Date of Award

8-2013

Document Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering

Department

Aerospace Engineering

Committee Chair

Dr. Sathya Gangadharan

First Committee Member

Dr. Reda R. Mankbadi

Second Committee Member

Dr. Nagendra Somanath

Abstract

A multidisciplinary design analysis optimization (MDAO) process is defined for a composite wind turbine blade to optimize its aerodynamic and structural performance by developing a fluid-structural interaction (FSI) system. The objectives are to maximize aerodynamic efficiency and structural robustness while reducing blade mass and total cost. In the previous research, a MDO process of a composite wind turbine blade has been pioneered as an effective process to develop structurally optimized blade design. Present MDAO process is defined in conjunction with structural and aerodynamic performance of the blade which is divided into three steps and the design variables considered are related to the shape parameters, twist distributions, pitch angle, material and the relative thickness based on number of composite layers at different blade sections. Maximum allowable tip deformations, modal frequencies and allowable stresses are set as design constraints. The results of the first step are aerodynamically optimal angle of attack of airfoils for the blade cross-sections along the blade span wise direction, and the uniform pressure distribution along the blade at maximum lift and wind conditions. Airfoil performance is predicted with 2D airfoils analysis, while 3D CFD analysis is performed by ANSYS CFX software. The second step yields optimal material, composite layup distribution of the blade and involves fluid structure interaction system hence actual pressure loads on the blade can be used for the structural analysis. A parameterized finite element model of the blade created in ANSYS ACP composite prepost and used to define the composite layups of the blade. At the last step, the results of the CFD and the structural analysis are used for the optimization process accompanied by the cost estimation to obtain a compromised solution between aerodynamic performance and structural robustness. For the MDAO process number of design of experiments (DOEs) is defined by G-optimality method and a response surface is created. Additionally, by consideration of maximum power output, minimum weight and cost as prior objectives, an optimal blade design is found within the pre-defined design variable parameters and structural constraints. Sensitivity analysis is performed to observe the impact of input parameter on each output parameters for enhanced control of the MDAO process. Further, to improve aerodynamic performance of the blade, new design approach with modified Tip (winglet) and rotor section is studied and substantial improvement in power generated over high quality baseline wind turbine blade is presented.

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