US2487754A - Fuel igniter - Google Patents

Description

J. G. COHN FUEL IGNITER Filed NOV. 26, 1948 Nom 8, 1949 INVENTOR.

JOHANN @UNT'HER CQHN BY// AM( A TTQQNEY Patented Nov. 8, 1949 NITED STATES PATENT ()l;"I*`,ICI:

FUEL IGNITER Johann Gunther Cohn, East Orange, N. J., assignor toBaker-@r Co., 1nc.Newark,-KN.VJ., acorporation kof New Jersey ApplicationNovember 26, 1948, SerialfNo. 62,190

(Cl. 21S- 32) .3 .Claims .Il

The Ipresent invention KVdeals with the .ignition of .fuels and is concerned'more particularly with the provision of an automatic igniter yfor fuels, such asorganic `inflammable gases, .in nelydivided state.

Efforts have been made :for many years .torreplace-fthe open-.flame gas pilot light by more economic` and-safermeans. Electricignition by means ofan electrically heated Aincandenscent w-ireor the like brought -to the ignition temperature of the rfuelis, of course, superior to fthe open pilot light .insofar as safety is concerned, but other- Wise,onlysubstitutewaste of electrical energy for waste of fuel energy and, furthermore, requiresan expensive mechanism.

vIn my co-pending applications, No.;792,67.3 and No.792,6f7.4, Iihave described automatic igniters in .the :formof acatalyst of ne .diameter .Wire in the shape ofa coil electricallyheatedtoa temperature substantially below the ignition temperature of the fueLVthecOil of the igniterof application No. r792,674 being more particularlyso constructed as zto constitutea heterophase .catalyst wherein .tha catalyticreactionstarts at lone phase andignitionoccurs at another phase. -Such electrically heated catalytic igniter constitutes Lathe rst practical vautomatic :igniter capable of reliably igniting, on contact, finely divided fuels .irl ailowingffuel-.airmixture in which the fuel comprises inammable materials difficult to ignite, such as such saturatedhydrocarbon gases as butane, propane, or even methane, or the like.

The present invention deals more specifically with a further improvementupon the automatic igniter of my present co-pending applications above referred to.

T hechief object of this invention is to provide an automatic catalytic 'igniter which shall be highly superior in its function and efficiency in the ignitionof fuels most difficult to ignite, such as naturalgas and in particular a gas as difficult to ignite catalytically as methane, and which, in this function and itseiiiciency, is even superior to the igniters shown more specifically inmy co-pending application-No. 792,674. It is another object of this inventiony to provide such igniter forsuch flowing fuel-air mixtures comprising saturated gaseous hydrocarbons or. other finely divided organic yfuels whereinsuch ,mixtures may be substantially devoid of free hydrogen or wherein at least the free hydrogen, ifany, is practically ineffective in the -ignition process. vIt is another object to providea highly-efficient automatic igniter, of the catalytic type, suitable for the safe and reliable .ignition .of vany and all fuel-air mixtures containing inammable .constituents adapted to be catalyzed. It is a further objectof the invention toprovide such igniter which-shall operate reliably overa widerange of fuel-air com.- positions. It is another vobject of this invention to provide an .automatic .igniter .which .shall `be easyfand simpleto manufacture. AOtherobjects and :advantages of the Vautomatic; ,fuel :igniterrof my invention vwill appear .from the :description thereof hereinafter following.

As in my.co-pending.applications referred to, the catalyst wire-of the igniter mustnavea very small diameterand be shaped toform a coil. The wireconsists, or has atileast a surface, of catalyst metal adapted tocatalyze the fuel in the-fuelfair mixture :in a flameless combustion, the catalyst comprising suchmetal as platinum or .othermeta-l of .theplatinum group or alloy thereof. The coil is electrically heated to a Itemperature substantiallygbelowthe ignitiontemperature ofthe finely divided fuel, .such as methane or other saturated hydrocarbon gas, in the fuel-air mixture.

The specific ,feature 0f theigniterpffths vinventionis thatzthe @Oiled .Wire .iS-.inftwn Shared yinto a coiled or fothersuitable .structurei. ve. a Iprimary @.011 Qf nefcoil. diameter is formed, e. s. into asecondary coilvof larger coil diameter, as -for Ain- Stance a lfcoiled 0011- AReference Vvis .made t0 kthe drawings, forming partnered, in which:

Figure I-:repreSeHtS a diagram@ an ieniien System embodying the igniter.

