US1677156A - Apparatus for burning explosive gaseous mixtures - Google Patents

Description

.July 17, 1928.

A s. P. VAUGHN APPARATUS FOR BURNING EXPLOIVE GASEOUS MIXTURES MvENTOR' p mema .mi 17 1928.

` N msTA E smz'r. various, or THE UNITED s'ra'ms mvr,` cnoc raw coum'y, 'mssssrrr ASSIGNOB ro summer: comUsnoN COMPANY, or NEW YORK, N. Y., a comman- TION OF NEF` YORK. I

mana'ruep ou BUBNING EXPLOSIVE GASEOUS Minune;

Application filed December 23, 1925. Serial No. 77,383.

This inventionrelates to apparatus for burning explosve gaseous mixtures by which localized and continuous or non-explosive conbustion of the' mixture is Secured. To 6 accomplish such continuous and localized combustion of explosive gaseous mixtures it is. necessaryvto prevent back flash or backaward propagation of the flame through the advancing mixture toward the' source ofcsup- 10 plyl -Back'-flash may be prevented either by causing the explosive mix ture to flow toward the combustion zone with a velocity greater than the rate of propagation of inflamnation, or,` when the velocity 'of the explosive mixture is less than the rate of propagation of inflammation, by-interposing ag flameinterrupting screenbetween the combustion zone and the source of explosve mixture supply, ;and maintaining the flame.

interrupting qualities of such screen. "This invention relates part cularly to apparatus 'for burning explosive mixtures under the. lattcr conditions, that is, burning mxtures- .of combustible gas and air in proper. proportions where the gas is supplied under com paratively low pressure, and where the flow velocity of the resulting mixture through the flame interrupting screen is less than the rate of propagation of inflammation.

It will be understood that by the term eplosive gaseous mixture as used herein s meant a mixture of suitable combustion supportin gas, such as oxygen or air, with combustib e matter in a gaseous state or other fincly divided state in proper proportion for complete combustion or such that the -niixture will have the property of self propagation of inflammation. The mixture may be varied according to the desired character of the products of combustion.

It will be uderstood also that by the term flane interrupting screen as used herein is meant, one or a plurality of flame interruptin passage ways formed in an a'pparatus-{r burning explosive gaseous mixtures for the passage of an explosion gaseous mixture from the source of supply to the zone of.

combustion. The passa e ways to be such interruption when the walls of the passage ways are below the temperature of ignition v size that they will have t e property of fiame ing explosive gaseous mixtures' in which back-flashing shall be prevented by means for cooling a flame interrupting screen, 'forming a part of the burner, to a temperature below the ignition temperature of the mixture. In order to secure a relatively high efliciency it\ is necessary that a comparatively large number of orifices or supply passages, having dimensions suflicently small to prevent back-flashing when cool, be provided in' the flame interrupting screen, and for this purpose I` prefer using a wire mesh with the required number of meshes per square inch as the flame inter ruptmg screen. `In burning explosive gaseous mixtures when the gaseous fuel supply ssuing'fro'm an orifiee under "low pressure s required to entrain in a mixing tube the aurequired for combustion the best results are obtaned in burning the mixture at a relatively low rate fof combustion per square inch area in the flame interrupting screen,` for thereason that the greater the aggregate area of the passages in the flame ntcrrupting screen relative to the quantity of fuel burned the less will be the resistance to the flow of the mixture through the flame interrupting screen. Another advantage iu burning explosive gaseous mixtures at a low rate of' combustion per square inch area in the flame interrupting screen is that it is very easy to maintain the. flame interrupting qualities of the screen due to the large area over which the heat is spread.` The pre ferred means of withdrawing the heat absorbed by the flame interrupting screen, and' which is the essence of this invention, is a plurality of heat conducting metal bars or partitions arranged parallel beneath the screen on which the screen rests, and extende ing from the screen to the back of the burner casing. The metal bars or partitions should be in thermal contact with both the flame interrupting screen and the back of the casing and of such heat conducting Capacity that the screen will be kept at the required 1 0 temperature to maintain its flame interrupt ing properties. The heat absorbed and conducted by the metal bars or partitions ,will be dissipated through the back of casing into the surrounding air. v

Another' object is to reduce the resistance to flow of the explosive gaseous mixture in passing from the mixture chamber to the place of conbustion to a minimum with a resulting reduction in the pressure required in the mixture chanber. I accomplish this by forming the fiame interrupting screen of the bin-ner of wire mesh as stated above, and by spacing the heat conducting bars or partitions, provided *to maintain the fiame interrupting properties of the screen, in such a mamcr and such distance apart that they form com-paratively lar e passage ways for the passage o the explosive mixture from the mixing chanber to the flame interrupting screen. In no way is it intended that the passage'ways so formed between the heat condu ting bars or partitions be flame inter-' rupting passage ways, but rather the op osite and so spaced that they oficr little resistance to the flow of the mixture.

