Turbine nozzle outer band and airfoil cooling apparatus

A turbine nozzle assembly for a gas turbine engine, comprising:

• a plurality of turbine nozzle segments arranged in an annular array, each turbine nozzle segment comprising:
• an arcuate outer band segment;
• an airfoil-shaped turbine vane extending radially inward from the outer band segment, the turbine vane having a hollow interior;
• an impingement baffle assembly secured to the outer band so as to define an impingement cavity in cooperation with the outer band segment, wherein the impingement baffle assembly has at least one impingement hole formed therein which is arranged to direct cooling air at the outer band segment;
• and
• at least one impingement insert having at least one impingement hole formed therein disposed in the interior of the turbine vane, the at least one impingement insert mating with an opening in the impingement baffle assembly such that the at least one impingement insert is isolated from direct fluid communication with the impingement cavity;
• and
• an annular supporting structure surrounding the turbine nozzle segments;
• wherein the impingement baffle assembly includes a perimeter frame and an impingement baffle extending radially inward from the frame;
• and
• wherein each outer band segment includes a central portion, an arcuate, radially-outwardly-extending forward rail, and an arcuate, radially-outwardly-extending aft rail;
• and
• the forward rail, the central portion, and the aft rail all terminate at a common side face on each lateral side of the outer band segment;
• and each of the side faces of each outer band segment defines spaced-apart radially inner and outer rails with an open window therebetween that exposes the impingement cavity.