Particle dynamics in an electrohydrodynamic flow field investigated with a two-component laser-Doppler velocimeter
Particle dynamics in an electrohydrodynamic flow field investigated with a two-component laser-Doppler velocimeter
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使用二分量激光多普勒测速仪研究电流体动力学流场中的粒子动力学
DOI：
10.1002/ppsc.19930100203
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发表时间：
1993
影响因子：
2.7
通讯作者：
F. Löffler
中科院分区：
文献类型：
--
作者：
C. Riehle;F. Löffler
采用激光多普勒仪测量了电除尘器电流体动力流场中NaCl粒子的迁移速度。如果饱和电荷至少为90%，则1.40 μm颗粒的实测平均迁移速度（几何标准偏差为1.46的数量分布中位数）约为1.40 μm颗粒计算稳态速度的5 - 6倍。此外，主流方向上的颗粒速度也受电操作条件的影响。这两个观测结果都表明了电流体动力学流场的状态（运动的气体离子和中性气体分子的叠加）对粒子输运的重要作用，其特征在于无量纲电流体动力学数NEHD。比较了六种不同的电流体动力学状态，发现NEHD ε 1是气体离子与中性气相相互作用的临界值。当NEHD值大于1时，粒子的随机运动主要由负电晕的非稳态特性决定，而当NEHD值小于1时，粒子的速度波动则由中性流体的湍流度决定。这些研究结果对调整电除尘器的操作条件以获得最佳的颗粒分离效果有一定的指导意义
A laser-Doppler instrument has been used to measure the migration velocity of NaCl particles in an electrohydrodynamic flow field of an electrical precipitator. The measured average migration velocity of 1.40-μm particles (number distribution median with a geometric standard devitation of 1.46) is approximately five to six times higher than the calculated steady-state velocity for a 1.40-μm particle, provided there is a saturation charge of at least 90%. Further, the particle velocities in the main flow direction are also influenced by the electrical operation conditions. Both observations demonstrate the important role of the state of the electrohydrodynamic flow field (superposition of moving gas ions and neutral gas molecules) on the particle transport, characterizied by the dimensionless electrohydrodynamic number N EHD . A comparison between six different electrohydrodynamic states revealed that N EHD ≃ 1 is a critical value for the mutual interactions between the gas ions and the neutral gas phase. Whereas for N EHD values > 1 the stochastic particle motion is chiefly determined by the non-steady-state character of the negative corona, for N EHD values < 1 the particle velocity fluctuations are governed by the turbulence level of the neutral fluid. These findings might be helpful in adjusting the operating conditions in electrical precipitators for an optimized particle separation