Improving the efficiency of gas turbine-air bottoming combined cycle by heat exchangers and bypass control valves

Abstract

The present study is a comparative energy and exergy analysis of a Proposed gas turbine cycle (PGTC) with a simple gas turbine cycle (SGTC), maintaining the same rate of fuel supply in both cycles. In the PGTC, the air bottoming cycle is operated by exhaust gases from the topping gas turbine cycle by exchanging heat in the heat exchangers (H.E.s) by controlling the path of exhaust gases and compressed air through the bypass control valves. The bypass valve in the topping, as well as the bottoming cycle, direct the combustible product from the combustion chamber to the H.E., in such a way that it optimizes the performance of the proposed combined cycle as compared to SGTC. The results show that the maximum increase in Work net output and thermal efficiency in PGTC compared to SGTC is 65.7% at rp = 4 and turbine inlet temperature (TIT) = 1500 K, whereas the exergy loss by the exhaust gases in the PGTC is much less than the exergy loss by the exhaust gases in the SGTC. The maximum difference in the exergy loss by the exhaust gases in PGTC and SGTC is also observed at rp = 4 and TIT = 1500 K.