US1259029A - Apparatus for burning explosive gaseous mixtures. - Google Patents

Description

C. E. LUCKE.

APPARATUS FOR BURMNG ExPLoslvE GAsEous MlxTuHEs.

APPLICATION FILED MAY 20, I9I3- RENEWED JULY 2B. 1917.

Patented Mar. 12, w18.

2 SHEETS-SHEET I.

IIIIIIII fj i C. E. LUCKE.

APPARATUS FOR BURNING EXPLOSIVE GASEOUS MIXTURES.

2 SHEETS-SHEEVT 2.

Patented Mar. 12,

APPLICATION FILED MAY 20, I9l3. RENEWED IULY 28. I9I7.

Inv/amor:

CHARLES E. LUCKE, OF NEW YORK, N. Y., ASSIGNOR TO GAS AND OIL COMBUSTION COM- PANY, OF NEW YORK, N. Y., A CORPORATION 0F DELAWARE.

APPARATUS FOR BURNING EXPLOSIVE GASEOUS MIXTURES.

Specification of Letters Patent.

Patented Mar. 12, 1918.

Application led May 20, 1913, Serial No. 768,774. Renewed July 28, 1917. Serial No. 183,378.

To all wlw/1L t may Concern.'

Be it known that l, (li-mums E. Locke, a citizen of the llnited States, residing at New York city, in the county of New York and State of New York. have invented certain new and useful Improvements in Apparatus for Burning Explosive (laseous Mixtures, fully described and represented in the following specification and the accompanying drawings. forming` a part of the same.

rlhis invention relates to apparatus for burning explosive gaseous mixtures by which localized and continuous or non-explosive combustion ofl the mixture, as distinguished from non-continuous or intermittent combustion, is secured. To accomplish such continuous and localized combustion of explosive gaseous mixtures, it is necessary, first to prevent back-flash, or backward propagation of flame through the advancing mixture toward the source of supply, and. second. to prevent blow-off, or the carrying away of the fiame and dissipation or dilution of thel mixture in space, which Will usually occur when the velocity of the mixture at the surface or zone where the combustion is wanted exceeds the rate of propagation of inflammation of the mixture. Back-flash may be prevented by the cooling action of the Walls of small or narrow passages through which the mixture is caused to flow` or by causing the mixture to approach the combustion zone with a velocity greater than the rate of propagation of inflammation. Continuous and localized combustion may, therefore, be accomplished, first, by causing the mixture to flow with a velocity greater than the rate of propagation of inflammation and then reducing the flow velocity and preventing dissipation of the mixture or diffusion with other gas and burning the mixture at the surface where the flow velocity equals the rate of propagation of inflammation, and, second, by feeding the mixture through a flame-interrupting cooling passageway, partitionor screen at a rate low enough for the exit velocity to be less than or not much in excess of the rate of propagation of infiammation and burning the mixture at the exit side of the screen. The first of these two ways is usually, preferable because of its greater efficiency and of its permitting a higher rate of combustion and consequent production of higher temperatures, and also because of the difliculty which has heretofore been experienced in preventing the flame-interrupting cooling screen from becoming heated and losing its flame-interrupting property. The second way, that of relying on a fiame-interrupting cooling screen for preventing back-flash, has advantages, however, in somecases, especially on account of the possibility of using a lower pressure in supplying the mixture. This consideration is of especial importance in connection with apparatus for burning mixtures of gas and air where the gas is supplied under comparatively low pressure, as in the case of ordinary city gas, and Where it is desired to avoid the use of an independently driven pump or fan. or other means for supplying air under pressure and to depend upon the gas pressure alone for producing and supplying the mixture to the apparatus.

The present invention aims to provide a lovv pressure burner or apparatus for burning explosive gaseous mixtures in which back-flashing shall be prevented by means of a cooling, flame-interrupting screen formed to dissipate the heat conducted from the place of combustion to such extent as to maintain the flame-interrupting property of the screen and to prevent the portions of the screen adjacent the immediate source of supply of the mixture from becoming heated to the temperature of ignition of the mixture. ln order to secure a comparatively high eiiiciency of the burner or apparatus, it is necessary that a comparatively large number of supply passages having a dimension sufficiently small to prevent back-flashing shall be provided, arranged or grouped close together. The greater the number and the more closely together the passages are arranged, however, the greater is the difficulty in preventing back-conduction of heat through the walls of the passages or screen structure. On the other hand, itis desirable that the passages, While sufliciently long in the direction of flow of the mixture therethrough to permit of the desired dissipation of heat shall be as short as possible consistent With the attainment of the necessary cooling action in order that excessive friction loss and consequent higher supply pressure of the mixture to secure the desired rate of combustion shall be avoided.

