US2643107A - Heating device - Google Patents

Description

June 23, 1953 w. 1. E. KAMM ETAL HEATING DEVICE 4 Sheets-Sheet 1 Filed NOV. 28 1949 1W5 447M," INVENTORS. 1w:

u 23, 1953 w. l. E. KAMM ETAL 2,643,107

' HEATING DEVICE Filed Nov. 28, 1949 4 Sheets-Sheet z 0000000 0009 -o o oo o qylmff O a l, N \mx June 23, 1953 w. E. KAMM ET AL 2,643,107

HEATING DEVICE Filed Nov. 28, 1949 4 Sheets-Sheet 3 MAE ,mM ORs E Meal/r2252 ,By A. Zzusze A I June 23, 1953 Filed Nov. 28, 1949 w. E. KAMM ETAL HEATING DEVICE 4 Sheets-Sheet 4 m5 MMW m E K675707768 K 674/652 Patented June 23, 1 953 HEATING DEVICE Wunibald I. E. .Kamm and Willy Krautter, Dayton, and Kurt 'Staiger, Wright-Patterson Air Force Base, Ohio Application November 28, 1949, Serial No.,129;861

(Granted under'Title 35, U. 8. Code (1952),,

sec. 266) 1 Claim.

The invention described herein may bemanufactured and used by or for the United States Government for governmental purposes Without payment to us of any royalty thereon.-

This invention relates to air heating devices generally more particularly to pulse jet space heaters of the air circulation type operating in acoustic resonance, having for an object the provision of a highly efiicient heater, preferably of the liquid or gaseous fuel type, in which a maximum volume of air is heated, circulated, and delivered without the use of blowers, fans, or other auxiliary power operated devices.

A further object of our invention is the provision of a portable self-contained space heater that is light in weight, economical 'to manufacture, simple and easyto start, having means for efiiciently heating, circulating and delivering large volumes of air solely by the use of a resonant air heating and combustion heater unit of the liquid or gaseous fuel type, utilizing high frequency oscillations of rapid intermittent explosions of the fuel mixture to supply the heat, circulate the air to be heated, and cause delivery of heated air in appreciable volumes to the place 'or area to be heated.

A further object is the provision of a space heater having a combustion chamber with a carburetor and fuel supply nozzle therefor including an elongated discharge pipe, employing the acoustic resonant or pulse 'jet motor operating principle and utilizing the pulse jet discharge to heat, circulate and effect delivery of large quantities of heated "air from the heater, including means for reducing the back pressure effect on the carburetor fuel delivery nozzle for the combustion chamber following each explosion or pulse, incorporating fixedly associated means for securing a dryer and better vaporizing of the operating fuel mixture to produce an extremely efficient detonating effect in the pulse jet combustion cycle, particularly during the starting period, making it possible to initiate the pulse jet cycle into operation with ease and minimum de- .A further object is the provision of an improved pulse jetspaceheater utilizing the resonant pulse jet action and rapid pulse discharge from the combustion chamber for the heating, circulating and delivery :01" heated .air in large volumes to a predetermined delivery-point :or space to :be heat- 1 ed, incorporating heat exchange means for cooling the discharged products of combustion from the pulse jet structure and simultaneously heating and delivering an appreciable volume of fresh air itherewith to afirst delivery point inside of the heater .in which asp'irator means is provided adjacent the first delivery point for circulating, .heating and mixing :a second appreciable volume of air with the first volume of heated air and combustion products and effecting a rapid delivery 'of the :same to :a predetermined remote delivery point outside :of the heater without the use :of fans, blowers, ror other independent power operated air circulating .means.

A further object is the provision of an acoustically tuned resonant pulse jet type of air circulating heater which can be easily incorporated in aircraft power plant :inclosing structures to maintain the aircraft engines and cooperating accessories at a desired temperature at all times, particularly when the engines are not in use to provide easier starting and also reducing the preliminiary "warm-'11p;perio1ds of the engines to a desired :minimum.

vA :further object of our invention is the provision :of an improved resonant pulse jet operated air Pheating structure having .a portable cabinet including means for utilizing the radiant heat for regaining the vapor losses within the cabinet in which the cabinet comp-rises a light weight body or casing constructed to efficiently and effectively withstand excessive damage incident to hard usage while in :storage, and during shipment and arranged for nesting by superimposing and interengaging :any reasonable number of the cabinet heater units upon each other, whereby a battery of superimposed :heaters may be utilized and putinto simultaneous operation while nested to deliver :great volumes of heated air at substantially any desired point or space that is to be heated.

