timer means 16, all of which are mounted on suitable support means 18. In the presently preferred arrangement, the pre-heater apparatus is enclosed as a unit in a metal case measuring 13 1/2 inches high by 10 inches wide by 7 3/4 inches deep with external connections for inlet and outlet hoses, battery and fuel pump wires. The pre-heater fuel system 15 comprises fuel pump means 20, float bowl means 22, and shut-off valve means 24. The air system comprises a radially discharging impeller type blower fan means 26, FIG. 3, restricted air inlet means 28, air inlet control valve means 30, air inlet control valve actuating means in the form of a solenoid 32, and an air delivery conduit means 34. The burner apparatus, FIG. 4, comprises a burner housing 36 on which chimney means 13 is mounted. Coolant heating jacket apparatus 14 is mounted circumjacent the chimney means which is provided with a suitable exhaust conduit.

Referring now to FIGS. 4-6, a swirl chamber 42 is provided within the burner housing 36 which comprises a box-like bottom member 43, which may be in the form of an aluminum casting or the like, and a cover plate member 44. The burner housing is elongated and a downwardly depending fuel pot 46 is provided in the bottom and adjacent one end thereof. The level of fuel maintained in the pot is indicated by line 47. A combustion chamber outlet opening 48 is provided in the cover plate 44 directly above the fuel pot 46. Fuel residue outlet means 50, in the form of a removable threaded plug member having a flow passage extending from the bottom of the burner housing to the bottom of the member, is provided at the bottom of the other end of the burner housing opposite the fuel pot. An air inlet means 52 extends into the burner housing through the top plate at the other end of the burner housing opposite the fuel pot.

Fuel pot 46 is of generally cylindrical cross-section configuration, FIG. 6, and centrally spaced a substantial distance from the adjacent side wall 54 of the burner housing which is semi-cylindrical and concentric with the center of the pot at 56. Side wall 57 of the other end of the housing is also semi-cylindrical, but of small diameter than side wall 54, and is connected to side wall 54 by side walls 58, 60 which are outwardly diverging from the air inlet end of the housing to the fuel pot end of the housing.

A combustion chamber 62 is provided by an outer burner screen 66 fixedly mounted in the outlet opening 48 in cover plate 44 and depending from plate 44 into the burner housing above the fuel pot. Outer burner screen 66 is formed of sheet metal or the like and extends upwardly through and in sealing association with cover plate 44. The outside diameter of burner screen 66 is slightly less than the diameter of the top portion of the fuel pot and the bottom of the burner screen 66 is located slightly (e.g. one-sixteenth inch) below and inwardly of the bottom of the burner housing to provide a residue flow gap 67 therebetween. Screen 66 is cylindrical and, in effect, except for the one-sixteenth inch gap, forms a continuation of the side wall 68 of pot 46 and defines the combustion chamber 62 thereabove. A portion of the screen 66, intermediate the bottom surface 70 of the burner housing and the top surface 72 of the cover plate, is perforated by a number of substantially circular air inlet holes 74, evenly distributed in horizontal and vertical rows. However, the top row of holes is spaced a substantial distance from the bottom of surface 72 so that there is a length 76, FIG. 5, of imperforate screen providing a deflecting surface for inlet air and defining the only discharge path from the combustion chamber for the escaping gases and other products of combustion. The bottom row of holes is also spaced above the bottom of surface 70 of the swirl chamber to provide a deflecting surface for the inlet air. In the presently preferred embodiment, there are a total of 96 air inlet openings of approximately one-eighth inch diameter located with approximately one-fourth inch spacing between centers. Each opening is believed to act as a Venturi and create a kind of shock-wave-explosive effect within the screen as relatively cool deflected swirling inlet air on the outside of the screen 66 enters the relatively hot combustion chamber 62 on the inside of the screen 66. As a result, the temperature on the outside of the outer burner screen is substantially less than the temperature on the inside thereof.

