GB811455A - Improvements in or relating to jet nozzles for propulsion purposes - Google Patents

Abstract

811,455. Jet propelled aircraft; boundary layer control. ROLLS-ROYCE Ltd. Feb. 19, 1957. [Feb. 27, 1956], No. 6087/56. Class 4. [Also in Group XXVI] A jet propulsion nozzle comprises, for noise reducing purposes, a propulsive gas path having peripherally a series of angularly spaced flow channels extending axially of the nozzle from adjacent its inlet at least to its throat (see Group XXVI) and comprises deflector means which when operative receive the gas from the nozzle and direct it to have a forward component of thrust, and means for rendering the deflector means operative or inoperative. In Fig. 1, the convergent portion 14 of the nozzle contains six pyramidal structures 20 each comprising two triangular plates meeting at an acute angle on a line 21 extending from the wall 18 at the inlet to a sleeve 22 at the throat 24. The sector-shaped spaces between adjacent structures 20 at the throat form the flow channels, which are continued in the divergent section 15 and the deflector section 16, where they are open to the atmosphere at their radially outer parts, and contain vanes 34. A tube 40 rotatably mounted in sleeve 22 supports six structures each comprising a sector shaped front wall 44, radial walls 41, and a fairing 42. Normally, the walls 44 are aligned with the structures 20, so that the exhaust gases pass rearwardly through the flow channels and through the spaces between adjacent walls 44 as shown by arrows 13. To reverse the thrust, tube 40 is rotated through thirty degrees, so that the walls 44 blank off the flow channels, and the gases pass outwardly through vanes 34 and are directed forwardly as shown by arrows 46. Gas issuing from a bypass duct formed by walls 18, 19 similarly passes rearwardly, or outwardly through vanes 34. The walls 41 are continued radially outwardly of fairings 42, and form open channels 45, the induced flow in which reduces drag. In the modification of Fig. 6, the structures formed by walls 41, 42 and 44 are fixed so that the walls 44 are aligned with structures 20. The deflector section 116 is divided into twelve sectors by radial walls 133 mounted on a sleeve 123 rotatable on a rod 122. Alternate sectors contain deflecting vanes 134, 135, 136, and end walls 137, the remaining sectors being free of obstruction. When the latter sectors are aligned with the flow channels as in the lower part of Fig. 6, the gases pass rearwardly through the deflector section and through the spaces between adjacent walls 44. When the sleeve 123 is rotated through thirty degrees, the former sectors are aligned with the flow channels, and the end walls 137 cause the gases to pass outwardly over vanes 134, 136, 135. In a modification of this embodiment, the deflector section is itself divergent and the divergent section corresponding to section 15 of Gig. 1 is omitted. In a convergent nozzle, the deflector section is convergent and adjacent to a convergent section corresponding to section 14 of Fig. 1, as in Fig. 9 (not shown). In a modification of these constructions, the spaces enclosed by walls 41, 42, 44 are open at their downstream ends, and the fairings 42 are perforated. The depressions in these spaces caused by the rearward gas flow sucks the boundary layer from the exterior of fairings 42 into the spaces.