US2867977A

US2867977A - Self-stabilized burner

Info

Publication number: US2867977A
Application number: US383742A
Authority: US
Inventors: Richard S Buck
Original assignee: United Aircraft Corp
Current assignee: Raytheon Technologies Corp
Priority date: 1953-10-02
Filing date: 1953-10-02
Publication date: 1959-01-13
Anticipated expiration: 1976-01-13

Description

Jan. 13, 1959 FUEL (h1/05E PAGES@ UEE R. s. BUCK SELF-STABILIZED BURNER Filed oc't. 2, 1955 `VENT LINE /N VE N TOR /CHARD S. BUG/f 'A r ron/ver United States Patent O SELF-STABILIZED BURNER Richard S. Buck, Glastonbury, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application October 2, 195.3, Serial No. 383,742

3 Claims. (Cl. 60--35.6)

This invention relates to ramjet power plants and the like and more particularly to flamespreaders for such power plants.

It is an object of this invention to provide a flamespreader for a ramjet burner which is movable to vary the area of blockage created by the flamespreader.

Another object of this invention is to provide a movable flamespreader for a ramjet burner including mechanism for automatically controlling the movement thereof in response to pressure'in the power plant or any other desirable parameter of operation.

These and Aother objects will become readily apparent from the following detail description of the drawing in which:

Fig. l is a cross-sectional view of a ramjet power plant having a amespreader device according to this invention.

Fig. 2 is an enlarged schematic illustration of a modified form of the flamespreader actuating mechanism; and

Fig. 3 is a partial illustrati-on of the general form which the flamespreader of Fig. 2 may take.

Combustion efficiency in a ramjet power plant may be affected by various factors. First of all it has been found by tests that if the burner inlet pressure of a ramjet power plant is reduced, a reduction in burner efficiency results. This trend is accelerated in lower burner inlet pressures. The greatest burner inlet pressure variation results from variations in altitude for a given Mach number of the vehicle in which the power plant is located. Smaller changes in burner inlet pressure may be effected by changes in fuel-air ratio which can result when pressure pulses move upstream of the burner where these pulses can effect fuel flow out of f-uel injection nozzles. This invention is inten-ded to solve the foregoing problems.

Referring to Fig. l, a ramjet power plant is generally indicated at :and includes an outer casing 12 which terminates in an aft exhaust nozzle 14. An inner streamline body 16 is located within the casing 12 so that a diffuser passage 18 is formed therebetween which is intended to increase the pressure `of the airflow therethrough prior to exhausting such air into the combustion cham-l ber 20.

A main fuel tank 24 has a pressurizing tank 26 connected thereto so that fuel may be fed into the diffuser passage 18 by means of injection nozzles 2S. The fuel is injected as far as possible upstream of the burner so that a thorough mixing of the fuel land air is achieved.

The inner body 16 terminates adjacent the burner section 2li and carries a flameholder 30 which is in the form of a flanged member which has its -outer periphery intended for cooperation with the restriction 32 in the casing 12. The flamespreader -orl flameholder 30 is mounted on a rod 33 which in turn is fixed to `a movable piston 34. A spring 36 urges the piston 34 and the flameholder 30 toward the left which tends to decrease the flow area defined between the flamespreader 30 and the restriction 32. This in effect increases the amount of flow blockage produced by the ilamespreader 30. A line 40 senses the pressure adjacent the inlet to the combustion chamber. This pressure is conducted to the left side of the piston 34 so that it urges the piston 34 and the flamespreader 30 t-oward the right to increase the ow passage or in other words decrease the amount of blockage produced by the amespreader.

As stated above, it has been found that a reduction in burner inlet pressure reduced the burner efficiency. It has been found that by increasing the amount of blockage produced by the flamespreader when a reduction of burner pressure occurs the burner efficiency can be maintained at a higher level than is possible with a xed blockage flarneholder. Thus it will be apparent that when the inlet pressure in the line 40 is reduced the piston 34 will be moved toward the left by the spring 36 to increase the amount of blockage produced Iby the flamespreader or flameholder 30. The spring side of the piston 34 is vented to the combustion chamber by means of a passage in the rod 33.