Figure 2 r.represents an enlarged ,elevational View, Shownfschematcally, of the'igniter Of'ths invention, .and

.Figures 3 anderepresentglike views Qf Av10.deiil embodiments of the igniter.

.Referring :Imre partularlv @Figure .1, .the igniter I, illustratedschematically,only, is shown within a: Aclua1;[email protected] hfbacksystem. YThe burners to be lit, areindicated ati/2 and 2. Agaseous mixtureflowing fromme@ .aSh-back ports 3 and 3', enters thetWQaSh-.back tubeS'f-i f5 andoWS towardand into contact with theignitler l where it i s,;on contact, ignited. {I he'flamethen travels iniiash-back manner back to, the flash-back ports 3 and 3 and there establishes continuouslyburning arnesbywhich ,the gas flowing throughthe burners ,2 and 2 becomes ignited. 'While inthis Figure 1, Ihave illustrateda Z-burner unit, vit will be understood that the same principleapplies to the ignition of othermultiple burner, units ora single burnerlunit.

nReferring now more particularly Yto Figures .-2,

. .3 and fi, the igniter itself consistsof Ya4 coiled wire 5 of catalyst metal, e. g. platinum or metal of the platinum group or alloy thereof, shaped into a secondary form comprising a twisted structure of variated form. In Figure 2, the structure is shown as a coiled coil with a plurality of turns and in Figure 3 as a plurality of V-bends and in Figure 4 as a plurality of simple bends forming at least one S-shaped structure. The structures shown in Figures 2-4 are intended as illustrations, other twisted shapes and structures of the ne coiled wire being possible, such, e. g. as a simple loop.

The coiled coil in which a densely wound primary coil of small diameter is wound into the shape of a secondary coil having turns of larger diameter, relative to the diameter of the turns of the primary coil, and other such twisted structures, as shown, are of the nature of a heterophase catalyst in which the catalytic reaction starts at one phase and is accelerated to ignition at another phase activated by the phase at which the reaction starts.

The wire itself of the igniter must have a very flne diameter, of the order of a minimum of about 0.001", and a maximum of about 0.003". The primary coil may have an inner diameter of from about 0.002 to about 0.015 and a spacing of from about 50 to about 400 turns per lineal inch. The secondary coil, or winding, may have an inner diameter of from about 0.01 to about 0.1". For example, when a Wire of 0.001" or 0.002" is used, the primary coil may consist of a great number of close turns, e. g. of the order of 135 turns per lineal inch, the turns having an inner diameter of 0.005", whereas the secondary coil, of at least two or more turns, has an inner diameter of about 0.035. The igniter structure is electrically heated, by resistance, to a temperature well below the ignition temperature of the flowing fuel-air mixture and, of course, below the recrystallization temperature of the metal of the structure. Such heating is accomplished with extremely small current of low voltage and low amperage. On contact with the flowing fuel-air mixture, the reaction starts immediately and is almost instantaneously accelerated to ignition with an attendant increase of the temperature of the igniter, whereupon the burning gas is removed from contact with the igniter, as for instance by means of the flash-back system or f otherwise. The source oi electric power is indicated at 6, which may be either a battery or a transformer, with leads 'l and 'I'. The electrical heating may be continuous, or it may be controlled to coincide with the operation of the burner unit or units so as to occur only on opening of gas jets.

The igniter of this invention represents an extremely efcient device for the ignition of flowing fuel-air mixtures, even those wherein the fuel is such diiicultly ignitable a fuel as methane.

'I'he igniter of the present invention is superior in reliability of ignition to any other structural form of electrically heated catalytic igniter. In my co-pending application No. 792,674, I have more fully explained the heterophase principle of the catalytic igniter in that the catalytic reaction starts at one phase, the primary phase portion, which in turn heats up fast the secondary phase portion at which thereupon the nameless reaction at the primary phase portion is accelerated to flame formation and ignition. In the instant case, the igniter operates likewise on this heterophase principle. In the formation of the secondary coil or the like, the initially even and uniform 4 spacing between the turns of the coil is changed to an uneven spacing, the inner parts of the primary turns coming closer together and the outer parts spreading apart, resulting, thus, in a greatly variated structure in which numerous sections of closely spaced turns are adapted to act as primary phases alternating with numerous sections adapted to act as secondary phases, thus affording to the impinging fuel-air mixture a large number of starting points, primary phase, for the reaction and adjacent areas, secondary phase, Where the initial reaction can be accelerated to ignition.

