Aerodynamic performance sensitivity analysis of blade design for a 100 kW HAWT

Wind energy is gaining ever increasing popularity among renewable energy sources. In some European countries installed wind turbine capacity has reached over 20 % of the total power generation capacity. This paper examines aerodynamic performance sensitivity of wind turbine blades for main design variables. The sensitivity analysis has been conducted on a sample 100 kW three-bladed horizontal axis wind turbine (HAWT). Taguchi robust design techniques and orthogonal arrays have been used to perform experimental optimization using five main parameters: airfoil NACA profile, root chord length, tip chord length, root radius and chord profile distribution along the blade’s length. The airfoil profiles and their aerodynamic data are taken from the NACA airfoil database for which experimental lift and drag coefficient data are available. The airfoils for the studied blades have the same profile from root to tip. Three sets of analyses have been performed according to three different base load wind speeds. The sensitivity results have been presented for the optimal tip speed ratio values

Evaluation of pressure-stiffness coupling in brush seals

Brush seals are comprised of fine diameter fibers densely packed between retaining and backing plates. To achieve seal compliance bristles are arranged to contact rotor with some lay angle. When axial pressure load is applied, bristles interlock and get stuck at the backing plate, and seal stiffness varies under operating conditions. Operating stiffness is critical to determine seal-rotor contact pressure and wear life. Typically, seal stiffness is measured by pressing a curved shoe to brush bore as reported in open literature. Due to the complex nature of pressure-stiffness bristle behavior, static and unpressurized measurements cannot represent actual working seal stiffness. This work presents a brush seal stiffness measurement system that is capable of measuring seal stiffness under working pressure and speed conditions. Rotor speed is achieved by an integrated spindle drive, while contact forces are measured via sensitive load cells. Rotor excursions are applied through lateral motions of the seal housing that is actuated by a motorized linear slide. Stiffness testing methodology and calibration procedure are discussed. Comparative experimental data are presented for both static pressurized and dynamic-pressurized stiffness tests

On the Virasoro Structure of Symmetry Algebras of Nonlinear Partial Differential Equations

We discuss Lie algebras of the Lie symmetry groups of two generically non-integrable equations in one temporal and two space dimensions arising in different contexts. The first is a generalization of the KP equation and contains 9 arbitrary functions of one and two arguments. The second one is a system of PDEs that depend on some physical parameters. We require that these PDEs are invariant under a Kac-Moody-Virasoro algebra. This leads to several limitations on the coefficients (either functions or parameters) under which equations are prime candidates for being integrable.Comment: Published in SIGMA (Symmetry, Integrability and Geometry: Methods and Applications) at http://www.emis.de/journals/SIGMA