Bubble Formation under Microgravity

对于空间站和地球以外的其他星球上的化学燃料的基本设计，人们所知道的化学工程资料很少。对于微重力条件下的发酵罐、气体吸收器、化学反应器等气液接触设备，弄清各种因素对孔板或喷嘴处气泡体积和形状的影响是十分重要的。为了弄清微重力条件下静止液体中气泡的形成行为，在位于北海道上砂川的日本微重力中心（JAMIC）的落轴上进行了10 s的实验，研究了气体流速和表面张力对气泡形成的影响。为了从理论上描述微重力条件下静止液体中气泡的形成过程，本文采用了作者提出的非球形气泡形成模型，并将气泡体积的计算结果与实验结果进行了比较。该模型预测了在静止液体中，当气体流量较小时，在恒定流量条件下气泡体积增大，气泡不会脱离喷嘴。为了使气泡在液体中均匀分散，在微重力条件下，流动液体中形成气泡，并通过实验确定了液体流速和气液两相流方向（并流和错流）对气泡体积的影响。

For the basic design of chemical prants in space stations and on plantes except the earth, few chemical engineering deta have been known. For gas-liquid contacting equipment, such as fermentors, gas absorbers or chemical ractors opectors under microgravity conditions, it is important to make clear the effencts of various factors on the volume and shape of bubble formed at orifices or nozzles. To clarify the behavior of bubble formation in quiescent liquids under microgravity, the effects of gas flow rate and sturface tension on bubble formation were investigated experimentally during 10 seconds by the drop shaft of JAMIC (Japan Microgravity Center) at Kamisunagawa in Hokkaido. To describe theoretically bubble formation in quiescent liqiods under microgravity, the non-sperical bubble formation model proposed by the authors was used ant the calculated results of bubble volume were compared with the experimental ones. It is predicted by this model that bubble volume increases under constant flow condition and a bubble does not detach from a nozzle when gas flow rate is small in quiescent liquid. These calculated resurts of bubble volume agreed well with the experimental ones.To disperse bubbles uniformly in the liquid, bubbles were formed in flowing liquids under microgrkavity, and the effects of liquid velocity and the direction of gas-liquid flows, that is, cocurrent and crosscurrent flows, on the bubble volume were determined experimentally.