Effects of liquid properties on pressure loss in a passive rotation-based phase separator

The separation of liquid and vapor plays a crucial role in various engineering applications, especially in the use of cryogenic liquids for space exploration. The DynaSwirl ® (DS) phase separator is a passive rotation-based phase separator, which provides an effective solution for achieving efficient separation in microgravity environments. The DS phase separator uses multiple elongated tangential injection inlets into the separation chamber, which enable stable operation and allow high tangential velocities and low pressure at the core of the generated vortex leading to effective phase separation. This research delves into the fundamental physics that governs the operation of these systems. A DS phase separator is analyzed through both numerical simulations and experimental methods. The DS phase separator employs centripetal and centrifugal forces generated within a swirl chamber to facilitate separation. The effectiveness of separation improves with increasing swirl strength; however, this enhancement leads to greater pressure losses throughout the system. This paper identifies and analyzes the various flow and liquid characteristics that influence pressure losses. These factors include the physical properties of the working liquid, such as density and viscosity, and the swirl strength, which is influenced by viscosity. Additionally, the study examines the impact of incorporating a vortex blocker/killer (BK) attachment on these losses. To conduct the investigation, we examine a set of six selected liquids of interest to NASA, which includes four cryogenic fluids: LN 2 , LH 2 , LOX, and LCH 4 , along with water and a water/glycerin mixture. Additionally, two sets of six fictitious liquids, whose properties are derived from these, are analyzed to isolate the effects of the liquid properties. The pressure losses primarily occur in three areas of the DS phase separator: 1) the inlet slots, 2) the exit orifice, and 3) the swirling flow within the chamber. For the BK configuration, the pressure loss caused by the swirl accounts for about 70 % of the total pressure loss from the wall to the exit when the Reynolds number exceeds 24,000, whereas without BK, this contribution is approximately 90 %. This highlights the effectiveness of the BK in reducing swirl-induced pressure losses. For a given flow rate, reducing viscosity is shown to decrease friction pressure losses but also to increase swirl pressure losses due to a strengthened vortex. In contrast, decreasing the flow rate and density results in reduced pressure losses across all three components of the system. This paper provides a comprehensive analysis of the flow and liquid characteristics, offering valuable insights for the design and optimization of devices that involve strong swirl flows. • DynaSwirl separates phases through multiple tangential injections and strong swirl • Pressure loss in the separator due to friction, swirl, and exit orifice contraction • Increased viscosity increases friction loss but reduces swirl pressure loss • Increased density at a fixed viscosity raises all three pressure loss components • Vortex blocker/killer insert effectively reduces pressure loss across the separator