US 2882239 A
Description (OCR text may contain errors)
April 14, 1959 E. w. commas ET'AL .AEROSOL DISPERSION APPARATUS Filed July 20, 1944 4 Sheets-Sheet 2' A nl 14, 1959 E. w. commas ETAL AEROSOL DISPERSION APPARATUS 4 Sheets-Sheet 3 Filed July 20, 1944 Inllll)IIIIIII/IIIIIIIIIIIIII 4 Sheets-Sheet 4 April 14, 1959 E. w. commas E TAL AEROSOL DISPERSION APPARATUS. Filed July 20, 1944 I Fig. 6
2,882,239 AEROSOL msPEnsioN APPARATUS Edward W. Comings, Champaign, and Edgar D.-Shippee and Charles H. Adams, Urbana, Ill., assignors to the United States of America as represented by the Secretary of War Application July 20, 1944, Serial No. 545,844 1 Claim. 01. 252-1359 low. It is known that the most successful devices-developed for producing smokes from difiicultly vaporizable agents have operated on the principle of steam distillation by passing a stream of hot gases from a burning fuel over the agent, but these havenotbeen as eflicient as desired for many purposes. An effort was made to improve these devices by admixing large quantities of air with hot gaseous products of combustion from the fuel in order to increase the volume of heat carrier gas brought in contact with the smoke-producing agent. An improvement was obtained in this way by. increasing the extent of vaporization, but the improvement was accompanied by drawbacks of increased fuel requirements and low concentrations of dispersed agent in a carrier gas or lowvaporization efliciency. J
An object of the present invention is to provide a means and method for making an efficient useof fuel in obtaining a high rate of vaporization with minimized thermal decomposition of difiicultly vaporizable agents. Further objects of this invention will become apparent in the following description.
In a rudimentary phase of the invention, a two-compartment munition equipped with an air-entrainment injector device which serves to aspirate a sprayof liquid or liquefied agent into a hot gas stream wasdeveloped and 'foundtoac'complish the objects of this invention in.
dispersing diphenylaniinechloroarsine, diphenylaminecya- .narsine, chloroacetophenone, sulfur, paraflin wax, glaurin (diethyleneglycol .monolaurate), tertiary butyl stearate, and the like.- The munition is recommended to be used as a candle, particularly for smoke-forming agents that are too unstable thermally to be used in simpler candles and when highly concentrated smoke clouds are desired to be formed rapidly and extensively with fuel economy.
In'the injector, a principal feature of the munition, a liquid agent spray is rapidly vaporized by a hot gas stream. A special baifie above the discharge end of the injector removes liquid droplets from the gas stream and aids in recycling undispersed liquid agent. A candle embodying these features has dispersed 84.4% of diphenylaminechloroarsine as undecomposed smoke. It has also dispersed diphenylaminecyan'arsine with 91% of this agent undecomposed in the smoke. Using tertiary butyl stearate as a simulated noxious smoke agent, it was found that the unit could disperse 89%,of this material as unte atent thermal decomposition when their vapor pressures are decomposed smoke compared to 53% undecomposed in smoke dispersed by a standard toxic smoke candle.
General and specialized types of smoke generator designs embodying features of the invention are illustrated in the accompanying drawings, wherein:
Figure l diagrammatically shows a vertical section View of a compact, portable candle;
Figure 2 shows a cross section View of the candle taken along line 22 in Figure 1;
Figure 3 shows a cross section view of the candle taken along line 33 in Figure l;
Figure 4 diagrammatically shows a vertical sectional view of another candle modification;
Figure 5 diagrammatically shows a vertical cross section view of a large-size continuous smoke-generating unit;
Figure 6 shows a aerial bomb;
Figure ,7 shows a full bottom view of the bomb; and
Figure 8 shows a reduced elevational view of the bomb, to illustrate the relation and proportions of the sections detailed in Figure 6.
y In the several views of the drawings, parts having similiar functions are referred to by the same numerals.
