US2174818A - Burner - Google Patents

Description

K. P. BRACE BURNER Filed June l, 193'? 5 Sheejzs-Sheet l llllllll/llll. v

s l lz 16 104 1NVENTOR. AEMPEB P BE/wf ATTORNEYS.

Oct. 3, w39.. K. P. BRACE 2,174,818

BURNER Filed June" 1, 195'? 5 sheets-sheet 2 1NVENTOR /if/WREE P BEIGE BY We@ @y erm ATTORNEY.

K. P.. BRACE oct. 3, 1939.

BURNER Filed June l, 1957 5 Sheets-Sheet 3 INVENTOR.

O w A M n K. P. BRACE Oct. 3, 1939.

BURNER Filed June l, 1937 5 Sheets-Sheet 4 INVENTOR.

WEMPE@ P BEAGE BY I TM ATTORNEY.

K. P. BRACE di. 3 w39.

BURNER Filed June l, 1957 5 Sheets-Sheet 5 INVENTOR.

lfm/DEE AD 516465 ATTORNEY.

new?

Patented Oct. 3, 1,939 l i A .1

UNITED STATES PATENT OFFICE BURNER Kemper P. Brace, South Bend, Ind., assignor to International Engineering Corporation, Chicago, Ill., a corporation of Illinois Application June 1, 1937, `Serial No. 145,706

26 Claims. (Cl. 158-96) o This invention relates to heating systems, and vaporizerelement of the burner of Figure 2 is illustrated as embodied in a domestic heating showing a hot-wire ignition coil; system utilizing an oil burner. Figure 4 is a wiring diagram of an automatic An object of the invention is to provide effeccontrol circuit;

5 tive carburetion of large volumes of air, such as Figures 5-10 inclusive are longitudinal sections '5 are necessarily handled in domestic heating through several modified forms of refractory vaplants, by spreading the fuel over a very large porizer elements suitable for use in my novel heated surface over which the air is forced. burner: Preferably this is accomplished by causing the Figure 11 is a vertical section through a modifuel to seep through a porous refractory memfied form of my novel burner; ll0 ber arranged in the path of the air and pref- Figure 11a is a' partial section on the line erably of such shape and so arranged that the IIa-Ila of Flgure 11, showing a spark type combustion of the fuel has a considerable heatigniter;

ing effect on the refractory. Figure 12 is a rear elevation of the burner of l5 Various features of novelty relate to the co- Figure 11; 15 operative arrangement of the refractorymem- Figure 13 is a section on the line I3-I3 of ber and the air circulating means to insure the Figure 11; most effective action, and to the structure and Figure 14 is a view similar to Figure 11 of still arrangement in the burner of the refractory eleanother modification of my invention;

ment, and to the arrangement of the parts in Figure 15 is a partial vertical section through 20 a casing adapted to be mounted in the wall of a a boiler and furnace showing an installation of furnace and shaped to. provide an adequate supthe burner shown in Figure 11 with a novel fireply of secondary air for the burner. l box unit; and Another feature of the inventionrelates to a Figure 16- is a sec-tion on the line I6I6 of novel control system especially adapted for a Figure 15. 25

burner of this character, in that while .the fuel In the arrangement illustrated in Figure 1, a and the air-supplying fan arealll turned on when suitable furnace III of any desired type is prothe room temperature drops to ai predetermined vided for heatinga house or the like space under level, when the temperature rises again only the the control of a room thermostat I2. The botfuel supplyis turned off. the fan continuing to tom of the furnace I0 is lined with fire-brick 30 operate as long as there is any fuel still burning. It or equivalent refractory material, to such Since the porous refractory member in effect height as may be necessary.' My novel oil burner stores up a substantial amount of fuel, this novel is mounted to discharge through a refractory method of operation insures that it will be enshield I6 into the interior of the furnace.

