Turbine blade with triple pass serpentine flow cooling circuit

A turbine blade having a root portion and an airfoil portion, the root having a cooling air supply passage to supply cooling air to the airfoil portion, the blade comprising:

• an first serpentine flow cooling circuit including a first leg formed from a cooling channel on the pressure side of the blade, a second leg formed from a cooling channel on the suction side, and a third leg formed from a channel located on the pressure side, the first and third legs are substantially opposed to the second leg;
• a second serpentine flow cooling circuit located downstream from the first serpentine flow cooling circuit and including a first leg formed from a channel located between the pressure side and the suction side and adjacent to the trailing edge of the blade, a second leg formed from a channel located on the suction side and aft of the first leg, and a third leg formed from a channel on the pressure side of the blade and adjacent to the second leg;
• a plurality of cooling air trailing edge exit holes in communication with the first leg of the second serpentine flow circuit;
• a leading edge cooling supply channel located forward of the first serpentine flow circuit;
• and,
• a showerhead arrangement and a leading edge cooling channel located in the leading edge region of the blade and in communication with the leading edge cooling supply channel through a plurality of metering holes.