Energy and exergy analysis of air-film cooled gas turbine cycle: Effect of radiative heat transfer on blade coolant requirement

Abstract

Gas turbine blade cooling is critical to continuous reliable operation of gas turbines. Literature suggests that air-film cooling is one of the most widely used blade cooling techniques. This paper compares previously developed blade cooling models which are relevant to film cooling technique and it also proposes a gas turbine blade cooling model for the estimation of blade coolant mass fraction, considering radiative heat transfer from hot combustion gases to gas turbine blade surface. The proposed model gives an enhanced coolant mass fraction (≈5–6% over a wide range of TIT) as compared to previously developed models while analyzing gas turbine cycle. Gas turbine cycle performance has been evaluated based on two blade cooling models to compare blade coolant flow mass fraction, gas turbine plant specific work which are function of both compressor-pressure ratio and turbine inlet temperature. Both the blade cooling models closely follow each other with radiative cooling model. For the proposed blade cooling model, gas turbine specific work is around 417.39 kJ/kg (rpc = 22 and TIT = 1650 K) and gas turbine thermal cycle efficiency has been found to be 41.25% at (rpc = 22 and TIT = 1550 K). Exergy analysis of gas turbine cycle has also been done which shows combustor to be main source of exergy destruction (≈29%).