Airfoil and a method for cooling an airfoil platform

An airfoil, comprising:

• a. an outer surface having a leading edge, a trailing edge downstream from the leading edge, and a convex surface between the leading and trailing edges;
• b. a cavity inside the outer surface;
• c. a platform connected to the outer surface, wherein the platform defines a top surface around at least a portion of the outer surface;
• d. a plenum inside the platform in fluid communication with the cavity, wherein the plenum includes a plurality of separate chambers;
• e. a first plurality of trenches beneath the top surface of the platform upstream from the leading edge, wherein each trench in the first plurality of trenches is substantially parallel with the top surface of the platform and in fluid communication with the plenum;
• and
• f. a first plurality of cooling passages that provide fluid communication from the first plurality of trenches through the top surface of the platform.

A turbine, comprising:

• a. a casing;
• b. a plurality of airfoils circumferentially arranged inside the casing, wherein each airfoil includes an outer surface having a leading edge, a trailing edge downstream from the leading edge, and a convex surface between the leading and trailing edges;
• c. a cavity inside each airfoil;
• d. a platform connected to the outer surface of each airfoil, wherein each platform defines a top surface around at least a portion of the outer surface of each airfoil;
• e. a first plurality of trenches beneath the top surface of each platform upstream from the leading edge, wherein each trench in the first plurality of trenches is in fluid communication with the cavity inside each airfoil;
• and
• f. a first plurality of cooling passages that provide fluid communication from the first plurality of trenches through the top surface of each platform.