Particle nucleation and growth in a free turbulent jet
Particle nucleation and growth in a free turbulent jet
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DOI：
10.1098/rspa.1998.0267
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发表时间：
1998-09
期刊：
影响因子：
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通讯作者：
T. Lesniewski;S. Friedlander
中科院分区：
文献类型：
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作者：
T. Lesniewski;S. Friedlander
液体邻苯二甲酸二丁酯(DBP)颗粒是由一股充满DBP蒸汽的加热气流从喷嘴出来并与室温无颗粒空气混合时，通过均匀成核生成的。喷嘴直径分别为0.235和0.375 cm，喷嘴温度为413K，二苯基丁二烯蒸汽浓度为100ppm~500ppm。选择了使射流湍动(雷诺数4000-7000)并保持低成核率的条件，以便在没有凝聚的情况下和在向凝聚转变的早期阶段研究颗粒的生长。测量了不同位置和不同喷流速度下的气溶胶尺寸分布和数浓度。对于较低的DBP蒸气摩尔分数，颗粒尺寸分布呈单峰分布，气溶胶浓度符合喷流稀释分布，表明颗粒形成局限于喷流的初始区域。最终的气溶胶浓度通过简单的标度定律进行关联。对于较高的蒸汽摩尔分数，成核继续发生在剪切层下游，导致双峰尺寸分布。不同直径喷嘴的数据表明，通过将大喷嘴流动分成多个较小的流，可以降低总体颗粒形成速率。
Liquid dibutyl phthalate (DBP) particles were generated by homogeneous nucleation as a heated gas stream laden with DBP vapour exited a nozzle and mixed with room temperature particle–free air. The nozzle diameters were 0.235 and 0.375 cm, the nozzle temperature was 413K, and DBP vapour concentrations were 100–500 ppm. Conditions were chosen to make the jet turbulent (Reynolds number 4000–7000) and to keep nucleation rates low so that the particle growth could be studied in the absence of coagulation and in the early stages of the transition to coagulation. Aerosol size distributions and number concentrations were measured at different positions and jet velocities. For low values of DBP vapour mole fraction, the size distributions were unimodal and the aerosol concentration followed jet dilution profiles, indicating that the particle formation was confined to the initial region of the jet. The final aerosol concentrations were correlated by simple scaling laws. For higher vapour mole fractions, nucleation continued to occur downstream from the shear layer, resulting in bimodal size distributions. Data for nozzles of different diameters indicate that the overall particle formation rate can be decreased by splitting a large nozzle flow into multiple smaller streams.