US Patent 7785071 Turbine airfoil with spiral trailing edge cooling passages

A turbine airfoil such as a rotor blade or a stator vane with a row of spiral shaped cooling holes in the trailing edge region of the airfoil to provide cooling to the trailing edge region. An up-pass or last leg of a serpentine flow cooling channel extends along the trailing edge region of the airfoil and a row of the spiral cooling holes are connected to the supply channel to bleed off cooling air. The spiral cooling holes have a decreasing diameter in the airfoil streamwise direction and a constant diameter in the spanwise direction of the airfoil such that the spiral cooling holes are close to the pressure side and suction side walls of the airfoil in the trailing edge region. The cooling air flow increases in momentum as the trailing edge narrows and the spiral cooling holes decrease in diameter to enhance the heat transfer coefficient and provide better cooling in the hotter region of the trailing edge region where the airfoil is relatively thinner.