Performance and Endurance Enhancement by Means of Turbine Cooling

This article discusses how advancement in turbine cooling techniques has helped enhancing the performance and endurance of turbines. Gas turbine thermal efficiencies increase with higher temperatures of the gas flow exiting the combustor and entering the work-producing component—the turbine. The fundamental aim of a turbine heat transfer designer is to obtain the highest overall cooling effectiveness for a blade or vane, with the lowest possible penalty on thermodynamic performance. In the last 50 years, advances have led to an overall increase in turbine and vane cooling effectiveness, from 0.1 to 0.7. It started with convection only and has progressed with film cooling, thermal barrier coatings, and new materials and architectures. Temperature excesses in turbines are now as high as 1400°F (778°C) above alloy melting points. Film cooling is the key to attaining these levels, and to increasing them in the future, for yet higher gas turbine efficiencies.