Investigation on the aerodynamic properties of LM62 blade using blade element momentum theory by DNV/Risø and GH Bladed

Abstract The 5.0 MW permanent magnet direct-drive wind turbine generator, with a rated rotational speed of 11.64 rpm, features three (3) LM 62 blades. The turbine blades are suitable for an IEC Class II wind turbine generator. The rotor radius measures 63.7 m with a distance of 1.7 m from the hub centre to the rotor shaft Jlange. An aerodynamic analysis of the LM 62 blade was performed to examine the power output and power coefJicient at wind speeds ranging from 3.0 m/s to 25.0 m/s using the Blade Element Momentum Theory suggested by DNV/Risø and derived from GH Bladed. The blade includes Jive airfoils with a design tip speed ratio of 8.65. Axial and tangential induction factors, lift and drag coefJicients, aerodynamic forces, and torque proJiles as normalized rotor blade length functions were calculated and compared with two BEM models. Discrepancies in the induction factors appear in the inboard section of the blade. The results show that the two BEM models are nearly identical when the upstream wind speed exceeds 11.18 m/s. A Student’s t-test compared the power curves predicted by both BEM models with those from the GH Bladed software. The GH Bladed BEM model had a correlation coefJicient of 0.998 and a t-value of 1.4139, which is below the critical t-value when compared to the GH Bladed software output. This indicates that the power curves are statistically similar with over 95% conJidence. The sound power level of the LM62 blade was found to be 103 dB at rated wind speed.