A stainless steel wire mesh type generally cylindrical inner burner screen 80 is concentrically mounted inside the outer burner screen and is supported by pin-ring means 82 on a seat 83. The bottom edge 84 of the inner screen is located substantially below the bottom edge 85 of the outer screen, FIG. 5, and below the fuel level line 47 so as to be immersed in the fuel. The upper edge 86 of the inner screen terminates somewhat less than one-half the distance between the bottom 70 of the housing and the bottom 72 of the cover plate so as to be located in the burner flame and to concentrate the heat of combustion in the top center part of the fuel in the fuel pot.

A fuel pot inlet 87, FIG. 4, is connected by a line 88 to shut-off valve 24 and thence by a line 90 to the float bowl 22 and thence by a line 92 to fuel pump 20 which is connected to a suitable fuel supply as shown in FIG. 1. The pre-heater operates independently from the associated engine, but uses the same fuel as the engine obtained directly from the main fuel tank of the engine through a separate fuel pump and fuel line. The arrangement is such that the pot 46 is normally always filled with fuel at or about the level 47. When the preheater is turned off, as will be more fully described herein, shut-off valve 30 is also closed to smother the fire and trap a quantity of fuel in pot 46.

For purposes of starting the pre-heater, an electric fuel heater means 94 is mounted in pot 46 to heat and vaporize the fuel therein until sufficient heat is obtained for self-sustaining operation. A fuel igniter means 96 is mounted on the burner housing 43 and extends through a slot 98 at the bottom of the outer screen 66 as shown in FIG. 5.

The combustion air delivery system is provided with flow control means designed to promote particular flow characteristics in the burner housing. The flow control means includes vertical inlet conduit 28, the opening 97 to which is opened and shut by valve 30 upon actuation of solenoid 32. The size of the air inlet opening as defined by the space between the valve 30 and the top of the conduit 28 in the open position is adjusted to obtain the desired results in the combustion chamber. The heater is turned off by closing the inlet opening and stopping the supply of air which will snuff out the fire and leave the desired fuel supply in the pot 46 rather than allowing the fire to burn out as in prior art devices.

The fan air inlet conduit 28 communicates with an inlet chamber 100 mounted on the side of fan housing 102. Fan wheel means 26, in the form of a radial discharge squirrel cage impeller blade type, draws the air in centrally and axially from chamber 100 and discharges the air radially and circumferentially through an upwardly curved discharge elbow 104 and into the discharge conduit 34. An electric fan motor 106 is drivingly connected to the fan in a suitable manner. Conduit 34 is substantially U-shaped in side elevation, FIG. 1, and includes an upwardly extending leg portion 108, a cross-over portion 110 and a downwardly extending leg portion 112. Vapor lock prevention means are provided in the form of an air line 113 connecting air passage 112 to the float bowl 22. The air inlet passages, openings and impeller fan are arranged to obtain a consistent smooth relatively non-turbulent air flow at the discharge opening 114, FIG. 4, of chute means 52.

The curvature and position of the discharge chute are such as to provide a ring-like body of twisting incoming air generally directed toward the end wall 54 of the swirl chamber. Since the incoming aIr stays along the inside surface of the discharge chute, the front surface 118 of the discharge chute is positioned to direct the upper portion of the ring of air toward the upper portion of the screen 66 above the upper row of inlet holes and the bottom portion of the ring of air toward the bottom portion of the screen 66 below the bottom row of inlet holes. This arrangement prevents the incoming air from immediately escaping from the swirl chamber and creates the desired turbulence.

