Improvements in converging-diverging jet propulsion nozzle

894,450. Jet propulsion nozzles. GENERAL ELECTRIC CO. June 29, 1960, No. 22830/60. Class 110 (3). A convergent-divergent jet propulsion nozzle having a divergent wall defining the divergent section comprises a wall surrounding the divergent wall to form a plenum chamber and circumferentially spaced longitudinally-disposed openings in the divergent wall in communication with the plenum chamber to stabilize the shock-wave. A convergent-divergent nozzle, Fig. 1, comprises a converging section 10, a throat 11 and diverging section 12. A wall 14 defines a plenum chamber with the diverging section 12. During operation of the nozzle at pressure ratios less than the designed value a shock-wave 15 is formed. To stabilize the position of the shock-wave longitudinal slots 16 are provided to connect the areas of varying pressure before and after the shock-wave. Movement of the shock-wave causes variations of the flow through the slot to restore the pressure balance across the shock-wave and so compensate for the factors causing the movement. In practice, cooling air always flows radially inwards through slot 16 and movement of the shock-wave will cause a change in the relative flow through the slots in the vicinity of the shock-wave. In a modification, Fig. 6, the nozzle is of the variable area type formed by fingers 17 pivoted to the end of the tailpipe. Seals 23, 24 span the spaces between the inner and outer surfaces 21, 22 of the fingers. Stabilizing slots 25 are formed by the omission of a portion of selected seals. The slots 25 are exposed only under maximum speed conditions and are covered by the adjacent fingers under conditions of subsonic flight. The slots 16, 25 may be replaced by perforations and the slots 16 may be tapered from one end to the other.