Describe the cooling techniques used in modern gas turbine blades.

Gas turbine blades operate in environments exceeding material limits (1500°C+ gas vs 1000°C metal capability), requiring sophisticated cooling. Internal convection cooling uses compressed air through serpentine passages. Film cooling discharges air through surface holes creating protective boundary layer. Impingement cooling directs jets at hot surfaces for enhanced heat transfer. Transpiration cooling forces air through porous surfaces. Thermal barrier coatings (TBCs) of ceramic material add temperature drop across coating thickness. Design optimization balances cooling effectiveness against efficiency penalty from using compressor air. Advanced techniques include shaped holes, double-wall construction, and additive manufactured internal geometries.