Icing wind tunnel and detection of the formation of icing by heat crystallization

In the project SuLaDI (Supercooled Large Droplet Icing) research about the icing of aerofoils through large and super cooled droplets is done at the Institute of Composite Structures and Adaptive Systems (German Aerospace Center-DLR) and at the Institute of Adaptronics and Function Integration (Technische Universität Braunschweig). In the framework of the project an icing wind tunnel was built. It consists of a cooling chamber and a wind tunnel of the Eiffel-type therein. The icing of model takes place in the test section of the wind tunnel at temperatures below 0 °C. Between the flow straightener and the contraction section a spray system is built in, which sprays water droplets into the wind tunnel. The droplets are accelerated by the airstream and supercool on their way to the model. When hitting the model they freeze on it to rime ice, clear ice or mixed ice. At the model research about a structure integrated ice detection is done. This enables the detection of icing immediate at the place of formation. Adverse existing ice detection sensors, the sensor system can be manufactured without elements that are protruded into the airflow. The aerodynamics does not get influenced and corresponds to those without an ice detection sensor. This paper describes the structure of the icing wind tunnel and that of the sensor, and the method of ice detection through the heat of crystallization. The detection of the formation of ice is shown by measurements in the icing wind tunnel