A still further object "is the provision of a resonant acoustically tuned pulse jjet operated space heater incorporating an improved type of selfcontained starting device for initiating the detomating action, including :means for initially heating and introducing fuel and air into the combustion chamber under pressure in a dry and heated condition to eilect a convenient and easy automatic "starting of the space heater device,

even under low temperature and adverse weather conditions.

Other objects and advantages of the invention will become apparent from the following description, taken in connection with the accompanying drawings, in which like reference characters refer to like parts in the several figures.

Drawings Fig. 1 is a side elevation of a space heater incorporating our invention;

Fig. 2 is an end elevation of the space heater shown in Fig. 1;

Fig. 3 is a transverse vertical sectional view of the space heater shown in Fig. 1, taken approximately on the plane indicated by line 3-3 in Fig. 2 looking in the direction of the arrows, parts of the apparatus being shown away or shown in elevation;

Fig. 4 is a vertical sectional view taken approximately on the plane indicated by lines I-4 in Fig. 3, looking in the direction of the arrows;

Fig. 5 is an enlarged vertical fragmentary longitudinal sectional view taken through the supplemental fuel heating and supply means which supplies fuel and air to the pulse jet combustion chamber in a dry and heated state and heats the combustion chamber, primarily to start the resonant pulse jet action within the combustion chamber and tail pipe and illustrating the lower portion of the combustion chamber and valve chamber broken away and shown in section to illustrate the fuel and air inlet means, and the improved check valve arrangement;

Figs. 6 and 7 are enlarged detail views illustrating one of the forms of the combustion chamber check valve and seat arrangements that may be used, showing the same respectively in closed and open positions;

Figs. 8 and 9 are enlarged detail views of a modified form of check valve structure, including resilient actuators or spring means for accelerating the closing and opening actions of the check valve members following the detonation of the fuel mixture within the combustion chamber and discharge therefrom;

Fig. 10 is a somewhat diagrammatic view, illustrating a modified arrangement for supplying heated air to an aircraft engine and accessories mounted within a nacelle, in which the heated air supply conduits form a permanent structure within the nacelle, the improved heating apparatus being in the form of a compact individual detachable unit, capable of being applied to the aircraft structure for supplying heated air in appreciable volumes to the conduits; and

Fig. 11 is a plan view of the structure shown in Figs. 8 and 9.

Referring more particularly to Figs. 1 to 4 the reference numeral I denotes a rectangular or parallelepiped casing, formed of light sheet metal. The casing I is provided with spaced longitudinal skid members or supporting strips 2 on the bottom thereof while the top is provided with a central raised portion 3 having a width sufficient to interengage the adjacent side edges of the spaced skids 2 of a superimposed heater as shown diagrammatically in dotted lines in Figs.

ber 9. This inlet port has a large area so an appreciable volume of fresh air can be introduced or drawn therethrough into the interior of the cabinet I and is located in the upper portion of the cabinet. Extending inwardly from the port 8 toward the rear wall I0 is tubular fresh air inlet passage or duct I3 which is somewhat rectangular in cross section, although it may be cylindrical.

A second port of fairly large area is also located in the front wall I directly below the air inlet port 8 and constitutes a heated air outlet or discharge port I I for discharging heated air from the interior of the cabinet in an appreciable volume, together with the products of combustion from a resonant pulse jet air circulating heater 22, later to be described. The outlet port II also receives an extensible flexible heat conducting tube IZ which is collapsible within the port, or extensible for connection to any suitable space to be heated, such as an engine nacelle, or other chamber, or a compartment of an aircraft or vehicle, for the purpose of delivering heated air to the space to be heated.

Referring now to Figs. 3 and 4, the rectangular fresh air inlet duct or conduit I3 extends inwardly from the front wall 'I and terminates in spaced relation to the rear wall I0. A double walled tube forming the heated air discharge conduit is indicated generally at I5 and extends rearwardly within the casing from the outlet port II toward the rear wall I0 and comprises spaced inner and outer concentric cylinders I6 and I1, secured together at their inner ends at I9. The outer cylinder I1 is secured at one end to the front wall I, around the periphery of the discharge port II, and is supported at its other end by the standards 20, 2I, the annular space between the cylinders I6 and I1 thus provided, accommodates the flexible longitudinally extensible annularly corrugated tubular conduit I2, which is slidable into this annular space as shown, and collapsible between the cylinders I6 and I1 forming the inlet tube I5, or is extensible as desired.

