US1902541A - Method and apbabattts fob igniting combustible mixttlbbs - Google Patents

Description

March 21, 1933. G, (1 M ET AL 1,902,541

METHOD AND APPARATUS FOR IGNIZTING COMBUS'IIBLE MIXTURES Filed April 15, 1931 2/ INVENTOR- BY ma ATTORNEYS.

'the character indicated, and to Patented Mar. 21, 1933 UNIT D-- STATES PATENT OFFICE GEORGE G. BROWN AND MOTT SOUDERS, JR., ARBOR, MICHIGAN V mnon AND APPABATUS ron IGNITING comaosmnn mm Application filed April 15,

inflammation of combustible mixtures without, developing undesirable phenomena, particularly' s waves, and to provide suitableapparatus for accomplishin such end. More specifically, it is an obJect of the invention to' prov1de a method of effecting combustion incombustion chambers of the character indicated without 7 the development of traveling pressure phenomena of rovide means for eliminating or substantia ly suppressing vibrations or oscillations of appreciable amplitude'in the traveling flame and in conjunction with the igniting agent. A further ob'ect of the invention is to provide-means or controlling .the duration and intensity of i nition, articularly the duration of the e ecti'ic discharge which ignites the combustible mixture in acombustion chamber.

Other objects of the invention will in art be obvious and'will in part appear ereinafter. I

The invention accordingly comprises the several steps and the relation-and order of one or more of such steps with respect to ,each of the-others, and the apparatus embodying features of construction, combination of elements and arrangement of parts which are adapted to effect such steps, all as exemplified in the following detailed disclosure, and 'the scope of the application of which will beindicated in the claims For a fuller understanding of the nature and objects of the invention, reference should taken in connection with the accompanying drawing, in which:

Fig. 1 shows an oven provided with an lpngated combustion chamber adapted for tltespractice of the present invention; Fig. 2 is a viewpartly inplan and partly be had to the following detailed description 1931. Serial No, 580,270.

cated in Fig. 2 in accordance with the present invention.

In the industrial arts, it is frequently de- 50 sirable to enerate large quantities of heat in relative y small spaces'and in relatively short periods of time. The time interval permitted in many instances is so short that it is conventionally described as instantaneous. The generation of heat in this manner is required in various types of devices, for example, in heat engines, in internal combustion engines, in certain forms of ovens and in intermittent heating devices. It has been customary where space limitations are essential to emplo combustible mixtures as the medium supp ying the heat which'are ignited by any suitable means, for example, by a hot spot or by the passage of an electric spark.

While the liberation of heat under such circumstances may be said toapproach the instantaneous, it is known that there is a definite rate of combustion of the combusti- 30 ble mixtures in closed chambers, which rate is-determined by several factors, for example by the pressure, by the presence of foreign agents, and by the character ofthe igniting agent; When combustion of combustible mixtures is initiated in a local portion thereof, inflammation is propagated throughout the mixture at a definite rate, while accompanied by other phenomena, some of whicl are of a highly detrimental character, for example, the shock and intense traveling pressure waves, accompanying the flame propagation.

The pressure waves normally developed in explosive mixtures of the, character indicated, for example in a mixture of hydrocarbon vapors and air, travel with velocities of an order equal to that of [s ound, and it has been ascegtained that the have an accelerating effect on the rate 0 inflammation accompanied by a rise of pressure. It has been observedfthat when suchwaves exceed a predetermined minimum amplitude, the rate of'rise'of pressurev is affected by the presence of certain foreign agents, for example the rate is 'frequentl increased by tetra-ethyl lead, when intro uced in vapor form with the fuel va or. Where the waves are small of amplitu e, the tetra-ethyl lead has been observed to decrease the rate of rise-of pressure in the combustion induced b such waves. It is not easy, however, to

distinguish between the rate of rise of pressure in such combustion and the rate of reaction in anormal flame where induced by pressure waves. Decomposition of the foreign agent has been roposed to effect control, but it has been etermined that decomposed tetra-ethyl lead will not eliminate sound velocity waves under all practical conditions -in combustion of this character. The development of such waves into a pressure wave of. relatively great am litude, or socalled shock wave, has been '0 served within certain limits under such'circumstances. It is seen in consequence that such agents are not suflicient means for controlling, compen-.

