Analysis of the energetic/environmental performances of gas turbine plant - effect of thermal barrier coatings and mass of cooling air

Abstract

Zirconia stabilized with 8 wt. % Y2O3 is the most common material to be applied in thermal barrier coatings owing to its excellent properties: low thermal conductivity, high toughness and thermal expansion coefficient as ceramic material. Calculation has been made to evaluate the gains of thermal barrier coatings applied on gas turbine blades. The study considers a top ceramic coating Zirconia stabilized with 8 wt. % Y2O3 on a NiCoCrAlY bond coat and Inconel 738LC as substrate. For different thickness and different cooling airflow rates, a thermodynamic analysis has been performed and pollutants emissions (CO, NOx) have been estimated to analyse the effect of rising the gas inlet temperature. The effect of thickness and thermal conductivity of top coating and the mass flow rate of cooling air have been analysed. The model for heat transfer analysis gives the temperature reduction through the wall blade for the considered conditions and the results presented in this contribution are restricted to a two considered limits: (1) maximum allowable temperature for top layer (1200 oC) and (2) for blade material (1000 °C). The model can be used to analyze other materials that support higher temperatures helping in the development of new materials for thermal barrier coatings.