The fresh air inlet and heated air discharge tubes I3 and I5 terminate within the casing I in spaced relation to each other in about the same vertical plane, intermediate the front and rear walls I and II] as shown, so that fresh air entering and passing through the tube I3 must first pass into the relatively greater space of the interior of the cabinet before being introduced or drawn into the mouth or inner end of the hot air discharge tube I5. This arrangement produces a sound dampening or silencing effect in the space heater that will be explained later.

Located within the cabinet I, at one side of the air intake and heat discharge conduits I3 and I5, is a resonant pulse jet air heating and air circulating structure or unit, the reference numeral 22 indicating this unit generally. The resonant pulse jet unit 22 comprises a combustion chamber 23 having an elongated discharge conduit or tail pipe 24 leading therefrom and acoustically tuned to a resonant frequency to produce rapid explosion impulses and oscillations when a suitable combustible fuel mixture is fed into the combustion chamber from below. The tail pipe 24 extends toward the rear wall I0 and is rebent on itself as at 25 and then extends forwardly, having an outwardly flared discharge outlet or nozzle 26 which projects materially into the inner end of the inner hot air discharge tube or conduit I6, in concentric relation thereto,

aerator outer surface of the combustion chamber,- the shroud member 2"! havingan air outlet port 28 in the side thereof through which the tail pipe 24 extends. An air heating and conductingtube 29 surrounds the tail pipe 25, and is connected,

at one end to the port 28 in the shroud 21, its other end being flared and terminating in an outlet port or mouth 39, concentrically surrounding the flared outlet end 26 of the tail pipe 24. Suitable supporting spiders" 3| extend between the inner end of the heated air delivery tube l and the discharge end or mouth of the air conductor tube 29 and betweenthe mouth 30 and the tail pipe 24, maintaining these tubes in spaced concentric alignment.

Located immediately in advance of the discharge outlet ports of the tail pipe 24 and the air conductor tube 29 is a Venturi nozzle 32 which tapers forwardly within the inner tube 16 and terminates at the front wall 1 of the casing l. The combustion chamber 23, tailpipe 25, hood or shroud 2? and the air heating tube 29 being subject to extensive heat and vibrations, are therefore preferably constructed of stainless steel or other equally strong noncor rosive material. The combustion chamber 23 tapers downwardly from its head or dome portion and a check valve unit 33 is secured across the lower end of the combustion chamber as shown in more detail in Figs. 3 to 7.

We prefer to use free-floating or flying valves in the valve unit 33, as shown in Figs. 6 and 7, or resiliently actuated valves as disclosed in Figs. 8 and 9, in order to obtain a very rapid, completely free valve actuation.

The valve unit 33, as shown in Figs. 5 to 7 comprises an annular relatively heavy valve supporting plate 35 fastened at its periphery to the lower end portion of the combustion chamber, being formed with a multitude of closely spaced spherical depression or valve seats 35 each surrounding a combustible fuel mixture inlet port 37. The valves, denoted at 38, are very thin cup shaped disks each having a somewhat spherical curvature substantially conforming to the curvature of the seats 36'.

Located immediately above the supporting plate 34, in spaced relation thereto, is an annular thin foraminous retainer plate or screen 39, formed with downwardly projecting substantially spherical protuberarices having contours which substantially fit the interiors of the cup shaped valves 38 when the valves are raised or floated upwardly by air and fuel entering through the ports 31 from a carburetor or fuel and air supp-1y means located below indicated generally at 4!. When the valves 35 are seated on the plate 34 the ports 31 are closed. When valves are raised, air passes around the valves, through the perforations in the retainer plate 39 and into the combustion chamber 23.

A downwardly tapered fuel supply nozzle or tube, indicated at 42 in Fig. 5 is secured below the valve unit 33 and terminates in an outwardly flared Venturi inlet port 44 having a fresh air intake chamber 45. A central air and fuel mixing inlet tube 46 is suitably supported in the Venturi 44 at ll. concentrically located in the lower portion of the mixing tube 46 is a fuel jet 48 whichis carried by a supporting spider 49, the fuel j'et 48 being supplied with a suitable liquid or gaseous fuel through. the conduit from a carburetor 5|, being in turn supplied with a fuel, such as a liquid hydrocarbon, through the pipe 52 leading from a main fuel reservoir or tank 53 located within the cabinet I and supported by suitable standards 54, the tank 53 being provided with a filler opening and closure cap 55, accessible through the door 4.

