Aerodynamic testing

LM Wind Power’s wind tunnel is tailor-made for testing of airfoils for wind turbines. This sophisticated test facility allows our team of aerodynamic scientists and engineers a world-exclusive opportunity to conduct tests, 24 hours a day, 365 days a year, at test conditions that match the operation conditions for large Megawatt size blades. See a short presentation video of LM Wind Power’s wind tunnel.

By having unlimited access to a wind tunnel, we can work on all aspects of aerodynamic design. The wind tunnel is custom-made for testing wind turbine blades, delivering extremely high precision in our measurements. The speeds and the size of the test section are designed to reproduce dynamic operating conditions, for example starting from stall with varying angles of incidence. This allows us to examine different solutions for actively controlling the loads, for example by using flaps.

Wind tunnel design

The airline was designed with a closed return loop and a contraction ratio of 10:1. A honeycomb and turbulence screen help to ensure a high flow quality in the test section. A cooling system can remove the entire excess heat from the maximum fan power of 1 MW. The test section dimensions are 1.35 m width, 2.70 m height and 7 m length. This gives very little blockage and only limited streamline curvature for an airfoil model with a 900 mm chord.

Test setup

The test setup for the airfoil model involves a high accuracy turn table device for holding the airfoil model and an automatic traverse system holding a wake rake. In total almost 300 sensors are used to characterize the airfoil flow including differential pressure sensors and a load cell system. An automatic data acquisition system allows a high level of uniformity between different tests. The results from post processing of all sensors add additional 400 values.

Reynolds number

The results from the aerodynamic commissioning show that the maximum flow speed of 105 m/s could be obtained. This yields a maximum Reynolds number of more than 6 million for an airfoil model with a chord of 900 mm.

Facts:

Closed return system
Test section dimensions: (w) x (h) x (l): 1.35 m × 2.70 m × 7 m
Wind speed: 375 km/hour or Mach 0.3
Fan power: 1000 kW
Low turbulence
Reynolds number: 6 million for an airfoil with 0.90 m chord
Constant temperature control