US2492756A - Fuel vaporizing and combustion apparatus - Google Patents

Description

I 1949 H. J. DE N. McCOLLUM 2,492,756

FUEL VAPORIZING AND COMBUSTION APPARATUS Filed Jan. 26, 1946 3 Sheets-Sheet 1 v fl' -11 Q i' T K Q h 1 I 'l U" 3 5.3 U 2 I I i y i g 3, l/

g whim mzfuzl H. J. DE N- M coLLuM FUEL VAPQRIZING, AND OMBUSTION APPARATUS s Sheets-Sheet 2 Filed Jan. 26, 1946 Dec. 27, 1949 H. J. DE N. McCOLLUM 2,492,756

FUEL VPORiZING AND COMBUSTION APPARATflS Fild Jan. 26, 1946 L 3 sheets-sheet 3 Patented o... 21, 1949 FUEL VAPOBIZING AND COMBUSTION APPARATUS Henry J. De N. Mccollum, deceased, late of Chicare, 111., by Thelma McCollum, executrix, Chicage, 11]., assignor to Stewart-Warner Corporation, Chicago, m, a corporation of Virginia Application January 26, 1946, SeriaiNo. 643,598

'1 Claims.

The present invention relates to heating apparatus and, more particularly, to a liquid fuel burner intended for use with automobile and aircraft type heaters.

As a rule, burners for heaters of the above type require that some blower means be provided for forcing air through the combustion side of the heater. In the case of aircraft heaters, rams or scoops located exteriorly of the aircraft frequently have been used for this purpose. Although burners for more bulky types of heaters have frequently dispensed with combustion air blowers and have relied simply upon the rising action of the hot products of combustion in a stack or chimney to suppl the necessary draft, it will be appreciated that for this simple scheme to work requires either that considerable chimney height be provided or that the pressure on the combustion side of the heater be extremely low, or sometimes both. Since the pressure on the heater combustion side cannot be low unless the heat exchange passages be quite open, it is apparent that heaters that do not have forced circulation on the combustion side must necessarily be heavier and more bulky than heaters which do use some power consuming combustion air circulating means.

One of the objects of the present invention is to provide a burner for use in a heater having a moderately high pressure on the combustion side and which dispenses with the requirement of a blower or other power consuming means for circulating the combustion air.

An additional object of the present invention is to provide a burner which creates its own draft regardless of the position in which it operates.

Yet another object of the present invention is to provide a novel heater which supplies sufficient draft to operate the burner against a considerable combustion side pressure.

Other objects and advantages will become apparent from the following description of a preferred embodiment of the invention which is illustrated in the accompanying drawings.

In the drawings, in which similar characters of reference refer to similar parts throughout the several views:

Fig. 1 is a longitudinal sectional view of a heater having a burner embodying the present invention.

line l! of P18. 2;

Fig. 4 is a side view of the burner of an alternative form of the present invention with a portion of the burner broken away to show the interior in longitudinal section;

Fig. 5 is a transverse sectional view of the burner illustrated in Fig. 4 and may be considered as taken in the direction of the arrows along the line 5--5 of Fig. 4; and

Fig. 6 is a longitudinal sectional view of still another alternative burner embodying the pres-v ent invention.

Referring to Figs. 1, 2 and 3, a heater III is shown as comprised of a cylindrical case l2 enclosing a heat exchanger l4. The heat exchanger is comprised of a cylindrical shell 18 having fins I8 upon its exterior surface which transfer heat from the shell to air flowing through the cylindrical case. l2, the air passing around the shell i6 and between the fins l2.

At one end, the heater is provided with a burner 20 in which hot products of combustion are generated, these products passing into the shell ii and thence to an exhaust pipe 22 leading away from the space to be heated.

The burner 20, in which the invention principally resides, comprises a cylindrical combustion chamber 24 which has an opening 25 at one end connected to the cylindrical shell IS. The opposite end of the combustion chamber 24 is closed as at 28.

The combustion chamber 24 is provided at one side with a mixture forming chamber 30 which is generally cylindrical and which is arranged with its axis at right angles with the axis of the combustion chamber 24. The mixing chamber 30 is of considerably smaller diameter than the combustion chamber 24 and is offset below the axis thereof so that mixture enters the combustion chamber tangentially, thereby producing a swirling motion of the mixture within the combustion chamber. A second tubular extension forming a flash tube 32 is arranged with its axis parallel to the mixing chamber 30 and connects at one end with a port 34 in the side of the combustion chamber 24, but in a position to one side of the mixing chamber 30, so that swirling action within the combustion chamber produced by the mixing The section through theburner proper is stagchamber inlet position tends to cause the mixture gered as indicated by the line i-l on Fig. 2;

Fig. 2 is a side view of the burner illustrated in Fig. 1; 1

- Fig. 3 is a transverse sectional view through the in the combustion chamber to flow through the port 34 and into the flash tube 32. The mixing chamber 30 is. provided internally with a ring 38 which forms a Venturi throat closely adj acent the.

burner illustrated in Fig.2 and may be considered combustion chamber 24. 'Arow'of air inlet openlugs 38 is formed in the ing chamber 38 at a point closely adjacent the inlet side of the venturi 36, while a nozzle 46 formed in a circular plate 42 is arranged so that the plate 42 closes the cylindrical opening in the mixing chamber 38 with the nozzle positioned axially of the venturi 36 in a plane with the openings or ports 38.