Air discharge chute means 52, FIG. 4, directs the air into the burner housing swirl chamber 42 in a particular manner and is placed within the swirl chamber in a particular manner for purposes to be hereinafter described in detail. Referring again to FIG. 6, the discharge opening 114 is centrally located between the adjacent side walls 58, 60 of the housing and faces the burner pot 46 and screens 66, 80. The lower and rear surface 116, FIG. 4, of the discharge chute is formed on a relatively large radius to provide a relatively long smooth deflection surface. The front surface 118 of the discharge chute is slanted upwardly and away from the burner screens. In the presently preferred embodiment, the air discharge chute is mounted on the cover of the swirl chamber and held in place by a set screw (not shown) which permits adjustment of the position of the discharge opening. The chute is generally cylindrical copper material and has a 1 1/2 inch outside diameter at the top and a 1 1/4 inch inside diameter at the bottom. The back of the chute at the cover is 3/8 inch from the adjacent housing wall so that the air can pass behind it. The top of the discharge opening 114 is 1 3/4 inch from the outer screen 66 and the bottom is 1 5/8 inch from the outer screen and one-sixteenth inch from the bottom of the housing. With the heater started and the fan means 26 blowing air through discharge chute 52, the air in the swirl chamber 42 is believed to have a flow pattern comprising a central flow path of the ring of incoming air indicated generally by arrows 125, 126 extending from the air discharge opening 114 toward the outer burner screen 66, which causes the bottom and top portions of the ring of air to deflect therearound as indicated at 128, 129 and against the far wall 54 of the swirl chamber as at 130 which causes the air to deflect 180.degree. therearound as at 132, 133. The deflected air is driven rearwardly along the sides of the swirl chamber as at 134, 135, 136, 137 and onto the near wall 57 of the swirl chamber where the air is again deflected 180.degree. as at 138, 139. As a result, there is a swirling mass of air turning and twisting in many directions (i.e., turbulence), some of which is being forced through the air inlet openings 74 in the outer burner screen 66 to provide combustion air in the combustion chamber 62. The turbulence prevents the intake air from escaping too fast, resulting in holding adequate air to supply two atoms of oxygen to one atom of carbon liberated to form carbon dioxide (CO.sub.2). The air turbulence also counterbalances the electric motor R.P.M. drop due to lower battery strength. Another result is that there is a stream of air at the bottom of the swirl chamber moving first away from the fire pot toward the near wall 54 and then along the sides of the swirl chamber toward the far wall 57 in the direction of arrows 134, 135, FIG. 6.

In normal operation of the heater, the combustion chamber 62 is white hot with the heat of combustion centrally concentrated in and around and above the inner screen 80 which normally has a cherry red color and acts as heat transfer means maintaining a high temperature in the liquid fuel in the fuel pot and forming liquid particles and vapors that rise from the upper surface of the fuel. There is a substantial temperature and pressure differential along the inside and outside surfaces of the outer burner screen 66 which causes the swirling air to enter the combustion chamber at high velocity and to react in a kind of shock wave with the rising particles and vapor to burst the particles and completely vaporize the fuel in the combustion chamber. The swirl chamber disperses the relatively cold input air about the outer screen and the temperature differential between the combustion chamber and the incoming air causes violent motion of the fuel particles and vapors and agitates the remainder of the fuel in the fuel pot. As a result, some of the fuel in the pot attains such high velocity that it bursts through the surface film of the liquid fuel and escapes from the liquid as a gas. Some of the fuel is driven from the fuel surface in the form of small liquid particles which are vaporized as they rise into the combustion chamber. The fuel and the products of combustion are driven and drawn into the chimney 13 through the outlet opening 48 at the top of the outside burner screen, the swirl chamber 42 and combustion chamber 62 being otherwise sealed to prevent any significant escape of air along any other route.

In a pre-heater of this type, I have found that back end oil will not be vaporized and will float on the surface of the fuel and will eventually choke out the fire if not removed. The fuel oil back end cannot burn or vaporize because the boiling point required is higher than that obtained in the pre-heater. During fuel vaporization, velocity action forces the back end to the surface of the pot. One of the main advantages of the present invention resides in the provision of residue removal means in the form of a flow path extending along the bottom of the swirl chamber from the fuel pot to the bleeder means 50 whereat the back end residue is positively discharged from the burner housing. Velocity action in the pot pushes the residue into the pear-shaped swirl chamber through gap 67 against the near wall 54 where air turbulence forces it along the side walls 58, 60 to the rear wall 57. Unexpectedly, it has been found that the residual removal means appears to work most advantageously when located some distance from the fire pot rather than closely adjacent thereto as might be ordinarily expected. In the illustrative form of the invention, the flow path from the fuel pot to the bleeder means is provided by gap 67 at the bottom of the outside burner and by the bottom surface 70 of the burner housing along which the back end residue is carried by the air in the swirl chamber in a path which extends from the fuel pot to the end wall 54 and then along the side walls 58, 60 to the end wall 57 where it accumulates about the bleeder means 50 and is removed by drainage therethrough. Diametrically opposed air holds the residue over the bleeder means where it drains free from the swirl chamber.

