Bubble Formation under Microgravity

对于空间站和除地球以外的植物上的化学试剂的基本设计，人们所知的化学工程数据很少。对于微重力条件下的气液接触设备，如发酵罐、气体吸收塔或化学反应器，弄清各种因素对孔口或喷嘴上形成的气泡的体积和形状的影响是很重要的。为了弄清微重力作用下静止液体中气泡的形成行为，利用日本微重力中心在北海道龟仙川的下降轴，在10秒内对气体流量和表面张力对气泡形成的影响进行了实验研究。为了从理论上描述微重力作用下静止液体中气泡的形成，采用了作者提出的非球面气泡形成模型，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，在恒定流量条件下，气泡体积增大，当静止液体中气体流量较小时，气泡不会脱离喷嘴。为了使气泡在液体中均匀分散，在微腔条件下，在流动的液体中形成气泡，实验测定了液体速度和气液两相流动方向(顺流和横流)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.