The pulse jet unit is supported in any convenierit manner, such as by suitable standards or brackets secured to the interior of the casing,

'or as shown, by a-supporting bracket or strap 56 which is clamped around the exterior ofthe hot air outlet tube l5, as shown in Figs. 3 and 4, with the ends thereof secured to the combustion chamber 23', at or near the check valve unit 33. The combustion chamber 23 may be provided with a jump spark plug 5'! as indicated in Fig. 5 and associated suitable high tension current supply means 58 for supplying an electric spark to initially explode the combustion mixture within the combustion chamber to start the pulse jet cycle after a jet of compressed air under high velocity is directed into the fuel intake mixing tube 45 and past the fuel nozzle 38 to introduce a combustible fuel and air mixture through the check valves 38 and into the combustion chamber 23. We prefer however, to utilize an automatic, self-contained starting unit or set which is indicated generally at 59. The use of this starting unit 59 eliminates the use of pumps, air pressure supply tanks, conduits, valves, etc., also eliminating the use ofbatteries,- high tension coils, switches, spark plugs, etc'., and providcs other advantages later to be pointed out.

Once the pulse jet heater unit is setinto operation there will be a vertically vibrating column of air andfuel within the intake nozzle 5?. and the central fuel and air mixing intake tube 46 and in order to prevent back pressure at the fuel nozzle @8- as the check valves 38 close at the time of explosion within the combustion chambers 23, an upwardly tapered baffle member 60 is provided which is supported on a spider 6| directly above the n-ozzle lii, best seen in Fig. 5, directing the downwardly moving column of the fuel mixture at this time outwardly away from the fuel inlet jet or jet 48.

The starting unit or set 59, as best seen in Fig. 5 comprises a combined fuel tank and pressure boiler 62 having a filler and deaerating opening and closure cap 63 and a drain passage and closure cap 64. Located directly below the boiler 52 is a suitably ventilated heating torch and wick compartment 55 having an asbestos wick 65' in the bottom thereof. A suitably valved fuel supply nozzle or tap 5'! is preferably connected to the main fuel tank 53, or to the carburetor supply pipe 52 by a conduit 68 having a shut-off control valve 69' therein. A door H3 provides free access to the torch compartment for lighting the wick 66, suitable vents or apertures H being provided which supply the necessary air for the burning of the fuel in the heating' wick compartment and for combustion in the heating retort tube 15.

Located concentrically within the wick com' partment' 65 is a: fuel jet nozzle 12 having a needle valve 13 which is controlled by a hand wheel 14. Extending upwardly from a port in the bottom of the boiler 62 is a central upwardly flared Venturi and retort heating tube l5 having its inlet end directly above and concentric to the fuel jet 1'2 and its outlet end at 1'6, above the topend closure of the boiler 52. Adjacent the side of the boiler 62 and the wick and torch chamber 65 is a gasous fuel nozzle 'II having a fuel jet I8 and an elongated gaseous fuel pressure chamber 19, the chamber I9 being connected at its lower end by a conduit 80 to a chamber in the interior of the main fuel retort nozzle I2 and connected at its upper end by a fuel supply pipe 8| which passes through and is sealed in the wall of the boiler, extending upwardly therein and wrapped around the upper portion of the retort tube l within the boiler as indicated at 32, a gaseous fuel inlet port 83 being formed at its upper end just under the top end of the boiler 62.

The boiler 92 carries a laterally offset closed chamber 84 which surrounds the fuel jet (1. A gaseous fuel and air mixing tube 85 projects upwardly from a port in the top of the offset chamber 84 and is formed with a flared lower end 86 connecting the chamber, the upper end of the mixing tube 85 being in communication through a port at 81 with the interior of the combustion chamber 23. The tube 85 is welded or otherwise secured to periphery of the port just mentioned and forms a supporting arm for the starting unit 59.

The laterally offset chamber 84 is provided with a fresh air inlet port 88 in the top thereof which is controlled by a loose disk or flap valve 89, suitable guides therefor being provided. A vertical push rod 90 is slidable in a suitable guide passage 9| for the purpose of forcing the flap or disk valve 89 closed to prevent fresh air from entering the offset chamber 84.

