Cooling of aerofoil shaped blades

Claim 1

A hollow aerofoil-shaped blade for use in a fluid flow machine, said blade having a convex side and a concave side, each side being made up of an inner sheet having inner and outer faces, an outer sheet having inner and outer faces, and an intermediate sheet therebetween and respectively adjacent to the outer and inner faces respectively of said inner and outer sheets, the outer and inner faces respectively of the inner and outer sheets of at least one of said sides adjacent to the intermediate sheet being grooved, each inner sheet and outer sheet of the at least one of said sides having defined therein apertures which extend through the thickness of the sheet and communicating with the grooves therein, the apertures of the inner sheet being out of alignment with the apertures of the outer sheet, said intermediate sheet of the at least one of said sides having apertures defined therein which communicate with said grooves in the said outer and inner faces respectively of said inner and outer sheets but which are out of alignment with said apertures in both said inner and outer sheets of the at least one of said sides, whereby in operation cooling fluid supplied to the hollow interior of the blade passes to the exterior thereof by following a tortuous path through said apertures and said grooves from the interior to the exterior of the blade.