tirely burned before the air supply stops, thereby The burner, in the form illustrated, includes a '35 guarding against explosions. This method of generally cylindrical casing I8 having a conical operation also has the effect of burning off any end projecting through the vshield I6 and open deposits of carbon which may have formeddurat the end opposite the furnace, for the intake ing extended periods of operation. Preferably of air. The casing I8 is mounted on a suitable 40 the circuit for this control system also includes support 20. Inside the casing there is a ledge 40 a novel safety igniter circuit associated with the or dam 22, forming a sump into which excess fuel-supply and fan-motor circuits. fuel drains, and directing the fuel away-through The above and other objects and features of a suitable drain conduit 24. This conduit may, the invention, including a novel igniter arrangeif desired, lead to one of the standard commerment and various other novel arrangements of cial safety devices (not shown) for opening the 45 the parts and certain desirable mechanical concontrol circuits of the burner in case of excessive structions thereof, will be apparent from the foldrainage of fuel therethrough. mwing description of the illustrative embodiments In the open end 0f the casing I8. and arranged shown in the accompanying drawings, in which; coaxially'with respect thereto, suitable brackets 5o Figure 1 is a vertical section through a do- 26 SuppOIta 11101101' 28 provided With air-Circu- 50 mestic steam heating boiler and furnace showlating means such as a fan 30 on the motor shaft.

ing an installation of my novel burner; The blast of air from the fan 30 is preferably Figure 2 is a vertical section on a larger scale directed through a set of guide vanes 32, which through the burner shown in Figure l; are mounted in the casing I8 just beyond the Figure 3 is a front elevation of the refractory fan, and which in the form shown insure a sub-4 55 stantially straight flow of the air current and prevent other movement of the air. The shape and arrangement of these vanes may be suitably modified if it is desired to direct the air otherwise than in a straight path.

In the conical end of the casing I8 suitable brackets 34, riveted at their outer ends to the casing, support (coaxially of the outer casing I8) an inner casing 36. The space between the casings |8 and 36 provides an annular outer passage for secondary air from the fan 30. The inner casing 36 has in its end adjacent the fan 30 a reduced-diameter opening 38 forming an intake for. primary air from the fan 30.

The oil or other fuel is supplied, for example through a conduit 40 controlled by a suitable fuel valve 42 operated by a solenoid 44, and in the arrangement illustrated feeds slowly through a feed conduit 46, to a porous refractory member 48, and seeps down through the porous structure of that member to be vaporized and taken up by the primary air.

The fuel need not necessarily be supplied on the upper surface of the refractory member, as the capillary action of its porous structure will distribute the fuel satisfactorily even if it is supplied at a lower point.

In the form shown in Figures 1 and 2, the refractory member 48 has its outlet end conical in form, so that its surface parallels the conical outlet end of the casing I8. Thus combustion of vaporized fuel and air serves to heat the tip and thereby increases the capacity of the burner. Other suitable shapes are shown in Figures 5, 6, '1, 8, 9, and 10.

The member 50 shown in Figure 5 has its intake end cylindrical, to t into the casing 36, then has a reduced-diameter neck from which it flares outwardly and then converges again to form a generally-conical end. The member 52 shown in Figure 6 iscylindrical, and has a conical recess in its discharge end. The member 54 in Figure 7 is cylindrical, the same as member 52, but has a generally conical recess in its end. The member 56 of Figure 5 is cylindrical, as is the member 58 in Figure 9, but the former has a series of annular grooves 51 in its outlet end and the latter has two successively smaller cylindrical bosses projecting from annular recesses 59 on its outlet end. The member 60 of Figure 10 has a surface generated by rotating a parabola about its axis.

'I'he members 48, 50, 52, 54, 56, 58, and 60 have straight passages 62 or 64 therethrough parallel to their axes. The passages 64 of the members 56 and 58 open respectively into the annular grooves 51and 59.

The fuel conduit 46 discharges onto the refractory member 48, or one of the illustrated equivalents, on the upper surface thereof in the arrangement of Figures 1-3, and the fuel seeps through the porous structure thereof and crosswise of the passages 62 or 64. yThe heat of the combustion taking place around the end of and in the passages of the refractory member vaporizes the fuel and it is taken up by the primary air. This gives unusually effective carburetion for the large volume of primary air required in a burner of this character.

