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How fast is the air?

Measuring systems from Althen at Windenergy Hamburg

11 August 2022
How fast does air move, what do different wind conditions do to wind turbines and how does knowledge about air pressure help to find the optimal rotor geometry? Althen will be showing various applications for measurement technology in the wind industry at Windenergy 2022 in Hamburg. Aerodynamics has long been a key topic for sensor and measurement technology specialist Althen, as have offshore applications and renewable energies in general.

When a rotor starts to turn is largely determined by its geometry. In rotor design, work is being done to make ever better use of the available air flow. In order to measure the rotor blades and the behaviour of the air pressure as a function of rotational speed and air velocity, the multiple pressure scanner (MPS) pressure measurement technology is the ideal solution. Pressure scanners help to optimise aerodynamics. For this purpose, small holes are made in the rotor blade. Air hoses are connected to these holes via pressure patches, which in turn are connected to the MPS4264. The Althen pressure scanner MPS64 measures small to medium pressures (4 millibar to 3.5 bar) with a very good accuracy of up to ±0.04 %. Its 64 measuring channels are housed in a casing barely the size of a cigarette packet. The MPS64 has an Ethernet interface for cascading. Via a switch, it is possible to connect any number of scanners, for example in a master-slave operation. The sensor technology is designed for temperatures of 0 - 70 °C, a thermal protection housing allows operation even in frost or higher temperatures.

A coordinate system of the air

Computational models reach their limits when it comes to concrete aerodynamic conditions, for example between the turbines of an offshore wind farm. The turbulences that arise here can best be mapped with a three-dimensional air velocity model.

For this purpose, a drone is equipped with a micro air data computer and a 5-hole pitot probe (pitch-yaw probe). The air speed is measured at fixed distances/measurement points.

The compact Micro Air Data Computer processes the measurement data obtained with the help of the probe and uses algorithms to generate wind speeds and wind directions (vectors). By combining the measurement results of each measurement point, a 3D image can then be generated.

Larger plants, more measurements

Strain gauges are versatile. Wherever rotation, torsion or other movements occur in structures, damage can be detected at an early stage with this measuring method. In a wind turbine, from the statics in the base to the tower inclination and the acceleration of the generator pulpit, practically no element is unaffected by constant movement. At the same time, the development towards ever larger wind turbines requires more and more measurements.

Research also uses the procedure with strain gauges to test the behaviour of new materials. Especially in composites, where plastic meets metal, critical points arise whose stress level can be determined with strain gauges.

Althen at Windenergy Hamburg in Hall B7.FG, Stand 007

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