Numerical study on the effect of blade surface deterioration by erosion on the performance of a large wind turbine

Abstract

As the demand for the development of onshore wind farms in areas with low wind speeds and large offshore wind farms increases, the size of the wind turbine and its rotor has also increased rapidly. An increase in the rotor diameter implies an increase in the relative wind velocity (with respect to each cross section in the radial direction of the blade) near the tip region of the blade. This in return accelerates the surface damage caused by the erosion of the leading edge, thereby increasing the frequency of maintenance and lowering competitiveness in the cost of energy. In this study, computational fluid dynamics (CFD) analysis was performed to analyze the correlation between the leading-edge erosion damage and output performance of the blade. CFD simulations were performed using a tip airfoil (NACA 64_618) and a full-scale wind turbine (NREL 5 MW) based on the state of erosion of discarded blades considering approximately 12 years of maintenance-free operation. The irregular erosion at the airfoil leading edge results in premature stall phenomena and reduces the aerodynamic efficiency. Thus, the accurate analysis of the flow separation point and flow change is necessary. Therefore, three-dimensional transient CFD analysis was performed to consider the complex flow generated on the blade surface. The erosion at the leading edge reduced the airfoil lift by up to 23% and drag by 100%, reducing the aerodynamic efficiency, which in effect reduced annual energy production by up to 4%.

Impact of turbulence and blade surface degradation on the annual energy production of small‐scale wind turbines

“…46 As occurs with turbulence-related effects, surface roughness issues can be addressed either empirically, through experimental tests 46,[48][49][50] and field-related data, [51][52][53] or via numerical simulations. 45,54,55 Nonetheless, roughness-accounting simulations are computationally demanding, and they usually require empiricallyderived data for reproducing the spatial and temporal distributions of roughness-inducing environmental agents. 45,54 The variable aerodynamic behaviour within the transitional region, coupled with the effects caused by turbulence and roughness, causes highly demanding fatigue loads and surface damages.…”

“…45,54,55 Nonetheless, roughness-accounting simulations are computationally demanding, and they usually require empiricallyderived data for reproducing the spatial and temporal distributions of roughness-inducing environmental agents. 45,54 The variable aerodynamic behaviour within the transitional region, coupled with the effects caused by turbulence and roughness, causes highly demanding fatigue loads and surface damages. The affected blades are required to undergo inspections and repairs, which are accounted as operation and maintenance (O&M) costs of the system.…”

“…Although the mentioned case corresponds to a LSWT device, accumulation and erosion patterns are acknowledged to have similar effects on SHAWTs, 46,47 with the power coefficient decreasing up to 23.7% and considering the additional handicap that the degraded blades are liable to produce acoustic emissions 46 . As occurs with turbulence‐related effects, surface roughness issues can be addressed either empirically, through experimental tests 46,48–50 and field‐related data, 51–53 or via numerical simulations 45,54,55 . Nonetheless, roughness‐accounting simulations are computationally demanding, and they usually require empirically‐derived data for reproducing the spatial and temporal distributions of roughness‐inducing environmental agents 45,54 …”

“…As occurs with turbulence‐related effects, surface roughness issues can be addressed either empirically, through experimental tests 46,48–50 and field‐related data, 51–53 or via numerical simulations 45,54,55 . Nonetheless, roughness‐accounting simulations are computationally demanding, and they usually require empirically‐derived data for reproducing the spatial and temporal distributions of roughness‐inducing environmental agents 45,54 …”

Leading edge topography of blades–a critical review

“…The computational fluid dynamics (CFD) method is one of the most widely used wind turbine blade simulation methods to accurately predict the boundary layer and various unsteady flow characteristics resulting from blade leading edge roughness [145][146][147][148]. The experiments were conducted mainly using a pre-designed model of the damaged wing installed in a wind tunnel, where the leading edge damages were simulated based on the measurements of ex-serviced turbine blades [149,150].…”