US2550678A

US2550678A - Ram air operated fuel pump

Info

Publication number: US2550678A
Application number: US654484A
Authority: US
Inventors: Walter K Deacon
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-03-14
Filing date: 1946-03-14
Publication date: 1951-05-01
Anticipated expiration: 1968-05-01

Description

May 1, 1951 w. K. DEACON RAM AIR OPERATED FUEL PUMP Filed March 14, 1946 ammo/r1154 WALTER k. DEACON Patented May 1, 19 51 r --UNITED STATES PATENT OFFICE RAM AIR OPERATED FUEL PUMP Walter K. Deacon, United States Navy A plication March 14, 1946, Serial N0. 654,484

(01. GIL-35.6)

(Granted under the act of March 3, 1883; as

3 Claims.

amended April 30, 1928; 370' 0.- G. 757) This invention relates to ram jet engines and in particular to the fuel system therefor.

It has been recognized that the fuel requirements for combustion in a ram jet engine vary directly with the square root of the dynamic'head or ram pressure created by the forward velocity at any given altitude and also that the fuel flow through a nozzle also varies with the square root of the pressure drop thereacr'oss. Itis apparent, therefore, that the ram pressure becomes a convenient fuel pressure source to deliver fuel in accordance with engine requirements. When used'di'rectly however, it has the disadvantages that with an increase in altitude at a given velocity the fuel requirements decrease at a greater rate than the ram pressure available for a given Mach number thus tending toward enrichment, and at low speeds the ram pressure available is not sufiici'ent to insure optimum fuel atomization' or to compensate for sudden pressure changes in the combustion chamber.

This invention obviates the disadvantages ahcve mentioned and has, therefore, as one of its objects, the provision of a ram jet fuel system which delivers the optimum amount of fuel under the variable conditions of velocity and altitude.

Another object is the provision of a ram jet fuel" system which utilizes available an pressures for delivering fuel to a combustion chamber thereby eliminating cumbersome pumping d'eviceswhi'cn require for theiroperati'o'n a source of energy carried by the unit, thus decreasing the complexity and overall Weight thereof.

Another object is the provision of a rain jet fuellsyste'm which utilizes air at ram pressure to pump fuel at a pressure'in excessof combustion chamber fuel pressure requirements.

Another object is the provision of a rain. jet fuel systemwhich incorporates a fuel pump operable by ram pressure capable of delivering fuel at a pressurehigher than ram pressure.

Further objects, advantages, and salient features of the invention will become apparent from a consideration of' the description to follow, the accompanying drawing and the appended claims} The accompanying drawing isaside' elevational' view, partly insection, of an embodiment of the iriyention;

Referring tothe drawing, i resp'resents a fuel tank from' which it is desired to deliver fuel to ,conduit 2, the latter being connectable to any -suitable fuel nozzle system in a ram jet combustiorr chamber illustrated" diagrammatically at H or" other engi'ne; Reference character 3' repr'e" sents a fuel pump and 321' its driving motor and 2 55 a regulator for controlling fuel delivery to conduit 2.'

Fuel pump 3 and motor to comprise apair of motor cylinders i, 4a having reciprocating pis tons 5, 5a therein connected respectively by pis ton rods 6, 6a to pump pistons F, la which recipro cate in" cylinders 8, 8a. Diaphragms 9, Sa and H], Ito, provide fiuid seals" for the pistons in the motor and pump cylinders, respectively. Ahell crankhaving arms Ii, la interconnects these units by 13111 and slot connections so that they are constrained to operate in opposite directions;

The motor is operated by air flowing in conduit 12 the end of which is located in any convenient position. where it may receive air at rain pressure as shown at 12c. Operation of the respective motor pistons 55,50, is eoiitroll'ed by a valve {3 having inlet valves l4, Ma and exhaust'ifalves I5, l5a. These alves have sliding movement on valve stem it, the valves of each pair ,eiiig" urged toward each other by suitahle compression springs H; Ila, i8 and i811. The lower end of valve stem I6 is" connected to bell crank arii'i H by link 2! and a toggle actuator comprising a pair of relatively moi/awe arms 22, 2'3 and an overcenter spring 24". p

In the position or parts, as shown, aif' fiofri conduit [2 enters valve 13 and then passes through intake valve M, which is held open by the upper shoulder on; valve stem [6, and thence to cylinder 4, urging piston 5 downwardly, exhaust valve [5 being held closed by spring ['81 Since piston 5a is moving upwardly at this time the air in cylinder 4a must be exhausted which is effected through exhaust valve [5c heldoff its seat by the valve stem shoulder thereunden The air then flows" to surrounding air at static pressure through conduit I9. Whenpiston 5 approaches the end of its stroke, arm 22, operated by H, reaches a position in line with arm '23. This stretches spring 24 to its maximum extent and as arm 22 mo'ves beyond the inline position spring 24 snaps" arm 23 downwardly. At this point spring I! urges inlet valve I 4 to its seat and the valve stem shoulder abo've valve [4a opens'tl'ie' latter to ad'mit air to cylinder 4awhich is" now"at the top of its stroke. Exhaust valve 15 is also closed under urge of spring [to and exhaust valve 15 is opened by the valve stem collar thereabove. As piston 5a moves downwardly, arm 22' moves upwardly to its overcenter position at which point 23" snaps back to the position sh'o'wn'at which point the" cycle is com pletedlf .i a

' Asthe" motorpisfons reciprocate; pump pistons I, la. receive fuel from tank I through inlet check valves 25, a, respectively, and deliver it to conduit 21 through check valves, 26, 26a. In order that the delivery pressure may be higher than ram pressure, the motor piston areas are larger than the pump piston areas hence any desired increase in delivery pressure over ram pressure may be achieved by suitable selection of this area ratio.

