Patent GB-819032-A (GB)
Title: Improvements in or relating to jet propulsion engines
Inventor: MATHIESON GEORGE CAMERON REID
IPC: F01D7/00
Filed: 1955-09-30
Abstract: 819,032. Gas-turbine jet-propulsion plant; axial-flow compressors. POWER JETS (RESEARCH & DEVELOPMENT) Ltd. Sept. 28, 1956 [Sept. 30, 1955; Oct. 5, 1955 (2); March 23, 1956 (2)], Nos. 27907/55, 28413/55, 28438/55, 9216/56 and 9230/56. Classes 110 (1) and 110 (3). A jet-propulsion engine comprises an air inlet, a combustion chamber, a duct interconnecting the inlet and the chamber, and compressor blading in the duct for increasing the pressure of air passing from the inlet to the chamber, means being provided for withdrawing at least some of the compressor blading partly or wholly from the duct. In the jet-propulsion engine shown in Fig. 3, an axial-flow compressor (not shown) is driven by a turbine 55 through a reduction gear-box 85 and a freewheel 86. The turbine 55 is driven by rocket gases discharged from rocket combustion chambers 53, the exhaust being led through pipes 87 to the main duct. To change over to ram-jet operation, the fuel supply to combustion chambers 53 is shut off and the whole fuel supply is led to the nozzles 93 of a ram-jet combustion chamber 52. In addition, a by-pass passage 58 surrounding the main duct is .put into communication with the main duct by uncovering an opening 61 downstream of the compressor by means of a flap 64 and uncovering an opening upstream of the compressor by a further flap, so that the compressor is by-passed. To reduce the pressure losses in the compressor still further, withdrawable compressor blading is retracted and any adjustable-incidence compressor blading is feathered. If some of the blading is neither withdrawable or of adjustable incidence, the compressor rotor windmills in the reduced air stream and may drive accessories. If the freewheel 86 is omitted, windage losses in the turbine may be reduced by closing valves 90 in the discharge pipes 87 and opening valves 91 in branch pipes 88, thereby connecting the turbine interior through a venturi 89 to a region of low pressure in flight and so partially exhausting the turbine. Alternatively, a clutch may be provided for uncoupling the turbine from the compressor. The air intake area may be adjustable during ram-jet operation, as by means of an axially slidable cone. Withdrawable compressor blading is shown in Fig. 4. Stator blades 100 protrude through slits in the outer wall 105 of the compressor duct with shoulders 108 abutting against the wall. Root portions 103 are pivotally mounted in a cylinder 104 coaxial with the wall 105. By rotating the cylinder 104, the blades 100 are withdrawn through the wall 105 as shown in Fig. 6. Similarly, rotor blades 101 can be withdrawn into the rotor drum 115 by relative rotation of an inner drum 114. An actuator 112 rotates the cylinder 104 and inner drum 114 simultaneously through suitable mechanism to withdraw both sets of blades. In alternative constructions, each blade is withdrawn radially by means of a screw and nut or a piston and cylinder. One blade row only, say the outlet stator blade row, may be withdrawable. If this blade row is located downstream of the compressor rotor, the blades may be withdrawn through the inner wall of the duct instead of the outer wall. Adjustable incidence compresses rotor blading is shown in Fig. 7. A number of circumferentially-spaced racks 24 mesh with pinions formed on the shanks of the rotor blades 13 and are attached to a ring 26 slidably supported on a rotor projection 27. Axial movement of an actuating link 30 is transmitted to the ring 26 through a roller 29 engaging a flange 28. The blades 13 are supported on tapered roller bearings 20. The first Provisional Specification describes an engine, Fig. 1 (Prov. 27907/55), which supplies air to the main duct and also to a bypass duct. The main duct can be closed at the inlet to a high-pressure compressor 11 by shutters 10, and can be closed at its exit end by moving a bullet 12 rearwards by means of a jack 13 and moving a cone 14 forwards by means of a mechanism 16. The engine is changed over from by-pass operation to ramjet operation in accordance with aircraft speed or air intake temperature by means of a control unit 29 operating through actuators 30 to 34 which control the blade feathering, the by-pass fuel supply, the main engine fuel supply, and the closing of the main duct. The changed position of the bullet 12 alters the outlet area of the by-pass duct to the correct value for ram-jet operation. The rotor blades 3 are feathered through the mechanism described above, and the stator blades 2 are feathered by rotatable rings 9. The second Provisional Specification describes an engine, Fig. 2 (Prov. 28413/55), in which the compressor is driven by a turbine 18 energized by rocket gases from a combustion chamber 22, the turbine exhaust gases joining the compressed air flow. A further combustion system is located in the jet pipe. To change over to ram-jet operation, shaft 8 is turned to feather the compressor blades and to slide a segmental circumferential ring 19 rearwardly to close the exhaust annulus of the turbine. At the same time, the fuel supply to chamber 22 is cut off and the fuel supply to the jet-pipe combustion system may be increased. The ring 19 is connected to the feathering ring of the last row of stator blading by rack-and-pinion mechanism. According to the third Provisional Specification, if the mixture of air and rocket combustion products is fuel-rich or oxygen-rich, an oxidant or additional fuel, as the case may be, may be injected to form a stoichiometric mixture. The compressor may be driven by the reaction of rocket or other gases discharged by nozzles carried by the compressor rotor. The fourth Provisional Specification describes a ducted-fan engine comprising an axialflow compressor, combustion chambers, an axial-flow turbine located in a main duct, and a fan located in a duct surrounding the main duct, the first rotor of the turbine driving the compressor and the second rotor driving the fan. Additional power can be provided by burning fuel in a combustion chamber in the fan duct downstream of the fan. To change over to ram-jet operation, in which the last mentioned combustion chamber is operated as a ram-jet combustion chamber, the main part of the engine is shut down, the fan blading is feathered, and part of the ram air is diverted into a duct by-passing the fan. The inlet to this by-pass duct comprises segments which at least partially close the fan duct when the inlet is open. The fan rotor blading and the supporting turbine blading may be as described in Specifications 587,528 or 587,571. The air intake to the main duct may be throttled or closed by the means described in Specification 799,504. A by-pass engine comprises high and low-pressure axial-flow compressors driven by separate stages of an axial-flow turbine; the compressors, main combustion chambers and turbine being located in the main duct. A by-pass duct surrounding the main duct and containing a ram-jet combustion chamber has two inlets communicating with the main duct respectively upstream and downstream of the low-pressure compressor. During by-pass operation, the second inlet is closed. To change to ram-jet operation, the second inlet is opened, and the gas-turbine part of the engine may be continued in operation for increased output or may be stopped, with the low-pressure compressor declutched from the turbine or with its blading feathered or withdrawn. The main duct may be completely closed by the means for closing the by-pass duct, so that the entire air supply is diverted to the latter. The closure means may comprise scoops slidable towards the axis of the main duct from positions in which they form part of the outer wall of the duct, or a rotatable or longitudinally slidable ring. Alternatively or additionally, there may be a separate intake to the ram-jet combustion chamber from atmosphere. Closable apertures may be provided for admitting air from the by-pass duct to the main combustion chambers. A reheat burner located downstream of the point at which the by-pass duct discharges into the main duct may form a ram-jet burner additional or alternative to that in the bv-. pass duct. Specifications 749,009 and 805,418 also are referred to.