US2858672A - Monofuel decomposition apparatus - Google Patents

Description

Nov. 4, 1958 ffl/5L 601774/4/5@ A. G. CLARK 2,858,672

MONOFUEL DECOMPOSITION APPARATUS Filed Oct. 29, 1954 n a l l #1.00/1

TURB/VE sTARrf/e United States Patent MoNoFUEL DEcoMPosrrIoN APPARATUS Albert G. Clark, Wayne, Pa., assignor to General Electric Company, a corporation of New York Application October 29, 1954, Serial No. 465,540

Claims. (Cl. (S0-39.46)

` My invention relates to apparatus for providing a pressurized, high energy uid. More particularly it relates to an improved and economical apparatus for the decomposition of monopropellants whereby a pressurized working uid is provided.

Monopropellants or monofuels, sometimes referred to herein as merely fuels, which do not require the addition or admixture of voxygen thereto for supporting their decomposition or combustion are very useful in generating a jet or stream of working uid which may be used to provide a propulsive force for the structure from which'the jet issues or to drive other apparatus. Starters for gas turbines are typical of such apparatus as are turbine driven pumps, etc.

However, such monopropellants of which normal and isopropyl'nitrate are exemplary are generally difficultly ignited. It has been established, for example, that a pressure of about 100 pounds per square inch and a temperature of about 800 F. are necessary to initiate the decomposition of the propyl nitrates. Present selfcontained systems for the decomposition of such materials, particularly for aircraft installations, require relatively large amounts of electrical power either for initiating the decomposition or for pumping the monopropellant to the decomposition chamber at the required pressure. "The requisite pressure and temperature might be obtained by spraying the monopropellant into an auxiliary electrically heated decomposition chamber. However, a typical heater for this. purpose is rated at -about four kilowatts. The drain on storage batteries for suchheat'- ing as-well as pumping the fuel is excessive resulting in frequent recharging and failure of such batteries particularly at low ambient temperatures.

In another system the fuel is pumped into an auxiliary chamber having therein residual air and is ignited by a spark to provide the proper decompositon conditions. In still another system a slow-burning powder cartridge is utilized to bring the decomposition chamber up to proper temperature and pressure. While the latter two systems are saving of electrical powerl as regards the ignition of the fuel, the power for pumping thefuel still constitutes a serious drain on the electrical system which particularly in aircraft is of as small capacity as possible in order to save weight for useful payload. A typical pump for systems such as those above is rated at about five kilowatts. l

It .will be evidentthen that a definite need exists for a monopropellant decomposition system which utilizes a bare minimum of electrical power. An object of my invention is to lprovide such a system.- Other objects will become apparent and the invention better understood from a consideration of the following description and the drawing in which the single figure illustrates my'invention.

, VBrielly stated, my invention comprises a decomposition chamber Ahaving a first fuel injection means, air inlet means and fuel ignition meansin `one end thereof, second fuel injection'means at the other end thereof and a fo' 2,858,672 Patented Nov. 4, 1958 2, raminous heat retaining or thermal structure extending across the chamber between the fuel injection means. Associated with the decomposition chamber is a pressurized air storage container and a fuel container. Pressurized air isutilized to displace a piston in the fuel container to force fuel intothe decomposition chamber and also to provide for pressurizing the chamber for the initiation of fuel decomposition. Means are also provided for selectively supplying fuel to the rst and second fuel injection means.in the chamber. The power required in my system is about two hundred watts compared to about tive thousand watts or more for prior systems. v l

Referring nowl to theY drawing, the decomposition chamber 1 may be in any desired shape, although I prefer that shown as having a cylindrical central section with semi-elliptical end caps. Mounted at one end of the chamber 1`is a first fuel injection means 2 which is yan ordinary spray or atomizing nozzle. Adjacent nozzle 2 is air entry means 3 which preferably takes the form of an annular chamber 4 having av plurality of holes or ports 5 so ydirected that Yair issuing therefrom' irn-y pinges and mixes with monopropellant injected from nozzle 2. A spark plug 6 is located adjacent the first fuel injectionmeans 2 and air inlet means 3.

