A blade cooling circuit feed and exhaust duct and related cooling structure are provided. The feed duct may include a feed chamber having a feed entrance fluidly coupled to a cooling fluid source and a feed exit to an elongate entrance to the cooling circuit, the feed exit including a ramped wall maintaining a flow velocity of the cooling fluid along the elongated entrance to the cooling circuit. The exhaust duct may include a substantially concave exhaust chamber including an exhaust entrance at a wider end of the exhaust chamber and in fluid communication with an elongated exit from the cooling circuit, and an exhaust exit at a narrower end of the exhaust chamber, the exhaust exit including an opening to an exhaust passageway from the exhaust chamber.