Performance evaluation of reheat gas turbine cycles

Abstract

The role of gas turbine power plants in electrical energy production has been considerably increased in the last two to three decades. Various methods have been proposed to improve the performance of gas turbine cycles. In this research, two methods, a reheat cycle (RC) and a cycle with a reheat and a heat exchanger (RHC), were investigated and compared with a simple cycle (SC). Today, to achieve a higher efficiency and capacity in gas turbines, higher turbine inlet temperatures (1300 °C and more) are used. Basically, application of such temperatures without turbine blade cooling is impossible. Therefore, analysis of gas turbine cycles without considering blade cooling in modelling will certainly not lead to a valid and correct result. The main objective of this paper is to study the performance of an RC and RHC under actual conditions. In this regard, all processes are treated as actual, and in particular a relatively simple and reliable approach is used to predict the amount of cooling air. It should be noted that there are many attempts being made to produce ceramic turbines, for which a much-reduced cooling requirement will be necessary. The results obtained on the basis of a model developed for this research show that reheating in the context of a realistic study may lead to an improvement both in efficiency and in specific net work.