Warm Pressurant Effects on the Bubble Point for Cryogenic Liquid Acquisition Devices

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. Three fine-mesh screen samples (325 x 2300, 450 x 2750, and 510 x 3600) were tested in liquid hydrogen and liquid nitrogen using cold and warm noncondensable (gaseous helium) and condensable (gaseous hydrogen or nitrogen) pressurization schemes. Gases were conditioned from 0-90 K above the liquid temperature. Results clearly indicate degradation in bubble point pressure using warm gas, with a greater reduction in performance using condensable over noncondensable pressurization. Degradation in the bubble point pressure is inversely proportional to screen porosity because the coarsest mesh demonstrated the highest degradation. Results here have implication on both pressurization and liquid acquisition device system design for all future cryogenic propulsion systems. A detailed review of historical heated gas tests is also presented for comparison to current results.