At the end opposite the combustion chamber, the mixing chamber 30 is closed by a threaded plug 44 through which liquid fuel is introduced by way of a fitting 46 therein. The space between the plug 44 and the nozzle plate 42 is substantially filled by a vaporizing cartridge or generator 48 which is comprised of a cylindrical sheet metal can filled with a quantity of porous heat conducting material, such as copper wool 50. In order to provide a free path for the flow of fuel into and from the copper wool filling 68, the ends of the cartridge are perforated and dished inwardly, as at 52, to form small plenum chambers in the vicinity of the inlet fitting 46 and the nozzle 48.

The ports 38 lead from the interior of the mixing chamber 38 to the outside and a port indicated by the numeral 54 extends through the common wall separating the chamber 30 from the flash tube 32. Communication between these two chambers is, therefore, established through the port 54 and by way of combustion chamber 24. The flash tube 32 is provided with an igniter 56 of the hot wire type which is comprised of a heating coil 58 enclosed within a metal sleeve 60, the latter being threaded into the outer end of the tube 32. The coil 58 is provided at one end with an insulated terminal 62 which receives electric power through an igniter wire 64. The other end of the coil is grounded by brazing, as at 66, to the inner end of the sleeve 66.

Preferably the entire basic assembly, comprised of the combuston chamber 24, the mixing tubular wall of the mixchamber 36, and the flash tube 32, is formed as a-.-single casting of a material having a comparatively high rate of thermal conductivity, such' as bronze, copper or brass, for instance.

The device illustrated operates in the following manner. First, the igniter coil 58 is energized by way of the wire 64. This causes the igniter quickly to reach red heat and to heat the wall of the flash tube 32. conducted through the wall of the mixing chamber 30 and to the cartridge 48. The temperature of the cartridge and the copper wool fllling, therefore, is soon raised sufficiently to vaporize the fuel to be used. This fuel is usually, though not necessarily, gasoline and is introduced to the fitting 46 by a low pressure source, not shown, such as the ordinary automobile pump which supplies gasoline to an automobile carburetor.

Fuel entering through the fitting 46 passes into the hot cartridge 50 which acts as a boiler or generator and quickly changes the fuel to'vapor. The vapor issues through the jet 48 at comparatively high velocity, since it is under a pressure of approximately three to ten pounds per square inch. The nozzle 40 is the principal restriction in the fuel supply to the burner and, therefore, as rapidly as vapor leaves the nozzle 48 it will be replaced by fuel entering through the fitting 46. Thus, a steady jet of gasoline or other fuel vapor issues from the nozzle 40 and passes through the venturi 36 and on into the combustion chamber 24. This high velocity jet reduces the pressure in the vicinity of the venturi and inspirates air through the openings 38, the

This heat is rapidly air also passing through the venturi and into the combustion chamber 24. The resulting mixture entering the combustion chamber at substantial velocity causes the gases to swirl about therein so as to produce a higher pressure at the port 34 than at the port 54. This is because the veocity effect of the rotating gases in the combustion chamber produces a dynamic pressure at the port 34 which tends to cause these gases to flow through into the tubular extension 32. This flow effect is enhanced because the port 54 is connected to the upstream side of the venturi 36 which is a region of low pressure. A portion of the combustible mixture, therefore, flows through the port 34 toward the igniter 56 and through the port 54 where it is recirculated through the venturi '36. As soon as this combustible mixture comes in contact with the hot coil 58, it ignites and the flame flashes back through the port 34 and ignites the main portion of the mixture within the combustion chamber 24. Combustion, therefore, continues within the combustion chamber until the fuel supply to the fitting 46 is discontinued. If any flames should flash through the port 54 into the mixing chamber in the region upstream of the venturi 36, this is of no consequence as the mixture at this point is comparatively poor and does not readily burn, and, further, because the velocity of flow at this point exceeds the rate of flame propagation. The result is that combustion at this point cannot continue, but moves downstream and into the combustion chamber 24.

