Second Law Analysis of Thermodynamic Cycles for Aero Engines

This paper presents an evaluation of thermodynamic cycles with the help of second law thermodynamics. In common studies thermodynamic cycles are analyzed and judged mostly just by thermal efficiency and specific power output. Another way to describe the efficiency of a cycle and to identify the potential is the analysis of the entropy production of the system. In a previous study a general investigation of thermodynamic cycles was carried out [1]. The promising technologies identified were isothermal compression and expansion, internal heat transfer and constant-volume heat addition. Based on these theoretical and idealized investigations, estimations for component efficiencies and losses were made. The present study investigates the entropy production of the thermodynamic cycles including these promising technologies. This helps to understand the interaction of the components and the effect of single components and their losses on the whole cycle. Furthermore a distinction between internal and external entropy production is made. This identifies which part of the losses occurs in the components and which amount of exergy leaves the system unused. The results finally lead to a gas turbine cycle involving compression with intercooling, internal heat transfer and constant-volume heat addition.