用2D-PIV方法研究固-液方形搅拌槽内液相湍流

Investigation on Turbulent Flow Characteristics in a Solid-Liquid Square Stirred Tank Using 2D-PIV Method

采用粒子图像测速和分析技术,研究了固-液方槽体系中液相湍流特性.测得固体颗粒浓度从0增加到0.9%(φ)时,液相在桨叶区和近壁区的湍流流场分布.结果表明,随固体颗粒浓度增加到0.9%(φ),液相轴向平均速度<ν>持续减小,在桨叶区其衰减幅度Δv*与固体颗粒浓度Cv的关系为Δv*∝Cv0.776,近壁区为Δv*∝Cv1.474.桨叶区湍流动能分布较复杂,与单相相比,固体颗粒浓度从0增加到0.5%(φ)时,湍流动能增强;固体颗粒浓度从0.5%增加到0.9%(φ)时,湍流动能减小.在整个测量区域,随固体颗粒浓度增加,平均湍流动能呈减小趋势,拟合平均湍流动能k与固体颗粒浓度的关系为k/vt2ip∝Cv-0.073,平均湍流动能耗散率呈增长趋势,拟合平均湍流动能耗散速率ε与固体颗粒浓度的关系为ε/(D2N3)∝Cv1.113.

Two-dimensional particle image velocimetry and digital image analysis were used to quantify the hydrodynamics of solid-liquid suspension in a square stirred tank. Solid particle spheres with 750 μm diameter were employed as the dispersed phase with up to volumetric concentration of 0.9%（φ） in water. The magnitude of continuous phase mean axial velocity decreased in the impeller and near-wall regions, as the solid concentration increased, the relationship of the velocity drop and the particle concentration could be respectively described as △v^＊∝Cv^0.776 and △v^＊∝Cv^1.474. The turbulent kinetic energy distribution of the continuous phase was complex, because it increased in the impeller region with the solid volumetric concentration up to 0.5%（φ） and decreased above that. The average turbulent kinetic energy remained decreased as the particle concentration increasing from 0.2% to 0.9%（φ）, the relationship could be （k^-/v^2tip∝Cv^-0.073 ）described as （k^-/v^2tip∝Cv^-0.073.） By contrast, the average turbulent kinetic energy dissipation rate of the continuous phase was more enhanced than that in the single phase flow, which could be described as ε^-/（D^2N^3）∝Cv^-1.113.