Unlike conventional hydro and tidal barrage installations, water current turbines in open flow can generate power from flowing water with almost zero environmental impact, over a much wider range of sites than those available for conventional tidal power generation. Recent developments in current turbine design are reviewed and some potential advantages of ducted or “diffuser-augmented” current...

Ducted wind turbines are a kind of small wind turbine having a diffuser or any other shape around the rotor which increases the air flow through the blades and absorbs more power. In the present study, a small wind turbine was ducted with a relatively simple ring and its performance was investigated in a wind tunnel. The duct is shaped using rolling steel sheets on a sloping surface and finally...

An incompressible potential-flow vortex method has been constructed to analyze the flow field of a ducted wind turbine following that outlined by Lewis (1991). Attention is paid to balancing the momentum change in the flow to the total longitudinal forces acting on the duct-turbine combination: the pressure force on the actuator disk plus the pressure forces acting on the duct, which typically ...

The present study aimed at assessing a novel annular-ducted fan lift system for VTOL aircraft through computational fluid dynamics (CFD) simulations. The power and lift efficiency of the lift fan system in hover mode, the lift and drag in transition mode, the drag and flight speed of the aircraft in cruise mode and the pneumatic coupling of the tip turbine and jet exhaust were studied. The resu...

This paper presents a combined blade element (BE), computational fluid dynamics (CFD) method for performance analysis and optimization of ducted turbines. The model is similar to standard blade element momentum theory, except that CFD replaces the momentum equation for determining the induction factors. This eliminates many assumptions used in applying the typical blade element momentum (BEM) t...

This paper studies the effects of viscous loss, flow separation and base pressure for ducted turbine designs using computational fluid dynamics (CFD) simulation. Analytical model coefficients for inlet and diffuser efficiency and base pressure coefficient parameterize these effects and have been identified from CFD results. General trends are: the inlet efficiency is nearly unity for the simula...

In this multidisciplinary study a geared open rotor configuration is assessed and compared to an ultra high bypass ratio geared turbofan engine. Both designs assume a 2020 entry into service level of technology. The specific thrust level for minimizing block fuel and the resulting engine emissions for a given mission is sought. The tool used contains models that effectively capture: engine perf...