GB800517A - Improvements in or relating to gas turbines - Google Patents

Abstract

800,517. Gas turbine bladed rotors. ROLLSROYCE, Ltd. Nov. 16, 1956 [Nov. 28, 1955], No. 34080/55. Class 110 (3). In a gas turbine bladed rotor, the blades each comprise a vane portion 18, a root portion 19 which is mounted on the rotor disc 16, and a stem portion 21 extending between the vane and root portions, each blade being formed with a closed internal cavity 22 extending lengthwise of the vane portion and into the stem portion and containing a substance such as sodium which is at least in part in the liquid phase at the temperature attained by the blade in operation. Radially-extending passages are formed in the annulus constituted by the assembly of stem portions and means are provided to supply cooling fluid to flow outwardly through the radially-extending passages. In a first embodiment, two closed cavities 22 are formed in the blade. Radially-extending fins 23 are provided on the circumferentially-facing surfaces of the blade stem 21, the fins extending from a point radially-spaced from the root portion 19 to the blade platform 21a and the fins on adjacent stem portions co-operate to form the cooling fluid passages. An axially-extending manifold 24 is formed between the root portions 19 and fins 23 and is supplied with cooling fluid such as air tapped from the compressor of the engine, the cooling air flowing outwardly through the passages formed between the fins 23 and escaping into the working fluid passage as indicated by the arrows 30. Circumferentially-extending cooling fins 27 are formed on the upstream axially-facing surfaces of the blade stems 21. An annular blanking plate 25 is provided at the downstream side of the blade stem and root portions, the plate 25 engaging the rotor disc 16 also the blade platforms 21a thereby serving to prevent axial disengagement of the blades. In a second embodiment, Fig. 4, further passages 125 are provided extending through the vane portion 18. Cooling air flows through the passages between the fins 23 from a manifold 24 as in the first embodiment, but discharges from the passages into a second manifold 124 formed beneath the blade platforms 21a, the cooling air flowing from the manifold 124 into the passages 125 extending through the vane portion and discharging at the blade tip as indicated by the arrows 130. In the first embodiment, the passages between the fins 23 may discharge into an axially-extending channel, a single outlet leading from the channel to the working fluid passage, uniform flow through the passages being achieved thereby. This result may also be achieved by varying the sizes of the cooling fluid passages or the outlets therefrom. The cooling air may have a liquid sprayed into it; alternatively the cooling fluid may be a liquid.