In order to secure a maximum crosssectional area of passageway and to reduce resistence to flow, 1 find it desirable for best results to form the flame-interrupting screen with a plurality or multiplicity of closely adjacent passages relatively long and narrow in cross-section, which may be formed by a; plurality of thin plates set spaced slightly apart, and in connection with such plates 1 provide means for withdrawing the heat therefrom. Such heat withdrawing means in a small burner of simple construction may be simply heat discharging ribs or fins formed best by extensions of said plates beyond spacing 'means which define the limits of the passages. For larger apparatus the spaced plates are best divided into groups which are separated by partitions formed of conducting bodies of considerable mass which serve to receive or abstract the heat from the passage forming plates and convey it to the discharging surface which may have suitable heat discharging ribs or fins, or be otherwise arranged to give up heat to the atmosphere or other contacting iiuid or otherwise. rlhe passage-forming plates may be of any suitable heat resisting material. lt is desirable, however, that they shall be comparatively thin so that the supply passages shall be closely adjacent to give the desired large aggregate crosssectional area of passageway, and I find it desirable, therefore, to make these plates of metal, and l have obtained good results with plates of iron. The heat withdrawing bodies or partitions are best made of metal having a relatively high capacity of heat conduction, and l consider copper best suitable for the purpose. The passage-forming plates should be so formed that heat from the combustion zone following the paths of least resistance through the plates will mostly be passed off through the lateral portions of the plates, thus maintaining the portions of the plates adjacent the intake end of the supply passages at a relatively low temperature; and this result is best secured by making the plates of suflicient depth or dimension in the direction of liow of the mixture relatively to the width of the passages that the distance from any point at which heat is received by the plates to a lateral heat discharging point shall be substantially less than the distance from such point to the intake end of the passage.

A further object of the invention is to provide. a burner or apparatus which shall be adaptable for burning explosive mixtures under a range of pressure including pressures suficient to cause the mixture to flow through the supply passages with a velocity considerably in excessl of the rate of propagation of inflammation of the mixture as well as pressures not sufficient to cause such excess How velocity through the supply` passages; and in order that the burner may operate with the mixture supplied at pressures to give such excess velocities 1 provide at the discharge side 0f the flame-interrupting screen means for causing the mixture flowing from the supply passages to spread out with reduction of its fiow velocity, and such means is most desirably a porous and permeable combustion bed of refractory material formed to cause the mixture entering the same from the supply passages with an excess velocity to spread out and advance in increasing volume and with decreasing velocity. The velocity of the mixture will thus be reduced by the bed so that combustion may take place within or at the surface of the bed at the zone or surface where equality between the flow velocity and rate of flame propagation is attained.

Such a combustion bed, in addition to its purpose of localizing the combustion when the mixture is supplied under a pressure which causes a velocity of flow through the supply passages in excess of the rate of flame propagation, serves also as a heat absorbing and radiating body, becoming heated to incandescence both when the mixture flows through the supply passages with excess velocity and when it flows with a velocity less than the rate of flame propagation. The combustion bed may be of any suitable character to effect the desired result, but I consider best suited for the purpose a bed formed of loose or bonded granules or pieces of a suitable refractory material such as alundum, magnesite or chrome ore, or even a suitable fire clay or silica when extremely high temperatures are not to be produced.

If the burner is to be used only with a mixture supplied under a low pressure such that the flow velocity through the supply passages shall be less than or only slightly in excess of the rate of propagation of inflammation, then in place of the velocity reducing combustion bed a suitable perforate screen or diaphragm may be provided set slightly beyond the outlet side of the flameinterrupting screen to become heated by the highly heated products of combustion and to serve as a source of radiant heat. Such a screen of material not readily oxidizable and attaining incandescence at a lower temperature than the highly refractory material of which the combustion bed would ordinarily be composed may also advantageously be provided in connection with and set against or closely adjacent to the outer face of the combustion bed when the same is used, and such a perforate screen or diaphragm is also sometimes desirable for the purpose of retaining a bed of loose pieces of refractory material in place when, for example, a burner or combustion apparatus having such a combustion bed is to be used with the bed in such a position as to need to be so retained. Such perforate screen may bemade of a perforated sheet of a suitable material or of interwoven strands, or otherwise, as may be found suitable.

