Hybrid Surrogate-Based Rubber Engine Model for Aircraft Multidisciplinary Design Optimization

The engine design should be selected optimally in terms of the overall aircraft system taking into account snowball effects, since the engine size, weight and fuel consumption have a large influence on both the structural aircraft sizing process and the aerodynamics. But the Multidisciplinary Design Optimization (MDO) of an aircraft is a challenging task due to the high degree of coupling of various components and disciplines. Therefore, a scalable rubber engine model can be applied within the MDO to enable the optimal selection of an engine design while reducing additional complexity to a minimum. In this publication a hybrid surrogate-based rubber engine concept is proposed, which consists of surrogate-models covering a range of engine designs and a tool for thermodynamic cycle analysis. Thereby, dimensions, weight and center of gravity of different engine designs as well as the individual operating behaviour over the entire flight mission are made available for the MDO process. A generic three-spool unmixed turbofan design similar to the Trent 1000 is created. Design variations are performed to generate a rubber engine model that covers different thrust requirements and a range of bypass ratios. For the model creation, different methods for design of experiment and interpolation with a varying number of samples are assessed and compared.