An experimental and numerical study of the performance of a model turbine

Abstract

The performance of a 0.9 m diameter model wind turbine using the National Renewable Energy Laboratory S826 airfoil profile has been investigated both experimentally and numerically. The geometry was laid out using blade element momentum (BEM) theory, and a detailed description of the geometry is given here. The design was tested experimentally and gave a peak power coefficient of C P D 0:448 at the design tip speed ratio of D 6. After the model tests had been undertaken, numerical calculations were performed by means of fully three-dimensional computational fluid dynamics (CFD) simulations using a k ! turbulence model. It was found that the BEM correctly predicts the shape of the power and thrust coefficient curves, with the efficiency coefficient virtually identical to the measurements at the design conditions. At higher tip speed ratios, the performance is over-predicted. The estimated thrust was, however, consistently too low by a shift of the order of C T 0:1 in the normal operating tip speed range. The high-resolution CFD predictions (using about 3:5 10 6 grid points) reproduced the model thrust coefficient almost perfectly, and the predicted power coefficients were also very close to the measurements, although the agreement with the measurements at high tip speed ratios were only marginally better than those from the BEM method. At the design tip speed ratio, the CFD over-predicted the power coefficient by merely 2%. The good agreement between the measured and computed performance at model scale assures that accurate predictions of turbine performance at full-scale conditions are also possible with high-resolution CFD.

Wind Turbine Modeling for Computational Fluid Dynamics: December 2010 - December 2012

“…We have performed a validation of the actuator line model (ALM) that compares the numerical results with the experiments done at the low-speed closed-return wind tunnel at the Department of Energy and Process Engineering at the Norwegian University of Science and Technology, Trondheim [26] [27]. The tunnel has a test section of 1.85 meters (m) (height) × 2.71 m (width) × 11.15 m (length).…”

FD Wake Modelling with a BEM Wind Turbine Sub-Model

“…For this low TSR which is half of the optimal design TSR of the model wind turbine, see Krogstad and Lund (2012), the boundary layer on the blades separates and stalling occurs, decreasing the ratio between lift and drag. Taking out the angle of attack from the BEM procedure used for the given inlet velocity (10 m/s) and relative turbulence intensity 0.3% the angles of attack for the 18 elements used are all, with exception of the tip element, in the stall range, see α(ii) in Table 2 and airfoil data in Figure 18 and Figure 19.…”

“…In the figures comparing the simulations with experiments x/D is the non-dimensional distance down- The power and thrust coefficients generated by the BEM theory are given in Figure 16 and Figure 17 where they are compared with experimental values given in Krogstad and Lund (2012).…”

“…The TSR=6 is the design TSR of the wind turbine blades, see Krogstad and Lund (2012), and for the wind speed 10 m/s the wind turbine model is operating below or at rated speed. In this case the boundary layer on each blade stays attached to the blade.…”

Validation of the actuator disc approach using small-scale model wind turbines

“…1. 80, 4.50, 6.30 and 8.10 m. Further information on the details of the experimental investigations are reported by Krogstad and Adaramola (2012) and Krogstad and Lund (2012).…”