Multidisciplinary Optimization of Next-Generation Aero-Engine Fans

The last decade has seen rising concerns over the impact that the global civil aviation market has on climate. The role of sustainability in the modern aeronautics has gained a growing importance, and has been identified as a key challenge facing the aviation industry. Today, sustainability is one of the main agents pushing jet engine manufacturers towards the design of machines that consume less fuel and last longer. A key factor for achieving these targets is an increased adoption of high-fidelity numerical analyses and optimization methods, in order to effectively approach problems that can be efficiently, rapidily and affordably solved only through advanced mathematics. There is also the urge to deal with different engineering disciplines simultaneously, by formulating and solving multidisciplinary optimization problems, thereby saving time in the early design phases and delivering an improved, optimal product in the successive layout stages. An important aspect to be considered to improve aero-engine turbomachinery components’s life and performances is to control and reduce the secondary flows that develop in their blade passages. Secondary flows reduce the pressure ratio and efficiency of aero-engine compressors, alter their operations at off-design conditions and shorthen the life of downstream components. The work of this thesis makes use of multidisciplinary optimization and high-fidelity numerical CFD simulations, to control and reduce the secondary flows in aero-engine compressors, by using vortex generators. The capabilities of these devices are studied in an open testcase transonic compressor, the NASA Rotor 37, by carrying out an optimization and studying different metrics that measure the secondary flows intensity. Building on the gained knowledge, a single-objective constrained optimization of a vortex generator parameterized with 7 variables is performed on axial compressor representative of a real, modern high-bypass civil aero-engine fan. Different constraints are applied to ensure satisfactory performances. An additional weakly-coupled aero-structural analysis is also performed on the optimal vortex generator to assess its material integrity. A simplified vibrational analysis conducted on a representative downstream component demonstrates important reductions in the forced response, which is one of the primary responsible for the life of compressor blades.