Robust Approach to Engine Cycle Modeling to Enable Multidisciplinary Optimization of Advanced Aircraft

The increasing complexity of integrating propulsion and airframe systems in advanced and electrified aircraft requires engine models that are both accurate and robust enough to support large-scale multidisciplinary design optimization. This paper presents a formulation for modeling an engine’s thermodynamic cycle within an airframe-propulsion-trajectory optimization framework. The formulation includes a physics-based initialization method that generates analytically consistent starting conditions for all key thermodynamic state variables during on- and off-design evaluations, eliminating the need for manually tailored, well-conditioned initial guesses for the engine cycle. This is supplemented by two regulating mechanisms: an automated compressor bleed control to maintain operation within a prescribed stall margin and turbine operating constraints that prevent over-extraction and cycle closure failure. This comprehensive approach significantly improves convergence robustness and computational efficiency, allowing the thermodynamic cycle to be integrated within an aircraft multidisciplinary design optimization framework that couples the engine's design with the airframe and the aircraft operations. The model is used and demonstrated for a narrow-body aircraft optimization.