A full understanding of the invention can best be given by a description of preferred forms of apparatus embodying the same, and such a description will now be given in connection with the accompanying drawings; in which- Figure 1 shows, in section on line 1-1 of Fig. 2, a simple form of apparatus for burning an explosive mixture of gas and air;

Fig. 2 is a sectional view taken on line 2-2 of Fig. 1;

Fig. 3 is a sectional elevation of a modified form of apparatus;

Fig. 4 is a section on line 4-1 of Fig. 3;

Fig. 5 is a section on line 5-5 of Fig. 3;

Fig. 6 is a sectional elevation of another modified form of apparatus.

Referring first to Figs. 1 and 2, the form of burner shown in these figures is intended for use as a cook stove burner or for general heating purposes. The burner comprises a flame-interrupting screen 10 to the supply passages of which the mixture to be burned passes directly from asupply chamber 11 to which the mixture may be supplied through an inlet 12 from any suitable source. As shown a mixing injector is provided for supplying an explosive mixture of fuel gas and air,v the gas being supplied to the injector nozzle 15 under suitable pressure and air being drawn into the combining tube 16 of the injector by the gas jet and the gas and air then passing through the neck of the injector and through the discharge or pressure cone 17 to the supply chamber 11. The injector should be designed and the nozzle and combining tube set in proper relative positions. as by adjusting either one, to supply a mixture containing the gas and air in suitable couibining proportions, and the gas should reach the injector under sufiicient pressure to cause the mixture in the supply chamber to be maintained under such pressure as will cause the mixture to flow through the supply-passages of the iame-interrupting screen in quantity sufficient for the desired rate of combustion, though not necessarily with a velocity in excess of the rate of propagation of fiame through the mixture, as will be understood from the explanation hereinbefore given. The supply chamber 11 should be large enough to permit the mixture to move therein with such comparatively low velocity as to secure a substantially uniform supply of mixture to the supply passages in all parts of the screen 10.

In the flame-interrupting screen of the burner shown in F gs. l and 2, the supply 'spared apart to passages are provided between plates 20 form between adjacent plates supply passages or slots which are relatively long aud narrow in cross-section. The passage-forming within a surrounding and inelosing wall 21 and are subdivided into groups by heatwithdrawing partitions 22. The inclosing wall 21 and the heat-withdrawing partitions 22 should be of a material of high heat conducting capacity, such as copper or other suitable metal, and the passage-forming plates 20 are integral with, or set each with its ends supported by and in good thermal contact with, the wall and one of the partitions or with two of the partitions as the case may be. Heat withdrawing partitions extending only transversely to and intersecting and supporting the ends of the pas sage-forming plates might be used, but it is usually desirable to provide also cross partitions as shown unless the burner is of such size or so narrow that the plate intersecting partitions alone will give adequate withdrawal of heat. The partitions should be of sufficient size or mass, according to the material of which they are made and the crosssectional area of the screen, to have the required capacity of withdrawingthe heat from the passage-forming partitions. The outer wall 21 should also be of sufficient thickness to have the required heat carrying capacity for taking the heat from the partition plates to be discharged from its outer surface. Usually it will be desirable to provide means for facilitating or increasing the discharge of heat from the outer surface of the wall 21, and various means may be provided for this purpose. In small apparatus especially, it will usually be'desirable and entirely satisfactory to increase the radiating or discharging surface simply by means of ribs or fins 23 extending therefrom rather' than to depend upon means involving the circulation in contact with the outer surface of the wall of water or other cooling liquid or gas.

