US3199572A - Radiant gas burner - Google Patents

Description

Aug. 10, 1965 A. E.IBOULET 3,199,572

RADIANT GAS BURNER Filed Sept. 26, 1962 5 Sheets-Sheet 1 Aug. 10, 1965 A. E. BoULET 3,199,572

RADIANT GAS BURNER Filed Sept. 26, 1962 5 Sheets-Sheet 2 Flg. 8

Aug. l0, 1965 A. E. BOULET RADIANT GAS VBURNER 3 Sheets-Sheet 3 Filed Sept. 26, 1962 Fig.5

United States Patent O 3,199,572 RADEANT GAS BURNER Auguste Emile Boulet, La Palmeraie, Avenue Urbain Bosio, Nice, France v Filed Sept, 26, 1962, Ser. No. 226,396 1 Claim. (Cl. 15S- 116) This is a continuation-in-part of my application Ser. No. 828,625 ined July 21, 1959, now abandoned, and relates to improvements in gas burner units.

The conventional induction-type gas burner units generally comprise a gauged-opening injector for supplying gas to the inlet of a mixing chamber directly connected with the atmosphere, said chamber being shaped as a venturi formed with a constricted or neck portion at its inlet and widening out at its opposite end terminated by a head mem er pierced with holes or slits. The gas jet leaving the injector generating a partial vacuum carries along by friction combustion air. The widened-out portion, from said neck to the head member, causes the speed to be converted into pressure, whereby the mixture may escape through the outlet openings of the burner.

In most types of burners, a portion only of the combustion air, viz. the .so-called primary air is carried along by the gas jet in the venturi, the necessary complementary or secondary air being derived from the atmosphere adjacent the head member and forming a flame opposite each outlet for the mixture.

In order for the flame to be stable, it is necessary to meet the following conditions:

(1) The speed of the mixture leaving the burner should not exceed the propagation speed of the flame at said point, otherwise the llame will cut off.

(2) The speed of the mixture passing inside the burner, particularly through the outlet openings provided on a sufiiciently thick wall relative to the cross-section of said openings, should be high enough for a flareback tothe injector to be avoided.

ln such burners, the outlet cross-section of the openings is generally between 1.7 and 2.2 times the cross-section of the venturi constriction: the thermal output per square centimeter of the outlet section is then between 700 and 800 millith./hour for rich gases such as butane or rich gas mixtures, and about 1300 millith./hour for town gas or gases substitutable thereto. For gases having a high llame propagating velocity, the thickness of the wall formed with the outlet openings is twice as great as their diameter (generally 6 to 8 mm. thick).

The gas burner unit according to the invention generating an intra-red radiation comprises essentially, at the outlet of a mixing chamber supplied with gaseous fuel Vand air or other combustive gas, a single perforated screen topped by one or a plurality of tubes, exclusive of any other piece; the mixture leaves the chamber through the perforated screen, grid or other similar member, providing a passage of a substantially greater cross-section than indicated hereinabove, with respect to the section of the venturi neck, viz. about 10 times the section of said neck, although this may be veryrnuch larger; thus, the combustion mixture leaves at a very low velocity, so that combustion is localized at the level of the grid defining the outlet cross-section. On the other hand, due to the large outlet section provided on a thin Wall, there is substantially no counter-action to the primary air entrainment, so that the combustion of the mixture is complete, without any secondary air being required. There is moreover no risk of setting re at the injector on account ofthe presence of the screen or other similar element, which acts as a ameguard. On account of the large outlet cross-section,

'the thermal flow per section unit is substantially lower than in flame burners: 50 millith./hour at the most per square centimeter of outlet section.

Patented Aug. l0, 19565 The screen or grid may consist of a metal-wire netting or lattice with intervening voids, such as a wire gauze for instance. The wire diameten'and the spacing between adjacent wires, vary in accordance with the intended use. In any case, the area of the voids which constitutes the outlet section of the burner is substantially greater than the section of the inlet nozzle. The rat-io of these sections may moreover vary within comparatively wide limits, ranging from 25 to 50, although these limiting figures present no absolute character.

The ratio of the voids to the total area of the screen is selected as a function of the radiating effect it is desired to impart to the screen or grid. It may vary within substantially wide limits: thus, burner units have been built, whose void area is between 18 and,60% of the total surface, although these figures are in no way of an absolute nature.