Situated in the opposite end of chamber 2 is a second fuel injection means 7 ordinarily similar to nozzle2. In order to reduce vheat losses through the wall of chamber 1 a thin metal liner 8 is spaced from the cham ber wall andfixed thereto as by struts 9. Metal liner 8 may also advantageously be crimped to trap stagnant gas between it and the chamber Vwall to enhance further the insulating quality of the structure.

Mounted in chamber 1 about midway between the two fuel injection means is ajforaminous heat absorbing and retaining orfstoring structure 10 extending across the chamber. z This'structure may be made of any foraminous material which will store heat and at thev same time readily permit the passage of lluid. It may typically comprise a pluralityof layers of stainless steel kmesh held together in any convenient manner as by flanges 11 and bolt 12. A port 13`is provided in chamber 1 for the'attachment to the chamber of pressure sensitive electricl switches 1,'4 and 15, such switches being wellknown in the `art. At the lower end of chamber 1 is a conduit 16 as shown for the exit from the chamber of the pressurized fluid produced therein.l This conduit 16 leads to the point of utilization of the pressurized fluid such as a turbine wheel, a gas turbine engine starter, a rocket nozzle, and the like of usual design and represented by 51.

f Air is supplied to air injector 3 from a pressurized air container 17 through conduit 18. Air container 17v may be ,replenished and lpressurized as required by a compressor not shown. A pressure regulator 19 of any usual adjustable type is mounted in conduit 18.' Leading off from conduit .18 to a Apropellant supply container to be described hereinafter is conduit 20. A remotely controlled ,valve 21 is mounted in conduit 18 between regulator 19 and conduit 20 and a restriction orifice 22 is provided below'valve 21 to reduce the pressure in the conduit to a lower, more convenient pressure. There is also provided in conduit 18 between conduit 20 and ing gaskets y28. Closure 27 has a P01129 Ihtrtllrllh forl the passage of air" from conduit which is connected thereto. Downstream closure 26 has a port 30 therein for the passage of fuel to conduit 31. Slidably mounted inthe cylinder formed by walls is a piston or barrier 32 having sealingy r'ings or gaskets 28 therein to prevent passage of 'u'id past the piston. An air dump valve 33 isVv mounted on upstream closure 27 to release air trapped between theclosure and piston 32 as the latter moves upstream in the container 24 during recharging with fuel. This dumpv valve comprises a cap 34 having slidably mounted therein a cup 35 biased by spring 36 so that normally theV holes 37 in the cap and 38 in the cup are in line to ven't air therefrom. However, when air under pressure is flowing through conduit 20 the end of cap 3S'l1av`ir'1'ga smaller entry hole 39 than that of the conduit prsents' a solid shoulder to part of the air which biases spring 36 downstream and shuts off the vent holes. The monofuel omonpropellaht occupies that space in contfaiiier 24 between piston 32 and downstream closure 26.

Monoprpe'llant 'conduit 31 leading downstream from container 24 divides as shown into two branches, one conduit 40' leading to 41 and the second fuel injection means 7 and having therein a remotely controlled valve 41 and check valve 42, the latter to prevent reverse flow of fuel. v

The other branch 43 of the conduit 31 leads to the first fuel injection means 2 and has therein as shown a remotely controlled'valve 44 and a check valve 45. Branching off from eonduit 43 is conduit 46 leading to a fuel replenishment 'container 47 and having therein aL check valve 48. This latter conduit and its associated-equipment may, of course, be omitted if fuel replenishment is not indicated.

Controlling the'variou's remotely controlled valves 21,

23, 41, and 44 is a timer unit 49 which may conveniently be vof the usual clock movement type for providing any desired sequence ofevents. The control 49 is connected electrically to the valve actuating mechanism such as a solenoid not shown. It will be realized, of course, that the various valves can also be operated by other means such as hydraulically.

