Warm Pressurization Gas Effects on the Liquid Hydrogen Bubble Point

Abstract

This paper presents experimental results for the liquid hydrogen bubble point tests using warm pressurant gases conducted at the Cryogenic Components Cell 7 facility at the NASA Glenn Research Center in Cleveland, Ohio. 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. Three fine mesh screen samples (325x2300, 450x2750, 510x3600) were tested in liquid hydrogen using cold and warm noncondensible (gaseous helium) and condensable (gaseous hydrogen) pressurization schemes. Gases were conditioned from 0K -90K above the liquid temperature. Results clearly indicate a degradation in bubble point pressure using warm gas, with a greater reduction in performance using condensable over noncondensible 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 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] 2 ρ LH2 = Liquid hydrogen density [kg/m 3 ] θ c = Contact angle [degrees]

Screen channel liquid acquisition device outflow tests in liquid hydrogen

“…The parameters that affect bubble point, including screen mesh type, liquid, liquid pressure and temperature (i.e. the amount of subcooling), pressurant gas type and pressurant gas temperature have been systematically investigated in four primary cryogenic liquids, including LH2 and liquid nitrogen (LN 2 ) [9, [14][15][16], LOX [17][18][19], and liquid methane (LCH 4 ) [20,21], as well as room temperature liquids [12,22,23]. Equations 1 and 3 can be used to predict the breakdown point of a screen channel LAD in any given gravitational and thermal environment.…”