Abstract:

The effervescent atomizer is a gas-liquid two-phase atomizer. Due to the discrete distribution of gas phase, the gas-liquid flow parameters at the atomizer exit fluctuate violently. In this study, characteristics of both bubbly flow pattern and spray pulsating characteristics were investigated by experimental and simulation methods. A visual effervescent spray system and a gas-liquid two-phase flow simulation model were established, and the operating conditions corresponding to bubbly flow were determined based on the gas-liquid flow regime map. The results show that the bubble size is approximately normal distribution in bubble flow, and the bubble size decreased with the increase of liquid mass flow rate and gas-liquid mass ratio. Under the same operation conditions, spray morphology and gas-liquid flow parameters at the exit orifice section at various times were observed with great difference, and the spray half cone angle varied larger than 10°. When the number density of bubbles was small and the bubble diameter was large at the same time, the spray cone angle was relatively small, and the spray pulsation was intense as well. With the increase of bubble number density, the average spray half cone angle showed a rapid increase followed by a slowly increasing trend, whereas the variation coefficient of the spray half cone angle increased rapidly first, then gradually decreased and tended to stable. Complex flow field structure was the main reason for the variation of bubble shape in the atomizer and the pulsation of gas-liquid flow parameters at the exit section of the atomizer.

Key words: effervescent atomizer, bubble, gas-liquid flow, spray, visualization, simulation

摘要：

采用实验和仿真方法，对一特定气泡雾化喷嘴泡状流时混合室内的气液两相混合形态以及喷孔出口喷雾脉动特征进行了研究。研究结果表明，泡状流时气泡尺寸呈近似正态分布，气泡尺寸随液相质量流量和气液质量比增大而减小；喷雾形态和喷孔出口气液流动参数存在较大脉动，喷雾锥角脉动超过20°；气泡数量密度小且气泡直径较大时，喷雾平均锥角相对较小，且喷雾脉动现象比较严重；随着气泡数量密度增加，喷雾平均锥角呈现先快速增大后缓慢增大趋势，而喷雾锥角变异系数先快速增大随后逐渐减小并趋于稳定；复杂的流场结构是喷孔内气泡表观形态发生较大变化以及喷孔出口气液流动参数产生较大脉动的主要原因。

关键词: 气泡雾化喷嘴, 气泡, 气液两相流, 喷雾, 可视化, 模拟