Patent GB-827870-A (GB)
Title: Pressurised gas supply from gas turbine engines
Inventor: SIMONIS EDWARD ALEC
IPC: B64C23/00
Filed: 1956-09-03
Abstract: 827,870. Gas turbine plant. DE HAVILLAND ENGINE CO. Ltd. Aug. 28, 1957 [Sept. 3, 1956], No. 26945/56. Class 110 (3). [Also in Groups XXIX and XXXIII] An apparatus for bleeding a pressurized gas supply from the main working gas streams of two or more aircraft gas turbine engines and feeding this pressurized gas supply to one or more points for heating, de-icing, boundary layer control or other purposes, comprises a duct system including a bleed passage communicating with the working fluid passage of each gas turbine engine, and one or more Venturi type restrictions through which the bleed gas flows from that engine to a common duct, a closure valve being provided in each bleed passage being controlled by a pressureresponsive device sensitive to the pressure difference developed across at least one of the Venturi restrictions associated with each engine and arranged to close the closure valve if the pressure difference is reversed in direction by more than a predetermined value. The embodiment shows a system in which hot air is tapped from the compressors 2 of two gas turbine engines 3 disposed in an aircraft and is utilized for boundary layer control and for de-icing of the wing 9. The air from each compressor 2 is led through a duct 1 which is branched into two passages each having a Venturi restriction 11 and controlled by a valve 12, the branch passages from both compressors leading to a common manifold 4. Two passages 5, 6 lead from each end of the manifold 4 being selectively controlled by means of a change-over flap valve 7 under the control of a solenoid 8, the passages 5, 6 leading to de-icing and boundary layer control equipment respectively. The valves 12 are controlled by means of a solenoidcontrolled ram 13 which comprises a spool-type piston 17, the end portions of which are mounted in different diameter cylinders 18, 21, air under pressure tapped from the duct 15 interconnecting the two ducts 1 being led through the duct 19 to the space between the two end portions of the piston 17. When the control port 22 is closed by means of the valve spindle 23, the piston 17 is urged to the left, as shown in Fig. 2, thereby acting to close the valves 12 in the branch passages. When the switch 34 (which is conveniently connected to the pilot's flap selecting control 35) is closed, the solenoid 24 is energized, thus causing the valve spindle 23 to open the control port 22, whereupon the piston 17 moves to the right (as shown in Fig. 2) thus causing the valves 12 in the branch passages to open. A pressure-responsive switch 29 is connected by ducts 31 to the duct 1 on each side of the Venturi restriction 11, and comprises a diaphragm 30 which causes the electrical contact 32 to open should the compressor delivery pressure fall by a predetermined amount below the pressure in the manifold 4. For de-icing purposes a de-icing selector switch 36 is arranged in series with the change-over valve solenoids 8, the switch 36 being arranged so that it is not possible to select de-icing air when the flap control 35 is in the operative position. A de-icing relay 37 is connected in the de-icing circuit so that when the switch 36 is closed, the relay 37 is energized so as to close the contacts 38 so that current can flow to the pressure-responsive switch 29 and to the solenoid 24 of the ram unit 13. The solenoid 14 may be energized by means of an emergency flap control switch 39 in the control circuit 25. An emergency mechanically-operated control is also provided, part of the mechanism being shown at 28 in Fig. 2.