Warm Pressurant Gas Effects on the Static Bubble Point Pressure for Cryogenic LADs

Abstract

This paper presents experimental results for the liquid hydrogen and nitrogen bubble point tests using warm pressurant gases conducted at the NASA Glenn Research Center. The purpose of the test series was to determine the effect of elevating the temperature of the pressurant gas on the performance of a liquid acquisition device (LAD). Three fine mesh screen samples (325x2300, 450x2750, 510x3600) were tested in liquid hydrogen and liquid nitrogen using cold and warm non-condensable (gaseous helium) and condensable (gaseous hydrogen or nitrogen) pressurization schemes. Gases were conditioned from 0K -90K above the liquid temperature. Results clearly indicate degradation in bubble point pressure using warm gas, with a greater reduction in performance using condensable over non-condensable pressurization. Degradation in the bubble point pressure is inversely proportional to screen porosity, as the coarsest mesh demonstrated the highest degradation. Results here have implication on both pressurization and LAD system design for all future cryogenic propulsion systems. A detailed review of historical heated gas tests is also presented for comparison to current results. Nomenclatured shute = Diameter of the shute wire [μm] d warp = Diameter of the wap wire [μm] D p = Effective pore diameter [μm] g = Gravitational acceleration [m/s 2 ] HEX = Heat exchanger LL = Liquid Level above LAD screen [m] l s = Distance between consecutive shute wires [μm] n shute = Number of shute wires per inch of screen [1/m] n warp = Number of warp wires per inch of screen [1/m] PCA = Pressure control assembly t = Screen thickness [μm] ΔP BP = Bubble point pressure [Pa] ΔT = Temperature difference between liquid and pressurant gas [K] ε = Porosity γ = Surface tension [mN/m] ρ LH2 = Liquid hydrogen density [kg/m 3 ] θ c = Contact angle [degrees]

Research on Surface Tension Tank Technology of Aerospace Cryogenic Propellant

“…The storage gas pressurization technology has the advantages of simple structure, high reliability and strong function realization, and is widely used in the space field. Hartwig [12] studied warm pressurant gas effects on the static bubble point pressure for cryogenic liquid acquirement device (LAD).…”