Even a mere bend, or loop, of the fine-diameter coil creates an efficient automatic igniter, although the preferred form of igniter in accordance with this invention is one in which the primary coil is shaped into a large-diameter coil or other structural forms having a plurality of primary and secondary phases.

The superiority of the igniter of this invention over other electrically heated catalytic igniters and over other types of such heterophase igniters is evidenced by its performance.

For instance, a 0.002 wire wound into a primary coil having an inside diameter of 0.005, 135 turns to the lineal inch, and then Wound into a secondary coil of two or three turns and having an inside diameter of about 0.035" invariably ignited methane in a flowing methane-air mixture on heating with from about 0.25 watt to about 0.6 watt with a voltage of from 1.30 volts, and 0.2 ampere, to 2.5 volts and 0.225 ampere. A straight single coil would be unable to ignite methane under any such or similar conditions.

A similar igniter in the form of the twisted structure of Figure 3 or of Figure 4 operates in like manner. For instance, such igniter of 0.002"

wire coiled into a primary coil having an insider diameter of 0.004, 135 turns to the lineal inch,

i and shaped into the W-structure of Figure 3 and heated with 0.5 watt, or 1.9 volts and .26 ampere, ignited methane in the above-mentioned methane-air mixture instantaneously. The S-structure of Figure 4 requires for like performance a slightly higher power, e. g. 0.55 watt for a wire coil as above stated, or 0.29 ampere and 1.9 volts.

The number of turns of the secondary coilmay vary, there being at least two such turns. Normally, it is safest to employ three or four turns and if desired, there may be more such turns of the secondary coil. The voltage and the amperage of the electric heating current, and the total wattage input, must be sufficiently small, correlated to the wire diameter, to maintain the temperature of the coil at the specified low temperature. Generally speaking, the igniter of my invention will not glow when not in contact with the owing fuel-air mixture, although a slight glow may occur in some cases.

The catalyst metal of which the wire, or at least the surface of the wire, is formed, is usuallyplatinum or an alloy of platinum with another metal of the platinum group, e. g. such alloys of platinum and rhodium or platinum and iridium,

the platinum content normally being at least or of the alloy, 0r With other suitable metal or metals, such for example as nickel, tungsten, and so forth. The wire material may be in the form of a sintered agglomerate of the catalyst metal or metals, with or without other metals, e. g. tungsten, and, preferably, with a small percentage, or fraction of a percent, of refractory oxide distributed therethrough, such as thorium oxide, beryllium oxide and so forth. The wire may have any desired cross-sectional shape,

usually,v however, circular. Stranded wire. may also be used in the formation of the structural igniter of this invention, in which case the overall thickness of the wire composed of the individual strands should correspond in electrical resistance to that of the wire herein described otherwise; in this case, the individual strands need not necessarily be composed of the same metal but may consist of dilerent metals or compositions.

Experiments with the igniter of this invention have shown, further, that it is far superior to other igniters even in the ignition of city gas, i. eso-called manufactured gas, which contains a certain amount of hydrogen. In general, in the ignition of such gas, the power input has been found to be about less for ignition by means of the igniter of this invention compared with an otherwise similar simple straight coil, for obtaining ignition. However, the most significant difference is found when the igniter is used for the ignition of such gas in multipleburner unit, since in such arrangement, see e. g. Figure l, the combustion products flowing from one ignited flash port, e. g. 3, through flash tube 4 and impinging on the igniter I, mingle with the gas stream to be ignited which is flowing from flash port 3 through flash tube 4', and tend to blanket the igniter and interfere with the second ignition. A single straight coil is apt to become unreliable, or slower in its ignition action than a coil according to the present invention. The far greater reliability of the present igniter when used to light two or more burners, either together or in succession, is of the greatest importance in assuring maximum safety.

The fuel-air mixtures in the experiments described resulted from a jet of fuel, e. g. methane, through nozzles, into air, and are thus the customary mixtures encountered in practical systems such as gas range burners. The flames were of the characteristic blue color. The pressure of the jet varied over wide ranges as encountered in heating practice.