The lower part of the member 48, at its outlet end, has arranged crosswise thereof a hot-wire igniter 68, connected by supporting posts 10 to the lead wires described below. This igniter is arranged in a recess formed in the refractory member, out of the direct path of the primary air, in-a sort of eddy current,due to the passage of the primary air. Preferably it is in direct contact with the surface of the refractory member, so that a small part of the latter is heated up to vaporize the fuel therein and bring about immediate ignition thereof in the air of the eddy current.

It will be seen that so long as fuel is supplied and the motor 28 operates, the fuel and primary air mixed in the passages 62 burns and then in turn is mixed with an outer envelope of secondary air from the annularpassage between the casings 36 and I8. It will be noted that the combustion takes place immediately adjacent the refractory Y member, and to some extent actually in the passages 62, heating the refractory member to a high enough temperature to cause rapid vaporization of the fuel.

Figure 4 shows one manner of controlling the described burner. A source of current, such as the secondary of a transformer 14, is connected through line wires 16 and 18, one of which has connected thereto a switch operated by the room thermostat I2, to the motor 28. The switch 80 has a second contact so that it also closes a parallel circuit through wires 82 and 84 and the igniter 68. The wires 82 and 84 have connected therebetween, in parallel with the igniter 68, the fuel-valve solenoid 44. Thus closing the switch 80 closes three circuits through (l) the motor, (2) the igniter, and (3) the fuel valve solenoid.

As a safety measure, in order to shut off the fuel supply after a predetermined interval if the igniter does not operate, there is connected in shunt with the igniter a heating resistance 86 which, after the desired time interval, deflects abimetallic strip 88, causing a plunger 90 to open a switch contact 92 in the line 82, thereby shutting off both the fuel valve and the igniter.

The wires 18 and 82 terminate in contacts 94 in an enlarged upwardly extending space 96 in a member 98 of suitable insulating material. This member is formed with a lower horizontal passage I00 of capillary size, communicating at its ends with the space 96 and with another and somewhat higher upwardly-extending enlarged space |02 which is open to the atmosphere through a porous plug |04 held by a perforated threaded cap |06. The space |02 contains contacts |08 connected to the lines 1G and 18 around the room-thermostat switch 80.

The above passages form a U-shaped passage containing a globule of mercury,A shown in the space 96. The mercury can pass through the passage |00 only-when forced by a substantial pressure thereon. The mercury cannot pass the porous plug |04', nor a similar plug held by a perforated locking ring I3 leading to a passage ||5 .communicating with the mouth of a sealed air bulb I|1.

The bulb is arranged in the path of the burned gases from the burner, for example in the flue connection from the furnace as shown in Figure 1. It is not necessary that the burned gases actually impinge on the bulb, but the air in the bulb must be subject to the heat of the gases so that it expands when the burner is going and contracts when it is not going.

The above-described stack control shown in Figure 4 is claimed in my application No. 184,971, flied January 14, 1938.

In operation, when the room temperature drops to a predetermined level, the thermostat I2 closes the double contact switch member 80, thereby closing the three circuits through the motor and the solenoid 44 and the igniter. The globule of mercury is at this time in the space 96, and completes the igniter circuit.

As soon as the burner ignites, the hot exhaust gases act on the bulb 1 to expand the air therein, driving the globule of mercury through the capillary tube into the space |02, thereby breakingi'the igniter circuit at 94 and closing the contacts |08.

When the room temperature rises, the thermostat l2 operates switch member 80 to open the circuits it controls, breaking the circuit through the solenoid 44 and shutting off the fuel supply. A substantial amount lof fuel remains in the pores of the member 48, however, so the burner is not immediately extinguished. The motor circuit remains closed through contacts |08, therefore, until this fuel is all burned. Thereupon the air in the bulb |l1 cools and contracts, and the atmospheric pressure in space |02 pushes the mer cury globule back through the capillary passage |00 into the space 96, leaving the circuits ready for the next cycle. Excess air, after the mercury has been pushed from one side to the other, merely bubbles idly through the mercury.

Figures 11 and 12 and 13 show a second embcdiment of my invention incorporating some features claimed in application No. 117,459 filed December 24, 1936 by Kendall Clark. In these figures, parts corresponding to parts in Figures are indicated by the same reference characters increased by 100.

