Pressure vessel priming analysis for a regulated liquid propulsion system

An investigation was performed to determine the pressure transient levels and time required to reach pressure equilibrium in a regulated liquid propulsion system due to the priming of a propellant tank during system initiation. An experimental fluid flow test setup was designed and fabricated using a pressure vessel to house distilled water as a propellant simulant for liquid hydrazine and high-pressure gaseous nitrogen as the pressurant. A snubber orifice was installed downstream of the high-pressure gaseous nitrogen bottles to protect a regulator from high-pressure transients, prior to the regulation of incoming gas to beginning of life propulsion system propellant tank conditions. Experiments were conducted to measure pressure transients and time to pressure equilibrium by varying initial system pressures, snubber orifice diameter, and system ullage volume. A mathematical model was developed and compared against the experimental regulated system priming results to predict the system pressures and time to reach system pressure equilibrium during the pressurization period for regulated propulsion systems given initial conditions.