The hot exhaust gases are carried up the chimney 13 an over and around a vertically adjustable heat exchange baffle means 150 to an exhaust conduit 41. Threaded adjustment means 151 permits necessary adjustment of the bottom of the baffle means relative to the flame which extends from screen 66. Coolant in jacket 14 is heated thereby and tends to rise from the coolant inlet 152 at the bottom of the jacket to the coolant outlet 154 at the top of the jacket. A thermostat 155 is provided to sense the temperature of the coolant and provide means to control the apparatus. The coolant jacket outlet 154 is connected by a line 156 through restrictor means 157 to the engine cooling system 158. A similar restrictor means 159 is associated with the coolant inlet to control flow of coolant through the coolant jacket. The restrictor means 157, 159 act to delay passage of the coolant through the heater thereby maintaining higher coolant temperatures as well as higher heater temperatures. The inlet 160 to the engine cooling system is located about the coolant jacket outlet at an elevation sufficient to insure a thermosiphoning effect, e.g., a distance of one-half inch in the illustrative embodiment. The engine cooling system is directly openly connected to the heater coolant jacket inlet 152 by a line 161 without any intervening valves or the like except for the restrictor means so that the heater coolant jacket will be an integral part of the cooling system and effective immediately during start-up to cause a circulation of heated coolant through the cooling system.

In the presently preferred embodiment, the inside diameter of the inlet 152 and outlet 154 are the same (i.e. one-half inch) but the outlet restrictor 157 is larger (e.g., seven-sixteenths ID) than the inlet restrictor 159 (e.g. three-eighths ID). The difference in restrictor size helps prevent reverse flow as well as delay flow and increase pressure.

OPERATION

The pre-heater of the present invention is particularly adapted for use with engines used commercially in vehicles on and off-the-road and stationary equipment which use pure anti-freeze instead of water for coolant. Although ice may form whenever the ambient temperature drops below +35.degree. due to condensation inside the heat exchanger and burner housing, the ignition system on the pre-heater always starts in the time allowed for ignition.

In operation, the heater may be automatically started by timer means 16 or by a manually operable start-up switch (not shown) which cause simultaneous or successive energization of the fuel valve solenoid 162, the fuel pump 20, the pot heater means 94, the igniter means 96, the air valve solenoid 32, and blower fan means 26 by suitable circuitry (not shown) associated with the vehicle electrical system and energizer or with a separate electrical system and energizer. In the presently preferred arrangement, electric current for the heater is supplied by the vehicle or engine battery. The current is required for the following items: electric motor for the fan, air valve solenoid, sump fuel shut-off valve solenoid, fuel pump, vibrator coil for energizing the igniter plug and the heating unit. The igniter plug and heater operate for approximately 3 minutes at 0.degree. and for approximately five to six minutes at <20.degree.. The electric current consumption at -0.degree. is approximately 2.325 (12v) and 1.162 (24v) ampere hours per hour. In any event, the pot heater means 94 heats the fuel in the pot and causes fuel vapors to rise into the combustion chamber 69 where they are ignited by the igniter means 96. After a few minutes operation, sufficient heat will have been generated to make the combustion process self-sustaining at which time thermostat means 155 may be employed to shut off the pot heater means and the igniter means. At this time there is a continuous vaporization and burning of the fuel in the pot. The level of the fuel is maintained by the fuel system float bowl and combustion air is supplied under pressure as hereinbefore described. Coolant in the coolant jacket is heated and a thermosiphoning effect is begun with heated coolant rising from the coolant jacket outlet to the vehicle cooling system inlet and with coolant flowing from the vehicle cooling system outlet to the coolant jacket inlet. As the coolant circulates, the coolant is gradually heated until a substantially uniform vehicle cooling system temperature is reached. Then the heater apparatus is turned off either automatically by thermostatic control or manually by de-energizing the air valve solenoid to close the air valve and smother the pot fire. The fuel valve is also closed so as to trap a supply of fuel in the pot and the fuel pump is de-activated. It will be understood that the exact theory and/or manner of operation of the various components of the pre-heater may not be completely understood at this time and that the explanation herein given is intended to be illustrative of the results obtained rather than an exact theory of operation.