As the width of the supply passages or slots must be very small in order to prevent back-flashing therethrough, it is necessary in order to secure a large aggregate crosssectional area of passageway that the passage-forming plates shall be comparatively thin, and I find it best to make these plates of a suitable metal such as iron. lt is desirable, also, that heat conducted backward through the plates from the place of combustion shall find a path of less resistance to a heat withdrawing partition or thV outer wall than it finds to the portion of the plate or any portion of the screen adjacent the supply chamber 11. This result is best secured by making the plates of sufficient length in the direction of the flow of the mixture, that is by making the screen of plates are mounted suicient depth or thickness; and in practice 1 have-found it 'usuallyvdesirable that the length of the plates in the direction of the thickness of the screen shall be at approximately equal to or greater than the width of the plates or distance between the heat withdrawing means with which the edges of the plates engage. For example, a burner having a iameinterrupting screen formed of a bank of plates .028 of an inch thick, one inch long in the direction of the thickness of the screen or the movement of the mixture, and

of an inch Wide, spaced .028 of an inch apart has been successfully operated continuously over long periods of time with the explosive mixture supplied at a loW pressure such that the velocity of flow through the supply passages of the screen was less than the rate of propagation of inflammation of the mixture.

1n the burner shown in these figures a porous and permeable combustion bed 25 of suitable highly refractory material is mounted against the outer or discharge face of the screen 10. rlhis combustion bed, in order that it may serve to localize the combustion within it or at its outer surface if the mixture is supplied to the burner under a pressure such as to cause it to move through the passages ofthe screen with a velocity substantially in excess of the rate of propagation of ame therethrough, should be of such a character as to cause the mixture entering and owing through it to spread out and be distributed through the bed and have its velocity rapidly reduced. A porous andA permeable bed having intercommunicating passages formed of broken or other suitable pieces of highly refractory material such as alundum, chrome ore or magnesite or re clay ll consider most suitable for the purpose, the pieces or granules forming the bed being eit er loose or bonded together. rlhe bed should be of at least sufficient superficial area to extend over all of the supply passages at the outer or discharge side of the screen, and, of course, the bed should have a greater cross-sectional flow area for a given cross-sectional area of the bed, that is, should be of greater permeability, than the screen. Ordinarily it will be comparatively thin and composed of comparatively small pieces or granules. For example in a burner such as shown in Figs. 1 and 2 of about the proportions shown and havinga combustion bed about three inches across the bed might be about gv of an inch, moreor less, thick and of granules averaging say g of an inch, more or less, in diameter. The bed is positioned in the burner shown by a ring or band 26 of refractory material set or formed against the upper edge of the wall 21 of the screen. This retaining band should best be of a material which is a poor conductor of heat such as a Leagues high grade fire clay or a suitable refractory cement so\as to avoid so far as possible loss of heat from the bed and also to protect the wall 21 from becoming excessively heated from the bed. To protect similarly the partitions 22 against becoming excessively heated from the bed, protecting ribs or bars 27 of suitable refractory cement or other comparatively non-conducting and highly refractory material are set to extend through the bed over the outer edges of the partitions.

rThe screen wall 21 and heat-withdrawing partitions and the casing forming the chamber 11 may be constructed in any suitable manner, but are conveniently formed by a single casting as shown, and the casting may be -formed with a Hangs 30 extending out- Wardly and upwardly fromthe upper edge of the wail 2l to provide a cup-shaped shell or casing to receive the band or filling 26. A perforate screen or diaphragm 31 which may be of suitable non-oxidizing and highly refractory metal is shown as secured by clipsl 32 to the outer edge of the ange 30 to extend over the vbed 25, this screen or diaphragm thus serving to retain the bed in position if the burner is used in other than a horizontal or approximately horizontal position, and also acting as a radiating body when heated by products of combustion passing from the bed or by the products of combustion if the bed is removed.

1n using the burner, when the explosive gaseous mixture supplied to the chamber 11 is maintained only under such lov:T pressure therein that the velocity of How of the mixture through the passages of the screen 10 is less than or equal to or not much in excess of the rate of propagation of ame through the mixture, the combustion, when the mixture has been ignited, will take place at or slightly Within the discharge ends of the supply passages. 1f a greater pressure is maintained in the supply chamber so that the mixture is caused to flow through the supply passages with a velocity appreciably in excess of the rate of propagation ofv inflammation, then the mixture leaving the passages with such excess velocity will have its velocity reduced as it advances through the combustion bed 25 and the surface or zone of combustion will then locate within or at the outer surface of the bed at the zone or surface where equality between the flow velocity and the rate of propagation of inflammation is attained. 1f the combustion bed is removed, the burner will still operate with the combustion located at or closely adjacent to the outer face of the screen 10 so long as the flow velocity through the supply passages of the screen is less than or not greatly in excess of the rate of propagation of inammation. However operating, heat conducted backward through "and conducted to the outer wall 21 of the screen to be discharged therefrom. The flame-interrupting property of the screen will thus be maintained and the portions of the passage-forming plates and other parts of the screen adjacent the supply chamber will be prevented from becoming heated to a temperature which would cause ignition of the mixture in the supply chamber. Such a screen will continue during long periods of operation to perform its function of preventing back-flashing therethrough.