In any case, the outlet wall having a reduced thickness and being formed with a plurality `of adjacent openingsoffers practically no resistance to the passage ofthe lluid.V

The structure, which is perpendicular to the screen or grid and arranged directly on Vtop thereof, may `have various shapes according to the size of the head member, the use desired, etc. It may comprise a plurality of tubes forming a multicellular partition system or grating, or else a single tube forming so to say a monocellular partition system. The one or several of the chimneys or tunnels formed above the screen have preferably a height of the same order of magnitude as the transversal dimension thereof.

in the case of a multicellular partition structure, the partitions limiting the cells or chimneys are thin and thus do not atiect the escaping of the combustion gases.

The combustion takes place without a llame, on the outer surface of the wall, without the intervention of secondary air and provides a very high temperature. The absence of a llame enables the combustion to be` considered as catalytic, and since no catalytic bodyi.e. no catalysthas to be present, the combustion may be considered as auto-catalytic.

However, it is also an object of the invention to provide an embodiment according to which the metal constituting Vthe tube possesses catalytic properties. The auto-catalytic combustion mentioned above is then supplemented by an ordinary catalytic combustion, resulting in the burner being practically inextinguishable.

it is another object or the invention to provide an embodiment of a burner wherein the metal constituting the perforated screen presents a catalytic property.

The perforated screen or grid serves also as a relector for infra-red rays transmitted by the wall of the tube or tubes. Moreo e-r, it performs in itself a radiating function, the importance of which depends on the ratio of the voids to the total surface. In addition, the screen denes the combustion area, thus preventing flare-backs, Y

Although the mixture of fuel gas and air flows at a very low speed, .as proved by the .silent operation of the burner, lthe gases resulting from the combustion, of a volume substantially greater than `that of said mixture, are evacuated at high speed, without being restrained in any point, on account of the absence of any piece other than the screen and the tube. This evacuation is accelerated by the presence of one or a plurality of tubes which may function as chimneys when the screen is substantially horizontal.

The height of the tube or tubes may vary within wide limits according to the result desired. The shorter the tube or tubes, the higher the temperature of the burnt gases at the outlet thereof. Y

According .to another feature of the invention, burners .are provided having comparatively long tubes, withra high efficiency of infra-red radiation and a comparatively low convection heating.

On the other hand, radiation wave-lengths may be modified by varying the length of the tube or tubes, and consequently the temperature thereof.

Thefburner unit according to the invention is adapted to deliver a neutral combustion atmosphere, i.e. neither oxidizing, nor reducing, by simply adjusting the air in the venturi, or by other means.

It is .thus possible to use for building the burner, and in particular for mak-ing the perforated screen, any currently available material, such as iron. An iron-made burner unit has withstood thousands of hours of operation, in spite of the high temperatures reached.

The burner unit may also be adjusted to deliver an oxidizing or a reducing atmosphere of burnt gases, over a comparatively wide composition range in either case. The resulting reducing atmosphere may be used, for instance, for a de-oxidizing process, such as the removal of rust from ferrous surfaces, whereas an oxidizing atmosphere is used for room heating.

The burner unit according to the invention may be supplied with a fuel gas naturally containing sulfur compounds, without impairing its operation. The burner will not produce hydrogen sulfide, as proved by testing a perforated screen made of silver which was not attacked during the experiment.

Burners are known having a cellular partition structure located near a at outlet diaphragm for the mixture, but insuch burners the diaphragm comprises at least two adjacent, substantially parallel wire ganzes between which the combustion takes place. The main function of the partition structure is .to avoid the harmful inlluence of draughts and, although said structure exercises a certain radiating elfect on the diaphragm, this effect has no decisive influence on the operation of the burner, which remains satisfactory (in an atmosphere without the presence of draughts) when the partit-ion structure is removed from the burner, in contradistinction with the burner according to the invention, wherein the removal of this structure basically affects the operation thereof.

The invention will be best understood from the following description and appended drawings, wherein:

FIG. 1 is a plan View, with the partition structure and the fastening member removed.

FIG. 2 is a plan View of the partition Structure.

FIG. 3 is a cross-sectional view along line 3-3 of FIG. 1.

FIG. 4 is a view, at an enlarged scale, of a portion of FIG. 3.

FIG. 5 is an elevational `side view of the device.

FIG. 6 is a cross-sectional view along line 6 6 of FIG. `5.

FIG. 7 is a side view at right `angle of FIG. 5.

FIG. 8 is a diagrammatic view of an embodiment, illustrating a single-type burner.

FIG. 9 is a plan view of an alternative embodiment of the device illustrated in FIGS. 1 to 7.

FIG. 10 is an elevational View, with parts broken away, corresponding to that shown in FIG. 9.

