Optimisation of Ducted Propellers for Hybrid Air Vehicles Using High-Fidelity CFD

• Published in: Aeronautical journal Vol. 120; no. 1232; pp. 1632 - 1657
• Main Authors: Biava, M., Barakos, G. N.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.10.2016
• Subjects: Aerodynamics; Aircraft; Airspeed; Algorithms; Computational fluid dynamics; Computational physics; Computer simulation; Efficiency; Fluid dynamics; Fuel consumption; Geometry; Hybrid vehicles; Iterative methods; Mathematical models; Methods; Navier-Stokes equations; Numerical analysis; Optimization; Propulsive efficiency; Restarting; Reynolds averaged Navier-Stokes method; Reynolds number; Shrouded propellers; Software; Turbulence models; Variables; Vehicles; optimisation; ducted propellers; Hybrid air vehicles; computational fluid dynamics; adjoint method
• ISSN: 0001-9240; 2059-6464
• DOI: 10.1017/aer.2016.78

This paper presents performance analysis and design of ducted propellers for lighter-than-air vehicles. High-fidelity computational fluid dynamics simulations were first performed on a detailed model of the propulsor, and the results were in very good agreement with available experimental data. Additional simulations were performed using a simplified geometry, to quantify the effect of the duct and of the blade twist on the propeller performance. It was shown that the duct is particularly effective at low flight speed and that the blades with relatively high twist have better performance over the flight envelope. Design of the optimal twist distribution and of the duct shape was also attempted by coupling the flow solver with a quasi-Newton optimisation method. Flow gradients were computed by solving the discrete adjoint of the Reynolds-averaged Navier-Stokes equations using a fixed-point iteration scheme or a nested Krylov method with deflated restarting. The results show that the ducted propeller propulsive efficiency can be increased by 2%.