Naslov
Numerical evaluation of the performance curve for the NASA rotor 67

Autori
Žužul, Josip

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, diplomski rad, diplomski

Fakultet
Fakultet strojarstva i brodogradnje

Mjesto
Zagreb

Datum
31.03

Godina
2017

Stranica
133

Mentor
Jasak, Hrvoje

Ključne riječi
CFD, foam-extend, Transonic Turbofan, NASA Rotor 67, Mesh Generation, CAD Generation

Sažetak
Computational Fluid Dynamics (CFD) is nowadays frequently used for the analysis of complex fluid flows for industrial and academic purposes. In order to improve and expand CFD codes which are capable of solving wide range of physical phenomena, new code formulations have to be developed and validated on a large number of test cases with comprehensive experimental data. Within this thesis, a new formulation of compressible, turbulent flow solver for rotating turbomachinery, implemented in open-source CFD package foam-extend is tested. For problems of emphasized transonic and compressible character of a flow in rotating turbomachinery, commonly used test case is a transonic NASA Rotor 67 axial-flow turbofan, due to the availability of detailed experimental data provided by National Aeronautics and Space Administration (NASA). In order to perform numerical simulations of the NASA Rotor 67, a case needs to be prepared within the preprocessing steps which include geometry and mesh generation. As a first step, geometry in terms of 3D Computer Aided Design (CAD) model is generated using a Solidworks CAD software. The created CAD model is a basis for the second step - generation of a spatially discretised grid of finite volumes, which was done using a meshing software Pointwise. Since NASA Rotor 67 turbofan has 22 equally spaced blades, only one blade passage is examined in order to reduce computational cost. This can be done by using a special, cyclic and periodic boundary condition which require identical cyclic mesh boundaries. Because of highly twisted rotor blades and cyclic boundary condition requirement, generated mesh is commonly of insufficient quality. Thus, to avoid bad mesh quality and to carry out a simulation for a single blade passage, the General Grid Interface (GGI) is used within the foam-extend CFD package. GGI allows the use of the non-conformal mesh boundaries in order to overcome grid quality issues. After successfully accomplished preprocessing steps, a number of numerical simulations is performed with the so-called "frozen rotor" approach in order to assemble a performance curve for NASA Rotor 67 turbofan at the nominal angular velocity. Results are presented in terms of graphical representations of flow field quantities at various sections of the domain. Furthermore, overall computed turbofan characteristics like power, efficiency, mass flow and total pressure ratio are also shown. Additionally, a basic working principle of turbocompressors and turbofans is presented along with the restrictions for stable operating range. Furthermore, an overview of common instabilities which occur in turbocompressors is also given. Finally, the adequate formulation of a CFD model capable of solving turbulent, transonic and compressible flow is presented.

Izvorni jezik
Engleski

Znanstvena područja
Strojarstvo

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