Influence of Different Steam Cooling Techniques for High Pressure Turbine Blades on the Performance of Gas Turbine

Abstract

Gas turbines are always intended to give more specific work output for which continuous exposure to hot combustion gases is necessary. To increase the lifespan of the turbine blades active cooling should be applied to the High Pressure (HP) turbine blades. In the present work, a simple open cycle gas turbine is modeled to carry out thermodynamic analysis with different open loop steam cooling techniques: steam internal convection cooling (SICC), steam film cooling (SFC) and steam transpiration (STC) cooling. The effect of Turbine inlet temperature (TIT), Turbine blade temperature (T_b), and Compressor pressure ratio (CPR) on the coolant flow requirement and effect of T_b on the performance are estimated. The entire analysis is carried out with contemplation of variable specific heat (VSH) along with constant specific heats (CSH) for air and gas. Between VSH and CSH approaches, the former analysis leads to better performance from the first and second law efficiencies point of view. Irreversibility and Entropy generation rate are maximum in the combustor and they are less for VSH case in all cooling schemes and are decreased by 38.53%, 40.01%, and 40.40% for SICC, SFC and STC schemes respectively when compared with CSH(at TIT=1580 K, T_b=1123 K, CPR=19.1) analysis.

Keywords

• gas turbine blade cooling
• internal convection cooling
• film and transpiration cooling
• irreversibility
• entropy generation rate