Rotor blade twist

Adaptronics for rotorcraft was very much driven by concepts in the early 1990s looking at rotor blade twist to improve aerodynamic performance as well as reduction of the negative drawbacks of lead lag damping. Individual blade control has become key in rotorcraft technology and it became quickly... 

The rotor blades shall be of the tapered/twisted, free vortex, reaetion design (Figure 5-21). The blades shall be speeifieally designed for the dirty FCC flue gas applieation. Seller shall provide a Goodman Diagram for the highest stressed loeation... 

Cesnik, C.E.S. Shin, S.J. and Wilbur, M.L. Dynamic response of active twist rotor blades. Smart Mater. Struct., 10 (2001), pp. 62-76... 

Fig. 2.9. Scaled active twist rotor blade with piezoelectric fiber composite patches attached to the spar fi om Cesnik [44].

All the results shown above have been calculated for a fiber volume fraction 1/ = 0.475. This value represents the optimum for the direct twist actuation and is very close to the optima of the other schemes. In Figure 10.10, the dependence of tip twist as well as layer orientation and thickness is exemplarily depicted for the direct twist scheme. The layer thickness Hi therein is obtained by taking the formulation for one of the exactly preserved stiffness coefficients of the example rotor blade, see Remark 10.8 and Table 10.3, supplying it with all the known constitutive and configurative data, and solving it for the required value. As obvious here but applicable also for the other cases, it is found that the influence of the fiber volume fraction is rather good-natured, confirming the calculations with a collective value of the fiber volume fraction. 

P.C. Chen, I. Chopra, Hover testing of smart rotor with induced-strain actuation of blade twist. AIAA J. 35(1), 6 16 (1997)... 

D.H. Hodges, E.H. Dowell, Nonlinear equations of motion for the elastic bending and torsion of twisted nonuniform rotor blades. NASA Technical Note NASA TN D-7818, National Aeronautics and Space Administration, Washington DC (1974)... 

Veloeity triangles at the mean seetion of the blading are to be submitted by the Seller. The blading shall be designed to minimize blade erosion eaused by tlie partieulate entrained in the flue gas witli tapered and twisted rotor and stator airfoils. The blade design used shall have at least tliree years of sueeess-ful operating time in FCC serviee for tlie frame proposed. 

C.E.S. Cesnik, S. Shin, W.K. Wilkie, M.L. Wilbur, P.H. Mirick, Modeling, design, and testing of the NASA/Army/MIT active twist rotor prototype blade, in Proceedings of the American Helicopter Society 55th Annual Forum (AHS, Montreal, 1999). 

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