GB887132A - Variable flap plug type jet propulsion nozzle - Google Patents

Abstract

887,132. Jet propulsion nozzles. UNITED AIRCRAFT CORPORATION. April 29, 1960 [May 5, 1959], No. 15094/60. Class 110 (3). A jet propulsion nozzle comprises a fixed inner body diverging at its forward end and converging at its after end concentrically surrounded by a divergent-convergent outer duct terminating at a point aft of the region of maximum diameter of the inner body but short of the after end thereof, the outer duct being convergent at its after end to a greater degree than the convergent part of the inner body and a plurality of flaps pivotally attached to the after end of the outer duct and adapted to be pivoted between an inner position in which they form with the inner body a convergent duct and an outer position in which they form a convergent-divergent duct. The jet propulsion nozzle 20 comprises an inner body 34, an outer member 36, a plurality of inner flaps 38 and a plurality of outer flaps 40, together with actuating means 42. The inner body has an after end 46, which terminates in a point (not shown), made of sheet metal bolted along a flange 56 to the forward end 44. The surface 48 of the inner body is divergent-convergent to the axis 24. The outer member 36 comprises an inner wall 74 and a substantially cylindrical outer wall 76. The inner wall 74 comprises a divergent fixed portion 82 and a movable portion 84 which is convergent to the axis 24. The movable portion 84 carries, at its downstream end, a plurality of flaps 38. The outer wall 76 carries, at its downstream end a plurality of flaps 40. Actuating means 42 can move the wall portion 84 axially forwardly from the position shown, in which the nozzle acts as a convergent one, to a position in which the nozzle acts a convergentdivergent nozzle, Fig. 3 (not shown). The member 84 is connected through a link 135, roller 140 and guide 132 and link 138 to the flaps 40. The movement of the flaps 38 is controlled by the roller 134 and guide 133. In the position shown, the flaps 40 are positioned so that the air flow over the outer wall 76 tends to hold the gas flow on to the inner body 34 under subsonic conditions. Under supersonic conditions, the flaps 40 are extended outwardly to form a substantially cylindrical extension of the wall 76. This arrangement is stated to reduce the base drag. An arrangement in which the flaps 38, 40 are pivoted together at their downstream ends is also described.