Aeroelastic tailoring in wind-turbine blade applications

This paper reviews issues related to the use of aeroelastic tailoring as a cost-effective, passive means to shape the power curve and reduce loads. Wind turbine blades bend and twist during operation, effectively altering the angle of attack, which in turn affects loads and energy production. There are blades now in use that have significant aeroelastic couplings, either on purpose or because of flexible and light-weight designs. Since aeroelastic effects are almost unavoidable in flexible blade designs, it may be desirable to tailor these effects to the authors advantage. Efforts have been directed at adding flexible devices to a blade, or blade tip, to passively regulate power (or speed) in high winds. It is also possible to build a small amount of desirable twisting into the load response of a blade with proper asymmetric fiber lay up in the blade skin. (Such coupling is akin to distributed {delta}{sub 3} without mechanical hinges.) The tailored twisting can create an aeroelastic effect that has payoff in either better power production or in vibration alleviation, or both. Several research efforts have addressed different parts of this issue. Research and development in the use of aeroelastic tailoring on helicopter rotors is reviewed. Potential energy gains as a function of twist coupling are reviewed. The effects of such coupling on rotor stability have been studied and are presented here. The ability to design in twist coupling with either stretching or bending loads is examined also.

[1]  H. Currin,et al.  North Wind 4kW passive control system design , 1981 .

[2]  Palmer Carlin.  Analytical expressions for maximum wind turbine average power in a Rayleigh wind regime , 1997 .

[3]  A. H. P. Swift,et al.  Dynamics of an experimental two bladed horizontal axis wind turbine with blade cyclic pitch variation , 1981 .

[4]  S. M. Rock,et al.  Effects of Blade Bending on Aerodynamic Control of Fluctuating Loads on Teetered HAWT Rotors , 1995 .

[5]  Inderjit Chopra,et al.  Aeroelastic optimization of a helicopter rotor , 1989 .

[6]  R. E. Hutton,et al.  Effect of Spanwise and Chordwise Mass Distribution on Rotor Blade Cyclic Stresses , 1956 .

[7]  P. W. Carlin,et al.  Results from the NREL Variable-Speed Test bed , 1998 .

[8]  P. Shanthakumaran,et al.  Aeroelastic tailoring of rotor blades for vibration reduction in forward flight , 1983 .

[9]  G. W. Bottrell,et al.  Passive cyclic pitch control for horizontal axis wind turbines , 1981 .

[10]  R. B. Taylor,et al.  Helicopter Vibration Reduction by Rotor Blade Modal Shaping , 1982 .

[11]  Inderjit Chopra,et al.  Design sensitivity analysis for an aeroelastic optimization of a helicopter blade , 1987 .

[12]  J. L. Tangler,et al.  NREL airfoil families for HAWTs , 1995 .

[13]  Peretz P. Friedmann,et al.  Development of a structural optimization capability for the aeroelastic tailoring of composite rotor blades with straight and swept tips , 1992 .

[14]  P. C. Klimas.  Tailored airfoils for Vertical Axis Wind Turbines , 1984 .

[15]  Inderjit Chopra,et al.  Structural behavior of two-cell composite rotor blades with elastic couplings , 1991 .

[16]  E. Smith,et al.  Formulation and evaluation of an analytical model for composite box-beams , 1991 .

[17]  Inderjit Chopra,et al.  Experimental and theoretical analysis of composite I-beams with elastic couplings , 1991 .

[18]  Inderjit Chopra,et al.  Aeroelastic optimization of a composite helicopter rotor , 1992 .

[19]  Charles A. Gates,et al.  Investigation of Helicopter Blade Flutter and Load Amplification Problems , 1957 .

[20]  Roberto Celi,et al.  Optimum design of helicopter rotors for longitudinal handling qualities improvement in forward flight , 1989 .

[21]  L. A. Schmit,et al.  NEWSUMT: A FORTRAN program for inequality constrained function minimization, users guide , 1979 .

[22]  R. H. Blackwell,et al.  Blade Design for Reduced Helicopter Vibration , 1983 .

[23]  Inderjit Chopra,et al.  Aeroelastic Tailoring of Composite Couplings and Blade Geometry of a Helicopter Rotor Using Optimization Methods , 1997 .

[24]  Peretz P. Friedmann,et al.  Structural optimization with aeroelastic constraints of rotor bladeswith straight and swept tips , 1988 .

[25]  Peretz P. Friedmann,et al.  Optimum design of rotor blades for vibration reduction in forward flight , 1984 .

[26]  George W. Brooks,et al.  A dynamic-model study of the effect of added weights and other structural variations on the blade bending strains of an experimental two-blade jet-driven helicopter in hovering and forward flight , 1955 .

[27]  M. C. Cheney,et al.  Self-regulating composite bearingless wind turbine☆ , 1978 .

[28]  R. H. Miller,et al.  Helicopter Blade Vibration and Flutter , 1956 .

[29]  R. Bielawa,et al.  Techniques for stability analysis and design optimization with dynamic constraints of nonconservative linear systems , 1971 .

[30]  P. G. Migliore,et al.  ENHANCED PERFORMANCE OF HAWTS USING ADAPTIVE BLADES , 1996 .

[31]  Mark W. Davis,et al.  Application of Design Optimization Techniques to Rotor Dynamics Problems , 1986 .