The fuel nozzle 18 is controlled by a spring tensioned needle valve 92 slidable in a suitable guide passage formed in the lower portion of the nozzle structure below the elongated gaseous fuel chamber I9. A tubular extension 93 is formed on the lower end of the nozzle 18 having a spring seat at its lower end, housing a compression spring 94 which exerts valve closing thrust against a spring seat flange formed on the needle valve 92. The lower end of the needle valve 92 carries a bifurcated head 95 thereon which is formed with a vertical slot for receiving an actuating pin 96 that is fixed on an actuating lever 91. The lever 91 is pivoted at its inner end to a link 98, which in turn is pivoted to a bracket or ear 98 projecting from the heating torch wick compartment 65. The lever 91, as shown in Fig. 5, extends laterally beyond the lower end of the flap valve closing push rod 90 and is loosely connected to the push rod at 99 so that when the lever 91 is swung downwardly it will first lower the push rod 90 to release or free the flap or disk valve 89 and then continued downward movement will withdraw the needle valve 92. The extremity of the lever 9! carries a manual actuator or push button I00 for actuation thereof. A tension spring IOI is connected between the push rod guide SI and the lever 91 for yieldably urging the lever upward to its closing position.

A pressure gage I02 is preferably provided which is connected to the interior of the boiler 62 by a suitable conduit I03, so as to determine the starting or fuel vapor pressure within the boiler 62. A safety valve I03 is connected to the conduit I03.

A heat and flame conducting and air mixing tube I04 is supported, as shown in the drawings, by a web I05, from the fuel introducing pipe 85, the tube being flared outwardly above the retort tube outlet I6 and also flared at its upper end with the upper end located closely adjacent to the side of the pulse jet combustion chamber 23. The tube I04 inclines upwardly toward the combustion chamber so as to direct all of the heat from the starting unit against the side of the combustion chamber 23 to form a hot spot I 06.

Operation In starting the pulse jet heating unit the shut off valve 69 is first opened to saturate the wick 66 with fuel and is then closed. The door I0 is opened and the saturated wick is ignited in any convenient manner, such as by a match. Air entering the apertures II supports the combustion and the flame passes upwardly through the central heating retort tube I5, heating the same to cause some evaporation of fuel and a low pressure within the boiler 62. The heat also ascends the tube I04 and warms the pulse jet combustion chamber 23. After a short interval of time the hand wheel I4 is turned to open the needle valve I3 and nozzle jet I2 starting the retort. Fuel in the boiler is boiled, evaporated, and thus superheated by the coil 82. The gaseous fuel then passes down pipe 8 I through the elongated chamber I9 and pipe and through the fuel jet nozzle I2. Air is drawn through apertures II in the wick chamber 65 and the superheated gaseous fuel from the nozzle burns with intense heat which is directed upwardly through the tubes I5 and I04 against the side of the combustion chamber 23 heating the same to provide a very hot or igniting spot thereon as indicated diagrammatically at I06.

In the meantime, due to the intense heat passing through the boiler 62, pressure within the boiler will build up rapidly and the gage I02 should be noted to determine when a desired pulse jet starting pressure is reached, preferably in excess of 80 pounds. When the starting pressure is reached and the glowing spot is hot enough the push button I00 is depressed, releasing the flap valve 89 and withdrawing the needle valve 11, causing an explosive mixture of super heated fuel and air to be injected through the supporting conductor pipe and into the combustion chamber 23 building up an explosive mixture therein under some pressure. This mixture finally reached the hot spot I06, which is still being heated by the starting set 59, and the mixture explodes, initiating the resonant pulse jet cycle. So long as the push button I00 remains depressed, fuel and air will be injected and sucked through the pipe 85 and into the combustion chamber, and when exploded the mixture column in pipe 05 will also explode, but the flap valve 89 will close, preventing escape of the combustion products through the port 88. When the push button I00 is released the needle valve 92 closes and the flap valve 89 is forced upwardly shutting off the air supply and starting fuel in the offset chamber 84 and the column of air in the pipe 85 becomes dead and only vibrates vertically in resonant frequency with the rapid explosions of the pulse jet cycle within the combustion chamber 23. The hand wheel I4 can now be turned to close the needle valve I3 and shut off the starting unit 59.

