Patent GB-924789-A (GB)
Title: Improvements in or relating to air intakes for supersonic aircraft
Inventor: GOODALL DONALD GEORGE
IPC: F02C7/057
Filed: 1960-01-26
Abstract: 924,789. Supersonic intakes for aircraft power plant. ROLLS-ROYCE Ltd. Jan. 13, 1961 [Jan. 26, 1960], No. 2873/60. Class 110 (3). [Also in Group XXIX] A supersonic intake for an aircraft power plant having both external and internal shock compression and probe means to sense the position of the final shock waves has control means to alter the position of the final shock wave which moves it more rapidly in a downstream than in an upstream direction. An annular air intake, Fig. 1, comprises an outer annular wall 11 which terminates at its upstream end in a leading edge lip 11a and a centre body 12 comprising an apex 12a, an intermediate portion 12b and a downstream portion 12c to form a convergent-divergent passage. The parts 12a, 12b, 12c may be displaceable axially so that the intake may be varied for different flight conditions. At a speed above about Mach 1.4 shock compression occurs not only externally of the intake at 15, 16 but also internally of the intake at 17, 18. The flow downstream of the shock wave 18 is subsonic. To stabilize the position of the shock wave 18 a bleed vent 20 controlled by a valve 21 is provided. The valve 21 is controlled by a ram 22 under the control of mechanism 23 which is in turn controlled by sensing means 24. The sensing means 24 comprises a flexible diaphragm 26 separating two chambers 27, 28. The chamber 27 is connected by a pipe 29 to a point between two restrictors 31, 32 in a pipe 30 the ends of which are connected to two pressure sensing probes 33, 34. The probes 33, 34 have orifices facing downstream at axially spaced positions corresponding to the limits of permissible travel of the final shock wave 18 in the duct 14. The chamber 28 is at a reference pressure determined by restrictors 36, 38 in a conduit 35 joining a probe 37 facing forwardly in the duct 14 and an atmospheric pressure sensor 39. The diaphragm 26 operates a lever 41a carrying a valve 41 which controls the flow into and pressure in the chamber 43. The chamber 43 is connected to a low pressure conduit 46 through a restrictor 44. The chamber 43 is connected by conduit 48 to the control mechanism 23. The pressure in the conduit 48 also acts on a piston 51 attached to the valve 41 to give a negative feed-back to prevent hunting. If the pressure in the duct 14 increases the shock wave 18 will move upstream of the probe 33 and the means 24 will operate to reduce the pressure in the chamber 43 and thus in chamber 53. The piston valve 52 then moves to the left and allows pressure fluid from the duct 61 to enter the chamber 22a and the low pressure duct 46 to be connected to the space 22b. The piston 22c moves rapidly to the left and opens the valve 21. If the conditions in the duct 14 are such that the shock wave moves downstream of the probe 34, the diaphragm 26 will operate the valve 41 to increase the pressure in the chambers 43, 53, to cause the piston-valve 52 to move to the right. Pressure fluid from duct 61 will enter chamber 22a and the chamber 22b connected through chamber 55 and restrictor 59 to the low pressure duct 46. The restrictor 59 allows the piston 22c to move slowly to close the valve 21. There may be more than one valve 21 and they may be interconnected. A modified form of control mechanism 24 comprising a pair of pressure responsive capsules is also described. The intake may be of the single or double slot type. Alternatively the control system may vary the configuration of the centre body to control the mass flow through the intake.