, Referring particularly to Figures 1, 2 and 3, the candle unit shown comprises a lower fuel compartment 1 conbroken vertical section view of an N taining a fuel block 2 and attached to an upper agent .to above the surface of the agent. end l iof the venturi tube isplaced a curved baffle 15. A
compartment body 3 by stud bolts 4 which are fastened to the base plates 5 underneath the fuel compartment bottom and side brackets 4 in body 3. A heat-resistant packing material, such as a valve stem packing, is placed as a seal 6 held by wire 7 between the exterior side wall of the fuel compartment 1 and the telescoping side wall of the agent compartment body 3. Sufficient space is provided around the fuel compartment for passing hot gaseous products of combustion from the fuel to exit orifice 8 from which they pass through an air gap into the venturitube throat 9 affixed to the agent compartment body I 3 and concentrically aligned with the hot gas stream exit orifice 8. Air is admitted from outside the unit through opening 16 to form the air gap surrounding the jet of hot gases flowing from orifice S to the converging inlet 11 of the venturi tube.
The smoke-forming agent 12 rests on an inclined pan 13 in the upper compartment to receive heat indirectly from hot combustion gases of the fuel which circulate below the pan 13 and radiant heat from the fuel 2 undergoing combustion. The diverging walls 14 of the venturi tube project up through the body of the agent 12 Above the discharge hole '16 in the baffle 15 allows the hot gases mixed with vaporized and dispersed agent to flow upwardly and out through exit slits or holes 17 in the cover 13. Cover 18 is bolted to an upper flange 19 of body 3 with a gasket seal 20 in between. v
In the body 3 above the top of the inserted fuel compartment and in close proximity thereto is provided an entrance 21 for an igniting means such as electric wires 22 sealed by high melting point plastic 23 and leading to electric squib 24 slightly buried in starter fuel on top the fuel block 2, or other suitable igniting fuse for igniting the fuel without permitting substantial gas leakage, e.g., an Ensign-Bickford fuse with a pull wire snugly inserted or sealed by a modeling clay. In the operation of a model candle designed as illustrated in Figures 1, 2 and 3, the fuel 2 burns after being ignited, and radiant heat from its surface is transmitted directly to the bottom of the pan 13 holding the agent 12.
This heat is conducted to the agent 12, causing the agent ,to melt after increase in its temperature. Hot gases from velocity, and entrain air on passing into the ,4 inch diameter throat 9 of the injector. The liquid agent flows through a hole 25 of about 0.204 inch diameter in the throat 9 of injector and is broken into a fine spray by the high velocity gas stream. Flow of the melted agent through this hole or several of such holes is induced by pressure in the agent compartment as well as by the hydrostatic liquid head of melted agent 12. The finely divided liquid droplets of the spray are subjected to rapid heat transfer and evaporation for a very short time, in the order of 0.001 to 0.01 second. Following this almost instantaneous evaporation, the stream of gases and vapors undergoes rapid expansion with heat absorption as it is discharged from the injector. Droplets of liquid which are not evaporated or entrained as an aerosol dispersion in the gas stream are thrown out by the baffie 15 and returned to the body of agent surrounding the injector above pan 13. The gas stream carrying the vaporized agent flows through the hole 16 in the baffle 15, then through about forty Vs-inch holes 17 at the top or upper side of the candle.
A suitable fuel for the described model candle as it was used in demonstrating the invention was a 1400 g. composition made up as follows: The igniting or surface layer 2a is a small pressed disc of 20 g. of powder made up in the proportions of 54.1 g. KNO 40 g. Si and 5.9 g. of powdered charcoal. To 20 g. of this mix is added 6 cc. of a 4.8% solution of cellulose acetate in acetone. The main fuel block under the starter is composed of two layers 2b and 2. The upper layer 2b is a mixture of 86 g. of 60-mesh ammonium nitrate and 14 g. of ZOO-mesh charcoal. With these ingredients in the upper layer is mixed 30 cc. of a 4.5% solution of Celluloid (cellulose nitrate) in acetone. The main bottom layer 2 is composed of 100 g. of ammonium nitrate, 163 g. of powdered charcoal, and 100 g. of ammonium chloride, these ingredients being mixed with 300 cc. of a similar Celluloid-acetone solution. The separate mixtures are added in layers and pressed under a pressure of about one ton or more total load. After the mixture is all in the fuel blockcontainer 1, it is pressed under a total load ranging from a few tons to about 25 tons. The completed block in the container is oven dried for several hours or at room temperature for several days.