Referring to the drawings, the burner unit as shown in the embodiment illustrated 4in FIGS. 1 through 7, comprises a body 100, of a material such as cast aluminium, extending along a rectangular plane in the example given, and formed with a peripheral edge 101, the base of which lpresents a groove portion 102. In said groove portion there is located a gasket 103 supporting a cellular structure 104 comprising a plurality of juxtaposed squareshaped prism elements, opened at their upper and lower sides. At the base of the prism-defining partitions, there are formed semi-circular notches 105. A wire-gauze 106, surmounted by said structure, rests peripherally on the rim 107 of a U-sectioned frame 108 bounding the partition framework, the hanged rim 109 of said wire-gauze resting against the upper edge 110 of said frame 108. The

l partition and wire-gauze assembly forming an unitary structure will thus rest with its rim 107 on a joint 111 located in groove 102. A ring of rectangular contour 112, bearing against edge 101, enables the structure to be fixed in position.

The structure forms the upper perforated Wall of a space 113 bounded by body 100 into which leads the mixing chamber proper 114. The latter is bounded by an inner wall 115, cast in one piece with body having an extension 116, along the axis of which is an injector 1-17 having a calibrated opening shown at 118. `The supply of fuel gas takes place through conduit 119, the adjustment being effected through pin-cock 120. Injector 117 is located adjacent two windows 121 and 122 through which the primary air is entrained, the ow area of which may be adjusted by means of a slide-ring 122 (shown in broken lines in FIGS. 1 and 5), which may be firmly ixed in position. Starting from opening 118, the cross-section of the mixing chamber first decreases, the increases, the narrow-section area or venturi neck portion thus formed by the convergent-divergent portion being shown at 123. At the outlet of chamber 114, there is provided a zig-zag- -shaped deflector 124 (FIG. l) also cast in one piece with the body 100, with rounded angular portions, a plate 125, secured by means of a screw 126 and preventing direct communication between the partition structure and chamber 1'14.

The combustion gas supplied by nozzle 119 escaping through the injector opening entrains, by induction, the combustion air which enters through the windows or openings 121 and 122. The mixing takes place in chamber 114 and the outflow through the vertically extending (in this ligure) ports 127, 128 provided between the end portion of wall 11S and the detlector 124 the shape `of which is such as to provide a homogeneous distribution of the mixture over the entire underlying portion of the wire-gauze 106. The combustion occurs on the upper side of the latter and, immediately after ring, is effected without producing a llame, under the conditions and with the advantages already mentioned.

In a practical embodiment of the burner, the diameter of the body of the inlet nozzle is 13 mm., i.e. a cross-sec- .tion of 1.33 sq. cm. The area of the head-member is 111.4 sq. cm. |The wire-gauze is formed of 0.2 mm. diameter wires, with 256 meshes per sq. cm. The area of the voids relative to the overall wire gauze surface is thus equal to 46%; the total area of the voids (outlet section) was equal to 51 om?. Thus, the ratio of the outlet section to the section of the venturi constriction is 38.5.

The partit-ion framework on top of the screen of Wiregauze is square-shaped, the partitions being 0.6 mm. thick and each one of the cells having a section of 7 x 7 mm. The partition framework is 7 mm. high. The output of such a burner supplied with butane gas at a pressure of 112 g./ sq. cm. was found to be 1891 millitherms/hour, i.e. a thermal output of 117.1 millith./hour/ sq. cm. of the outlet section. The pressure difference on both sides of the outlet wall was of the order of 0.1 to 0.2 mm. of water.

Obviously, the above numerical designations are not to be considered as limitative, but demonstrate the advantageous features of the burner according to the invention.

Referring now to FIG. 8, the embodiment of the burner shown herein comprises essentially a square, circular, hexagonal etc. cross-sectioned tube 20, closed at the base thereof by means of a perforated screen 21, the assembly being mounted over a mixing chamber 22 supplied with a combustive substance and fuel, for instance by means of a venturi 23, an inlet injector 24 for the fuel gas and an air-intake 2S. The ratio of the height of the tube to the mean size of the perforated screen may vary within wide limits, according to the result to be obtained and the gases used.

At the instant of lighting the burner, a blue flame occurs above screen 21 and progressively fades out, the combustion proceeding without producing any llame, at a very high temperature, the combustion area being limited by screen 21.

It is assumed (this applying to the above described embodiment) that the portion of wall 20 which is adjacent screen 21, when heated by the name occurring at the starting of the lighting, will rst transmit infrared rays, then red rays which cause the ilarne to be irradiated and thereafter to disappear, the screen 21 being rendered incandescent. During the operation of the unit, this catalytic-like phenomenon which activates the combustion is further produced, rendering the latter complete and enabling the burner to evacuate only burnt gases, at high speed, the evacuation taking place without interference at any point, on account of the absence of obstacles above the screen, but, on the contrary, being accelerated by the presence of the tube.