The combustion bed is heated to and maintained at a very high temperature whether the mixture is supplied to the burner under a pressure which causes the mixture to iow through the supply passages with a velocity in excess of the rate of flame propagation or at a low pressure which will not cause such excess flow velocity, the bed becoming more or less highly incandescent and the heat generated by the burning of the mixture being made available not only through the escaping highly heated products of combustion but also to a large degree as radiant heat from the incandescent refractory bed, provided the rate of combustion, or amount of mixture supplied and burned, is sutlicient to maintain the bed at the temperature of incandescence of the bed. If the rate of combustion is not sufficient to develop the amount of heat required to raise the bed to incandescence, the screen or diaphragm 31, if the burner is provided with the same, may still, because of its lower temperature of incandescence, serve as a source of radiant heat, and will also serve such purpose when the burner is operating as a low pressure burner without any bed.

By the construction shown in Figs. 1 and Q, a burner is provided which is very compact, simple and highly efficient, the screen being of comparatively small thickness and occupying but little space between the supply chamber and the combustion space, and the supply passages being comparatively short in the direction of the flow of the mixture therethrough so that the friction loss in forcing the mixture through the passages is thus further reduced in addition to the reduction resulting from the cross-sectional shape of the passages.

Figs. 3, el and 5 show a form of burner in which the flame-interrupting screen l0a is formed by a single bank or group of passageforming plates Q0 spaced apart by narrow spacing plates or bars 40 to form narrow slot-like passages extending from the supply chan'iber lla. The screen is not provided with any intersecting heat-withdrawing bodies or partitions, and as shown the plates are not incased, although a suitable surroundin wall or casing might, of course, be provide For withdrawing heat from the passage-forming plates 20a, heat discharging ribs or fins 23a are depended upon, these tins being best formed by extending portions of the passage-forming plates themselves. As shown in this figure, also, the burner head 42 is formed by a metal or other suitable casing 43 supported by the screen and having a filling or lining 44 of refractory material of poor conducting properties recessed to receive a bed of loose pieces of `refractory material 25a or other suitable combustion bed to serve as a heat absorbing and radiating body and also for localizing the combustion if the burner is supplied with the mixture at a pressure sulicient to cause excess velocity flow through the supply passages of the screen.

Fig. 6 illustrates a form of apparatus in which the flame-interrupting screen is formed by a bank of closely set tubes of small internal diameter. In the construction shown in this ligure the tubes 50 providing the supply passages extend through a wall of a supply chamber llb at one end, and at the other end through the lower or inner wall of an open shell or casing 51 which has a filling or lining 52 of suitable refractory material, preferably a suitable refractory cement, which is formed with a recess 53 adapted to receive a mass of broken or other granular refractory material to form a combustion bed. The lining or filling 52 has holes or passages communicating with and forming continuations of the bores of the tubes 50 as indicated at .54. The tubes 50 forming the flame-interrupting screen should be of such small internal diameter as to prevent back-flashing therethrough so long as the tubes are maintained sufliciently cool, and they should be of such length that the discharge of heat from their outer surfaces will prevent their becoming heated to such an extent as to cause them to lose their flame-interrupting property. I have used with good results steel tubes having an internal diameter of .05 of an inch set so closely together that over seven hundred tubes were grouped in a circle four inches in diameter.

It will be understood that the invention is not to be limited to the exact illustrative embodiments thereof shown and to which the foregoing description has been largely confined, but that it includes changes in and modifications thereof within the claims.