Another object is to provide a burner for converting the heat of combustion into radiant energy and for this purpose I place on theexit side of the flame interrupting screen a thin porous and permeable refractory combastion bed in loose or bonded form and having intercomnunicating passage wvs formed thercin for the passage of the exlosive gaseous mixture to the zone of comustion. Combustion of the mixture will be localized on the exit side of the refractory bed or in the refractory bed, depending upon the rate of conbustion, and the heat of conbustion will cause the refractory bed to become highly incandesccnt and radiate heat.

In burners where a very low rate of combustion and a maximum radiating efficiency are desired a perforate screen or dia hragm may be provided in lieu of the re ractory bed and ilaced a short distance beyond the outlet .sitio of the flame interrupting screen to become heated to incandescence by the highly heated products of combustion.

Another ObJCt is to provide a simple neans for obtaining the quantity of air required for high rates of combustion when using gaseous fuels at low pressures and when a large jetvolume of such gaseous fuel would not ordinarily entrain a sufiicient amount of air in the Venturi or mixing tube for complete combustion in a refractory bed such as described above. I attain this ob ject by completely cnclosing the refractory combustion bed and forming a chamber above it with an opening connected with a chimney or pipe which creates a draft through the refractory combustion bed and drawsin the required amount of air for complete combustion through the Venturi or mixing tube.

Another object is to keep the explosive aseous mixture as cool as possible while eing mixed in the mixture chamber and while flowing to the place of combustion, especially in apparatus where a jet of gaseous fuel entrains the proper proportions of arin a Venturi or mixing tube. A change in the temperature of the mixture in the mixture chamber will cause a change in the quantity of air entrained by the fuel jet entering the Venturi or nixing tube, which is *not desirable where a perfect combustion is required. By keeping the mixture ata uni form temperature -a uniform pressure is maintained in the mixture chamber which makes it possible to keep the proportions of air entrained uniform without requiring further adjustment of an air register after it is once set for a predeternined mixture. A cool mixture assists in keeping the fiame interrupting screen at a temperature low enough to maintain its fiane interrupting properties which p'events back-flash. To nccomplish this I keep the mixture chanber as far as possible from the zone of combustion and cause the mixture to fiow from the mixture'chamber to zone of combustion as quickly as the pressure used will allow. In such an apparatus as described herein the 'walls of the mixture chamber should be made very thin and have a very small heat conducting Capacity which will result in very little heat being transmitted to the mixture in the mixture chamber.

I attain the above objects in the manne'r described herein and as illustratecl in the accompanying drawings showing two forms of the apparatus made in accordance with the present invention. In said drawings like numerals refer to like parts throughout the several views and:

Fig. 1 is a front view of one form of burner formed as a radiator of heat for household use and cut away in sections to show the general arrangement.

Fig. 2 is a sectional view on line w-a Fig. 1.

Fig. 3 is a plan view of another form of burner with the top removed and cut away in sections.

Fig. 4 is a lan View of the burner shown in Fig. 3 witii the top, refractory bed, and fiame interrupting screen removed to show the general arrangement of the heat conducting bars or partitions provided to maintain the flame interrupting properties of the screen.

Fig. 5 is a vertical sectional view on the line b-b of the view shown in Fig. 3.

Fig. 6 is a vertical sectional view on line c-c of the view shown in Fig. 3.

InFig. 1 I show a form of apparats particularly adaptable foruse as a radiator of heat for household use, but which ma be -used for many other purposes with s ight modification in design. It comprises a metal body or casing 1 for-med to provide a burner in t e front of the upper part of the casing and a gas mixture chanber 2 in the lower part of the casing. The form of burner used comprises a fleme interrupting screen 5 made of a metal wire mesh and e porous and IUU llU