Referring now to Figs. 3 to 6 particularly, each explosion within the combustion chamber exhausts the heated gases therefrom through the tail pipe 24 at high velocity and they are discharged from the flared end 26 into the Venturi mouth 32. The jet of exhaust gases leaving the end 26 at high velocity creates a low pressure area at the discharge end of the tail pipe which causes a. surrounding column, or fresh air to pass into the. hood; or; shroud 21., whichv surrounds the hot.- testportion of the combustion chamber, and move along; the hottest. portion of the exterior of the tail pipe 24, through the surrounding hot. air pipe 29 in heat exchange relation, and be; delivered at. the end of the tail pipe into the Venturi nozzle 32. in surrounding relation to the column of hot combustion gases from the tail pipe. The rapid; movement of these twocolumns of products of combustion and fresh heated air into: the mouth of the. air delivery tube I5, and through the aspiratormouth 32 causes. a large quantity of: fresh air, and. any fuel or combustible vapors that may be. present within. the cabinet;. tobe withdrawn burned anddischarged. through the; air delivery tube in. a. second surrounding CO'IUZIIIL. This air being cooler thanthe innertwo columns prevents the. hottest portions of: the columns frombeing on the outside, at least until after the'heated air has been mixed with thecoolerair and conducted materially through. the flexible air delivery hose I2 toward the space to, be heated.

Following each explosion or pulse the inertia of: the rapidly expelled gases causes a reduction of pressure within the combustion chamber 23'. This pressure reduction, as shown in Fig. 7, causes the free light weight or flying valves 38 to float. upwardly against the. screen 45] allowing the explosive mixture from below to enter from the valve ports 3! and pass through the screen or foraminous retainer plate 4!! into the combustion chamber 23.. The reduction of interior pressure in the combustion chamber now causes rapid return; of, a portion of. the hot gases within the tail pipe, and the return inertia of these gases causes a rise in pressure within the combustion chamber which. immediately forces the flying valves 38 closed; as shown in Fig. 6. The heat of the returned gases fires the new mixture causing the following explosion or pulse. The length and diameter of the tail pipe relative tothe combustion chamber is important and determines the frequency in acoustic resonance to provide an extremely rapid pulse jet action which produces a continuousfiow of a large volume of heated air through the. heated air discharge pipe I5 and flexible conduit I-2'. The flying valve structure provides an. ex.- tremely rapid resonant pulse jet action because the valves have very'little weight and inertia I and are always free-to move, no springs being used for'closing. Fresh air is, of course, allowed to flow freely into the cabinet I through the fresh air inlet tube: I3 in great volumes to replenish the heated air that is withdrawn and discharged from the cabinet through the flexible conductor pipe I2- On the suction cycle, the fuel from the fuel jet 4-8 is induced to. flow upwardly with an air column passing through the central air and: fuel mixing intake tube 46 (Fig. 5-) which passes. around the deflector or bafiie 69. The. flow of air and fuel just described induces, through' Ven-turi action, a surrounding flow ofv air, entering the chamber 45 from below, to flow into; the tapered chamber 42 located below thevalves 38;. The fuel and air mixed therein is in the form: of a vibrating column which moves upwardly and through the valve plate during the continued resonant pulse jet action continuing. until the fuel supply valve III-'I is closed. Back pressure in the rising. vibratingcolumn of. the fuel and air mixture withinv the tube 4.6. is deflected away from: t e fuel jet nozzle 48; by the baflle 60'.

In order to improve the flying valve action by resiilently actuating the free or fiyingvalves, a novel and improved arrangement may be employed, as illustrated in Figs. 8 and 9. In this form cup shaped light weight valves 38 are pro- Vided which are freely movable between a valve supporting plate 34, having fuel mixture inlet ports 3'I therein, and a spaced flat valve retainer plate or screen 39 having the apertures 3-9" therein in communication with the combustion chamber. A flat annular valve return spring I08 of disk shape is provided, having a resonant frequency substantially related to the desired pulse. jet resonant frequency of the pulse jet, unit one spring for each valve 38 which is supportedv inspaced relation to the apertured retainer late.- 39. as shown.

Thelower valve plate. 34 is provided with valve receiving" depressions 36*, covered by a thin apertured resilient plate I09 as shown, having a resonant frequency similar to the resonant frequencyof the upper spring plates or disks 18. When the pulse jet unit is in operation at its tuned acoustic resonant frequency the spring plates I08 and I09 snap the valve cups 38 to their closed and open positions in resonance, greatly accelerating the valve movement with a material increase in the efliciency of the pulse jet unit; Fig. 8 illustrates one of the cup. shaped valves t8 when moved toward closed position, with its lower spring. actuator I09. undertension, while Fig. 9 illustrates one of the cup valves 38 when movedupwardlytoward fully open position, with the other spring actuator I08 placed under tension. The actuators I09 also cushion the return actuation of the valves 38 against their seats during operation, reducing wear.

