Influence of Pitch, Twist, and Taper on a Blade’s Performance Loss due to Roughness

[+] Author and Article Information
J. L. Tangler

National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO 80401-3393

J. Sol. Energy Eng 119(3), 248-252 (Aug 01, 1997) (5 pages) doi:10.1115/1.2888027 History: Received September 01, 1996; Revised February 01, 1997; Online February 14, 2008


The purpose of this study was to determine the influence of blade geometric parameters such as pitch, twist, and taper on a blade’s sensitivity to leading edge roughness. The approach began with an evaluation of available test data of performance degradation due to roughness effects for several rotors. In addition to airfoil geometry, this evaluation suggested that a rotor’s sensitivity to roughness was also influenced by the blade geometric parameters. Parametric studies were conducted using the PROP93 computer code with wind tunnel airfoil characteristics for smooth and rough surface conditions to quantify the performance loss due to roughness for tapered and twisted blades relative to a constant-chord nontwisted blade at several blade pitch angles. The results indicate that a constant-chord nontwisted blade pitched toward stall will have the greatest losses due to roughness. The use of twist, taper, and positive blade-pitch angles all help reduce the angle-of-attack distribution along the blade for a given wind speed and the associated performance degradation due to roughness.

Copyright © 1997 by The American Society of Mechanical Engineers
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