The tube 20 may be solid or perforated. It may be made of refractory material, such as steatite, melted cement, clay, porcelain, silica etc., or of metal, and may be adapted to transmit red and infra-red rays.

The perforated screen 21 may be of the same material to that forming the tube mounted above it, or be of a different material. In many cases, it is built of a wire-gauze or a perforated shed-iron and its size features correspond to the requirements mentioned herein above.

The screen is lighted and heated at its upper portion by the phenomenon mentioned above, its lower portion being cooled by the supply of fresh, unburnt combustion gases.

The gas burner unit according to the invention operates without requiring any secondary air, thus enabling the unit to bev used under very different ambient conditions. It may work in an airless atmosphere, and may therefore be utilized for heating kitchen stoves or industrial ovens, etc., wherein gases derived from a previous combustion may be stagnant. It may function at high altitudes or in a damp or dust-charged atmosphere, or in water or other liquid.

A good operation of the burner may be obtained for various adjustments of the gas mixture, to which corresponds an oxidizing, neutral or reducing atmosphere of burnt gases.

For the emission of infra-red and/or red rays, the adjustment is preferably selected to deliver a neutral atmosphere at the outlet of the burner.

It is for such an adjustment, delivering a neutral atmosphere at the outlet of the burner, that the wall of the tube and the perforated screen are brought to the maximum temperature.

By making use of a constituent material for the tube or for that tube portion adjacent the perforated screen, and/ or for the perforated screen, such as thorium, cerium, etc. of great brilliancy, the burner provides a bright light, which may be used for lighting purposes.

In any case, the operation of the burner is completely noiseless and may take place in any desired position: Vertical, horizontal, reversed.

The burner unit according to the invention has high versatility. For instance, without modifying the adjustment of the air, the pressure of the fuel gas may be varied within comparatively wide limits. It is also pos-sible, when using butane gas for heating purposes, to vary the pressure of the butane in the range from g./sq. cm. to

g./sq. crn. without affecting safety conditions and health regulations.

The unit described with reference to FIGS. 1 to 7 may be considered as formed of an association of several burners-single or mono-burners-as shown in FIG. 8.

FIGS. 9 and 10 illustrate another embodiment of the device, resulting from an association of a plurality of identical single burners supplied with a gas mixture from a common chamber, the perforated screen of the monoburners being part .of the same general screen. On a perforated screen 30, secured tightly at the upper portion of a mixing chamber 31 fitted with an air-intake 32 and a gas inlet 33, are mounted partitions 34 in perpendicular relationship with the screen, which, in the example illustrated, form juxtaposed, hexagonal, cells 35. This apparatus is constituted by juxtaposing a plurality of mono-burners as described hereinabove, each elementary screen of which is topped by a hexagonal-sectioned tube, one wall being common to two adjacent tubes. The partitions are in contact with the perforated screen, and no discontinuities are left therebetween. It is'however arranged for a communication between the tubes or chimneys of each burner to be provided, by forming the lower portion of a partition element with a notch, as shown at 36. This will facilitate the propagation ofthe ame when lighting the apparatus.

The external wall of the partition framework is preferably heat-insulated, in order not Vto reduce the output of the peripheral burners, as shown at 37.

What I claim is: Y

A device for the combustion of a gas comprising an enclosure having a narrow inlet end and a widened output end, fuel gas injection means at the narrow inlet end and an opening for the admission of ambient air under the entraining action of the injected gas, a single wire gauze at the outlet end having a total area of voids which ranges from 25 to 50 times that of the narrow inlet end, partition means surmounted on said wire gauze in coutact relationship therewith, said partition means being constituted of thin partitions the height of which is subsantially of the same order of magnitude as the width of the cells bounded thereby, each partition being provided with a notch on the edge thereof which is in contact with sar wire gauze to provide communication between the ce s.

References Cited by the Examiner UNITED STATES PATENTS 50,678 10/ 65 Birkey 158-111 547,959 10/95 Main 158-112 769,568 9/04 Roberts et al. 158-112 X 1,259,029 3/ 18 Lucke 158-99 1,304,755 5/19 Ellis 158-99 1,900,217 11/33 Adams 126-92 X 3,029,866 4/ 62 Honger.

3,040,805 6/ 62 Lambert.

3,044,538 7/62 Honeger 158-116 FOREIGN PATENTS 1,108,655 9/ 55 France.

JAMES W. WESTHAVER, Primary Examiner. FREDERICK L. MATTESON, JR., Examiner.

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