Just as the design may be modified to suit the needs for any given agent while using the principles of the invention, there may be changes in the type of fuel, the method of igniting fuel and in the proportions of admixed air or other carrier gas. A stratified layer which may be effectively used is one in which the bottom layer comprises an intimate mixture of a cooling compound, such as ammonium chloride, in a proportion of from 10 to 20% by weight with 80 to 90% fuel, the fuel being composed of 80 to 90% ammonium nitrate with 10 to 20% char coal. An intermediate starting layer is composed of the fuel with little or no cooling compound. Above this starting layer is placed an igniting mixture comprising a finely divided metal and an oxidizing agent, such as metal oxide, chlorate or nitrate. With this arrangement a fuse or electric squib very rapidly starts a uniform burning of the fuel block containing a large proportion of the cooling compound. Although ammonium chloride is a preferred cooling compound on account of its availability and suitability, various other compounds may be similarly employed, as, for example, ammonium carbonate, ammonium sulfate and ammonium oxalate.
The use of the agent-aspirating injector has several advantages. It provides one of the most efiective ways of bringing about good contact between the hot gas and the liquid agent attenuated in a small space. This good contact results in efiicient heat transfer and rapid vaporization, so that the hot gases leaving the candle are nearly saturated with vapor, thus permitting the use of a lower temperature in the agent compartment and a decreased amount of admixed air for effecting vaporization.
The capacity of the candle is largely determined by the heat available and the quantity of carrier gas required. With a definite amount of heat or fuel, the weight of agent that can be handled is smaller when more carrier gas is required. On the other hand, the temperatures within the agent compartment tend to be lower when more carrier gas is used. However, the aspirating injector, in using a low amount of admixed air, gives a lowered temperature in the agent compartment through increased latent heat of vaporization. If agents with the same vapor pressures and molecular weights are considered, a candle with no air entrainment should be capable of dispersing the greatest weight of agent, provided thermal decomposition is not a factor. Accordingly, it is desirable to reduce the requirement of admixed air to a minimum without excessive thermal decomposition in order to increase the agent capacity of the candle for a given limited amount of fuel. With this in view, the candle of the present invention was designed to reduce the requirement of admixed air to a small fraction of what would otherwise be required and to completely dispense with admixing of air.
The agent-aspirating injector, particularly with a short throat, creates a relatively high pressure in the agent compartment, e.g., 15 to 30 inches of water, in the described model candle; and this produces the necessary high velocity through the small exit holes. The high velocity coupled with rapid dilution by mixing with air and cooling of the vapor-saturated gas leads to the formation of smaller smoke particle size which is conducive to greater gas mask canister penetration.
The bafile provides a continuous path over which the liquid remaining unvaporized or undispersed may flow back into the agent compartment for recycling to the injector tube. The bottom of the agent compartment is inclined sufliciently to allow operation of'the candle on sloping terrain with more complete use of the agent. In the model candle shown in Figure 1, it was found desirable to drill the'0.204 inch diameter inlet hole 25 for the liquid agent into the throat 9 of the injector tube at a center inch above the bottom of the agent pan 13. With this hole thus spaced above the bottom of the pan, the agent has a better opportunity to melt in the region surrounding the throat of the injector tube below the point at which vaporization and cooling tend to occur.
In the modification of the candle illustrated by Figure 4, the fuel container 1 is clamped at its upper flange to the body of the agent compartment 3 with a suitable ring gasket, such as pressed asbestos, to make a gas-tight seal. Gases from the burning fuel block 2 pass through nozzle 8 as a jet into the injector tube throat 9. This jet of hot gases entrains air from funnel-shaped opening 10 and passes through the injectors throat 9 into the upper agent compartment by way of the enlarged passage 14. Some of the direct radiation from the surface of the burning fuel block 2 strikes the injector tube and thereby imparts additional heat indirectly to fluid passing through the injector tube throat 9. A diminished amount of direct "radiation from the burning fuel strikes the bottom 13' of the agent compartment to furnish heat indirectly for melting a solid agent 12 or heating a liquid agent. A wax plug or similarly a low melting alloy plug 26 may be placed in the liquid agent duct 25; and when this plug melts, the liquid agent runs down through the duct 25 into the throat 9 of the convergentdivergent injector where the liquid, e.g., molten sulfur, is broken into a fine spray by the entering high-velocity gas mixture. While the vaporization of the spray is occurring with absorption of latent heat, additional heat is being imparted to the gases carrying the vaporizing droplets. In this modification, the agent is given added protection against excessive heat from the fuel compart- -ment while the vaporization is made more effective due to the heat transfer from the fuel compartment to the vaporizing zone of the injector. The gas and vapor mixture with any entrained liquid spray strikes the baffle plate 15, and liquid droplets are deflected down into the agent compartment. The mixture of carrier gases and vaporized agent passes out through the discharge nozzle 17 at the top of the agent compartment.
