An experimental and analytical study of the fundamentals of a gas-liquid separation device are presented, The separator design comprises a stationary cylinder, into which a two-phase fluid is injected tangentially, near the cylinder wall. The injected fluid creates a free vortex radially from the point of injection to the wall. The deceleration of the fluid, to satisfy the no- slip condition on the wall, results in a pressure rise across the liquid film, which lifts the gas phase to the liquid free Surface and self-pumps the liquid across radial drain-out holes on the perimeter of the stationary cylinder. The gas- phase is accumulated in the core and vented through a stainless steel mesh demister. Testing of the free-vortex separator was performed in the NASA KC-135 reduced- gravity test facility. Controlled, measurable two-phase flows of varying mass velocitv, quality and liquid viscosity were injected into the separator at the onset of a microgravity manuver. Both air-water and air-glycerin/water mixtures were tested. Separator performance was characterized liquid carry-over, i.e. liquid entrained in the gas phase, and depends primarily on injection momentum. During a test sequence, consisting of approximately 40 trajectories on the KC-135, the total liquid carry-over was limited to 100 mL, representing a fractional carry-over of 0. 1 percent of the total inlet liquid flow. The phenomenon of liquid carry-over is evaluated further. A modified Weber number is postulated to reflect the stability of the annular liquid film and droplet deposition rates and ultimately the liquid carry-over, but is a function of the unknown film thickness. An analytical model of the tangential and radial flow velocity is developed, which are applied to predict the Pressure rise across the liquid film. The film thickness and ultimately the Weber number are determined from this pressure drop formulation. The Weber number both increases and decreases with injection Reynolds number and displays a maximum value, indicative of minimal liquid carry-over. Overall, the free-vortex separator is very robust, capable of fast startup operation and operation over an extended range of design and off-design conditions.
Schrage, D.S., Shoemaker, J.M., Operational Characteristics of a Two-Phase Free-Vortex Separator for Micro-Gravity Environments, 30th National Heat Transfer Conference, ASME, New York, NY, Vol. 307, pp. 97-104, August, 1995.