permeable refractory combustion bed 6, in

loose or bonded form, placed on the exit side of `the flame interrupting screen, in which the explosive gaseous mixture burns and raises the refractory-to an incandescent state. The flame interrupting screen 5 i's kept at the proper temperature to maintain its 'flame nterrupting properties by a 'series of heat conducting bars or partitions 8, having the necessary heat conducting capacity, extending froni the screen to the back of the casing and in thermal contact with both so that the heat maybe conducted `from the screen 5 to the back of the casing l through whichit is dissipatecl into ..the surrounding air. The heat conducting metal bars or partitions are spaced parallel and forma series of pasu sages 4 connecting the gas mixing chamber 2 withthe passages in the flame interrupting screen 5 through which the explosive gaseous mixture passes to zone of combustion. 'To reduce the quantity of heat conducting metal required in the bars or partitions 8 to a minimum they are formed in the shape of a triangle or right triangle with the base endextending to the mixing chamber 2 and forming the entrance to the passages 4:. One edge of the bar is kept in thermal contact with the back of the casing 1, and the other edge 'of the bar forms the exit of 'the passages 4 and is kept in thermal contact with the flame interrupting screen 5. In such const'uction the cross sectional area of 'the assages 4' formed by the parallel heat con ucting bars or partitions '8 gradually decreases from the mixture chamber toward the outer end of the bars or artitions. The ratio of the entrance area o the passages 4 to that of the discharge or exit area should be such that theentrance to the passages will not in any sense beso constrictedas to cause any undue resistanceito the flow of the explosive gaseos mixture through the passage& In practice I have found that assages formed by iron heat conducting ars or artitions thick and spaced apart an( having a d entrance area give very satisfactory results as to low resistance to flow of the mixture, and heat dissipation by the bars When gaseous fuel such as city gas under low pressures is used. i If a gaseous :fuel under relatively high pressures is used the entrance area to the passages may be reduced with a conse quent reduction in' the amount of metal used in theheat conducting bars or partitions. The heat conducting bars or partitions may be moulded' as an integral part of the casing 1 or they may be assembled separatelyas a unit and placed in position in the casing;

"In the'particular form of apparatus shown in the 'drawings the explosive gaseous mixture is obtained by injecting a fuel in a gaseous or vapor state, such as ordinary city gas or vaporized gasolina, through a gas orischarge area about twice the ducting bars or fi'ce 9 into a Venturi or nixing tube 10 where it entrains air in suflicient quantity to form an explosive mixture. The resulting mixture enters the mixture chamber and flows to the zone of combu'stion through the passage ways 4, formed by the heat conductmg bars or partit-ions 8, and the passages formed in the fiame interrupting screen 5.

I have found it advisable to keep the mixture chanber 2 as far away from the zone of combustion as structuralfeatures permit so that the walls of the mixture chanber will be kept cool. If the walls of the n'ixture chamber 2 become heated by conductance or radiation of heat from the zone of combustion, the gaseous mixture becomes heated expands and causes avariation in the amount' of air entrained by the gaseous fuel,

into two sections, the upper section forming the burner chamber 13 and the lower section forming' the mixture chamber 2', with a constricted passage 16 connecting the two chambers. In such a Construction the 'nixture chamber is placed beneath the burner chamber and the walls of the mixture chamber should be of such thickness as to have a very small heat conducting Capacity so that little if any heat is transmtted from the burnerto the gaseous mxture in the mixture cham ber. In the' burner chamber forned by the upper part of the casing is a multiplicity of heat conductingbars or partitions 8' spaced crosswise the passage 16 connecting the mixture chanber with the burner chamber and in thermal contact with the side walls and the bottom of the burner chamber. A flame interrupt-ing screen 5', made preferably of wire mesh or perforate screen with openings thereinof such cross sectional dinensions as to have the property 'of flame interruption when kept below the ignition temperature of the explosive mixture, is placed on top of and in thermal` contact with the heat con artitions 8' and forms the hurner pro er o the apparatus. The beat conducting ars or partitions 8' should be of v such dimensions as to have the necessary the ignition temperature of the explosive gaseous mixture and should be of such shape and SO spaced as shown that'they form a multiplicty of non-flame interrupting passage ways 4' with a horizontal cross seclUO tional area that rapidly increases from bottom to top for the assage of the explosive mixture from` the mxture chamber 2' to the openings in the flame interrupti ng screen 5'. The flame interrupting screen 5' supports a po'ous and permeable refractory combustion bed 6' in loose or bondecl form in which or on the top !surface of which combustion of the explosive gaseous mixture takes place and raises the refractory to an incandescent state for the radiation of heat. lVhen an injector is used in this type of burner for supplying the explosive gaseous nixture and the gas pressure is low it mav be desirahle to burn the nixture at a higher rate of combustion than would he possible when depending entirely upon the injeetor to supply the required amount of air for complete combustion. To meet such a condition without using nechanical appliances to supply the .necessary air for conbustion, the casing 1' is extended above the 'efractory bed 6' and provided with a top 1:2 which forms a closed chamber 13 above the retractory bed. The chanber 13 is provided with an outlet 14 connected to a pipe or chimney 15 extending upwardly the required distance to create a draught through the ref'actory combustion bed when combustion takes place. The draught results in a greatcr quantity of air being entrained by the gaseous fuel jet in the injector, which makes it possible to burn a relatively large quantity of fuel. The radiant heat throwu off by the combustiou bed is transmitted to the top plate 12 for use for any desired purpose.

