Abstract
Ice accumulation on the blade of a wind turbine surface seriously threatens the operational safety of the turbine; therefore, the research on this problem is very important. In this paper, a new similarity criterion of icing shape for a rotational model was proposed based on the similarity criterion for translational motion models in the aviation field, and experimental studies on the similarity of the rotational model icing were carried out. To validate the similarity criterion, icing wind tunnel tests were carried out with aluminum cylinders with diameters of 40 mm and 20 mm. Key parameters for the experiment, such as wind speed, temperature, liquid water content, medium volume diameter, and test time, were selected based on the criterion. All the icing tests were carried out in a new self-designed icing wind tunnel test system based on natural low-temperature conditions. The icing shapes observed in the tests were confirmed after many repetitions. To quantitatively analyze the similarity between different sizes of ice shapes, a dimensionless method for evaluating the similarity of ice shapes of different sizes was defined based on the typical characteristics of ice shapes. The research results show that the similarity score between two sizes of ice shapes under different test conditions is 81%~90%. The accuracy and applicability of the icing shape similarity criterion were thus validated. The research results in this paper lay a theoretical and experimental foundation for exploring the icing shape similarity of a rotating model.
Highlights
A wind turbine, when operating in low-temperature and humid environments, collides with supercooled water droplets in the air
Well-known icing similarity criteria for translational motion models include the AEDC criterion proposed by the American Arnold Engineering Development Center (AEDC) and the ONERA criterion proposed by the French Space Agency [15, 16]
According to the selection principle of the experimental parameters of the icing shape similarity criterion, the experimental parameters of the subscale sample were selected and calculated as follows: (1) characteristic length dm was 20 mm; (2) subscale ratio κ was 1/2; (3) experimental wind velocity vm was 10 m/s, which was the same as vf ; (4) experimental temperature Tm was -15°C; (5) experimental environment pressure Pm was 101325 Pa, which was calculated by formula (23); (6) medium volume diameter ðMVDÞm was 50 μm, which was calculated by formula (21); (7) liquid water content ðLWCÞm was 0.58 g/m3, which was calculated by formula (22); (8) test time tm was 6 min, which was
Summary
A wind turbine, when operating in low-temperature and humid environments, collides with supercooled water droplets in the air. The methods of researching icing characteristics include icing wind tunnel tests and numerical simulation [11,12,13]. Few studies on the icing similarity theory of rotating models, such as wind turbine blades, have been carried out. As the icing similarity theory of aircraft wings is relatively well developed, based on the static icing similarity theory of wings, this paper discusses the droplet trajectory, impact characteristics, surface impact water quantity, and heat mass transfer characteristics of wind turbine blade icing under rotating conditions and develops a set of universal dynamic and static icing similarity criterion. Research on the similarity criterion of icing shape on a rotating cylinder surface under rime ice conditions was carried out. The significance of this study lies in the establishment of a novel icing shape similarity theory and the formation of icing experimental methods for further exploring the icing characteristics of rotary machines in the future
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