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Title: Performance of twist-coupled blades on variable speed rotors

Abstract

The load mitigation and energy capture characteristics of twist-coupled HAWT blades that are mounted on a variable speed rotor are investigated in this paper. These blades are designed to twist toward feather as they bend with pretwist set to achieve a desirable twist distribution at rated power. For this investigation, the ADAMS-WT software has been modified to include blade models with bending-twist coupling. Using twist-coupled and uncoupled models, the ADAMS software is exercised for steady wind environments to generate C{sub p} curves at a number of operating speeds to compare the efficiencies of the two models. The ADAMS software is also used to generate the response of a twist-coupled variable speed rotor to a spectrum of stochastic wind time series. This spectrum contains time series with two mean wind speeds at two turbulence levels. Power control is achieved by imposing a reactive torque on the low speed shaft proportional to the RPM squared with the coefficient specified so that the rotor operates at peak efficiency in the linear aerodynamic range, and by limiting the maximum RPM to take advantage of the stall controlled nature of the rotor. Fatigue calculations are done for the generated load histories using a range ofmore » material exponents that represent materials from welded steel to aluminum to composites, and results are compared with the damage computed for the rotor without twist-coupling. Results indicate that significant reductions in damage are achieved across the spectrum of applied wind loading without any degradation in power production.« less

Authors:
; ;
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
750209
Report Number(s):
SAND99-3103C
TRN: AH200007%%44
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: 19th ASME Wind Energy Symposium, Reno, NV (US), 01/10/2000--01/13/2000; Other Information: PBD: 7 Dec 1999
Country of Publication:
United States
Language:
English
Subject:
17 WIND ENERGY; HORIZONTAL AXIS TURBINES; AIRFOILS; WIND LOADS; STRESSES; OPERATION; A CODES; ENERGY EFFICIENCY; EQUIPMENT PROTECTION DEVICES

Citation Formats

Lobitz, D W, Veers, P S, and Laino, D J. Performance of twist-coupled blades on variable speed rotors. United States: N. p., 1999. Web.
Lobitz, D W, Veers, P S, & Laino, D J. Performance of twist-coupled blades on variable speed rotors. United States.
Lobitz, D W, Veers, P S, and Laino, D J. 1999. "Performance of twist-coupled blades on variable speed rotors". United States. https://www.osti.gov/servlets/purl/750209.
@article{osti_750209,
title = {Performance of twist-coupled blades on variable speed rotors},
author = {Lobitz, D W and Veers, P S and Laino, D J},
abstractNote = {The load mitigation and energy capture characteristics of twist-coupled HAWT blades that are mounted on a variable speed rotor are investigated in this paper. These blades are designed to twist toward feather as they bend with pretwist set to achieve a desirable twist distribution at rated power. For this investigation, the ADAMS-WT software has been modified to include blade models with bending-twist coupling. Using twist-coupled and uncoupled models, the ADAMS software is exercised for steady wind environments to generate C{sub p} curves at a number of operating speeds to compare the efficiencies of the two models. The ADAMS software is also used to generate the response of a twist-coupled variable speed rotor to a spectrum of stochastic wind time series. This spectrum contains time series with two mean wind speeds at two turbulence levels. Power control is achieved by imposing a reactive torque on the low speed shaft proportional to the RPM squared with the coefficient specified so that the rotor operates at peak efficiency in the linear aerodynamic range, and by limiting the maximum RPM to take advantage of the stall controlled nature of the rotor. Fatigue calculations are done for the generated load histories using a range of material exponents that represent materials from welded steel to aluminum to composites, and results are compared with the damage computed for the rotor without twist-coupling. Results indicate that significant reductions in damage are achieved across the spectrum of applied wind loading without any degradation in power production.},
doi = {},
url = {https://www.osti.gov/biblio/750209}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Dec 07 00:00:00 EST 1999},
month = {Tue Dec 07 00:00:00 EST 1999}
}

Conference:
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