After the burner has been in operation for a comparatively short while, the casting forming the burner rises in temperature so that heat is conducted back through the walls of the mixing chamber 30 to the cartridge 48, thereby keeping the cartridge at such a temperature that it will continue to act as a vapor generator. The igniter 56, therefore, can be de-energized after the heater has been in operation for a matter of a minute or so.

The burner illustrated in Figs. 4 and 5 is similar to the one just described excepting that the flash tube 18, similar to the flash tube 32 and similarly provided with an igniter I2, is surrounded with an annular vapor generator 14 in heat exchange relation thereto. This arrangeand therefore permits more rapid starting. The annular generator chamber 14 in heat exchange relation to the flash tube I6 is provided near the lower end with a fuel inlet fitting 16 which serves the same purpose as the fitting 46, while the opposite end of this chamber, that is, the upper end, is connected to one end of a U-shaped tube 18 having a nozzle at its opposite end. This nozzle extends into the flared mouth 82 at the inlet end of a mixing tube 84 which extends downwardly and is connected to the combustion chamber 86 tangentially. The flash tube 18 and the mixing tube 84 are parallel to each other so that the swiriling action in the combustion chamber 86 caused by the mixing tube 84 produces turbulence at the mouth of the flash tube 10 sufilcient to cause combustible mixture to move from the fuel supply is turned off. As in the previously described embodiment, the igniter can be deenergized soon after the burner has beenstarted.

8 Fig. 6 illustrate's'a burner embodyin present invention which has more the characteristic of a gun type burner in that it produces a linearly moving flame ratherthana swirling flame. It comprises a casting also formed'of a good heat conducting material which is formed to provide a Venturi throat 02 which is connectedv at its downstream end with the combustion chamber 04 of a heater, indicated generally by the numeral At a point slightly upstream of the throat of the venturi, the casting 00 has a row of ports 08 through which air for combustion can be inspirated. As in the previous embodiments, air flow through the ports 08 is produced by-a nozzle I80 supplied with gasoline or other iuel vapor un- In all ducribed embodiments of the invention,

itwill' be'seen that the energy necessary for moving combustion air through the burner and heat exchanger is produced by vaporizing 1 the fuel and by-directing this vapor as a jet into the burner in such manner that it aspirates air for combustion. .It has'been found that once the burner is balanced to a system or any certain pressure drop, and this balance can be achieved by using nomles oi. diiferentsizeor by using .diflerent size ports 88, thereafterthe burner has good throttling characteristics and will producemixtures of approximately the'same fuel-air ratio throughout a wide range of pressure varia- 1 tion at the inlet to the generator I02, 48 or II,

formed in common. As in the embodiment illustrated in Fig. 1, one of the ports 88-passes through the common wall and into the flash tube H2 so.

that circulation between the flash tube and the low pressure region in the mixing tube is established. Similarly, also an igniter of the hot wire type H4 is located within the flash tube in heat exchange relation thereto and is closely adjacent the generator cartridge I02 so that heat from the igniter H4 is readily conducted to the cartridge when the-igniter is energized.

The end of the flash tube H2 adjacent the combustion chamber 94 is closed excepting for a port H8 which connects the flash tube to the mixing tube at a point well downstream of the venturi 92. It is apparent, therefore, that fuel vapor discharged from the nozzle I00 into the throat 92 of the venturi will produce. a low pressure in the region of the ports '98 which will cause mixture to flow from the mixing tube, through the port H8, in a reverse direction through the flash tube, and finally through the proper port 98 back to the Venturi throat. As soon as the mixture comes into contact with the hot wire of the igniter H4, it is ignited and the flame flashes through the port H8 and into the mixing tube where it ignites the principal portion of the fuel and air mixture. The velocity of flow through the mixing tube adjacent the port H8 is well above the rate of flame propagation, with the result that the combustion zone quickly moves downstream and into the combustion chamber 90 where the flame hangs on around the end of the mixing tube because of. turbulence produced by the abrupt increase in diameter in the gas flow path at the juncture between the mixing tube and combustion chamber.

In some designs, it has been found that the velocity of air moving through the mixing tube and over port H8 produces a suiflcient drop in as the case may be.

