Abstracts Category : Other

INVESTIGATION OF PASSIVE CYCLONIC GAS-LIQUID SEPARATORPERFORMANCE FOR MICROGRAVITY APPLICATIONS

by Ming-Fang Kang

Gas-liquid separation is a key task for varioussystems that are utilized onboard the International Space Station,such as active thermal control and waste management. In most ofthese system designs, performance is either significantly degradedor the equipment undergoes increased wear if two phase flow is notfirst separated.Unlike being under the influence of Earth gravity,where gas and liquid separate spontaneously due to buoyancy forces,gas bubbles remain suspended within the liquid under microgravityconditions. In the passive cyclonic separator studied in thisresearch, the gas-liquid mixture is separated by the centrifugalforce created by tangentially injecting the two phase fluid into acylindrical housing. The inertia of the flow itself creates aswirling motion which generates the centrifugal acceleration. Dueto the density differences between the two phases, the lowerdensity gas phase moves towards the center of rotation creating agas core surrounded by an annular liquid film.In such an operation,the separation efficiency is strongly influenced by the gas corebehavior and the transport of bubbles within the turbulent liquidannulus. The main focus of the present study is to obtain physicalinsight into the gas core behavior as well as the bubble dynamicswithin the liquid film through experimentation and computationalmodeling.The experimental portion of this work entails theconstruction and operation of a specific cyclonic two phaseseparator operated across its useful parameter range under theinfluence of Earth gravity. The useful operating ranges andseparation efficiencies are mapped. The numerical modeling workincludes two hybrid-multiphase computational fluid dynamicstechniques coupled with large eddy simulation turbulence modelingand are implemented by using the OpenFOAM library.Data analysis andcomparison reveal that the injection nozzle design, swirl number,and volumetric gas quality all have a major influence on the gascore size. The control volume analysis reveals the importance ofthe skin friction coefficient. The trajectories of single gasbubbles are simulated numerically and graphed. It is found thatfluid turbulence tends to disperse small gas bubbles in the liquidfilm resulting in a longer residence time.Advisors/Committee Members: Kamotani, Yasuhiro (Advisor), Kadambi, Jaikrishnan (Advisor).