Abstract
In this study, the aerodynamic performance of a thick airfoil is analysed, after installing leading-edge roughness to emulate a severe state on the airfoil surface. The impact on aerodynamic coefficients has been quantified using two roughness methods: zig-zag tape and sandpaper. Wind tunnel tests are carried out at a Reynolds number of 3•106. At low angles of attack, zig-zag tape and sandpaper provide comparable lift and drag coefficients but significant variations of these coefficients are obtained for high angles of attack. Stalled flow is the cause of the most significant variation on the airfoil performance between smooth and rough surface states. Vortex generators are adapted to recover the lift coefficient value previously given by the airfoil under smooth conditions. As a result, vortex generators are able to reduce the loss of lift and the sensitivity of the airfoil to the rough state.
Highlights
The exposure of a Horizontal Axis Wind Turbine (HAWT) to atmospheric and environmental conditions substantially alters the designed performance of the machine
The increase in boundary layer thickness is reflected by the CD value which was mostly increased in the positive angle of attack (AoA) range
The presented work is focused on evaluating the aerodynamic impact variation of a 30% thick airfoil produced by different roughness testing methods
Summary
The exposure of a Horizontal Axis Wind Turbine (HAWT) to atmospheric and environmental conditions substantially alters the designed performance of the machine. Different sources of surface deterioration and erosion have been reported by insects, hail, sand grains, etc Their combination determines a modification of the blade surface from its design geometry. A reduction of annual energy production (AEP) is obtained along with a direct increase in the cost of energy (COE) As it is highlighted by Erhmann [1], the amount of power loss depends on the wind turbine controller scheme. The resulting lift loss produces a power regulation only dependant on the blade aerodynamics which can be significantly affected by the presence of roughness. This type of wind turbines experiences power losses of the order of 25% as it was measured by Corten [2] due to insects depositions on a 700kW wind turbine blade. Erhmann [1] demonstrated that pitch regulation reduces the roughness impact on power production, as the main power losses were found in the quadratic power curve region
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