What is claimed is:

ll. Apparatus for burning explosive gaseous mixtures comprising a supply chamber, a multiplicity of mixture supply passages leading from the supply chamber to the place where the mixture burns, said passages having a cross-sectional dimension Suiiiciently small to prevent backward propagation of infiammation therethrough, means for cooling the walls of said passages to maintain the flame-interrupting property thereof and to prevent said walls adjacent the supply chamber becoming heated by conduction of' heat of combustion to the temperature of ignition of the mixture, and means for causing unburned mixture flowing from the passages with a velocity greater than the rate of propagation ofinflammation to spread out with reduction of flow velocity.

2. Apparatus for burning explosive gaseous mixtures comprising a supply chamber, a multiplicity of mixture supply passages leading from the supply chamber to the place where the mixture burns, said passages having a cross-sectional dimension sulficiently small to prevent backward propagation of infiammation therethrough, means for cooling the walls of said passages to maintain the flame-interrupting property thereof and to prevent said Walls adjacent the supply chamber becoming heated by conduction of heat of combustion to the temperature of ignition of the mixture, and a porous and permeable bed of refractory material adjacent the discharge ends of said passages, said bed having intercommunicating passages.

3. Apparatus for burning explosive gaseous mlxtures comprising a supply chamber,l

a multiplicity of mixture supply passages leading from the supply chamber to the place where the mixture burns, said passages having a cross-sectional dimension suiiciently small to prevent backward propagation of inflammation therethrough, means for cooling the walls of said passages to :maintain the flame-interrupting property thereof and to prevent said walls adjacent the supply chamber becoming heated by conduction of heat of combustion to the temperature of ignition of the mixture, and

a bed of loose pieces of refractory material supported adjacent the discharge ends of said passages.

' 4. Apparatus for burning explosive gaseous mixtures comprising a mixture supply chamber, and a iiame-interupting screen formed to provide a multiplicity of closely adjacent mixture supply passages having a' cross-sectional dimension sufficiently small to prevent backward propagation of inflammation therethrough leading from the supply chamber to the place where the mixture burns, said screen having heat discharging surfaces exposed to access of the atmosphere and being formed to provide a path of less resistance to the flow of heat from any point adjoining the place where the mixture burns to a heat discharging surface than the path through the passage walls of theJ screen to the supply chamber, whereby heat conducted through the screen from the place where meable combustion bed of refractory material formed to cause mixture flowing therethrough to advance in increasing volume and with decreasing velocity, a supply chamber, and connecting means between the combustion bed and the supply chamber providing a multiplicity of mixture supply passages for the flow of the explosive mixture from the supply chamber to the combustion bed and each having a cross-sectional dimension sufficiently small to prevent backward propagation of inflammation therethrough, said connecting means being formed to limit backward conduction of heat to prevent ignition of the mixture in the supply chamber.

6. Apparatus for burning explosive gaseous mixtures comprising a mixture supply chamber, and a flame-interrupting screen formed to provide mixture supply passages having a cross-sectional dimension suliciently small to prevent backward propagation of inflammation therethrough leading from the supply chamber to the place where the mixture burns, said screen comprising passage-forming partitions and means for withdrawing heat from lateral portions of said partitions including heat dissipating fins for discharging heat to the surrounding atmosphere, whereby heat conducted through the screen from the place where the mixture burns will be dissipated to the atmosphere to maintain the flame-interrupting property of the screen and to prevent the raising of the passage-forming parti- 110 tions adjacent the supply chamber to the temperature of` ignition of the mixture.

7. Apparatus for burning explosive gaseous mixtures comprising a mixture supply chamber, and a Haine-interrupting screen 115 formed to provide mixture supply passages having a cross-sectional dimension suiiiciently small to pre'vent backward propagation of inflammation therethrough leading from the supply chamber to the place where 120 the mixture burns, said screen comprising passage-forming partitions and means for withdrawing heat from the lateral portions of'said partitions, and the thickness of the screen in the direction of the movement of 125 the mixture therethrough being such as to provide a path of less resistance to the flow of heat through said passage-forming partitions from any point adjacent the place where the mixture burns to said heat with- 130 drawing means than the path through the passage-forming partitions to the supply chamber, whereby heat. conducted through the screen from the place where the mixture burns will be withdrawn from said passagetorming partitions to maintain the flame.- interrupting property of the screen and to prevent the raising of the passage-forming partitions adjacentV the supply chamber to the temperature of ignition of the mixture.

