GB789733A - Improvements in or relating to structural elements for axial-flow compressors or turbines or the like machines - Google Patents

Abstract

789,733. Turbine and compressor casings. ROLLS-ROYCE, Ltd. Feb. 11, 1955 [March 22, 1954], No. 8379/54. Addition to 695,724. Classes 110 (1) and 110 (3). A structural element for use in an axial-flow compressor or turbine comprises a plurality of blades 11 for a blade row of the machine and a shroud structure for an end of the blades. The shroud structure comprises a first annular or part-annular sheet-metal skin 12 which affords a part of the wall of the working fluid passage of the machine, and a second ridged annular or part-annular sheet-metal skin 13 which is spaced from the first skin at the location of the blade row. The ridged skin is in contact with and is secured to the first skin between adjacent blade rows, the first skin being formed with slots 15 and the second skin 13 being provided with pairs of slots 16, the slots of each pair being radially-aligned with the ends of a corresponding slot 15 in the first skin. Each blade is mounted in the shroud structure by having an end extending through a slot in the first skin and by having portions extending through the two slots in the second skin and being secured thereto. In Fig. 1 the second skin is comprised of a number of sheet-metal rings 13, the flanges 13a of which are welded to the external surface of the shell 12. The angle-section part 14 of each ring is formed with pairs of slots 16 which are radially in line with the ends of slots 15 formed in the inner skin 12. The root end 11a of a blade projects through the slots 15, 16 and is secured, for example, by brazing 17, or by means of lugs 18 at the end of the blade root which are bent after assembly to engage the outer surface of the ridged skin. The rings 13 are provided with flanges 20 and these are secured to an outer casing 21. In the compressor casing shown in Fig. 5 the two sections 25, 26 are connected together by means of a ring 30 and bolts, the ring carrying a row of stator blades 31 which may support at their inner ends a bearing of the compressor rotor. The outer casing 21 is omitted in this construction. In Fig. 4 the root end of the blade is square and the ends of the two slots 16 in the ring 13 are at right angles to each other so that the blade root fits snugly in the slots, being secured by brazing 17. The ends of the blades in Fig. 1 are cut off parallel to the angled sides of the rings 13. In a further construction the blade roots are enlarged to a greater aerofoil section than the vane portions. The ridged skin may have ridges of curved cross-section.