The manner of connecting the igniter to the source of electric power may be conventional. In Figure 1 I have shown one particularly suitable method of mounting the igniter and connecting it to the electric power. Lead-in wire 'I' is connected to a metal sleeve 8 mounted on an insulated base 9, and lead-in wire 1 i-s connected to a contact I0, in the form of a sleeve, mounted within the base 9 and electrically insulated against the metal sleeve 8. The igniter I is mounted between the two leads II and II', which simultaneously serve as supports and which are mounted on a cap I2, lead-in II being soldered to or otherwise being in metallic contact with the cap I2 and lead-in II being isolated from the cap by means of a sleeve I3 terminating in a metallic tubular extension I4. The cap I2 is pressed down onto and over the sleeve 8, thus bringing the lead-in I I in contact with the conductor I and the lead-in II in contact with the contact sleeve I0 and thereby with conductor l, the entire assembly being held together by the frictional t of cap I2 over sleeve 8 and of the tube i4 within the sleeve I0.

The igniter may be used in domestic and industrial appliances, such as ranges, stoves, furnaces and so forth, whether direct, as e. g. in top burners of ranges, or indirect, as e. g. in range ovens or furnaces. It may also be used in instruments or other devices Wherever it is desired to ignite a gas-air or other fuel-air mixture. The source of electric power may be the line supply, with an interposed resistor or suitable transformer, or a battery, as may be desired. The electrical heating of the igniter may be continuous or limited to coincide with the presence,

of the air-fuel mixture at the time ignition is desired. As in my preceding applications, above referred to, the fuel-air mixture is withdrawn from contact with the igniter after ignition has occurred, as e. g. by means of the flash-back system. The igniter may also be used for the ignition of a gas which in turn is used for the ignition of another fuel which by itself is either too difcult to ignite or in which ignition is too unreliable.

What I` claim is l. An automatic igniter for organic fuels in nely divided state capable of being catalytically oxidized in a flowing fuel-air mixture in the presence of a catalyst, comprising an electrically heated heterophase catalyst having at least a primary phase portion to initiate the catalytic oxidation and a secondary phase portion to be activated by the heat of the reaction at the primary phase portion and thereupon to complete the catalytic oxidation to the state where the flameless combustion of the catalytic oxidation is converted into flame combustion, the said catalyst consisting of a closely spaced helical coil of catalyst metal, the wire of said coil having a diameter not in excess of about 0.003", said coil being in turn formed into a coil having a plurality of turns, a source of electrical power connected to said coil to heat said coil to a temperature substantially below the ignition temperature of said fuel in said fuelair mixture and below the recrystallization temperature of said catalyst metal, and means for terminating the contact between the catalyst and the ignited fuel.

2. An automatic igniter for organic fuels in finely divided state capable of being catalytically oxidized in a fuel-air mixture in the presence of a catalyst, comprising an electrically heated heterophase catalyst taken from the group of metals of the platinum group and alloys thereof, having at least a primary phase portion to initiate the catalytic oxidation and a, secondary phase portion to be activated by the heat of the reaction at the primary phase portion and thereupon to complete the catalytic oxidation to the state where the flameless combustion of the catalytic oxidation is converted into flame combustion, the said catalyst consisting of a closely spaced helical coil of said catalyst metal, the wire of said coil having a diameter not in excess of about 0.003, said coil having an inner diameter of from about 0.002 to about 0.015 and a coil spacing of from about 50 to 400 turns per inch, said coil being in turn formed into a larger coil having an inner diameter of from about 0.01 to about 0.1, a source of electrical power connected to said coil to heat said coil to a temperature substantially below the ignition temperature of said fuel in said fuel-air mixture and below the recrystallization temperature of said catalyst metal, and means for terminating the contact between the catalyst and the ignited fuel.

3. An automatic igniter element for organic fuel in finely divided state capable of being catalytically oxidized in a flowing fuel-air mixture in the presence of a catalyst, comprising a catalyst consisting of a closely spaced helical coil of metal taken from the group of metals of the platinum group and alloys thereof, the Wire of said coil having a diameter not in excess of about 0.003,

7 saidV coil being in turn formed into a coil having a, plurality of turns, a mounting for said catalyst and including lead Wires to opposite ends of said coil for connection to a source of electrical power of such order of magnitude as to heat said coil to a temperature substantially below the ignition temperature of said fuel in said fuel-air mixture and below the recrystallization temperature of said catalyst metal.

JOHANN GNTHER COHN.

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

UNITED STATES PATENTS Name Date Van Hoevenbergh Sept. 15, '1896 Number Number Number

Images