Having described the invention, what is claimed as new and useful and desired to be secured by Letters Patent of the United States is:

1. A liquid fuel burning heater comprising means forming a combustion chamber, a vapor generator of relatively large volume. a nozzle connected to receive vapor from said generator, an aspirator operatively associated with said nozzle and connected to said combustion chamber, said nozzle having a tip of minute size relative to the size of the generator to eil'ect a velocity of flow of vaporized fuel through the nozzle suflicient to aspirate air when vapor flows through said nozzle so as to form a combustible mixture and to introduce said combustible mixture into said combustion chamber, and ignition means having a heating element to ignite the combustible mixture in said combustion chamber, said heating element being in heat exchange relationship with the generator initially toheat the same and cause operation thereof to supply vapor for starting the heater and said aspirator forming the sole means for causing the flow or combustion air through the combustion side of said heater.

erator of relatively large size, a nozzle supplied .with vapor by said generator, an asplrator ineluding said nozzle, said nozzle having a tip of minute size relative to the generator to efiect a velocity-of flow of vaporized fuel into said aspirator sufficient to aspirate air 'for introducing air for combustion and mixing said air with-said vapor to produce a combustible mixture, means for introducing said mixture into said combustion chamber tangentially, a flash tube, an elec tric igniter of the hot wire type in said flash tube, said igniter being in heat exchange relation with said generator to heat the same to initiate operation thereof to supply vapor .for starting the heater, and means to produce circulation from said combustion chamber into said flash tube, said means including an opening in the combustion chamber communicating with said flash tube and facing against the direction of rotation of the gases in said combustion chamber and means forming a passageway between said flash tube and said aspirator. I

I 3. A liquid fuel burner comprising a vapor generator, a vapor nozzle connection to receive vapor from said generator, an aspirator including said nozzle for introducing air for combustion and mixing said air with said vapor to produce a combustible mixture, means forming a combustion chamber, conduit means for conveying said mixture to said combustion chamber, a flash tube communicating with said combustion chamber,

7 and an igniter oi the hot wire type in said flash tube, said flash tube including wall structure disposed in heat exchange relation with said igniter and generator and said combustion chamber and enerator.

4. A liquid fuel burner for a heater of the type .which' has high pressure characteristics on the combustion side,- said burner comprising a combustion chamben, a mixing tube connected to discharge into said combustion chamber, said mixing tube including'ain inlet openings, a vapor generator, a nozzle connected to receive vapor from said generator, said nozzle being aligned to project vapor substantially axially of said mixing tube and past said openings, a flash tube igniter associated with said mixin tube including an igniter element of the hot wire type, said element being arranged in heat transfer relationship to said generator, means forming a heat conducting path from said combustion chamber to said generator, said flash tube having two communicating connections to said mixing tube, one of these conhections being located relative to the IniXing tube downstream of the other, and said hot wire igniter element being closely adjacent the farther upstream of said connections.

5. A liquid fuel burner adapted for use with a heater having high combustion side pressure characteristics comprising means forming a cylindrical combustion chamber closed at one end, a heat exchanger connected to the opposite end of said combustion chamber, a mixing tube connected tangentially to said combustion chamber, said mixing tube having its opposite end open to the atmosphere, a flash tube arranged parallel to said mixing tube, said flash tube being connected to said combustion chamber tangentially thereof, an igniter of the hot wire type located in said flash tube, an annular vapor generator surrounding said flash'tube and at least a portion of the igniter therein, a liquid fuel connection to said generator at one end, a vapor outlet tube connected to the opposite end of said generator, said outlet tube having its opposite end formed to provide a nozzle, and said tube being bent to locate said nozzle adjacent theinlet end of said mixing tube so that said nozzle is adapted to direct a, jet of vapor into said mixing tube.

6. A liquid fuel burning heater comprising means forming a combustion chamber, a generator for vaporizing liquid fuel, an igniter of the hot wire .type, body structure for housing said ignite; and generator spaced from said combustion chamber and including a wall separating said igniter and generator and adapted to beinitially heated by saidigniter for heating said generator to start the heater,- said structure beingin heat exchange relation with said combustion chamber to maintain the generator heated during continued operation of the heater, means forming an aspirator in said body structure having an outlet communicating with said combustion chamber, and a nozzle arranged to discharge the vapor-'- ized fuel generated by said generator axially oi said aspirator for causing the same to aspirate air for mixture with the vaporized fuel to forms. combustible mixture, said body structure including a tubular portion establishing communica; tion between said combustion chamber and igniter for receiving a portion of the combustible mixture discharged into said combustion chamber to initiate combustion.

7. In a liquid fuel burning heater having a heat exchanger and a burner including means forming a combustion chamber for producing hot products of combustion and for passing said products of combustion to said heat exchanger, said burner comprising a vapor generator, a nozzle supplied with vapor by said generator, an aspirator including said nozzle {or introducing air for combustion and mixing said air with said vapor to produce a combustible mixture, means for introducing said mixture into said combustion chamber, a flash tube communicating with said burner, and an electric igniter of the hot wire type in said flash tube, said igniter and generator being separated by structure including a. wall in heat exchange relation with said generator and with said combustion chamber.

THELMA MCCOLLUM, Executria: of the Last Will and Testament of Henry J. De N. McCollum, Deceased.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Williams Nov. 30, 1948

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