Bucket platform cooling circuit and method

A method of cooling a platform of a turbine bucket having an airfoil portion, a root portion, and slash-face portions, said airfoil portion being joined to the platform and the platform extending over said root portion towards said slash-face portions, comprising:

• providing a cooling passage to extend along at least a portion of a concave, pressure side of the airfoil portion, said cooling passage including a first, part circumferential portion extending from said airfoil towards a slash-face of the platform and a second, part axial portion extending from said first portion at an angle thereto;
• flowing a cooling medium through a bore from a cooling medium cavity in a vicinity of an axial center of the airfoil portion to said cooling passage;
• and
• expelling cooling medium from said cooling passage through at least one outlet opening, each said outlet opening exiting solely through said slash-face,
• wherein said providing a cooling passage includes providing a first, part circumferential cooling passage portion extending from said airfoil towards a slash face of the platform and a second, generally linear cooling passage portion extending substantially parallel to said slash face,
• wherein said providing a cooling passage further comprises providing a second cooling passage to extend along at least a portion of a concave, pressure side of the airfoil portion, and wherein the method further comprises:
• flowing a cooling medium through a bore from another cooling medium cavity in a vicinity of an axial center of the airfoil portion to said second cooling passage;
• and
• expelling cooling medium from said second cooling passage through at least one outlet opening, each said at least one outlet opening exiting solely through said slash-face.

In a turbine bucket having an airfoil portion and a root portion with a platform at an interface between the airfoil portion and the root portion, a platform cooling arrangement including:

• a cooling passage defined in the platform to extend along at least a portion of a concave, pressure side of the airfoil portion, at least one cooling medium inlet to said cooling passage extending from an airfoil cooling medium cavity in a vicinity of an axial center of the airfoil portion, and at least one outlet opening for expelling cooling medium from said cooling passage,
• a second cooling passage defined in the platform to extend along at least a portion of the concave, pressure side of the airfoil portion, at least one cooling medium inlet to said second cooling passage extending from an airfoil cooling medium cavity in a vicinity of the axial center of the airfoil portion, and at least one outlet opening for expelling cooling medium from said second cooling passage, wherein each said cooling passage includes a first, part circumferential portion extending from said airfoil towards a slash face of the platform and a second, generally linear portion extending from said first portion at an angle thereto, wherein the linear portion of one of said cooling passages extends generally towards a leading edge of said platform, and the linear portion of the other of said cooling passages extends generally towards a trailing edge of said platform.