eating for, or eliminating the nomena referred to above. We have ascertained that the undesirable undesired phephenomena accompanying the inflammation I of combustible mixture are influenced, not

caseas a single direct discharge without onlyby the character and intensity of the ign ting agent, but also by the time and manner of application of the igniting agent. Where an electric discharge 1s.the ignitin agent this should be app ied in the idea nition be limited to a maximum duration which is usually'a small fraction of a second and dependsupon' the intensity of discharge, the frequency of oscillation and the degree of damping in the circuit, and the characteristics of the combustible mixture and the combustion chamber. .For example satis-' factory results may be obtained and the presence of shock wavesavoided if the duration of ignition be 0.025 seconds covering 1.5 cycles of a (SO-cycle damped discharge, when igniting hydrpcarbon vapor-air mixtures at atmospheric temperature and pressure in a relatively large closed combustion chamber,

atmospheres and a such as one 30 inches in length and 3 inches in diameter, which may be completely inflamed in 0.16 seconds after ignition. On the other hand, violent shock waves which will rupture the same a paratus are developed by simply increasing the number of discharges across the spark gap so asto y cupy a timeinterval of about 0.15 seconds.

As the rate of reaction is increased by an increase in pressure or temperature, it is necessary to decrease proportionally the duration of contact between the explosive mix-- ture and the electric igniting discharge. For example, the contact should be for about one ten-thousandth part of a second where the combustible mixture is' of hydrocarbon vapor and air at a pressure upwards of 5 200 degrees F.

In accomplishing combustion in accordance with the present invention, the commanner and brought to the desired condition of temperature and pressure without effecting ignition. This is 'then effected independently by suddenly applying an igniting temperature upwards of 'bustible mixture is provided in the, usual agent, such as an electric s ark directly as a substantially unilateral 'd1scharge-2for the desired brief interval of'time. Where an electric sparkis the igniting agent, any suitable electrical system may be employed for applying the'spark where its character and duration are determined by the electric properties of the system. A revolving commutetor in conjunction with a damping circuit has been. found suitable for controlling the duration of the discharge in relatively slow burning mixtures such as hydrocarbon vapor and air at substantially atmospheric pressure. 1

In the accompanying drawing is illustrated a practical manner in which combustion is effected by an electric spark in accordance with the practice of the invention. Here denotes an oven which is to be heated by the combustion that takes place in an elongated combustion chamber 11, here shown in the form of a sinous pipe disposed near the top of the oven. Th s pipe, as shown in Fig. 2, has a valved connection 12 for admitting and discharging at will gaseous agents to and from the interior of the chamber.

Electric means for eflecting ignition in the manner above indicated are shown at the left of the drawing in Fig. 2, where 13 denotes a commutator adapted to revolve at a relatively high rate of s eed. This commutator 'is shown as provide with a contact segment 14 made to span a relatively short are, which when revolved operates to reduce the time for the passage of the spark to the desired,

short interval. A conductor 15 leads from the commutator to an electrode 16 of a spark gap within the combustion-chamber The 65 chamber, since a other electrode 17 of this ga has a conductor 18 in series with an in uctance coil 19 and the contact 20 which bears on the commutator 13 and is adapted to make contact with the segment 14 when it sweeps under the same. This, system is arranged to be supplied with electrical energy through the winding 21, which is inductively related to the winding 19, the winding 21 being connected to any suitable intermittent or periodic source of electric current.

While a dischar e of suitable character and duration may ie pi'oduced. by an elec; trical system containing only inductance and a commutator arranged for closing the circuit for but relatively brief intervals, other electrical systems may be em loyed. Figs. 3, lfiand 5 show-exemplary orms of other electrical systems which may be substituted for that shown in Fig. 2. In Fig. 33 an inductance 29 is shown in series with the commutator 13, a condenser 24 and a,

spark gap 26-27. Here the condenser is shunted by The resistance, as is ObVlOllS, infects the time constants ofthe circuit and operates to insure the desired brief discharge, which is employed in the practice of the invention.

