Comprehensive Formulation of Power Balance and Exergy Analysis for the Assessment of Highly Integrated Transport Aircraft

In the context of future transport aircraft, advanced concepts of propulsion-airframe integration feature Boundary Layer Ingestion (BLI), Distributed Propulsion (DP), together with advanced propulsion technologies such as Open Rotor, and Ultra High Bypass Ratio (UHBR) engine configurations. These concepts have the potential for reducing overall aerodynamic drag but also introduce a strong coupling between thrust and drag, necessitating the use of comprehensive performance assessment methods like Exergy Analysis and Power Balance. The key advantage is that both methods eliminate the need to explicitly determine aerodynamic forces acting on the body and are applicable to steady-state compressible flows. A unified nomenclature has been developed in the present paper to enable meaningful comparisons between Exergy Analysis and Power Balance methods, and to clarify the types of physical phenomena each method can investigate. It is also shown that the terms in the Power Balance method can be deduced from Exergy Analysis by omitting the terms associated with heat transfer and associated entropy generation. Despite their differing capabilities in identifying specific loss mechanisms, both approaches provide complementary insight into system losses and remain valuable tools for uncovering opportunities to improve aircraft system efficiency.