The principal diierences are in the provision of an adjustable air intake cover I9, and in the arrangement by which the primary air circulates to the interior of the inner casing |36 through peripheral openings formed by striking up the vanes |32 from a cylindrical sheet-metal member 2| which forms the forward portion of the inner casing |36 and which holds the porous refractory member |48 in place. Also the motor |28 is housed in the end of the inner housing |36.

Another dierence is that the rear part of the outer casing ||8 is made of a casting and is provided at its discharge end with a generally conical extension 25, preferably composed of stainless steel, and which extends to the tip of the refractory |48. This member is intended to confine the flame around the refractory and to radiate heat to it to increase its vaporizing capacity. It will be noted that the forward portion of the outer casing inthe first modification performs this same function.

In Figure 14, which shows a third modification of my invention, parts corresponding to parts in Figures 1-10 and 11-13 are indicated by the same reference numerals plus 200 and 100 respectively.

In this modification the portion of the inner casing 236 containing the motor is substantially reduced and the sheet metal member |2|, which forms the forward portion of the inner casing, is tapered outwardly to receive the base of a much larger refractory 248. Primary air is admitted through a series of peripherally spaced openings 238 which may be adjusted by rotation of a ring 21 closely surrounding the member |2| and having correspondingly spaced openings.

Still another difference resides in alfurther division of the air passing through the burner by insetting the stainless steel extension |25 of the outer housing 2|8 and thus providing a peripheral opening between the cast part of the housing and the extension. It is found that in some cases to introduce all the air required for complete combustion as secondary air somewhat reduces the evaporating capacity of the refractory by cooling it. By subdividing the secondary air as described only approximately as much air as will combine with the fuel within the extension is introduced as true secondary air and the remainder is introduced as what may be called tertiary air through the peripheral opening outside of the stainless steel cone |25, to combine with the unburned fuel in the nre box.

While the proportion of secondary to tertiary air can be made adjustable by providing means for shifting the extension |25 longitudinally of the burner, it is believed that satisfactory operation under most conditions can be obtained without such an adjustment.

Figures and 16 illustrate how the burner of Figures 11-13 or 14 may be mounted in the side wall of a furnace 0, discharging at an angle downwardly into a nre-box or pair 23 of stainless steel, which in use becomes heated sufficiently to transfer most of the heat as radiant heat directly to the furnace walls. I have found that this construction amply fullls the requisite that all oil burners must -be supplied with a fire box of a particular size and shape, and at the same time is very cheap to manufacture and install in comparison to the old practice of building up the rebox with irebrick as shown in Figure 1.

The igniters |10 and 210 illustrated in the second and third embodiments are of the sparkegap type, arranged as shown in Figure 11a, and include two electrodes arranged in adjacent passages 62, the spark passing freely through the porous wall between the passages.

While three illustrative embodiments have been described in detail, it is not my intention to limit the scope of the invention to those particular embodiments, or otherwise than by the terms of the appended claims.

I claim:

1. A liquid fuel burner comprising a porous refractory element having generally horizontal air passages therethrough, means for delivering liquid fuel to said element to seep through the porous structure thereof, and a casing open at its ends and within which said element is mounted and one end of which is adapted to project into a furnace beyond said element and to be heated by the burning fuel and to radiate heat back to said element to aid in vaporizing the fuel.

2. A liquid fuel burner comprising a casing formed with an air outlet and provided with means for directing a current of air through said outlet including a porous refractory element mounted in the casing in line with said outlet and in intimate contact with which the current of air passes to the outlet, said element having a considerable number of parallel generally horizontal passages directing portions of the air current through said element and through said outlet, and means for feeding liquid fuel to said element to seep therethrough and be taken up by the air.

3. A liquid fuel burner comprising a casing formed with an air inlet opening at one end and with an air outlet at its other end and adapted to project through the side wall of a furnace with said outlet inside the furnace and provided with means for directing a current of air from the inlet opening through said outlet including a porous refractory element in said casing, said element having closely-spaced horizontal parallel passages directing air in intimate contact with the porous structure of said element and through said outlet, and means for feeding liquid fuel to said element to seep therethrough and be taken up by the air.

