Design and Detailed Analysis of Turbomachinery Blades using Truncated Domains

Licentiatavhandling, 2020

With the continuous growth in air traffic that we are seeing nowadays comes an increase in the requirements needed to be satisfied by an aircraft for it to be certified to fly. These stricter regulations affect aspects such as CO2 emissions, sound pollution and so on, pushing manufacturers to aim for lighter, more efficient, more robust designs. These required improvements needed to keep up with the regulations might come in two different ways; by improving/optimizing existing technology, or by developing new technological concepts. In either of the two scenarios, numerical tools, such as optimization methods or reliable fluid flow simulations play a paramount role.

In this thesis, the new capabilities implemented into the in-house Computational Fluid Dynamics (CFD) solver, G3D::Flow, are described. These new additions have been put in place with the objective in mind of performing broadband noise predictions of a fan/OGV configuration using hybrid RANS/LES simulations. Some of the additions to G3D::Flow include: phase-lagged pitch-wise and rotor-stator interfaces, sliding grids and synthetic turbulence injection. These methods have been then put together in order to simulate the flow around the ACAT 1 fan/OGV geometry.

In this work, an optimization framework called HAMON is presented. It is based on evolutionary algorithms and can be coupled with meta-modeling techniques to speed up processes where computationally expensive simulations need to be performed, such as 3D CFD simulations. HAMON can be used to fine tune an existing design, or as it has been used here, a black-box approach. It has been able to design counter rotating open rotors with more than acceptable performance were no knowledge about propeller aerodynamics was assumed, giving all the design variables more freedom than probably needed. This black-box approach might be specially useful when optimizing new technologies for which no prior knowledge exist, allowing not only to hopefully find good designs but also to show the trends of what a good design should be like.