Also connected tothe control 49 are pressure switches 14 and 15.` `Thecontrol unit and timed operational sequence is initiated by a starter switch 5,0.

With the monopropellant container 24 filled as in the drawngfand the air container 17 pressurized, the start switch 5'0 is closed `initiating the action of control 49, which opens valves 21 and 23 permitting pressurized air to flow through conduit 18 into air injection means 3, thence through Aports 5 into chamber 1. Simultaneously control unit 49 opens fuel valve 44 and energizes the spark plug 6 .providing a spark in chamber 1. Along with the admission of air through conduit 18 to chamber 1, air also builds up a pressure upstream of.piston 32 in fuel container Z4 moving the piston vdownstream andforc- I ing fuel through conduit 31 and valve 44 thence through conduit 43 and out of rst fuel injection means 2 into chamber l1. The pressure build-up in chamber 1 due to the atomized mixture of fuel and pressurized air is such that with the application of a spark through spark plug 6, the'air-fuel mixture ignites and burns heating up the chamber and the foraminous structure 10. A few seconds later depending upon the size of the chamber and in any case after the air-fuel mixture has brought chamber 1 to the desired temperature and pressure such as 100 p. s. i. and 800 F. for the propyl nitrates, control unit 49 energizes and opens valve 41 admitting fuel through second fuel injection means 7. At the same time air valve 23 is shut olf. The decomposition of the monofuel, having been initiated, will continue without furtherajr, assisted by the heat provided, by the foraminous structure 10.

in order to make the starting -of decomposition failsafe, a pressure sensitive switch 14 may be provided.

This switch is so arranged that fuel valve 41 may not be opened unless the chamber pressure is such that the contacts of switch 14 are closed. If switch 14 is not closed at the proper time for valve 41 to open, control fi-9 is arranged to shut off all power so that the cycle may again be initiated by means of switch 50.

The closing of air valve 23 causes a reduction in the air flow through restriction 22 to fuel container 24, for example, by a factor of about 6 to l with the result that the pressure on piston 27 rises to slightly less than the pressure setting of regulator 19 thus smoothly increasing the ilow of fuel through secondary fuel injection means 7 and increasing the chamber pressure smoothly up to the steadystate value for the particular run. This arrangement prevents excessive llow through the second fuel injection means when the chamber pressure is in the course of building up.

As an additional protective measure, control 49 may be arranged to shut yoff the system if steady decomposition has not started. A pressure switch 15 which closes with the establishment of the steadystate pressure may be provided for this purpose, control 49 yshutting olf the power if switch 15 is not closed after a certain selected period of time.

Again control 49 may be provided with another switch which after any chosen period of time terminates the decomposition. Such a switch is useful, particularly where only short runs such as in turning over a starting motor are desired. Of course such a timing sequence may be overridden by a speedlimit switch in the apparatus being driven.

If it is desired to replenish the fuel in container 24 valves 41 and 44 are closed and fuel forced by a pump into the.c"ontainer. Air trapped upstream of barrier or piston 32 is lvented through air valve 33 as described hereinbefore.

By my invention I have provided a simple, fail-safe means for the decomposition of `monofuel which consumes `a minimum of electrical energy, about ltwo hundred watts as compared to about ve thousand wattsor more for conventional systems.

While I have described my invention vwith particular reference to a relatively short operating cycle, it will be realized that once decomposition is initiated, it vmay be continued until the monopropellant is exhausted.

What I claim as new and vdesire to Isecnre by Letters Patent of the United States is:

1. Apparatus for the decomposition 'of a monefuel comprising a chamber, first means for introducing monofuel and air into one end of said chamber, means for igniting the monofuel-air mixture, second monofuel inlet means in said chamber oppositely disposed to said first means, a porous `heat absorbing and retaining 'structure 'disposed between the tw'o monofuel inlet means, an outlet in'said chamber between said second monofuel inlet means and said porous structure Vand rst and second pressure switches operated by the `pressure in said chamber.