To obviate surges in fuel delivery pressure which might occur at or near the ends of the piston strokes a surge motor and pump 28 is provided. This comprises a closed motor chamber 29 having a diaphragm 30 subjected to ram pressure through conduit 3i, and a pump chamber 32 having a diaphragm 33 connected to diaphragm 30 by rod 34. A conduit 35 provides liquid communication between chamber 32 and conduit 21. The area ratio of diaphragm 30' to diaphragm 33 is slightly less than the ratio of piston 5, or 5a to I, or la hence the surge pump is inoperative during constant fuel pressure delivery but when the fuel pressure tends to drop, diaphragm 30 temporarily operates pump diaphragm 33 to maintain delivery pressure substantially constant.

The fuel delivered by 2?, in the system so far described, may be conducted directly to a combustion chamber 5| if so desired, however, in many installations it will be more desirable to further control the metering characteristics of the pumping system. To this end, a flow controller 50 may be provided, this device comprising a chamber 36 having a diaphragm 31 forming one side thereof and operably connected to control valve 38. One side of diaphragm 31 is subjected to ram pressure through conduit 46 and a spring 39 aids ram pressure in urging diaphragm 37 to the left against delivery pressure. An adjustment to regulate the metering characteristics of valve 38 such as externally threaded valve stem and seat 3811 adjustably secured in tapped hole 33b in wall of chamber 36 and secured with locknut 380 may also be provided. The metered fuel, after entering chamber 42 is delivered to conduit 2 which may be connected to any fuel delivery system for a combustion chamber.

To also provide control under variable altitude a variable orifice 43 may be incorporated in conduit under control of a suitable barostat device 44 and an orifice 4| for controlling the pressure drop between chamber 36 and ambient static pressure. The evacuated barostat being responsive to air pressure changes moves valve 43 toward its closed position with increase of altitude thus reducing the pressure in chamber 36 which in turn permits delivery pressure to move valve 38 toward its closed position. This reduces the quantity of fuel delivered to the combustion chamber which is necessary since the mass flow of air through the combustion chamber decreases with increase in altitude, assumingvelocity to be constant.

From the foregoing description it becomes apparent that at low ram pressures which are normally insufficient to directly deliver fuel at optimum pressure, this invention delivers fuels at any desired pressure above ram pressure depending on the design of the areo ratio of the motor pistons to pump pistons. As velocity increases and hence the quantity of air flowin to a combustion chamber increases, requiring greater increase in fuel flow, the ram pressure alsoincreases which in turn will render the pump operable to deliver fuel at the higher pressures and hence higher quantities requisite for proper combustion. The final metering being under control of the pressure drop between ram and static pressures provides a means to regulate the optimum fuel flow for variation of velocity at any fixed altitude. To further control flow at variable altitude a barostat augments the previous controls.

The fuel system described, being automotic in operation under variable flight conditions is well adapted to aircraft or other installations where no human pilot or operator accompanies the craft, such for example as guided missiles. It is, of course, not so limited and may be used also in operator controlled vehicles of any type which have speed characteristics sufficient to establish the requisite ram pressures for its operation.

While a single embodiment has been described it is apparent that other modifications will occur to those skilled in the art and it will be understood that the illustrated construction is not presented by way of limitation but that the invention comprehends all constructions coming within the scope of the appended claims. The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. In a device of the class described the combination comprising; a conduit open forwardly to receive ram air, fluid motor means connected to said conduit for operation by said ram air, a fuel delivery line, a fuel pumping means driven by said fluid motor means, said fluid motor and pumping means having operative pistons of relative diameters such that the fuel is delivered to said delivery line at a pressure in excess of said ram pressure, a chamber having a movable wall, said chamber being connected to said conduit for directing ram pressure to said wall, and a fuel accumulator in communication with said delivery line having a second movable wall, said movable walls being connected for simultaneous movement in response to ram air and fuel delivery pressure tomaintain substantially constant fuel delivery to said delivery line between pump strokes.

2. In a fuel feed system for ram jet engines the combination of a conduit opened forwardly to receive air at ram pressure, a two-cylinder air motor with opposed pistons connected to said conduit to be operated by said ram pressure, a reciprocating piston in a cylinder for pumping fuel connected to each of said motor pistons, the cross sectional area of the pumping pistons being less than the cross sectional area of the motor pistons whereby the pump delivery pressure is in excess of ram pressure, fuel supply means and fuel delivery means connected to said pumping pistons, a fuel accumulator with a flexible wall responsive to ram air pressure in said conduit and connected to said fuel delivery means, and metering means in said delivery means for controlling the rate of fuel delivery to a combustion chamber, said metering means being responsive to variations in ram air pressure and ambient atmospheric pressure.

3. The device as set forth in claim 2 in which said fuel accumulator has a first flexible wall responsive to ram air pressure on a second flexible wall connected thereto and said second flexible wall and said first flexible wall having a ratio 5 of slightly less than the ratio of areas of said Number motor pistons to said pumping pistons. 1,888,749 WALTER K. DEACO-N. 2,233,307 I 2,274,224 REFERENCES CITED 5 2,402,363 The following references are of record in the file of this patent:

Number UNITED STATES PATENTS 625,104 Number Name Date 10 799,253

1,369,672 Koenig Feb. 22, 1921 6 Name Date Urquhart Nov. 22, 1932 Dodson Feb. 25, 1941 Vickers Feb. 24, 1942 Bradbury June 18, 1946 FOREIGN PATENTS Country Date France Apr. 19, 1927 France Mar. 27, 1936