S. Apparatus for burning explosive gaseous mixtures comprising a. mixture supply chamber, and a dame-interrupting screen formed to provide mixture supply passages having a cross-sectional dimension suiiiciently small to prevent backward propagation of inflammation therethrough leading trom thc supply chamber to the place where the mixture burns, said screen comprising passage-forming partitions and means for withdrawing heat from the lateral portions of said partitions and for discharging heat to the surrounding atmosphere, and the thickness ot' said screen in the direction of movement of the mixture therethrough being such as to provide a path of less resistance to the flow of heat through said passage-forming partitions from any point adjacent the place where the mixture burns to said heat withdrawing means than the path through the passage-forming partitions to the supply chamber, whereby heat conducted through the screen from the place where the mixture burns will be dissipated to the atmosphere to maintain the iiame interrupting property of the screen and to prevent the raising of the passage-forming partitions adjacent the supply chamber to the temperature of ignition of the mixture.

9. Apparatus for burning explosive gaseous mixtures comprising a mixture supply chamber, and a flame-interrupting screen formed to provide mixture supply passages having a cross-sectional dimension sutticiently small to prevent backward propagation of inflam- -mation therethrough leading from the supply chamber to the place where the mixture burns, said screen comprising passage-forming partitions and means for withdrawing heat from the lateral portions of said partitions, and the thickness of the screen in the direction of the movement of the mixture therethrough being such as to provide a path ot' less resistance to the flow of heat through said passage-forming partitions `from any point adjacent the place where the n'iixture burns to said heat withdrawing means than the path through the passage- 'forming partitions to the supply chamber, 50 whereby heat conducted through the screen from the place whereby the mixture burns will be withdrawn from said passage-forming partitions to maintain the flame-interrupting property of the screen and tt prevent the raising of the passage-forming partitions adjacent the supply chamber to the temperature of ignition of the mixture, and a porous and permeable combustion bed of refractory materiall supported against the discharge side of the screen formed to cause gas tjowing therethrough to advance in increasing volume and with decreasing velocity.

10. Apparatus for burning explosive gaseous mixtures comprising a mixture supply chamber, and a flame-interrupting screen formed to provide mixture supply passages having a cross-sectional dimension suiiiciently small to prevent backward propagation of inflammation therethrough leading ilrom the supply chamber to the place where, the mixture burns, said .screen comprisingr passage-forming partitions and means tor withdrawing heat t'rom the lateral portions` oi said partitions, and the thickness ot the screen in the direction of the movement oi the mixture therethrough being such as t0 provide a path of less resistance to the flow ot heat. through said passage-forming partitions from any point adjacent Vthe place where the mixture burns to said heat withdrawing means than the path through the passage-forming partitions to the supply Chamber, whereby heat conducted through the screen from the place where the mixture burns will be withdrawn from said passageforming partitions to maintain the flameinterrupting property of the screen and to y prevent the raising of the passage-forming partitions adjacent the supply chamber to the temperature of ignition of the mixture, a bed ot loose pieces of refractory material supported against the discharge side of the screen, and a perforated screen or diaphragm positioned against the outer face of said bed.

11. Apparatus for burning explosive gaseous mixtures comprising a mixture supply chamber, and a flame-interrupting screen having supply passages extending from the supply chamber to the place where the mixture burnsv` said screen comprising passageforming partitions and a heat withdrawing partition intersecting said passage forming partitions.

12. Apparatus for burning explosive gaseous mixtures comprising a mixture supply chamber, and a flame-interrupting screen formed to provide mixture .supply passages having a cross-sectional dimension suiiiciently small to prevent backward propagation ot intiammation therethrough leading trom the supply chamber to the place where the mixture burns, said screen comprising passage-forming partitions and a heat withdrawing body ot a metal of high heat conducting capacity connected with said partitions, whereby heat conducted through the screen from .the place where the mixture burns will be withdrawn from said passageforming partitions by said heat- Withdrawing body to maintain the flame-mterruptmg property of the screen and to prevent the raising of the passage-forming partitions adjacent the supply chamber to the temperature of ignition'of the mixture.

