结冰风洞中液滴相变效应数值模拟

为明晰结冰风洞中液滴相变效应，发展了基于Euler法的气液两相传质传热耦合流动计算方法，探索了3 m×2 m结冰风洞主试验段构型相变效应对液滴传热过程的影响，开展了参数影响研究，评估了试验段内液滴过冷状态。结果表明：构型内液滴经历了先蒸发后凝结两个阶段，蒸发效应促进了准一维传热阶段液滴温度的下降趋势，使液滴温度趋于湿球温度，而凝结效应则抑制了三维收缩阶段液滴温度的下降趋势，进而增大了试验段液气温差，影响液滴过冷状态；增大初始相对湿度和试验段气流速度，会导致蒸发效应减弱而凝结效应增强，进而增强了相对湿度和气流速度对液滴过冷状态的影响程度，与此相反，初始液滴尺寸的增加，则会导致蒸发效应和凝结效应均减弱，进而减弱了液滴尺寸对液滴过冷状态的影响程度；在典型工况下，小尺寸液滴（液滴直径范围为40~100 μm）在高风速时（试验段气流速度大于164 m/s）将偏离过冷状态（液气温差超过3℃）。

Numerical investigation of phase transition effects of droplet in icing wind tunnel

To understand the phase transition effects of the droplet in an icing wind tunnel, a method based on the Euler theory is developed to simulate mass and heat transfer of coupling of momentum of gas-droplet mixed flows. Using this method, the droplet phase transition effects on the process of the droplet heat transfer are explored for the main test section configuration of a 3 m×2 m icing wind tunnel. Parametric studies are then conducted to evaluate the supercooling state of the droplet in the test section. Results show that the droplets experience firstly evaporation and then condensation in the configuration. The evaporation effects enhance the trend of decrease in the droplet temperature in the quasi-1D stage, and then make the droplet temperature close to the wet-bulb temperature. However, the condensation effects inhibit the trend of decrease in the droplet temperature in the 3D contraction stage, so that the temperature difference between droplet and gas in the test section is increased. As a result, the droplet phase transition has an effect on the supercooling state of the droplet in the test section. In addition, the increased initial relative humidity and test section velocity reduce the evaporation effects, but enhance the condensation effects. Therefore, the effects of relative humidity and test section velocity on the supercooling state of the droplet are enhanced. On the contrary, effects of both evaporation and condensation are reduced, as the initial sizes of the droplet increases. Therefore, the effect of the droplet size on the droplet supercooling is reduced. In typical test conditions, small droplets (the diameter is bigger than 40 μm and smaller than 100 μm) in the center of the test section deviate from the supercooling state (the temperature difference between droplet and gas is higher than 3℃) at the high velocity (the velocity is higher than 164 m/s).