In the arrangement shown at Fig. 4, an inductance 39 is shown in series with a commutator 13 and a spark gap ,36-.37. The gap here is shuntedb acondenser 34 havlng in series therewit a high resistance 35 which attenuatesthis spark and also affects the time characteristics: of the discharge. Fi 5 shows another system similar to that in ig. 4, butdifiers therefrom in having a grounded connection 40 whereby a relatively constant spark characteristicis at all times denser-34 being accomplished outside of the mutator prior to the recharging stage. The systems shown in Figs. 3, 4 and 5 are arranged to be supplied with electric l-energy through the windings 21 which are inductively related to' the. windings 29 and 39' respectively, the winding 21'being connected to any suitable intermittent or periodic source of electrical current in a manner similar tothat shown in and described in rela-.

tion to Fig. 2. I

In operation, the chamber 11 isfilled with a combustible mixture at a desired pressure and temperature. The commutator 13 may be kept constantly revolving if desired, so that when itis desired to ignite the mixture the circuit containing winding'21 is closed. This effects the combustion desired.

While a closed combustion chamber has been illustrateda's one to which the process of the present invention-is applicable, it is apparent that the' practice of the invention is not limited to such variety of combustion such a relatively high resistance 25. a

mixtures in combustion nsured; the complete discharge of thecon-.

, the accom animent of'shock .pheifes, and igniting the same b chamber through which the gaseous agents are adapted to flow may be employed eq'uall well. rate of fiow and the interval between the passage of the igniting spark are respec-. tively so timed that the chamber is substantially filled with fresh mixturebefore firing. Since certain changes in carrying out the above method and apparatus and in the constructions set forth,.which embod the invention may be made without eparting from its scope, it is intended that all matter contained in the abovedescription or shown in the accompanying drawing shall be interpreted as illustrative and not in a limitin sense.

aving described our invention, what we claim as new and desire/co secure by Letters Patent, is: 1.The method of i iting combustible mixture in combustion c ambers'without the accompaniment of shock waves which comprises introducing a combustible. mixture within a combustion chamber, after igniting the same bythedirect application of. an igniting agent for a period of time of the order of a ten thousandth ,part of a second.

In such case, the.

and therev 2. The method of igniting combustible.

chambers withoutv h as it combustible mixture at a desired pressure and temperature,

passage of an electric discharge for a relatively brief interval of time. i

' 3. The method of igniting combustible chambers without the accompaniment of shock waves which comprises filling a combustion chamber with a combustible mixture at a desired. pressure and temperature, and igniting the same by a substantially unilateral passage of an electric spark for a. period of time not exceeding a small fractionof a second.

-4.'.The method of ignitln'g combustible mixture in combustion chambers without waves which comprises lling a combustion chamber with a combustible mixture at a desired temperaseveral atmosture j and at a pressure of a substantially unilateral passage of an e ectric spark of desired intensityt ior a period of time of the order of. a ten-thousandth part of a second. i

5. The method of igniting combustible mixtures in combustion chambers without the accompaniment of shock waves 1 which comprises filling a combustion chamber with a combustible mixture containing hydrocarbdn'fuel vapors and air at a pressure of the order of several atmos heres' and at a temperature below that o ignition, and ignit; ing the same by a substantially unilateral and igniting the same by a substantially unilateral passage of an, electric s ark of desired indischarge to substantially unilateral tensity for a period of fame of the order of a ten-thousandth part of a second.

the ignition of I 6. Apparatus for efiecting combustible mixture without the accompaniment of shock waves, comgerising in combination a combustion cham r having an inlet-and a discharge, and electric means for ignitin the mixture, said means being constructe to control the intensity of the igniting effect and to limit the time of its application to a desired period.

7. Apparatus for effecting the ignition of combustible mixture without being accomnied by shock waves, comprising in comination, a combustion chamber having an inlet and a discharge, and an electric system arranged to ignite the mixture in said chamber by the passage of an electric discharge, said system including electric elements for controlling the intensity of said discharge and an element for limiting the assage for a period of time of the order 0 a tenthousandth part of a second.

8; Apparatus for eflecting the ignition of combustlble mixture without being accomanied by shock waves, comprising in comination, a combustion chamber having an inlet and a discharge, and an electric system arranged to ignite the mixture in said chamber by the saidsystem inc uding electric elements for contro ling the intensity of an igniting spark and a commutator for limiting the spark to substantially unilateral passage for a period of time of the order part of asecond or less.

In testimony natures. I

' GEORGE G. BROWN. MOTT SOUDERS, Jn.

assage of an electric spark,

of a ten-thousandth whereof we aflix our sig-

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