Patent GB-931601-A (GB)
Title: Fuel control system for ramjet engine
Inventor: WORLEY WILLIAM E
IPC: F02K7/10
Filed: 1960-05-27
Abstract: 931,601. Ram jet-engines. BENDIX CORPORATION. May 27, 1960, No. 18929/60. Class 110 (3). [Also in Group XXIX] In a fuel supply system for a ram jet-engine, valve means are provided in the conduit through which fuel is delivered from a source to the combustion chamber, the valve means being controlled as a function of Mach number by control means responsive to an air pressure derived from ram air pressure and to atmospheric air pressure, further means responsive to atmospheric air pressure being provided for modifying the derived air pressure as a function of flight altitude. The ram jet unit shown in Fig. 1, comprises an air intake 12 and diffuser section 14, a main combustion zone 20 to which fuel is supplied by main burners 21, a pilot combustion zone 16 to which fuel is supplied by pilot burners 18, and a propulsion nozzle 30. Fuel is contained in an annular tank 42 which is pressurized by means of an annular bladder 54 to which nitrogen under pressure is supplied from a tank 56 through a pressure regulator 60 and duct 58. Fuel passes from tank 42 to an air turbine driven fuel pump 40 by means of a conduit 44 controlled by a shut-off valve 52, fuel passing from the pump to a main fuel meter 34 and thence to the main fuel nozzles, also through a pilot fuel meter 38 to the pilot fuel nozzles. The main fuel meter 34 is shown in Fig. 2 and comprises an inlet 64 from the pump 40 and outlet 66 to the main fuel burners 21, the fuel flow being controlled as a function of Mach number by a slide valve 74 and as a function of altitude by a slide valve 210. The valve 74 controls the variable area orifice 70, the pressure of the fuel upstream of the orifice being P 1  and downstream of the orifice being P 2 . The rod 82 of the valve is connected to a plate member 96 which with the fixed casing 62 affords a chamber 110 which is connected to fuel pressure P 3  downstream of the second variable area orifice 72. A pin 106 fixed to the valve rod 82 bears against a piston 102, the space 122 to the right of which is subjected to a pressure Pr<SP>1</SP> and to the left of which is subjected to atmospheric pressure Pa, the pressure Pr<SP>1</SP> being proportional to ram pressure Pr. The chamber 122 is vented to atmosphere through duct 138 and restriction 140. The chamber 122 is also vented to atmosphere through a second circuit in parallel flow with the duct 138 and comprising ducts 142, 150 and 124 which is controlled by a spool valve 152. The spool valve is positioned as a function of Mach number by a bellows system comprising an inner bellows 164 and an outer bellows 166, the space between the bellows being evacuated, the space outside the outer bellows being subjected to the atmospheric pressure and the space within the inner bellows subjected to a pressure Pr<SP>11</SP> which is derived from ram pressure Pr. The pressure in the space 168 outside the outer bellows 166 is controlled by an acceleration responsive " g " weight 187 which during launching moves to the right so as to open the passage 185 to atmospheric pressure. The space 168 is normally connected to atmospheric pressure through line 176 and plenum chamber 177. The pressure Pr1<SP>1</SP> within the inner capsule 164 is controlled as a function of altitude by an evacuated bellows device 190, the bellows controlling a variable area orifice 186 by which the pressure Pr<SP>11</SP> within the inner capsule 164 is communicated via duets 182 and 202 to atmosphere. The second slide valve 210 which controls the area of the second variable area orifice 72 as a function of altitude is acted on at its right-hand side 230 by a servo-pressure Ps. The position of the servo valve 242 is controlled by means of an evacuated bellows 256 which is subjected at its outside to atmospheric pressure Pa, the servo valve controlling flow of fuel at inlet pressure P 1  through ducts 232, 250, the pressure of the fuel Ps being communicated through passage 248 to the space 230. The sleeve valve 238 within which the servo-valve 242 slides is connected by means of a rod 252 with the slide valve 210. The pilot fuel meter 38 is shown in Fig. 3 and comprises an inlet 302 from the fuel pump and an outlet 304 to the pilot fuel injectors, the fuel meter acting to meter the fuel in accordance with ram air pressure Pr. The fuel flow is controlled by a first slide valve 312 controlling the inlet ports 308, and by a second slide valve 322 controlling the ports 318. The slide valve 322 is acted on to the left by a servo-pressure Ps communicated to the space 330, fuel at pressure P 2 <SP>1</SP> in the chamber 314 passing through duct 350 to the servo-valve device 344 and thence through the duct 332 at pressure Ps to the space 330. The servo-valve device comprises a servo-valve 344, the position of which is controlled by an evacuated capsule 358 in response to ram pressure Pr communicated to chamber 360, and a sleeve valve 338 which is connected to the slide valve 322 by a rod 374, the sleeve valve acting as a followup member. An acceleration responsive " g " weight 390 is disposed adjacent the slide valve 312 so that it normally closes the orifice 387. When the weight is moved due to acceleration during launching, the orifice is opened and communication is established between chambers 314 and 384. The pressure in the chamber 384 P 3 <SP>1</SP> is communicated from the outlet chamber through duct 386, the slide valve 312 controlling the area of the ports 308 in accordance with a predetermined constant pressure drop P 2 1-P 3 <SP>1</SP> across the sleeve valve 322. The nitrogen flow regulator 60 is shown in Fig. 4 and comprises a bottle of nitrogen of high pressure N 2 , the nitrogen flowing through duct 414, past the shut-off valve 412, shown in the open position, to the duct 418. A first portion of nitrogen then flows through duct 428 to the outlet 404 at pressure N 2  to act on the fuel shut-off valve 52 shown in Fig. 1. A second portion of nitrogen flows through duct 430 to a first stage pressure regulator 432 and then to a second stage pressure regulator 434 at pressure N 3 , the nitrogen at pressure N 4  then passing to the outlet 408 to inflate the bladder 54, Fig. 1. The pressure regulators each comprise a cylindrical slide valve 436 having ports 440 which co-operate with an annulus 442 to vary the effective flow area. Nitrogen gas leaks past the damping piston 452 to cause the slide valve to move against the force of spring 444. The second stage regulator chamber 446 is vented to atmospheric pressure Pa via a port 450, and the first stage regulator chamber 446 is connected to conduit 430 downstream from the second stage regulator by means of a passage 451. A pressurerelief valve 462 is disposed downstream of the second stage pressure regulator. Nitrogen is supplied to the bottle 56 through a filling connection 476, the pressure of the gas causing the shut-off valve 412 to move to the left, thereby closing off the duct 418. The gas flows through duct 484 in the shut-off valve to duct 414 and bottle 56. When the missile is launched, the acceleration responsive weight 496 is moved to the right so opening the ducts 490 and 474 to atmosphere and the shut-off valve 412 is moved to the open position shown, so allowing nitrogen to flow to the ducts 418, 428 and 430 as described.