Influence of wind turbine operation on the transport characteristics of dilute phase particles

Abstract: Severe weather has posed a great threat to safe production in a wind farm, such as sand storms and salt fog. The collision of dilute particles can inevitably cause some erosion on the surface of the blade under such weather conditions for a long time, leading to degrading the aerodynamic performance of the wind turbine. The wind turbine wakes can also determine the distribution and transport characteristics of dilute particles. The complex and diverse operating environment of offshore and onshore wind turbines can be often related to the flow field of dilute phase particles, such as salt fog, rain, and sand dust (the volume fraction less than 10-6). However, little is known about the interaction of the particles with wind turbine wakes. This study aims to characterize the transport behavior of dilute phase particles within the turbulent wake of a wind turbine under various weather conditions. A wind tunnel experiment was also carried out to establish the model of the wind turbine, where the wind was taken as the carrier fluid, and the sand as an inertial particle. Three groups of sand inflow with the particle size were ranged from 0 to 100 μm, >100 to 200 μm, and >200 to 300 μm after the standard sieve test. A measurement was made on the sand flux of sand particles at 1 d, 2 d, 3 d, 5 d, and 8d (d was the diameter of the rotor) after the plane of the wind turbine, and the sand flux at the placement where the wind turbine was installed. The results show that the wake vortex structure in the operation of the wind turbine was dominated the transport characteristics of sand dust after the original Gaussian distribution. The distribution of sand flux presented three peaks in the vertical direction, where the sand dust near the blade root height changed from the large to the small, and the sand flux near the blade tip height changed from the small to the large. Small spikes appeared at the blade both tip and root height, indicating the selective cluster of the wake vortex to the sand dust particles. There was a different influence of the wind turbine on the transportation of sand and dust with different particle sizes. At the blade tip height, there were a positive difference and the maximum of sand flux in a wind turbine under the particle size of >100-200 μm, indicating that the blade tip vortex was posed the greatest effect on the cluster of sand particles. At the blade root height, there was a negative difference of sand flux in a wind turbine, and the absolute maximum under the particle size of >100-200 μm, indicating that the interaction of central vortex and hub posed the greatest blocking effect on the transport of sand and dust with the particle size of >100-200 μm. At the tip of the blade, there was the largest difference of sand flux in a wind turbine under the particle size of >100-200 μm, followed by 0-100 μm, and the smallest of >200-300 μm, indicating that the tip vortex posed the strongest effect on the cluster of >100-200 μm, followed by 0-100 μm, and the smallest effect on >200-300 μm. The difference of sand flux decreased for the weak performance in a wind turbine, and the peak position of sand flux decreased, with the increase of transport distance, indicating the greater gravity settlement than the wake. There was the longest transportation distance of >100-200 μm particles, while the shortest of >200-300 μm particles in the sand flux of the wind turbine at the 8d section. In general, the wind turbine hindered the transport of sand dust, with the greatest hindrance on the >100-200 μm particle size, indicating the influence of wind turbine on the transport characteristics of sand dust. The finding can also provide a strong reference for the particle transport of salt fog.