Case RB rotor blade validation

The RB-70 rotor blade has been developed by Polymarin for wind turbines measuring 70 m in diameter with a rated power of 1.5 MW. The tested blade, however, has a length of 28.75 m since a part of the tip has been removed [28]. The natural frequencies of this rotor blade have been determined from hand-excited displacement measurements carried out by the Stevin Laboratory (SL-DUT), as well as by a modal

3 20

5 10

UJ 0

Figure 4.10: The relative errors for the first three flap and first two lead-lag eigenfre-quencies of the RB-51 rotor blade as function of the number of superelements Nse. Dashed-dotted horizontal lines: + 2% and - 2% error bound respectively.

analysis carried out by TNO under contract of Delft University of Technology [124]. In the first column of Table 4.6 the resulting differences between the two methods are listed. It can be concluded that the differences are small. The right column shows the comparison of the eigenfrequencies calculated by MARC relative to both the TNO and SL-DUT measurements. The prediction in flap direction is worse than the prediction in lead-lag direction.

RB-70 rotor blade

Mode

Difference SL-DUT w.r.t. TNO measurements

Difference MARC w.r.t. TNO (SL-DUT) measurements

1si flap 1si lead-lag

2 nd flap 2 nd lead-lag

- 1.4% + 1.2% + 0.2% + 0.6%

- 1.5% (-2.1%)

Table 4.7: Comparison of eigenfrequencies determined from the displacement measurements performed by the Stevin Laboratory of Delft University of Technology (SL-DUT) to the ones resulting from the modal analysis performed by TNO (left) and comparison of the eigenfrequencies calculated by MARC relative to both the TNO and SL-DUT measurements (right) [124].

Table 4.7: Comparison of eigenfrequencies determined from the displacement measurements performed by the Stevin Laboratory of Delft University of Technology (SL-DUT) to the ones resulting from the modal analysis performed by TNO (left) and comparison of the eigenfrequencies calculated by MARC relative to both the TNO and SL-DUT measurements (right) [124].

2nd Flap

1st Flap

1st Lead-Lag

2nd Lead-Lag

The errors for the first three flap and first two lead-lag eigenfrequencies of the RB-70 rotor blade are plotted relative to the TNO measurements as function of the number of superelements in Fig. 4.11. The first flap mode is predicted very accurately. For Nse = 6, the bias of the first, second and third mode in flap and lead-lag direction are —0.1 %, 6.2 % and 7.8 % respectively, while the bias of the first and second mode in lead-lag direction are 9.3% and 12.3% respectively.

2nd Lead-Lag

2nd Flap

2nd Flap

1st Flap

1st Lead-Lag

Figure 4.11: The relative errors for the first three flap and first two lead-lag eigenfre-quencies of the RB-70 rotor blade as function of the number of superelements Nse. Dashed-dotted horizontal lines: + 2% and - 2% error bound respectively.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

Get My Free Ebook


Post a comment