PERFORMANCE AND ANALYSIS OF MIRROR GAS TURBINE AT VARIABLE SPECIFIC HEAT

Abstract

There have been many developments on the thermodynamic analysis of various combined or cogeneration cycle schemes, with more advance heat recovery capabilities. One of such novel cycles is the mirror cycle. The mirror gas turbine is a conceptual combination of Brayton and inverted Brayton cycles with a heat sink by intercooling. And options chosen for further development seem to aim at more marketable system in recent years. The split-shaft engine can offer better flexibility of operation for the needs of combined or cogeneration system. In this work, performance analysis of the mirror gas turbine associated with split-shaft engine is obtained. The obtained results provide significant guidance to the performance evaluation and improvement of the mirror gas turbine. Heat energy of exhaust gas of gas turbine is extremely large and therefore can be retrieved by cogeneration system in modern industrial gas turbines [6]. However, there may be a possibility for reutilization of exhaust gas directly if the inverted Brayton cycle is adequately used in bottoming cycle. This new conceptual combination of Brayton and inverted Brayton cycles is dubbed as a "Mirror Gas Turbine" [3] This Mirror Gas Turbine Cycle has been evaluated and analyzed for different method to improve performance of gas turbine such as intercooling in stages of compression and reheating in stages of expansion in turbine. Computer programs have been generated for analysis of mirror gas turbine cycle at variable specific heat of air. In analysis different parameters such as specific output, thermal efficiency, power ratio, and specific fuel consumption have been studied for optimum performance of Mirror Gas Turbine Cycle. It is revealed that number of intercooler in stages of compression of bottoming cycle should be optimized to two and reheating is not beneficial in respect of thermal efficiency.