Aerodynamic Design System for Non-Axisymmetric Boundary Layer Ingestion Fans

Non-uniformities at the engine inlet call for novel design techniques to cater to the performance and aeromechanical challenges. The purpose of the fan system is to mitigate the effects of distortion in the flow and to provide thrust to the vehicle. This paper discusses a harmonic based open source design system (NAX) and demonstrates its capabilities for applications in a boundary layer ingesting fan system. First, a primary baseline design was obtained using a typical axisymmetric design approach for the rotor and OGV (Outlet Guide Vanes). This baseline design now serves as the basis for further development, based on user-defined design features. Subsequently, using this baseline design, a circumferentially non-axisymmetric design of the OGV is obtained by means of inducing perturbations in blade leading edge metal angles using Fourier coefficients and phase values. The other parameters that can be varied radially as Bezier curves and tangentially as Fourier modes are: trailing edge metal angle, chord, lean, sweep, curvature and thickness. A smooth spanwise curvature controlled 3D design of OGV is discussed using the open-source geometry generator, T-Blade3. The OGV geometry files along with the detailed documentation are also available for download on the T-Blade3 website and NAX source code on Github website. This design is further optimized to improve the non-axisymmetric geometric distribution against the distorted flow conditions. The design system proposed here helps in exploration of user-specified parametric design space for development of a non-axisymmetric fan stage. Further, since the design system is modular in nature, it can easily be integrated at multiple process levels for other types of turbomachinery design applications.