Optimization for Propulsion Airframe Architecture set-up

The Ultra High Bypass Ratio Turbofan (UHBR) has the potential to provide an important reduction in noise and burnt fuel compared to the existing subsonic engines. Unfortunately, its integration in our commercial aircraft induces some problems that have not been solved yet: between them, the increased weight of the propulsion architecture with, consequently, higher inertial and aerodynamics loads. The present work is the result of an internship at Airbus and it aims to investigate the possibility of an innovative Power Plant Structure design to make the UHBR integration easier and more efficient. The Free Size Optimization and the Topology Optimization were used for this purpose. Several design criteria were taken into account during the optimization processes: the stiffness of the Power Plant Structure, the loads on the Outlet Guide Vane blades and the impact of tip clearance variation into the Thrust Specific Fuel Consumption. Firstly, we investigated through the Free Size Optimization the possibility to control the tip clearance variations by optimizing the design of the Inner Fixed Structure of the Thrust Reverser Unit. Secondly, the Topology Optimization method was used to optimize the Power Plant Structure under given load cases. Before the present work, the Design Space used for the Topology Optimization was supposed to be glued to the engine at the interfaces: that made the structure to have a high Degree of Static Indeterminacy. Since the hyperstatic structures can not well support thermal deformations and in order to make the optimization solutions more manufacturable, in this work the glued interfaces between pylon and engine were replaced by discrete assemblies. Three different configurations of discrete assemblies were considered and compared. Moreover, two formulations were adopted for the Topology Optimization problem: the Classic Formulation which aims to minimize the compliance under a volume fraction constraint and a Complete Formulation where upper bounds were introduced to the Thrust Specific Fuel Consumption and to the loads on the blades of the Outlet Guide Vane. This work provided a deep understanding about the best design for a Power Plant Structure and a better knowledge concerning the impact of important design criteria on the optimal solution.