GB921727A - Combined thrust reversing and noise suppressing device for turbo-jet aircraft engines - Google Patents

Abstract

921,727. Jet propulsion plant. CANADAIR Ltd. July 7, 1959, No. 23288/59. Addition to 911,202. Class 110 (3). [Also in Group XXXIII] A combined thrust reversing and noise suppression device for turbo-jet engines of aircraft as claimed in Claim 1 of the parent Specification, has means to increase the effective ratio of the peripheral length of the corrugated stream of exhaust gases for a given cross-sectional area of the nozzle orifice to effect a change of noise frequency of the exhaust gases. The tail pipe 5, which has an outer shell 7 and inner shells 8 and 9, is secured to the engine casing (not shown) by a flange 6. The outer and inner shells define forward and rearward annular chambers 10 and 11 separated by a reverse thrust nozzle compartment 12 having outlet ducts 16 each bounded by walls 17 and 18. The wall 18 supports a ring member 22 which carries a plurality of brackets 35 to which are pivotally mounted arms 33, each forming part of a V- section sector-shaped element 23 provided, on its inner side with a tapered finger 32. The fingers 32 give a pronounced V-toothed shaped configuration to the nozzle aperture in its forward thrust setting, thereby increasing the peripheral length of the nozzle for a given cross-sectional area of nozzle opening to silence the jet. The elements 23 are swung from the positions shown in Fig. 1, in which they do not obstruct the rearward flow of the jet, to the positions of Fig. 2 in which they block the jet nozzle, by mechanism comprising links 36 each attached to a ring 37 and secured by a common pivot 73 to an arm 33 and one end of a jack 72, the other end of which is connected by a common pivot 78 to one end of a rod 71 and a link 75 pivotally attached to a fixed bracket 74. The other end of rod 71 is connected to a braking flap 68 which is pivoted at 69 to open and close the respective duct 16. Rod 71 rests within an external recess 76 in flap 68 when closed and a separate flap 77, hinged to bracket 74 and pivot 78 encloses the remainder of the mechanism. The ring 37 is connected to sleeves 40, each slidably mounted on a rod 41 and pivotally connected to the piston-rod of a jack 38 so that operation of the jacks will simultaneously operate elements 23 to close the jet pipe and open ducts 16 to permit forward deflection of the jet. With elements 23 in their inoperative positions the jacks 72 may be operated independently to open a selected flap 68 to provide yawing control of the aircraft or they may be operated in unison to provide a braking effect. The nozzle is formed with openings 46 which entrain ambient air to be directed into the elements 23 which are hollow and formed in their tapered fingers with discharge outlets whereby the previously mentioned corrugation of the jet by the fingers is supplemented by air jets, which serve also to cool the jet. Additionally, each element 23 may be supplied with compressed air from a common source. This may be controlled selectively to act upon the jet stream to deflect it laterally to provide a control effect.