GB820366A - Improvements in or relating to retractable guards for air intakes - Google Patents

Abstract

820,366. Gas turbine plant. ROLLS-ROYCE Ltd. Jan. 4, 1957 [Jan. 6, 1956], No. 601/56. Class 110(3). A retractable guard for an air intake duct of non-annular form comprises two guard portions each of which is located wholly within the duct and is mounted to pivot about an axis extending across the duct, between an operative position in which the guard portions together extend across the fluid passage, one edge of each guard portion co-operating with a corresponding edge of the other guard portion and another edge of each guard portion co-operating with a wall of the duct and an inoperative position in which the guard portions are substantially out of the path of the fluid flowing through the duct, the guard portions being shaped to conform with the wall of the duct against which they lie in the retracted position. The air intake duct 13 of a gas turbine engine nacelle leads to the entry of an axial-flow engine compressor 16. A pair of guard grid portions 17, mounted to pivot about an axis 25, each comprise a number of rectangular bars arranged in two sets 18, 19. The bars 18 of one set lie in parallel planes and, in the position shown, extend parallel to the axis of the duct 13. The bars 19 of the other set are in planes at right-angles to the planes in which the bars 18 lie. In the operative position, the bars 19 also lie in planes parallel to the axis of the duct 13. The bars 18, 19 may be interconnected by a halving joint. The edges of the guard grid portions are strengthened by parts 21, 22 provided with sockets 26 which engage spigots 27 carried by the nacelle wall 11. A recess 23 is provided in the wall 11 to receive debris collected on the grids when they are moved to the inoperative position. The part 21 co-operates closely with the edge 24 of the recess 23 to prevent this debris becoming loose in flight and entering the intake of the compressor. The part 22 co-operates with the partspherical surface 34 during movement of the guard portions 17 for the same purpose. The portions 17 may be operated by pneumatically or hydraulically-operated rams. A separate ram may be provided for each portion in which case appropriate stops will be necessary. As shown, the portions 17 are interconnected by a pair of links 31 provided with a roller 32 engaging a track 33 and operated by a single ram 28. In addition to the guard grid portions 17, there may be provided a pair of imperforate panels 35, Fig. 3. The rear part 36 of each panel is of part-spherical form and lies outside of the part 34 of the inner wall 11. The panels 35, which contain the recess 23, are pivoted on the spigots 27 and held in the inoperative position by latch mechanism 37. It may be arranged that the aerodynamic forces on the panels 35 are such that on release of the mechanism 37 the panels move to their operative position over the guard grid portions and abut one another on a horizontal plane. In a modification, the guard portions may be made imperforate so that when in the operative position they prevent the flow of air into the engine and so stop it windmilling.