风力机运行对稀相颗粒输运特性的影响

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

    • 摘要: 风力机的运行环境复杂多样,海上盐雾、雨滴、沙尘等(体积分数小于10-6)的稀相颗粒流场是当前海、陆风力机经常面临的工作环境,然而风力机运行对稀相颗粒输运特性的影响尚不明晰。该研究采用风洞试验的方法,研究风力机对稀相颗粒输运特性的影响规律。该试验中,风为载流体,沙粒作为惯性颗粒,分别测量了0~100、>100~200、>200~300 μm粒径沙尘在距离风轮平面后1d、2d、3d、5d、8d(d代表风轮直径)处的输沙通量分布。研究发现,三组粒径条件下在1d断面位置处风力机的输沙通量随高度增加出现3次先增大后减小的变化,风力机运行改变了沙尘的输运特性,叶尖高度处出现沙尘聚集现象,叶根高度处的输沙通量则被削弱;通过对比三组粒径条件下风力机的阻沙量发现,叶尖位置>100~200 μm粒径下风力机的阻沙量最多,0~100 μm粒径下风力机的阻沙量次之,>200~300 μm粒径下风力机的阻沙量最少,体现了叶尖涡对不同粒径沙尘颗粒的选择性聚集;对比不同断面位置风力机的输沙通量发现,随着输运距离的增加,风力机尾流逐渐恢复,输沙通量也逐渐减小;总体来看,风力机的存在阻碍了沙尘的输运,且对>100~200 μm粒径的颗粒阻碍作用最大。该试验结果揭示风力机对风沙输运特性的影响特征并对海上盐雾颗粒输运研究具有借鉴意义。

       

      Abstract: 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.

       

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