In a unit represented by the diagrammatic view of Figure 4, as in the unit illustrated by Figure 1, the fuel block burns in the absence of air and generates a pressure of about 2 to 4 lbs. per square inch. The jet of hot gaseous products of combustion from the fuel entrains the air and passes through the throat of the venturishaped tube whereby is produced a pressure of about 5 to inches of water in the upper compartment to aid in forcing the liquid agent down through the opening in the throat of the injector. The thin stream of liquid agent, on meeting the hot gas stream, is broken into a fine spray and is vaporized or gasified. The rest of the operation is similar to that described with respect to the illustration in Figure 1. In producing sulfur smoke with the unit, sulfur is melted in the agent compartment, and the liquid sulfur broken into a spray in the injector tube becomes gasified.
A continuous unit for producing sulfur smoke according to the principles described is diagrammatically illustrated in Figure 5. The sameprinciples may be applied to units of any desired large capacity for producing smoke from oil, paraffin wax, or vaporizable toxic agents which can be melted without thermal decomposition. In the continuous unit illustrated in Figure 5, the fuelburning compartment 1 is in the nature of a furnace to which is supplied a heating oil by tube 27 with sufficient air by inlet 28 to support combustion of the oil. The furnace is provided with a water jacket 29 or similar means, such as a heating coil supplied with water from line30, for converting water to steam by heat developed in the fuel-burning compartment. Some of the heat developed in the furnace may also be used for. melting a solid agent or preheating a liquid agent, e.g., liquid. agent supplied to the tubular conduit 31 which passes through a portion of the furnace or is at least contacted by hot gases which. flow from the furnace to an agentvaporizing compartment 3. A solid agent, e.g., sulfur, is supplied to the melting pot 32 from hopper 33 through star valve 34, the liquid agent enters the agent compartment 3 through connection 31 and is retained in a body above pan 13. Steam formed from the heated water in jacket 29 is conducted to a nozzle 25 from which a steam jet passes to the injector tube throat 9 with entrained hot gases from the furnace, and liquid agent is aspirated into the throat through the hole 25. Liquid is deflected back into the body of liquid agent while the gases mixed with vaporized smoke agent flow past the baffle through hole 16 to be dischargedthrough. a number of small orifices or slots 17, whence issuing vapors form smoke.
To carry out the operation of generating sulfur smoke with a continuousunit illustrated in Figure 5, about 14 lbs. of fuel oil per hour and 55 cu. ft. of air per minute are supplied to the fuel-burning compartment to develop hot gases which have a temperature of about 3165 F. at the outlet from the fuel compartment. With the amount of heat thus developed, about 400 lbs. of sulfur per hour can be melted and passed continously to the agent-vaporizing compartment. At the same time about 46 lbs. of steam can be formed per hour for injection through the injector tube with hot gaseous products of combustion. A suitable temperature of about 1425 F. is maintained beneath the pan holding the molten sulfur, and a. suitable temperature of 650 F. is maintained in the discharge duct leading to the discharge orifices from the agent compartment.
A unit of the type described is comparable in capacity to 100 gallon-per-hour oil smoke generator. The unit may be'provided with a power-driven fan and fuel pump and is adaptable as a relatively small, compact, mobile field unit. A unit of this size may be used in screening in design to the continuous unit described. It has the.
advantage of freedom from wear, less weight, still greater compactness, and freedom from operating difliculties. There are no moving parts in such a unit except such valves and gages as may be desired for control, e.g., a steam pressure gage and a valve on the fuel line, a steam coil valve, an atmospheric vent valve for excess combustion gases, and needle valves for adjusting the inflow of molten sulfur into the vaporizing throat of the injector.
The unit may be heat insulated, e.g., by a layer of fiber glass. Briefly, a unit of this type weighs only 197 lbs. When uncharged and stands 3 /2 ft. high by 20 inches in diameter. With this unit, lbs. of sulufur are converted to smoke per hour while 10 lbs. of gasoline as fuel and 30 lbs. of water are consumed. The fuel burner and combustion zone are preferably surrounded by a wound coil for generating steam and the injector provides draft for air.
The sulfur smoke generator can be produced with little or no use of critical materials. It is very advantageous where sulfur is more available than oil. Furthermore, sulfur is a more convenient material to transport under wartime conditions, since it can be shipped in open holds and can be carried to the generators in paper bags.
