GB619634A - Improvements relating to internal combustion turbines and like apparatus working with gases at high temperatures - Google Patents

Abstract

619,634. Making turbines. MOORE, N. P. W., and GROOTENHUIS, P. Dec. 17, 1946, No. 37145. [Classes 83 (ii) and 83 (iv)] [Also in Group XXVI] Powder metallurgy. - Blades, combustion chamber walls and other parts of gas turbines and like apparatus which are subjected to very high temperatures are made wholly of, or with at least a surface layer of, porous material through which a cooling fluid is caused to percolate. The porous material may be produced by sintering powdered metal, preferably stainless steel, or by spraying metal, or may be of ceramic material. Turbine blades made wholly of sintered metal are made hollow with passages through the roots for the admittance of a cooling fluid. The roots are strengthened by using a smaller particle size, or by cementing with a low-melting point alloy. A blade may have a non-porous metal core with grooves k, Fig. 4, in its surface which run into cross grooves l and so make connection with a cooling fluid inlet s in the root. The core is then covered with a sintered metal which is kept out of the grooves. In another form, a solid core has several lengthwise bores and smaller distributing bores radiating from them to the surface of the core and the inner surface of the porous shell. In another form, the blade core is formed from sheet metal welded at the trailing edge and its surface is covered with perforations. The blade surface may be formed by bending a sheet w, Fig. 8, of porous metal, and this is spot-welded to a central post x integral with the root y. Blades for different turbine stages may be made with different degrees of porosity and individual blades may be made with a varying porosity to give greater porosity where a greater cooling effect is necessary. The cooling fluid may be a gas such as air or carbonic acid gas, or it may be a liquid. In the latter case, the flow is arranged to secure the evaporation of the liquid at, or just below, the blade surface. The cooling fluid may be a fuel and its combustion on emergence used to provide re-heating of the working fluid within the turbine. Fig. 9 shows a turbine shaft 14 protected from the hot gases, which enter the casing at 10, by a sleeve 11 of porous material. A cooling fluid is admitted at 12, percolates outwards through the sleeve 11, and passes into the turbine rotor and so to the turbine blades.