'2. Apparatus comprising a chamber for the decomposition of a monofuel, air and first monofuel inlet means and fuel ignition means in saidchamber, second monofuel inletmeans oppositely disposed in said chamber, a foraminous'metal heat absorbing structure between said rst and second monofuel inlet means, outlet means for the decompositionproducts of said monofuel -and a g-as turbine starter disposed to utilize such products.

3. Apparatus for producing a pressurized uid comprising a reaction chamber having an outlet for said fluid, inlets for air and fueland fuel ignition means at one end of said chamber, an inlet for fuel at the other end of said chamber and a forarninous metal structure between Ysaid fuel inlets and extending across said chamber.

4.v Apparatus for producing a working fluid from the decomposition of a monopropellant comprising a chamber, air and rst monofuel inlet means 'and ignition-means in said chamber, a second inlet for fuel in said chamber, a porous heat absorbing and storing structure between said first and second fuel inlet means, outlet means in said chamber for said Working tiuid and means for utilizing said fluid.

5. Apparatus for producing a working fluid comprising a chamber, air and first fuel inlet means and fuel ignition means in said chamber, second fuel inlet means in said chamber oppositely disposed to said first fuel inlet means, a foraminous heat storing structure between said first and second fuel inlet means, means for sequentially introducing pressurized air into said chamber and fuel to said lirst fuel inlet means for a period of time, to stop the introduction of air into said chamber and simultaneously introduce fuel through said second fuel inlet means and gas outlet means for said working uid.

6. Apparatus for producing a jet of hot gases comprising a combustion chamber, a foraminous screen separating said chamber into a first part and a second part, fuel and air admission means and fuel igniting means in said first part and in said second part fuel admission means and gas outlet means.

7. Apparatus for producing a jet of working fluid comprising a combustion chamber, a foraminous heat storing structure separating said chamber into a first part and a second part, fuel and air admission means and fuel igniting means in said first part, and in said second part fuel admission means and outlet means in said second part for the exit of said working fluid. i

8. Apparatus for producing hot combustion products comprising a chamber having a liner therein, air and first fuel inlet means and fuel ignition means in said chamber, second fuel inlet means in said chamber oppositely disposed to said first fuel inlet means, a metallic foraminous structure between said first and second fuel inlet means and gas outlet means in said chamber for said combustion products.

9. Apparatus for producing a working fluid from the decomposition of a monopropellant comprising a decomposition chamber, air and first monopropellant inlet and ignition means therein, second monopropellant inlet means in said chamber oppositely disposed to said first monopropellant inlet means, a porous heat absorbing and storing structure between said first and second monopropellant inlet means, pressurized air storage means, valved conduit means for the passage of air from said air storage means to said air inlet means, monopropellant storage means, a movable piston in said monopropellant storage means adapted to be displaced by air pressure bearing thereon, valved conduit means between said monopropellant storage means and said first and second monopropellant inlet means, co-nduit means for introducing air to said monopropellant storage means from said air storage means whereby said movable piston exerts pressure on the monopropellant therein and gas outlet means for said working fluid.

10. Apparatus for producing a working liuid from a monofuel comprising a chamber, air and first monofuel injection and ignition means in one end of said chamber, second fuel injection means in the opposite end of said chamber, a porous heat storing structure between said first and Vsecond fuel injection means, working fluid outlet means in said chamber, an air container, a container for" monofuel rand means to sequentially introduce airk to said chamber and mono-fuel through said first fuel injection means, means to energize said ignition means for the ignition of the monofuel-air'mixture, means to shut off the flow of air to said chamber and simultaneously introduce monofuel through said second fuel inlet means.

References Cited in the le of this patent UNITED STATES PATENTS 617,753 Pontios Jan. 17, 1899 1,253,522 Patterson Ian. 15, 1918 2,056,198 Lasley Oct. 6, 1936 2,174,266 Jackson et al Sept. 26, 1939 2,433,943 Zwicky et a1. Jan. 6, 1948

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