13. Apparatus for burning explosive gaseous mixtures com rising a mixture supply chamber, and a ame-interrupting screen formed to provide mixture supply passages having a cross-sectional dimension sufficiently small to prevent backward propagation of inflammation therethrough leading i'from the supply chamber to the place where the mixture burns, said screen comprising passage-forming partitions and a metal inclosing wall to which said partitions are connected, .said wall serving as a heatwithdrawing and discharging body, whereby heat conducted through the screen from the place where the mixture burns will be withdrawn from the passage-forming partitions and discharged from said inclosing wall to maintain the flame-interrupting property of the screen and to prevent the raising of the passage-forming partitions adjacent the supply chamber to the temperature of ignition of the mixture.

14. Apparatus for burning explosive gaseous mixtures comprising a mixture supply chamber, and a llame-interrupting screen having supply passages extending from the supply chamber to the place Where the mixture burns, said screen comprising passa-geforming partitions and an inclosing wall and partitions dividing the space within the wall and intersecting said passage-forming partitions, said Walls and intersecting partitions being of a metal of. high heat-conducting capacity to serve as means to withdraw heat from the passage forming partitions and to discharge the same.

15. Apparatus for burning explosive gaseous mixtures comprising a mixture supply chamber, and a flame-interrupting screen formed to provide mixture supply passages extending from the supply chamber to the place where the mixture burns which are relatively long and narrow in cross-section and the Width of which is sufficiently small to prevent backward propagation of inflammation therethrough, said screen comprising passage-forming partitions and means for withdrawing heat from the lateral portions of said partitions, and the thickness of the screen in the direction of the movement of the mixture therethrough being such as to provide a path of less resistance to the flow of heat through said passage-forming partitions from any point adjacent the place where the mixture burns to said heat withdrawing means than the path through the passage-forming. partitions to the supply chamber, wherey heat conducted through the screen from the place where the mixture burns Will be withdrawn from said' passageforming partitions to maintain the flameinterrupting property. of the screen and to prevent the raising of the passage-forming partitions adjacent the supply chamber to the temperature of ignition of the mixture.

16. Apparatus for burning explosive gaseous mixtures comprising a mixture supply chamber, and a flame-interrupting screen formed to provide mixture supply passages extending from the supply chamber to the place Where the mixture burns which are relatively lon and narrow in cross-section and of a widt suificiently small to prevent backward .propagation of inflammation therethrou h, said screen comprising a multiplicity o closely spaced thin metal plates and having means for withdrawing heat from the lateral portions of said plates, and said plates being of such dimension in the direction of flow of the mixture through the passages that the distance from any point adjacent to the place where the mixture burns through any such plate to such. heat withdrawing means shall be less than the distance from such point to the supply chamber.

17. Apparatus for burning explosive gaseous mixtures comprising a mixture supply chamber, and a llame interrupting screen having supply passages extending from the supply chamber to the place where the mixture burns which are long and narrow in cross-section, said screen comprising a multiplicity of closely spaced thin metal plates and a heat withdrawing partition intersecting said plates and dividing the same into groups,l said heat withdrawing partition being of high heat-carrying capacity.

18. Apparatus for burning explosive gaseous mixtures comprising a mixture supply chamber, and a ame-interrupting screen' having supply passages extending from the supply chamber to the place where the mixture burns which are relatively long and narrow in cross-section, said screen comprising a multiplicity of closely spaced thin metal plates and an inclosing wall and partitions dividing the space within the wall intersecting said plates and separating them into groups, said wall and said intersecting partitions being formed of a metal of high heat-conducting capacity, and means for withdrawing heat from the wall.

19. Apparatus for burning explosive gaseous mixtures comprising a mixture supply chamber, and a flame-interrupting screen having supply passages extending from the supply chamber to the place where the mixture burns which arerelatively long and narrow in cross-section, said screen comprising a multiplicity of closely spaced thin metal plates and an inclosing wall and par" titions dividing the space Within the Wall inclosing Wall and intersecting garttiens or i0 intersecting sait plates and separating them the screen from direct contact with said bed. into groups, said wail and said intersecting In testimony whereof I have hereunto set partitions being formed ot' 1 metal of high my hand n the presence of two subscribing heat-conducting capacity, bed of granular Witnesses.

refractory material rest-ing against the dis CHARLES E. LUCKE. charge side of said screen, bodies of re- Witnesses: fractory material of iow heat, conducting FRED. J. VIHELAN? capacity arranged to protect the edges of the A. L. KENT.

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