4. A liquid fuel burner comprising a casing having an air outlet in one end and constructed and arranged at its other end for the intakeof air, said casing being adapted for mounting in an opening in the side wall of a furnace, a motor-driven fan in said casing for forcing air through said outlet, a porous refractory element arranged between the fan and said outlet and which is formed with a plurality of passages through which the fan forces air to said outlet, and means for supplying liquid fuel to said element to seep through the porous structure thereof and be taken up by the air.

5. A liquid fuel burner comprising a casing having anair outlet in one end and constructed and arranged at its other end for the intake of air, a motor-driven fan in said casing for forcing air through said outlet, a porous refractory element arranged between the fan and said outlet and which is spaced from the wall of the casing to form an annular air passage around the refractory element leading to said outlet and which `is formed with a plurality of passages through which thefan forces air to said outlet, and means for supplying liquid fuel to said element to seep through the porous structure thereof and be taken up by the air.

6. A liquid fuel burner comprising a casing having an air outlet in one end and constructed and arranged at its other endv for the intake of air, a motor-driven fan in said casing for forcing air through said outlet, a porous refractory element arranged between the fan and said outlet and which is formed with a plurality of passages through which the fan forces air to said outlet, air-directing means between the fan-and the refractory element including vanes to control the direction of the air currents, and means for supplying liquid fuel to said element to seep through the porous structure thereof and be taken up by the air.

7. A liquid fuel burner comprising a casing having an air outlet in one end and constructed and arranged at its other end for the intake of air, a motor-driven fan in said casing for forcing air through said outlet, a porous refractory element arranged between the fan and said outlet and which is spaced from the wall of the casing to form an annular air passage around the refractory element leading to said outlet and which is formed with a plurality of passages through which the fan forces air to said outlet, air-directing means between the fan and the refractory element including vanes to control the direction of the air currents, and means for supplying liquid fuel to said element to seep through the porous structure thereof and be taken up by the air.

8. A liquid fuel burner comprising a casing having an air outlet in one end and constructed and arranged at its other end for the intake of air, a motor-driven fan in said casingfor forcing air through said outlet, a porous refractory element arranged between the fan and said outlet and which is spaced from the wall of the casing to form an annular air passage around the refractory element leading to said outlet, air-directing means between the fan and the refractory element including varies to control the direction of the air currents, and means for supplying liquid fuel to said element to seep through leading to said outlet. a porous refractory element mounted in one end of the inner casing in line with the outlet, said inner casing having means for admitting air to the face of the refractory element opposite said outlet, a motordriven fan in the outer casing adjacent said air intake means and arranged to force air through said annular passage and into the inner casing and thence through the refractory element, and means for supplying fuel to the refractory element to seep therethrough and be taken up by the air forced through said element.

10. A burner comprising an outer casing having an air outlet in one end and air intake means atI the other end, an inner casingI supported in the outer casing and spaced therefrom to leave between the two casings an annular air passage leading to said outlet, a porous refractory element mounted in one end of the inner casing in line with the outlet', and having passages therethrough opening into said outlet, said inner casing having means for admitting air to the face of the refractory element opposite said outlet, a motor-driven fan in the outer casing adjacent said inlet and arranged to force air through said annular passage and into the inner casing and thence through the refractory element, and means for'supplying fuelvto the refractory element to seep therethrough and be taken up by the air forced through said element.

11. A burner comprising an outer casing having an air outlet in one end and air intake means at the other end, an inner casing supported in the outer casing and spaced therefrom to leave between the two casings an annular air passage leading to said outlet, a porous refractory element mounted in one end of the inner casing in line with the outlet, said inner casing having an opening in its opposite end so arranged that the air intake means and the outlet of the outer casing and said refractory element and said opening in the end of the inner casing are all in line, a motor-driven fan supported in the outer casing between said air intake means and the end of the inner casing formed with the opening, and means for supplying fuel to said refractory element to seep therethrough and be taken up by the air forced through said element by the fan.

