Application of a Multidisciplinary Design Process to Assess the Influence of Requirements and Constraints on the Design of Military Engines

Abstract

The design of supersonic military aircraft is a complex multidisciplinary optimization process in which the dependencies and strong interactions between engine and aircraft must be imperatively considered. Applying a fully coupled propulsion-airframe design system is a highly challenging task, since it requires a set of numerically stable analysis tools capable of optimizing multiple design variables simultaneously. To improve computational efficiency, the application of low-fidelity design of experiment (DOE) methods aids in narrowing down the selection of suitable combinations of design parameters. This approach allows the division of the multidisciplinary process into subsystems, each of which can be served by specialized engineers. Interactions between the disciplines are then considered by exchanging DOE-based sensitivities. This paper presents the multidisciplinary design process developed at the German Aerospace Center (DLR) - in which the airframe and propulsion system are designed simultaneously while effectively utilizing DOE-based sensitivities. Guiding the work is an application case on the preliminary design of military engine concepts considering its effects on overall integrated aircraft architecture. The design process is used to investigate the influence of important engine parameters such as overall pressure ratio (OPR), bypass ratio (BPR), and turbine entry temperature (T4) on the design of military aircraft. Furthermore, the impacts of thrust requirements and technological constraints of the engine are analyzed.