As also noted above, variations in fuel-air ratio can cause changes in burner inlet pressure while also pressure surges can be built up so that an unstable operation ensues. In other words, pressure waves can originate in the combustion chamber and tend to -move upstream. With a fixed blockage flameholder construction these pressure surges can move upstream where they will effect the flow from the -fuel nozzles 28 thus in turn varying the fuelair ratio so that the original pressure fluctuations may be amplified to further reduce efiiciency due to rough combustion. With this construction of ameholder, in the event a pressure wave tends to move upstream from the burner, this pressure will act on the flameholder tending to close off the air passage between the fiameholder and the restriction 32, or in other words, increase the blockage so as to reduce, momentarily 4at least, the pressure in the combustion chamber. In the event that the pressure waves find their way upstream where they might produce a feedback on the fuel system the passage 40 will sense the pressurewave prior to its moving upstream of the diffuser to decrease the blockage produced by the flamespreader so as to relieve the flow upstream thereof to reduce any feedback component from the pressure pulses.

A tank 46 may be provided within the inner body 16 for carrying combustible ingredients which can be piped via the line 48 to a point 50 on the downstream side of the flameholder 30 to provide a continuous pilot flame on the problem area on the downstream side of the flameholder.

Fig. 2 illustrates a modified form of flameholder actuating mechanism. Here for example a ameholder element is operatively connected to a bellcrank 62 which in turn is intended to be actuated by a piston 64. The piston 64 is urged toward the left by a spring 66 an-d toward the right by pressure admitted to the chamber 68. Fuel under pressure from the line is controlled by a pilot valve 72 which will maintain a predetermined pressure in the chamber 68 dependent upon the position of the pilot valve. The pilot valve is lactuated by an evacuated bellows 76 which is exposed on its outer surface to the static pressure in the burner which pressure is conducted to the outer surface of the bellows Via a line 78 and into chamber 80. The mechanism just described is intended to operate similar to that shown in Fig. l with the exception that fuel under pressure is utilized as the motive force for controlling the piston 64. The f'lameholder member 60 is shown schematically and is one of a plurality of overlapping flap members such as y84 illustrated in Fig. 3. The actual operating linkages for a plurality of flaps may take :any form as for example well known devices for operating aircraft engine cowl flaps. These flap members may be actuated similar to the Fig. l and Fig. 2 devices and opened and closed similar to an iris action.

Although several embodiments of this invention have 3 t been illustrated and described herein it will be apparent that various changes and modifications may be made in the construction and arrangement of the various parts without departing from-the scope of this novel concept.

What it is desired to obtain by Letters Patent is:

f l. In a rarnjet power plant having a diffuser, a combustion chamber downstream of said diluser Iand receiving gases from said diiuser, an exhaust nozzle for discharging gases from said combustion chamber, means for injecting fuel into said combustion chamber, means for igniting the fuel-air mixture located downstream cf said inject ing means, akflamespreader adjacent said igniting means comprising a member blocking la portion of the passage formed lby said combustion chamber, and means for automatically adjusting the position of said member in any one of a number of positions in a range including mechanism for sensing the pressure of the gases approaching said combustion chamber, the amount of blockage of said passage being proportional to the pressure sensed by said sensing mechanism.

2. In `a ramjet power plant having a dituser receiving air from the airstream, a combustion chamber forming a passagedownstream of said diffuser and receiving gases from said diffuser, an exhaust nozzle for discharging gases from said combustion chamber, means for injecting fuel into the power plant, means for igniting the fuel-air mixture located downstream of said injecting means, a amespreader adjacent said igniting means comprising at least one member blocking a portion of the passage formed by said combustion chamber and creating a protected area on the downstream side thereof, means for automatically positioning said member to vary the amount of blockage of said passage, a source of fluid under pressure, said positioning means including a fluid operated servo device connected to said member, means for controlling the amount of `fluid flowing from said source to said servo to position said member, and means for sensing the pressure of the gases approaching said combustion chamber for positioning said controlling means in a plurality of positions in proportion to the value of said pressure.

3. In a ramjet power plant having `an outer casing, a streamlined body within said casing forming an annular diffuser passage between said body and said casing, a combustion 'chamber receiving gases from said diiuser and having an exhaust nozzle therefor, said inner body terminating adjacent the upstream end of said combustion chamber, means for injecting fuel into said passage upstream of said combustion chamber, a flamespreader adjacent the downstream end of said inner body comprising :it least one imperforate flangelike member extending transversely of the axis of liuid ilow through the power plant and blocking a portion of said passage, means for moving said member relative to said inner body for varying the amount of blockage of said pasage by proportional increments, means for biasing said member in a decrease blockage direction, and means responsive to the pressure of the gases approaching Isaid combustion chamber for urging said member in a blockage increase direction proportional to the pressure of said gases.

References Cited in the le of this patent UNITED STATES PATENTS 2,655,787 Brown Oct. 20, 1953 2,696,709 Oulianorf Dec. 14, 1954 FOREIGN PATENTS 648,497 Great Britain Jan. 3, 1954