Heat transfer analysis for a multistage gas turbine using different blade-cooling schemes

The heat transfer analysis of gas turbine blades using air or steam as coolants is investigated under various operating conditions. A general model of the combined system is developed and is used to compare the performance of three main schemes of the blade cooling, namely air-cooling, open-circuit steam cooling (OCSC) and closed-loop steam cooling (CLSC). The heat transfer model permitted the calculations of the cooling mass ratio that is required to reach a certain blade temperature. The results showed that steam appears to be a potential cooling medium, when employed in an open-circuit or in a closed-loop scheme. The combined system with CLSC gives better overall performance than does air-cooling or the OCSC.