Although in statically fired smoke generators, it is desirable to augment the volume of heat carrier gas by entraining air with fuel combustion gases and earlier models were designed to cool hot gases from the burning fuel block by entraining air, later it was found that air entrainment could be omitted in using a high-velocity injector vaporizer. This is an important discovery with respect to simplification of the smoke generator and adapting the candle to the form of a practical aerial bomb for producing vapor and aerosol dispersions of persistent toxic agents.
Tests have proved that the vapors of persistent Vesicant agents, such as mustard (dichlor diethyl sulfide), are powerful, aggressive, casualty producers against gas-masked men at concentrations in air obtainable with an efficient vapor generator and a practical expenditure of agent.
A cloud of mustard vapor in adequate concentration is more effective than the best non-persistent type of agents, e.g., phosgene. The method of generating mustard vapor herein set forth converts the liquid to vapor in a short time. It avoids ground losses incurred from liquid dissemination. The area attacked can be occupied safely by friendly troops as soon as the vapor cloud has blown away. This allows the advantageous use of persistent (normally liquid) agents as assault weapons although hitherto they were considered useful only for defense in areas which were not to be occupied by friendly troops. A high vapor concentration of the highly injurious vesicant agents commonly classified as persistent agents makes a very effective weapon against occupants of foxholes and pill boxes. It affects all parts of the body not fully protected by antivesicant, impregnated clothing.
Mustard vapor can be generated rapidly in a munition of simple design, without excessive decomposition, by bringing liquid mustard droplets into intimate contact with a high-velocity stream of hot gases from a burning fuel block for a short period. The vapor concentrations near the bomb or candle generator may be higher than those required to saturate the air, thus causing partial condensation of the vapor to aerosol particles; but the atmospheric dilution, as the particles are carried by wind, tends to reduce the vapor concentration and evaporate the aerosol particles and thus maintain a high vapor concentration.-
In the illustration of a bomb model shown in Figure 6, the design is somewhat simplified compared to the candle models illustrated in Figures 1 and 4. This bomb model was designed to make use of cases and-other parts already made for standardized oil incendiary bombs.
At the nose end of the bomb case is a hollow nose cup 40 with an inner impact diaphragm 41 resting against the base of a fuel block container 1 charged with fuel block 2. A battery sealing compound is used to form a seal 6 around the container 1. At the surface of the fuel block 2 is placed a spitter fuze 24 to act as an igniter.
A suitable fuel block for use in container 1 comprises stratified layers compounded as follows:
Layer Ingredients Proportions NH4NO| 1,000 g. Charcoal 163 g. Bottom (main) N H401 100 g.
5% solution of Celluloid in 300 cc.
acetone. 61 4 7 8- arcoa g. Intermediate solution of Celluloid in 30 cc.
acetone. N O; 54%. Sillflnn 40%, Top (starter p ll Charcoal 6%.
5% solution of Celluloid in acetone.
The finely powdered materials in dry condition are mixed with the solutions in proportions like those indicated and each mixture is compressed in proper order into the fuel container under a high-pressure ranging up to a full load of 25 tons. A fuel of the type described produces hot gases with temperatures ranging from about 500 C. to 1000 0., depending upon the proportion of the cooling agent, ammonium chloride.
A flanged metal disc 13 with a central aperture acts as the bottom of the compartment holding the chemical agent 12. Below this disc may be placed a heat insulating material, e.g., asbestos, as a cover for reducing heat transfer to the agent.
At the upper end of the agent compartment, a flanged disc 42 serves as the top closure. Disc 42 has a central opening for holding the outlet end 14 of the venturi tube, held at the throat end 9 by the central aperture in disc 13. A threaded fill plug 43 with recessed outer surface is used for closing the agent-filled compartment between discs 13 and 42. The liquid agent surrounds the axially disposed venturi tube which extends through the compartment.
The venturi tube converges from an inlet opening of about /2 to inch diameter to throat 9 of about A inch diameter and then diverges to a diameter of about inch.
One or more small holes 25 are drilled into the throat 9 of the venturi tube for bringing the agent into the hot gas stream when the bomb is in action. These holes 25 are sealed tight by a fusible metal ring 26 cast in place over the holes 25 in the throat. Ring 26 may be made of a low-melting alloy, such as Woods metal, which melts rapidly after the fuel begins generating hot gases. Also, one or more small drill holes 44 (e.g., No. 55 drill size, about 0.052 inch diameter) made in the upper end of the venturi tube and normally sealed by fusible metal or the like function when the fusible plug 44 is melted to transmit pressure on the agent.