The extensible; flexible. heat conducting tube I2 is not necessarily subjected to excessive heat since the outer column: of cooler fresh air within the cabinet I enters through the intake tube 9v and passes through the conduit I2 in surrounding relation to the; hot gases from the combustion chamber 23: and; from the heating shroud 2'! and tube: 29. The delivery tube I2 can thus be made of accordion pleated fabric, rubber (synthetic), plasticor other suitable material, and when in use the outer end will be disposed in communication with a space to be heated.

, Referring to Fig; 10' a modified heating unit is disclosed in. which a portion thereof is built into the engine nacelle which includes, if desired, a part of: the pulse jet combustion chamber. The balance of the heating unit, including the remainder of. the combustion chamber, starting unit, fuel tank, and other associated parts are built into a small compact cabinet, or inclosing casing or structure, which is easily and conveniently attachable to an aircraft engine nacelle: when the aircraft or other vehicle is on the. ground and not in operation. When attached and initiated into operation. it, will keep the power plant, oil tanks and. other accessoriesat temperatures which are desirable for quick,, easy and; convenientv starting, even under severe Arctic winter weather conditions. 7

In. Fig. 10- an aircraft power plant necelle is indicatedat- I Ii), theengine at I i I, engine accessory' group at. H2, oil tanks, intercoolers etc. at 13- and H4. Venturi. nozzles are located at H5 and. I I6, having heat conductor pipes III, I I8, H9 and. I2Itleadingtherefrom to surround.- ingshield or heat. deflector means, for directingheat. from the-pipes justv mentioned around the parts to be maintained in the desired heated condition.

The reference numeral I denotes an inclosing casing containing the major part of the resonant heatin and starting units, fuel tank, etc. The fuel tank is denoted at I33 having a filler opening and cap 55 the tank supplying fuel to a carburetor I The combustion chamber of the pulse jet unit comprises an upper portion 23 which is supplied with fuel and air at 42 similar to Fig. 5, supporting the starting unit 59 also similar to the starting unit 59 as disclosed in Fig. 5.

The upper portion of the combustion Z3 chamber however is split transversely and flanged, having suitable quick detachable securing means I2I therefor. The upper or dome portion of the combustion chamber is indicated at I22, having one or more acoustically tuned resonant tail pipes as indiicated at I23 and I24 leading therefrom and are conveniently fixed within the nacelle H8, their discharge ends being located respectively in the inlet openings of the Venturi nozzles H5 and H6.

The resonant pulse jet heating unit I is started in the same manner as the unit shown in Figs. 1 to 5. There are certain advantages however in this last described construction, especially in compact high speed planes. All hot and fresh air conduits can be conveniently and permanently located within the nacelle or engine compartment, and the tail pipes I23 and I24 which can be made of proper diameter and length to provide the desired acoustically tuned resonant frequency of the pulse jet unit and being welded to the dome portion I22 of the combustion chamber and opening externally of the compartment, no direct flame or fire can be introduced into the compartment and cause a fire hazard, also the tubing employed can be very light in weight and suitably strong.

The resonant pulse jet unit I may be carried within the plane, or kept at the landing and servicing depots where it can be easily attached by the quick detachable connections I2I and initiated into operation. The fresh air which is induced at the Venturi nozzles H5 and H6 is heated by the hot gases leaving the flared outlet ends I223 and I24 of the tail pipes I23 and I24. This fresh air enters the nozzles H5 and H6 in surrounding relation to the hotter gases thus completely isolating the hot gases until a heat exchange and cooling of the hottest gases takes place. A secondary heating shroud and surrounding pipe for the combustion chamber and tail pipe, similar to the shroud 2'! and pipe 29 in Fig. 3, may be provided, if desired to effect further heat exchange.

This form of resonant pulse jet heater concentrates the heat where it is most needed and no heat is wasted, also no fans or electrical apparatus are required for starting, circulating, and mixing the heated air.

