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Thermodynamic modelling and efficiency analysis of a class of real indirectly fired gas turbine cycles

Ma Zheshu (Department of Power Engineering, Jiangsu University of Science and Technology, Zhenjiang City, Jiangsu Province, P.R. China)
Zhu Zhenhuan (University of Manchester, School of Mechanical, Aerospace and Civil Engineering, Manchester, UK)

Indirectly or externally-fired gas-turbines (IFGT or EFGT) are novel technology under development for small and medium scale combined power and heat supplies in combination with micro gas turbine technologies mainly for the utilization of the waste heat from the turbine in a recuperative process and the possibility of burning biomass or 'dirty' fuel by employing a high temperature heat exchanger to avoid the combustion gases passing through the turbine. In this paper, by assuming that all fluid friction losses in the compressor and turbine are quantified by a corresponding isentropic efficiency and all global irreversibilities in the high temperature heat exchanger are taken into account by an effective efficiency, a one dimensional model including power output and cycle efficiency formulation is derived for a class of real IFGT cycles. To illustrate and analyze the effect of operational parameters on IFGT efficiency, detailed numerical analysis and figures are produced. The results summarized by figures show that IFGT cycles are most efficient under low compression ratio ranges (3.0-6.0) and fit for low power output circumstances integrating with micro gas turbine technology. The model derived can be used to analyze and forecast performance of real IFGT configurations.

Keywords: indirectly fired gas turbine, thermodynamic analysis, bioenergy, biomass utilization, micro gas turbine