Electrochemical machining process for forming surface roughness elements on a gas turbine shroud

摘要

The back side recessed cooling surface (12) of a shroud defining in part the hot gas path of a turbine is electrochemically machined to provide surface roughness elements (28) and spaces (26) therebetween to increase the heat transfer coefficient. To accomplish this, an electrode (20) with insulating dielectric portions (22) and non-insulating portions (24) is disposed in opposition to the cooling surface. By passing an electrolyte between the cooling surface and electrode and applying an electrical current between the electrode and a shroud, roughness elements and spaces therebetween are formed in the cooling surface in opposition to the insulating and non-insulating portions of the electrode, hence increasing the surface area and heat transfer coefficient of the shroud.