The heater apparatus is associated with a thermosiphon system for circulating the engine coolant through the cylinder block coolant jacket. The heater apparatus includes a 7 and 1/2 inch fire pot and coolant jacket. It is made with a 2 and 3/4 inch I.D. inner tube and a 3 and 1/4 inch O.D. outer tube. The coolant jacket is between these two tubes with a coolant capacity of one and one-quarter pints. The coolant outlet of the pre-heater needs only to be one-half inch lower than the engine block coolant inlet to obtain the thermosiphon function. The pre-heater can be installed several feet away from the engine.

The pre-heater output temperature rise is from approximately 0.degree. to +205.degree. in less than 10 minutes after ignition, and this temperature remains constant during the time required to heat the coolant in the engine block jacket to normal operating temperature. The time required depends on the engine coolant jacket capacity (which can be, e.g., 4 to 8 gallons) and the ambient air temperature, plus the velocity of the wind.

Claims

I claim:

1. A heater for an engine or the like comprising:

a fuel pot,

a combustion chamber formed above said fuel pot,

a closed swirl chamber having a side wall spaced from and surrounding said combustion chamber and said fuel pot,

forced air inlet means in said swirl chamber and spaced from said combustion chamber and said fuel pot and establishing a predetermined path of air flow to said combustion chamber including a path portion extending away from said fuel pot, and

fuel residue removal means in said swirl chamber and spaced from said fuel pot and located in said path portion whereby fuel residue is carried by the air flow along said path portion to said removal means.

2. The invention as defined in claim 1 and said fuel residue removal means being located closely adjacent said side wall beyond said forced air inlet means opposite said fuel pot and said combustion chamber.

3. The invention as defined in claim 1 and said swirl chamber being elongated and said fuel pot and said combustion chamber being located at one end of said swirl chamber and said air inlet means being located at the other end of said swirl chamber.

4. An engine pre-heater comprising:

an elongated enclosed burner housing having a bottom wall, a top wall, and a side wall defining an air chamber,

a fuel pot at one end of said burner housing,

burner means at the one end of said housing defining a combustion chamber above said fuel pot,

air inlet passage means connected to said aIr chamber at the other end of said burner housing,

fan means connected to said air inlet passage means to force air through the air chamber to the combustion chamber,

and said inlet passage means including a first vertically extending portion connected to the atmosphere,

a second vertically extending portion spaced from said first vertically extending portion and being of equal length and connected to the air chamber through said top wall of said burner housing, and

an intermediate cross-over portion therebetween and defining a generally U-shaped flow path reducing turbulence of the air delivered to the air chamber.

5. The invention as defined in claim 4 and having a curved elbow connected to said second vertically extending portion and extending into said burner housing and having a discharge opening facing said fuel pot and burner means and directing the air toward the combustion chamber in a path generally transverse to the longitudinal axis of said fuel pot and said combustion chamber.

6. An engine pre-heater comprising:

an elongated burner housing having top, bottom, and side walls and being closed except for an outlet opening for products of combustion in the top wall at one end of the housing and an inlet opening for combustion air in the top wall at the other end of the housing,

a perforated outer cylindrical screen mounted in said outlet opening and extending into said burner housing and terminating closely adjacent the bottom of said burner housing,

a fuel pot located below said perforated cylindrical screen and connected to a source of fuel,

a perforated inner cylindrical screen mounted in said fuel pot and extending upwardly within said perforated outer cylindrical screen and terminating below the top of said burner housing,

a combustion chamber defined by said perforated outer cylindrical screen and said perforated inner cylindrical screen,

fan means connected to said air inlet opening to cause a flow of combustion air from the atmosphere through the housing, and

an elbow type conduit connected to the inlet opening and extending into the housing and directing combustion air from the one end of the housing to the other end of the housing onto and through said perforated outer cylindrical screen and into said combustion chamber and creating a zone of high molecular activity in the combustion chamber.