While I have shown only two forms of apparatus embodying 'the principles of this invention it will be understood that nany other forms may be constructed without departing from or exceeding the spirit of my claims.

What I claim is:

1. In apparatus :for burning explosive gaseous mixtures, the combination with a porous and permeable bed of refractory material, of a series of heat-conducting elements in thermal relation with the back of said bed for conducting away therefrom.

such excess heat as would cause back flash in the Inixture supplied to the bed, the passage between said elements being suficiently free and open to prevent said passage from serving' as flame-interrupting passages, and a mixture supply ehamber enclosing said elements.

2. In apparatus for burnin explosive gaseous mixtures, the combinaton with a porous and permeable bed of refractory material, of a plurality of spaced partitions in heat-absor bing relation with respect to said bed for conducting away from the back, thereof, such excess heat as would cause back flash in the mixture supplied thereto, the passage between said partitions being sufiiciently free and open to prevent said passage from serving as flame-interrupting passages, and a mixture supply chamber enclosing said partitions.

3. In apparatus for burning cxplosive gaseous mixtures, the combination with a porous and permeable bed of ref'actory material, of a series of heat-conducting elements in thermal relation with the back of said bed for conclucting away, therefrom, such excess heat as would cause back flash in the mixture supplied to the bed and a nixture supply chamber enclosing said elements, the passage between said elements being sufiiciently :free and open to prevent said passages from serving as flame-interrupting passages, said elements being in thernal contact with at least one of the chamber walls,'whereby the heat absorbed by said elements may be dissipated through said wall or walls.

4. In apparatus for burning ex losive gaseous mxtures, the combination o a foraminous flame-interrupting screen having relatively short flow passages therethrough, a gaseous-mixture supply chamber opening directly on said screen, a porous and permeable combustion bed of refractory material positioned acljacent the outer face of said screen, and a plurality of spaced heatconducting elements within the chamber and in thermal contact with said screen, said elements being spaced sufiiciently far apart to prevent the passages therebetween from serving as flame-interrupting passages.

5. In apparatus for burning explosive gaseous mxtures, a casing, a supply chamber within said casing for supplying the explosive gaseous mixture, a zone of conbustion separated from the source of supply of the explosive gaseous mixture by a screen having flame interrupting passage ways formed therein for the passage of the mixture to the zone of combustion, spaced heat conducting partitions within said casing in thermal contact with the screen and the casing, and non-flame interrupting assage ways between the spaced heat con ucting partitions for the passa e of the explosive mixture from the suppy chamber to the flame interrupting passage ways formed in the screen.

6. In apparatus for burning explosive aseous mixtures, a casing, a supply chamer within said casin heat conductmg partitions in contact wit said casing and forming non-flame interrupting passages for the gaseous mixture, and a flame interrupting screen in thermal contact with said partitions.

7. In an apparatus .for burning explosive gaseous mixtures, a casing, a supply cham er within said casin & flame interrupting screen separating t e..supply chamber from 'the zone of combuston, spaced lUO heat conducting elements in thermal contact with said casing and said flame nterrupting screen, and spacedto form non-fiame 1nterrupting passage ways for the passage of the explosve gaseous mixture fronthe suply chamher to the passage ways in the flame mterruptng screen.

8. In an apparatus for burning gaseous mixtures, a casng, a gaseous nixture supply chamber within said casing a flame interrupting screen havin relatvely' short flow passages therethroug and separating the said supply chamber from the zone of comties.

bastion, and non-flane interrupting passage ways for the passage of the gaseous mxture from the supply chamber to the passage ways in the flame interruptng screen, said non-flame nterruptng passage ways being formed by heat conductn elements in thermal contact with said casng and said fiame interruptng screen and of suflcient beat eonducting capacity to conduct the heat away from the flame nterruptng screen and maintain its flame interrupting propere sn sY r. VAUGI-IN.

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