12. A burner comprising an outer casing having an air outlet in one end and air intake means at the other end, an inner casing supported in the outer casing and spaced therefrom to leave between the two casings an annular air passage leading to said outlet, a porous refractory element mounted in oneend of the inner casing in line with the outlet and having passages therethrough opening into said outlet, said inner casing having an opening in its opposite end soarranged that the air intake means and the outlet of the outer casing and said refractory element and said opening in the end of the inner casing are all in line, a motor-driven fan supported in the outer casing between said air intake means and the end of the inner casing formed with the opening, and means for supplying fuel to said refractory elementV to seep therethrough and be taken up by the air forced through said element by the fan.

13. A burner comprising an outer casing having an air outlet in one end and air intake means at the other end, an inner casingv supported in the outer casing and spaced therefrom to leave between the two casings an annular air passage leading to said outlet, a porous refractory element mounted in one end of the inner` casing in line with the outlet, said inner casing having a motor in its opposite end and having an air spacebetween said motor and the refractory element and formed with openings in its walls providing communication'between said air space and the annular space between the two casings, a fan driven by said motor and arranged adjacent said air intake means and forcing air through said annular space toward said outlet, and meansV for supplying fuel to said refractory element to seep therethrough and be taken up by the air forced through said element by the fan.

14. A burner comprising an outer casing having an air outlet in one end and air intake means at the other end, an inner casing supported in the outer casing and spaced therefrom to leave between the two casings an annular air passage leading to said outlet, a porous refractory element mounted in one end of the inner casing in line with the. outlet and having passages therethrough opening into said outlet, said inner casing having a motor in its opposite end and having an air space between said motor and the refractory element and formed with openings in its walls providing communication between said air space and the annular space between the two casings, a fan driven by said motor and arranged adjacent said air intake means and forcing air through said annular space toward said outlet, and means for supplying fuel to said refractory element to seep therethrough and be taken up by the air forced through said element by the fan.

15. A burner comprising an outer casing having an air outlet in one end and air intake means at the other end, an inner casing supported in the outer casing and spaced therefrom to leave between the two casings an annular air passage leading to said outlet, a porous refractory element mounted in one end of the inner casing in line with the outlet, said inner casing having a motor in its opposite end and having an air space between said motor and the refractory element and formed with integral vanes turned outwardly from the walls around said space and leaving openings providing communication between said air space and the annular space between the two casings, said vanes being arranged to extend parallel to the axis of the casing and forming means to straighten out the air current flowing through said annular passage, a fan driven by said motor and arranged adjacent said air intake means and forcing air through said annular space toward said outlet, and means for supplying fuel to said refractory element to seep therethrough and be taken up by the air forced through said element by the fan.

16. A burner comprising an outer casing having an air outlet in one end and air intake means at the other end, an inner casing supported in the outer casing and spaced therefrom to leave between the two casings an annular air passage leading to said outlet, a porous refractory element mounted in one end of the inner casing in line with the outlet and having passages therethrough opening into said outlet, said inner casing having a motor in its opposite end and having an air space between said motor and the refractory element and formed with integral vanes turned outwardly from the walls around said space and leaving openings providing communication be'- tweenA said air space and the annular space between thetwo casings, said vanes being arranged to extend parallel to the axis of the casing and forming means to straighten out the air current owing through said annular passage, a fan driven by said motor and arranged adjacent said air intake means and forcing air through said annular space toward said outlet, and means for supplying fuel' to said refractory element to seep therethrough and be taken up by the air forced through said element by the fan.

'17. A liquid fuel burner comprising a casing formed with an air outlet and provided with means for directing a current of air through said outlet, a porous refractory element mounted in the casing in line with said outlet and in inti- `mate contact with which the current of air passes to the outlet, said element having a considerable number of parallel generally horizontal passages directing portions of the air current through said element and through said outlet, means for feeding liquid fuel to said element to seep therethrough and be taken up by the air, and an igni- .tion device arranged immediately adjacent said refractory element.

