An Exploratory Study of Motion and Loads on Large Flap-Hinged Rotor Blades

The Path From Functional to Detailed Design of a Coning Rotor Wind Turbine Concept

“…Indeed, teetering of two-bladed machines is almost essential for viable performance [30,31], in the same way as hinges are required for successful helicopter designs [32]. A number of researchers have examined two and three-bladed machines with individual discrete flapping hinges [3,17,[33][34][35][36][37] or combined flexible hinging and teetering [38,39]. However, only the Carter machine has achieved any widespread deployment in the past.…”

“…Veers et al [42] provides a good overview of the static possibilities, and highlights the dynamic stability bounds and strict manufacturing tolerances required to practically execute such a strategy. Aerodynamic blade loading may be tailored with soft structures, most notably in the blades themselves, such as bend-twist coupling [24], flapping flexbeams [43], or by discrete flapping/teetering hinges [35]. All act to dynamically change the angle of attack at the blade sections by configurational change, so that negative feedback of load is achieved.…”

“…Lighter, cheaper blades then feed back to reduced edgewise gravitydominated loads, further reducing blade weight and cost. Recent commercial efforts [34] and research studies [35,45] have highlighted the effectiveness of flapping blades in this respect. Obviously, any design with significant flapping must have a downwind orientation, in order to avoid tower strike.…”

“…• Public acceptance and aesthetic studies have indicated this preference [3] • Lower optimal tip-speed ratios for on-shore siting issues • Aerodynamic performance loss for two-bladed rotors is significant [17] • Two blades are not necessarily cheaper than three when size (solidity) and loads are accounted for 7 • Cyclic rotating imbalance-type hub loads [35] should be less in a three-bladed rotationally symmetric flapping rotor The imbalance loads were not mentioned as significant in the original coning rotor work [33], but were in the twobladed flapping study [35]. The latter study also suggested high tip-speeds to maintain a relatively flat rotor (to keep energy capture high) with the potential for attendant dynamic instability resulting from the low-solidity rotors required.…”

Tower shadow induced blade loads for an extreme‐scale downwind turbine

“…Innovations that can reduce loads can allow for larger turbines, which generate more power and still allow for a decreased cost of wind energy. One such innovation is the downwind load‐aligned wind turbine . Downwind indicates the rotor is positioned downstream of the tower.…”