Conceptional Design Modeling of Gas Turbine Cycle for Maximum Work Output, First Law and Second Law Efficiency 2001-01-2544
The present paper discusses gas turbine operating ranges of values of controlling cycle parameters for maximum first law efficiency ηI, second law efficiency ηII, and work output wnet. Three cycles have been studied: simple cycle, recuperative cycle and general open cycle. Correlation equations relating maximum values of ηI, ηII, and wnet to the controlling parameters (compressor and turbine efficiencies, maximum cycle temperature, isentropic temperature ratio, fuel/air ratio, heat exchanger effectiveness and pressure drops in combustion chamber and heat exchanger) have been determined and discussed.
The present paper reveals that the cycle performance parameters ηI, ηII, and wnet drastically depend on cycle controlling parameters. There is no narrow region of values of controlling parameters that produce concurrent optimum values of ηI, ηII, and wnet. The maximum cycle temperature for the three cycles considered has a linear effect on ηI, while other controlling parameters have nonlinear effects on ηI, ηII, and wnet. For the general open cycle, the pressure drops ΔPcc and ΔPex have equal decreasing effects on ηI, ηII, and wnet, while both fuel-air ratio ƒ and heat exchanger effectiveness ηX have equal increasing effect on these performance parameters. The present correlation equations, augmented with other experimental and detailed design studies for each of the cycle units, could provide a good basis for the realistic design process of actual turbines.