Pressed into the upper or tail end of the bomb case 31, a tail cup 45 opening outwardly holds a centrally disposed hub 46 threaded on the inside for engaging an externally threaded fuse 47 of the inertia type. The fuse 47 includes a striker 48 normally held away from a primer 39 of a long flame type by a perforated cup 50. Impact of the bomb nose 40 on an unyielding surface, such as the ground, gives an inertia movement to striker 48, which thereupon breaks through the perforation in the cup 50, then sharply strikes the primer 39. The primer set oif by the striker sends a flame down the length of the venturi tube to ignite the spitter fuze 24, which in turn starts combustion of the fuel block 2.
Within a recess surrounding the hub 46 in tail cup 45 is placed a set of gauze streamers 51, e.g., about four streamers each 60 inches long. Each streamer has one end fastened to a ring'52 securely attached to hub 46 and a loose end. The streamers are folded into the tail cup 45 so that the loose ends are pulled out by the air stream when the bomb falls. The extended streamers act to stabilize the fall of the bomb with its nose end plummetted downwardly and to retard the rate of fall. Bombs dropped in this manner on hitting the ground sink vertically into the ground to a depth of about to foot.
A number of small holes 17 drilled into the bottom of the tail cup act as vents for emitting vapors generated within the venturi tube.
Tests of bomb models incorporating the principles described indicate chemically and physiologically that from 75 to of the mustard charged is dispersed in a cloud of high concentration for a long distance (up to approximately yds.) in a period of about 3 to 4 minutes. Such munitions of practical bomb size weighed 12% lbs. with a capacity of 5 lbs. of liquid mustard included a fuel block weighing only 3 lbs.
Various modifications may be made in the location and type of fuse and tail assembly, e.g., the fuse may be placed in the nose end of the bomb and an extendible metal tail fin may be used. The bombs may be made up into aimable clusters for precision bombing, and in the clusters additional safety and arming mechanisms for preventing premature firing may be used, such as are known to be used in clustering incendiary bombs.
It is to be understood that although the underlying principles of the invention have been described with reference to simplified embodiments that indicate progressive developments and various adaptations of the invention, many modifications may be made in designing different kinds of apparatus embodying these principles.
In accordance with usual engineering practice, changes may be made in the arrangement, sizes, and shapes of parts, also in the kinds of control mechanisms for obtaining optimum operation and capacity for limited space, weight and material requirements in any type of unit. For example, the continuous sulfur smoke generator involving the principles of melting sulfur, feeding a jet of molten sulfur into the throat of a venturi injector, and using steam as a source of energy for jetting combustion gases through the throat may be modified as in the following respects: (1) the vapor-emission vent slot areas may be changed; (2) the combustion space and steam coils may be scaled to requirements; (3) the sulfur melting pot made of steel plate instead of cast iron may be given an increased volume by providing simply a swing-lid covered hopper and having the molten sulfur from the pot flow directly by gravity to the agent chamber instead of through a tube; (4) by altering size and form of the injector, and similar changes.
An aerosol generator comprising a lower fuel compartment adapted to contain a solid fuel block and open at its top, an upper agent compartment body mounted in telescoping relationship with said fuel compartment, an inclined pan in said upper compartment body, said pan being so positioned as to substantially close said agent compartment and being adapted to receive a body of meltable, vaporizable aerosol forming agent, a venturi tube passing through said pan at the lowest point thereof, and having its constricted portion in contact with said pan, an aperture in the constricted portion of said tube immediately above said pan, said tube having an upper open end within said agent compartment, an air opening in said agent compartment body below said pan, wall means within said agent compartment body surrounding said air opening and isolating said air opening from said fuel compartment and forming an air gap, said venturi tube having an enlarged lower portion jointed to the upper portion of said wall and opening into said air gap, at hot gas stream exit orifice in the lower portion of said wall and in alignment with said venturi tube, and discharge openings, in the upper portion of said agent compartment; said parts being so constructed and arranged that hot gasses from combustion of the fuel will flow first in contact with said pan thereby meltingthe aerosol forming agent then through said exit orifice and across said air gap into said venturi tube, drawing air in thru said air opening and forming a hot, high velocity mixed stream, which flows through said venturi tube, drawing molten agent through said aperture and atomizing and vaporizing the same, the mixture of air, gases and vaporized agent then flowing out through said discharge openings into the atmosphere where said agent condenses to form an aerosol.
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