Phase Separation of Liquid from Gaseous Hydrogen in Microgravity Experimental Results

Abstract

Metal screens are commonly used as components for fluid handling in spacecraft and rocket tank designs. In most cases the screen performs a passive separation of the gaseous from the liquid propellant phase. This means that the liquid is able to flow through the screen, causing a flow through screen pressure drop, while the gaseous phase is blocked due to the pressure jump across a curved liquid-gas interphase at the small screen pores. As long as the flow through screen pressure drop is smaller than the bubble point pressure, phase separation is possible and allows the provision of gas-free liquid for the spacecraft or rocket engine. The opposite, the separation of the liquid from the gaseous propellant phase, is more challenging. Liquid-gas phase separation means that the gaseous phase is allowed to enter the phase separation device while the liquid phase is blocked. The separation of the liquid from the gas is possible due to a double screen element, as the work of Conrath et al. (Int. J. Multiphase Flow 50, 1–15, 2013) and Behruzi et al. (2013) has shown for storable liquids in Earth’s gravity and microgravity as well as for cryogenic liquids in Earth’s gravity. The liquid-gas phase separation of cryogenic liquids in microgravity however has not been investigated yet. Therefore, an experimental campaign consisting of six drop tests in microgravity using the drop tower at the University of Bremen, has been conducted. The experimental results confirm predicted governing physical phenomena and give evidence about further fluid mechanical and thermodynamical effects.