Turbine blade

A turbine comprising:

• at least one stage having a plurality of fixed blades, each of said fixed blades being of at least approximately constant aerofoil cross-section from a root at a radially inner end of a respective blade to a tip at a radially outer end of the respective blade, each blade being substantially symmetrically curved between the root and the tip so that a pressure face of the blade is convex in a radial direction between the root and the tip, the blade having a trailing edge which is substantially straight from the root to the tip, the blade comprising a plurality of aerofoil sections stacked between the root and the tip and lying in respective planes, the convex curvature of the blade pressure face in the radial direction being achieved by rotational displacement of the aerofoil sections in said respective planes about the substantially straight trailing edge, and adjacent fixed blades having a throat and a pitch in a ratio giving the sine of an outlet angle for the blades which is in the range 7.degree. to 11.degree. at the root of the blades.

A turbine comprising:

• a series of turbine stages adapted for decreasing fluid density of a turbine working fluid, each of said stages comprising a plurality of blades, each of said blades being of at least approximately constant aerofoil cross-section from a root at a radially inner end of a respective blade to a tip at a radially outer end of the respective blade, each blade being substantially symmetrically curved between the root and the tip so that a pressure face of the blade is convex in a radial direction between the root and the tip, the blade having a trailing edge which is substantially straight from the root to the tip, the blade comprising a plurality of aerofoil sections stacked between the root and the tip and lying in respective planes, the convex curvature of the blade pressure face in the radial direction being achieved by rotational displacement of the aerofoil sections in said respective planes about the substantially straight trailing edge, a setting angle at the root of the blades being constant throughout the series of stages, and a setting angle for the aerofoil sections at a mid-height of the blades being such as to maintain a predetermined throat area for the blades of each stage.