7. The invention as defined in claim 6 and the flow of air causing a flow of fuel residue from the fuel pot along the bottom of the burner housing, and residue removal means in said burner housing in the flow path of the fuel residue and located in spaced relationship to the fuel pot to receive and remove fuel residue from the fuel pot.

8. A heater adapted to burn a liquid fuel, such as diesel fuel, having a burnable constituent and an unburnable constituent during continuous self-sustaining operation and comprising:

pot means to hold a quantity of the liquid fuel with a free upper surface maintained at a predetermined level within the pot means,

burner means extending upwardly from the pot means and defining a combustion chamber located above the pot means and the free upper surface of the liquid fuel, heating means to heat and vaporize the burnable constituent of the fuel for delivery of fuel vapor to the combustion chamber,

an air chamber surrounding said pot means and said burner means to delivery combustion air to said combustion chamber, and

drainage means located in said air chamber beyond said pot means to continuously drain the unburnable constituent during continuous self-sustaining operation.

9. The invention as defined in claim 8 and having air delivery means to establish a flow path of air through said air chamber to said combustion chamber, said drainage means and said pot means being located in said flow path whereby the unburnable constituent is carried by the air from the pot means to the drainage means.

10. The invention as defined in claim 9 and wherein said air chamber being elongated and comprising:

a first side wall portion being located relatively closely adjacent said pot means,

a second side wall portion being spaced from said pot means a greater distance than and located opposite said first side wall portion, said air delivery means extending into said chamber between said pot means and said second side wall portion and having a discharge opening facing said pot means and said first side wall portion to establish an air flow extending from said pot means to said first side wall.

11. The invention as defined in claim 10 and said first side wall portion and said second side wall portion being arcuate and connected by generally tangentially extending side wall portions, said flow path extending from said first side wall portion along said tangentially extending side wall portions.

12. The invention as defined in claim 11 and said drainage means being located between said air delivery means and said second side wall portion.

13. The invention as defined in claim 12 and said drainage means comprising an opening in the bottom of said air chamber spaced inwardly from said second wall portion and centrally located on a line extending between the centers of the first wall portion and the second side wall portion.

14. The invention as defined in claim 13 and said air delivery means being spaced inwardly from said second side wall portion to facilitate flow of air from said first side wall portion along said tangentially extending side wall portions to said second side wall portion.

15. The invention as defined in claim 14 and the flow path of air in said air chamber being such as to establish a low pressure zone and to hold the unburnable constituent over said drainage means.

16. A heater adapted for continuous self-sustained burning of a vaporizable liquid fuel comprising:

fuel pot means for holding a quantity of the liquid fuel,

burner means extending above said fuel pot means and defining a combustion chamber thereabove receiving vaporized fuel therefrom,

an elongated air chamber extending laterally from said burner means for supplying air to said combustion chamber,

a first side wall portion of said air chamber being spaced closely adjacent said fuel pot means and said burner means, a second side wall portion of said air chamber opposite said first side wall portion being located more remotely from said fuel pot means and said burner means than said first side wall portion,

forced air supply means for supplying combustion air to said air chamber,

an air inlet conduit connected to said forced air supply means extending into said air chamber between said second side wall portion and said fuel pot means and said burner means and having an air inlet opening facing said first side wall portion and said fuel pot means and said burner means and directing incoming combustion air theretoward.

17. The invention as defined in claim 16 and wherein said fuel pot means and said burner means are generally cylindrical and are concentric, said first side wall portion being arcuate and concentric with said fuel pot means and said burner means.

18. The invention as defined in claim 17 and wherein said second side wall portion being arcuate and connected to said first side wall portion by tangentially extending side wall portions.

19. The invention as defined in claim 18 and wherein said air inlet conduit includes a cylindrical tubular portion extending parallel to said burner means and being concentric with said second side wall portion, an elbow portion curving toward said burner means, and an outlet portion extending toward said burner means.

20. The invention as defined in claim 19 and said air inlet conduit being spaced inwardly from said second side wall portion to provide an air flow passage therebetween.

21. The invention as defined in claim 20 and having a fuel residue drainage opening connected to said chamber and located between said air inlet conduit and said second side wall portion.