GB749767A - Improvements in method of and means for the control of the air inlet opening of a jet propulsion unit or a gas turbine engine - Google Patents

Abstract

749,767. Jet propulsion plant. SOC. NATIONALE D'ETUDE ET DE CONSTRUCTION DE MOTEURS D'AVIATION. May 28, 1953 [June 5, 1952], No. 14915/53. Class 110(3) The flow of atmospheric air into the air intake casing of a jet propulsion unit is controlled by slots or orifices which are able to discharge, when desired, from the physical leading edge zone of the casing close to the stagnation line so as to form a generally continuous fluid wall about and forwardly of the physical leading edge zone. The intake 1 of a jet propulsion 'engine, Figs. 1 and 4, has a casing 2 which comprises an external surface 4 and an internal wall 3. When in normal use at low flight speeds the stream lines are as shown in Fig. 1 with a stagnation line at 5. For high flight speeds, compressed air from the compressor is supplied through pipes 7 under the control of valves 8 to slots 6. This causes a fluid wall to be substituted for the solid wall as indicated by the dotted line 10, Fig. 4. This increases the radius of curvature of the leading edge, reduces the effective area of the intake and alters the internal shape of the internal wall 3. By controlling the valves 8, the intake may be adapted to varying speeds of flight. In a modification, the invention is applied to an intake formed as a blister on the side or underneath of the fuselage. In another modification, Fig. 5 the invention is applied to an intake having a rectangular intake opening. The leading edge of the intake has a cylinder 40 which may be rotated by a crank 44 attached to a hydraulic motor. The cylinder has a central bore 42 which communicates with a slot 41 and can be supplied with compressed air from a pipe 43 controlled by a valve 15. During flight at moderate speeds, the cylinder 40 is rotated until the slot 41 is covered by the channel wall 3 and the valve 15 closed. At take off, the slot 41 is directed towards the outer wall 4 of the casing and the valve 15 opened, thus replacing the wall 4 by a fluid wall. At high speed, the slot 41 is directly forwardly inwardly and the valve 15 opened, thus displacing the stagnation line towards the interior of the casing. The cylinder 41 may be provided with two or more slots. In another embodiment, Fig. 10, a supersonic intake is adapted for use at subsonic speeds. As shown, the casing is in the condition suitable for supersonic speeds and has a sharp leading edge 52. A thin wall 53 adjacent the internal wall of the casing is movable together with a cone 58 along the longitudinal axis of the casing. The wall 53 is attached to a piston 55 and the cone 58 to a piston 60. The pistons 55, 60 are actuated together by pressure oil. When it is required to operate at subsonic speeds, pressure oil is supplied at 57b to move the wall 53 a nd cone 58 to the positions shown dotted . At the same time, the valve 64 is opened and compressed air supplied to the slot formed between the sharp edge 52 and thin wall 53. In a modification of this arrangement the thin wall 53 is dispensed with and compressed air is supplied to a slot formed between the leading edges of the walls 3, 4. This slot may be connected to a source of compressed air during subsonic flight and to a point on the exterior of the casing during supersonic flight. The intake is stated to be suitable for jet propulsion engines having a compressor driven by a piston motor or gas turbine or to ram jets.