Optimisation of ducted propellers for hybrid air vehicles using high-fidelity CFD

摘要

This paper presents performance analysis and design of ducted propellers for lighter-than-air vehicles. High-\udfidelity CFD simulations were first performed on a detailed model of the propulsor, and the results were in very\udgood agreement with available experimental data. Additional simulations were performed using a simplified\udgeometry, to quantify the effect of the duct and of the blade twist on the propeller performance. It was shown\udthat the duct is particularly effective at low flight speed, and that the blades with relatively high twist have\udbetter performance over the flight envelope. Design of the optimal twist distribution and of the duct shape was\udalso attempted, by coupling the flow solver with a quasi-Newton optimisation method. Flow gradients were\udcomputed by solving the discrete adjoint of the Reynolds Averaged Navier–Stokes equations using a FixedPoint\udIteration scheme or a nested Krylov method with deflated restarting. The results show that the ducted\udpropeller propulsive efficiency can be increased by 2%.