It is to be noted that the heater arrangement as disclosed in Figures 1 to 5 provides an improved sound dampening or silencing action. Most of the noise of the pulse jet unit is caused by the vibrations of the air emanating from the flared nozzle or discharge port 26 of the tail pipe 24. The outlet tube I6 surrounds the end of the tail pipe 24 and overlaps or extends toward the closed end of the cabinet, materially beyond the discharge end. Also the heat delivery hose I2 which is connected to the space to be heated, and the concentrically surrounding flared discharge nozzle 32 absorb and deaden most of the direct sound of the rapid explosions in front of the discharge pipe end 26. An appreciable amount of sound or vibrations are reflected rearwardly out of the hot air discharge pipe 3| and into the interior of the cabinet structure I. The location of the fresh air inlet duct I3 in spaced parallel relation to the hot air discharge tube I6, with both of their inner ends in communication with a much larger space or area within the cabinet, between the ends of these tubes, permits the noise vibrations to be deflected around the interior of the cabinet and by the walls thereof which may be coated with a conventional sound deadening covering, before the sound can be deflected out of the cabinet through the fresh air inlet duct I3. By this time most of the noise vibrations have been absorbed and reduced so that the noise of the pulse heater during its operation is not great or objectionable.

If desired the intake tube I3 may be provided with a, suitable butterfly valve as indicated at I25 which may be adjusted to regulate the amount of fresh air to be mixed at the Venturi nozzle 32. This will effect the volume of heated air that is delivered, but will also affect the temperature of the air at the final delivery point. As the valve I25 is turned toward closed position the temperature of the air delivered through the heated air delivery tube will be increased.

It will be obvious that various changes and modifications may be made in the apparatus as shown in the drawings, the ame being submitted as an illustrative rather than a limiting sense relative to the scope of the invention as defined in the following claim.

What we claim is:

In a resonant pulse jet air heating and circulating space heater, a substantially rectangular enclosing casing having vertically spaced air inlet and heated air outlet openings in one end wall thereof; a resonant pulse jet heater fixed within the casing, comprising an elongated vertical dome shaped combustion chamber having a fuel and air check valve controlled inlet port at its lower end in communication with the interior of the casing; means within the casing for supplying fuel and air to said inlet port to form a combustion mixture in the combustion chamber; said combustion chamber having an exhaust port in its side wall; a U-shaped tail pipe connected at one end to the exhaust port with its opposite end forming an exhaust end portion facing the heated air outlet opening in spaced relation to the outlet opening; air heating conduit means surrounding the upper portion of the combustion chamber and tail pipe in spaced concentric relation thereto having an air inlet and surrounding the combustion chamber and a heated air outlet surrounding the exhaust end portion of the tail pipe; means within the casing for heating the side of the combustion chamber opposite the exhaust port therein and below the air inlet of the air heating conduit means, for heating an area of the combustion chamber wall to a temperature suflicient to explode a fuel and air mixture when introduced into the combustion chamber, to initiate the resonant pulse jet cycle; manually controlled means within the casing having a fuel and air mixture supply conduit connected in communication with the interior of the combustion chamber at a point below the area heated by the combustion chamber heating means and above the check valve controlled inlet port, including manually controlled valve means 13 14 governing the fuel and air mixture supply con- Number Name Date duit and means under control of said manually 2,418,097 Ruff Mar. 25, 1947 controlled valve means for supplying heated fuel 2,427,845 Forsyth Sept. 23, 1947 and air under pressure into the vertical heated 2,445,466 Arnhym July 20, 1948 fuel and air mixture conduit; Venturi means eX- 5 2,464,165 Williams Mar. 3, 1949 tending inwardly from th heated air outlet port 2,496,351 Mazzoni Feb. 7, 1950 of the casing having a flared mouth facing the 2,503,584 Lipkowski Apr, 11, 1950 exhaust end portion of the U-shaped tail pipe 2,504,320 Gamble Apr. 18, 1950 and heated air outlet of the air heating conduit means in surrounding concentric spaced relation 10 FOR IGN PATENTS thereto Number Country Date WUNIBALD I. E. KAMM. 147,026 Great Britain Oct. 6, 1921 WILLY F. KRAU'ITER. 17 6,838 Great Britain Mar. 6, 1922 KURT STAIGER.

15 OTHER REFERENCES References Cited 1n the file of this patent Pages 11, 12 34 and 35 The AermResonator UNITED STATES PATENTS Power Plant of the V-l Flying Bomb by Ing. Number Name t Guenther Diedrich, Project Squid, Princeton,

1, 12,84 Klepel June 6, 1933 20 New Jersey, June 30, 1948.

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