Master thesis and internship[BR]- Master's thesis : Design and analysis of a ducted fan propulsion system for a prototype ultralight aircraft[BR]- Internship

Abstract

This thesis focuses on the design and analysis of a ducted fan propulsion system for the Mindus Belvedere ultralight aircraft. The aim is to design the rotor and stator of the ducted fan system according to specific aerodynamic performance requirements and to analyze the aerodynamic behavior of the system during cruise flight using Computational Fluid Dynamics (CFD).

The design phase involved the use of a reversed Blade Element Method (BEM) to determine the rotor and stator configurations, with a comparison of two airfoils, NACA 2412 and NACA 65-210. The NACA 65-210 was ultimately selected. The design was validated by a performance analysis, made using a BEM implemented in MATLAB and the DFDC (Ducted Fan Design Code) software. The analysis confirmed that the selected airfoil provides optimal thrust and efficiency, with good performance across varying operational conditions.

A CFD study was then conducted using an actuator disk to simulate the rotor, first in axisymmetry and then in two dimensions. The axisymmetric analysis revealed that the duct contributed with additional thrust at the design point. A more accurate representation of the thrust performances of the rotor could be made, using a more realistic axial velocity inside the duct than in the design phase. The analysis also highlighted how this axial velocity differed from the flight velocity, especially at low speeds and low collective pitch angles, affecting overall performance. The contribution of the duct to the thrust could be computed and appeared to be positive at lower flight velocity and negative at higher flight velocity.

Additionally, the two-dimensional analysis revealed significant variations in velocity and mass flow in the upper and lower part of the duct. A zone of turbulence and a zone of zero-magnitude velocity was found in the lower part of the duct. This flow distortion could lead to negative impact on the engine performance and structural problems.