18. .A burner comprising an outer casing having an air outlet in one end and air intake means at the other end, an inner casing supported in the outer casing and spaced therefrom to leave between the two casings an annular air passage leading to said outlet, a porous refractory element mounted in one end of the inner casing in line with the outlet, said inner casing having means for admitting air to the face of the refractory element opposite said outlet, a motor-driven fan in the outer casing adjacent said inlet and arranged to force air through said annular passage and into the inner casing and thence through the refractory element, means for supplying fuel to the refractory element to seep therethrough and be taken up by the air forced through said element, and an ignition device arranged immediately adjacent said refractory element.

19. A liquid fuel burner comprising an outer casing, an inner casing supported within the outer casing and spaced therefrom to form an annular air passage, a motor in one end of the inner casing, a refractory vaporizer element in the other end of the inner casing having passages therethrough, said inner casing being formed with openings intermediate the motor and the refractory element to admit primary air to the passages in the refractory element, means to vary the effective size of said openings, a fan driven by said motor for supplying air to pass through said openings and through said annular air passage, and means for supplying liquid fuel to the fractory element.

20. A liquid fuel burner comprising an cuter casing, an inner casing supported within the outer 'casing and spaced therefrom to form an annular air passage, a motor in one end of the inner casing, a refractory vaporizer element in the other end of the inner casing having passages therethrough, said inner casing being formed with openings intermediate the motor and the refractory element to admit primary air to the passagesy in the refractory element, means to vary the eifective size of said openings, said means comprising a ring surrounding the portion of the inner casing formed with said openings, said ring having corresponding openings and being rotatable to close or open said openings, a fan driven by said motor for supplying air to pass through said openings and through said annular air passage, and means for supplying liquid fuel to the refractory element.

21. A liquid fuel burner comprising an outer casing, an inner casing supported within the outer casing and spaced therefrom to form an annular air passage, a motor-driven air-circulating device adjacent one end of the inner casing, a refractory vaporizer element in the other end of the inner casing having passages therethrough, said inner casing being formed with openings intermediate the motor and the refractory element to admit primary air to the passages in the refractory element, a sheet metal extension of said outer casing surrounding and spaced outwardly from the refractory element to form an annular secondary air passage and spaced inwardly from the outer casing to form an annular tertiary air passage, a fan driven by the motor to force air through said passages, and means to supply liquid fuel to the refractory element.

22. In a liquid fuel burner, a refractory vaporizer element having passages therethrough for primary air, a casing part surrounding said element in spa'ced relationship thereto for directing secondary air in an envelope closely surrounding the refractory element, a casing surrounding said element and the end of said part and which is larger than said part for directing tertiary air in an envelope outside of and separated from the refractory element, and means for supplying fuel to the refractory vaporizer element.

23. A liquid fuel burner comprising an outer casing, an inner casingsupported within the outer casing and spaced therefrom to form an annular air passage, means for circulating air through said annular passage and through said inner casing, a refractory vaporizer element in the path of the air passing through the inner casing, said inner casing being formed with openings to admit air to the refractory element, a sheet metal extension of said outer casing surrounding and spaced outwardly from the refractory element to form an annular secondary air'passage and spaced inwardly from the outer casing to form an annular tertiary air passage, and means to supply liquid fuel to the refractory element.

24. A burner comprising a generally conicalended porous refractory element having passages therethrough parallel to 'its axis and having means to supply fuel thereto, and means for directing primary air through said passages and secondary air over the conical end surface of said element, said -means including a conical metal member directing the secondary air over the end face of the refractory element and arranged to be highly heated when the burner is in operation and to radiate heat onto said refractory element to aid in vaporizing the fuel seeping through said element.

25. A burner comprising a porous refractory element having passages therethrough and having means to supply fuel to seep through the porous structure thereof, means for directing primary air through said passages and secondary air to be mixed with the primary air after issuing from the passages, and a hot-Wire igniter in contact with the refractory element between said passages, said igniter being out of but immediately adjacent the pathrof the primary air.

26. A burner comprising a porous refractory element having passages therethrough and having means to supply fuel to seep through the porous structure thereof, means for directing primary air through said passages and secondary air to be mixed with the primary air after issuing from the passages, and a spark type igniter having electrodes arranged in adjacent ones of said passages and discharging through the wall between said adjacent passages.

KEMPER P. BRACE.

Images