EU-Horizon 2020 project titled MUSIC-haic aimed at furthering the understanding of ice crystal icing (ICI). Within the scope of this project we at TU Braunschweig provided experimental data to not only enable calibration and development but also validation of numerical models. At the end of the project we provided a comprehensive results that allowed simulating icing phenomenon usable for design and certification purposes. We focused on the fundamentals of icing physics studying inception, origins, heat transfer and quantitative analysis of ice crystal accretion and shedding phenomena. In addition to that we developed machine learning models for predicting particle fragmentation thresholds. Additionally, dedicated campaigns on characterizing the ice layers lead to better strength characterization and quantification of liquid water content, porosity and saturation of ice layers generated in the Braunschweig Icing Wind Tunnel. More details can be found on the official website, linked here.
Wind energy plays a crucial role in providing an environmentally friendly, reliable, and affordable energy supply. However, a major challenge in the operation of wind energy plants is ice formation on wind turbines, which is caused by freezing rain but also by the impact of supercooled water droplets - instruments, rotor blades, and nacelle are equally affected.
Ice accretion on the rotor blade poses the risk of ice shedding, which often requires a shutdown of the wind turbine for safety reasons. Even a small amount of ice leads to a loss of performance due to a reduction in aerodynamic efficiency, as well as an increase in maintenance costs and a reduction in the service life of the wind turbine due to the additional mechanical loads.
The icing-related losses of wind turbines vary greatly depending on climatic conditions and seasons. For example, losses of 8% (Canada, winter) and 10% or 50% (Scandinavia, annual average and winter, respectively) can occur. To reduce these losses, rotor blade heating systems are widely used nowadays. However, the heating systems' energy demand requires usually up to 5% of the wind turbine rated power.
To further increase the power production yield of future wind turbines and to reduce shutdowns due to icing, we have joined forces with the Landwind Group, Coldsense Technologies, and the Institute of Manufacturing Technology of the Technische Universität Dresden and initiated the research project: MicroIce.
The collaborative research project (MicroIce) investigates the effect of modified polymer films with superhydrophobic and ice-phobic properties, inspired by the lotus effect, on ice formation on wind turbine components.
The main goal of the project was to contribute with the physical understanding of splashing and to establish a high-quality database that describes this complex multiphase phenomenon. A flywheel experiment was designed in order to study the droplet impact at high velocity. Using this experiment, the impact of a single droplet can be simulated - as in the case of aircraft icing, vehicle fouling or wind turbine icing. Based on the experimental and numerical data generated, theoretical models were developed that allow to describe and predict the outcome of splashing for many technical processes.
More and more "atypical sites" need to be exploited by wind energy. Of these, icing sites represent a very attractive market with an estimated potential of 12 GW/year. However, these are associated with challenges that require technological and scientific solutions. Therefore, the development, deployment and validation of methods to predict and map ice accretion on rotor blades became necessary in the present project. To determine the aerodynamic characteristics of a wind turbine under icing conditions, it is necessary to know the airfoil polars that occur at the respective blade sections under different icing conditions. Polars are only accessible experimentally and can be generated, for example, in wind tunnel measurements. For the quantification of the response time and energy efficiency of the ENERCON blade heating and the development of new heating concepts, laboratory tests of the heating module under different icing conditions are essential, in addition to field tests.
This work focused on the further characterization of ice accretion in terms of porosity and roughness. The internal and external structure of the ice layers on an aero-engine nacelle model was studied with innovative measurements using micro-computed tomography. The porosity of the ice layer was quantified and the roughness was comprehensively described with a reduced set of parameters. Two algorithms were tested to produce synthetic ice accretions based on this set. The effect of the synthetic geometry on the airflow dynamics has proven to agree with the reference accretion. An improvement of the instruments used to model and to produce synthetic ice accretion geometries is therefore possible.
When exposed to deep convective clouds commercial aircrafts have been experiencing in-service events since the early 90's. Parts of the aircraft that are most afflicted and prone to mixed phase and glaciated icing are the heated probes and aircraft engines. High Altitude Ice Crystals (HAIC) project aimed at providing Acceptable Means of Compliance (numerical and test capabilities) and appropriate ice particle detection/awareness technologies for enhancing flying safety & control and aircraft certification.
Technical University of Braunschweig's participation in a 4-year integrated project aimed at providing experimental icing testing facilities to help calibrate and validate numerical models and tools. The project comprised 34 partners representing the European key stakeholders of aeronautical industry from 11 European countries and 5 partners from Australia, Canada and the United States. The project aimed at achieving TRL 6 and enhanced understanding of mixed phase and glaciated icing. Dr.-Ing. Arne Baumert was responsible for successful completion and contribution of TUBS towards the HAIC project.