GB878367A - Improvements in hot gas turbines - Google Patents

Abstract

878,367. Bladed turbine rotors. POICIT, R. April 15, 1958 [April 19, 1957; Jan. 15 1958], No. 12008/58. Class 110 (3). A gas-turbine rotor comprises discs 1a, 1b, the rim portions of which have radial slots 36 and form peripheral jaws 5a, 5b engaging the inclined heels 4a, 4b of the blade roots 9 and the similarlyshaped heels 29a, 29b of spacers 28 interposed between, and of complementary shape to, the blade roots, means such as screws and nuts 6, 6a being provided which keep the discs applied against each other in the axial direction so that the reaction between the jaws and the heels resiliently deforms the peripheral portions of the discs and holds the blade roots and spacers against one another in the circumferential direction. The rim portions may be integral with the discs (Figs. 1, 5) or may be formed on separate plates (Fig. 6) attached thereto, and are offset outwardly from the wheel body 1 so that the torque produced by the centrifugal force acting on them tends to increase the pressure of the jaws 5a, 5b on the heels. Each blade is made of metal, preferably of high thermal conductivity, and comprises front and rear portions 2a, 2b separated by an interval 8, the front portion having a thin layer 34 of protective material of low thermal conductivity and being surrounded by a sheet 11 of heatresistant material, such as nickel or a nickel alloy containing chromium, which overlaps the rear portion at its edges 11a, 11b and is gripped between the blade root and the adjacent spacers. Cooling air is fed to the interval 8 through a hole 10 (see Fig. 6) in the root and flows beneath the edges 11a, 11b of the sheet to issue as a laminar film over the surface of the rear portion of the blade. The cooling air, which is supplied through radial channels 20 and an annular chamber 19, is also fed to recesses such as 12-15 in the front portion of the blade beneath the sheet 11 and to radial channels 17, 18 within the front and rear portions. A shroud ring 25 (Fig. 1) is held by pins 26 (Fig. 5) carried by the blades, each pin having a base 26a which closes the end of an interval 8, and an annular spring 27 is interposed between the ring and the blades. Some of the recesses (12, 15) open laterally through notches in the sheet 11, and the other recesses (13, 14) and the channels 17, 18 open radially through holes in the spring and shroud ring, the air flowing from the front portion of the blade being projected in the form of a whirling ring. The outer surfaces of the spacers may be protected by sheets 32 of heat-resistant material, such as that used for the sheets 11, engaged between the heels and the jaws. In Fig. 6, the shroud ring 25 is tightly applied against the ends of the blades and cooling fluid which is supplied to a fixed chamber 41 upstream of the rotor leaks through a labyrinth seal 42 and circulates through grooves formed in the spacers under the plates 32, which have inlet and outlet apertures 43, 44 for this purpose. The cooling fluid may be recirculated by centrifugal action through divergent radial channels 45.