Analysis of turbine blade cooling effect on recuperative gas turbines cycles performance

Energy saving technologies are of prior importance to European environmental legislation. Gas turbines is a widely used technology, but is also considered a technology of important environmental footprint. Recuperation technology can be applied in gas turbines applications in order to achieve higher efficiency and reduced fuel consumption. In this work three different thermodynamic cycles are under investigation: the conventional recuperative cycle, the alternative and the SHR. All of these cycles have one or more heat exchangers integrated at different positions inside the gas turbine. In recuperative cycles the turbine inlet temperature is usually high, in order to achieve a beneficial temperature difference for recuperation. However, as this temperature increases the demanded mass flow for cooling the turbines gets higher. In order to obtain realistic results of high accuracy, the coolant mass flow cannot be neglected and must be carefully considered. In this paper, the required coolant mass flow is calculated for each cycle and for an extended range of operational conditions. The efficiency penalty due to the extracted air from the compressor is also calculated and presented. Different materials technology level is taken into account and therefore three allowable metal temperatures are considered for the calculations. The demanded coolant mass flow is calculated based on Young and Wilcock (2002). In order to underline the importance of taking into account the demanded coolant flow, an analysis of the performance of a helicopter engine is presented. The results show that both the thermal efficiency and the specific fuel consumption are affected when turbine blade cooling is taken into account.