Modeling of Ullage Collapse Within Rocket Propellant Tanks at Reduced Gravity

摘要

Orbital maneuvers of upper-stage rockets may generate propellant slosh waves and propellant breakup into droplets within the oxidizer and fuel tanks. When many droplets are created, increased propellant evaporation may occur and lead to a significant reduction in ullage gas temperature and pressure, known as ullage collapse. This work presents a new method that uses a numerical tool to predict the droplet distribution created during a maneuver, and subsequently uses an analytical model to calculate the droplet evaporation and consequent change in tank temperature and pressure. This new hybrid method uses less computational tune than a detailed computational fluid dynamics model and is capable of providing mission planners with an unproved tool to assess the impact of propellant evaporation on the requirements of additional helium mass for tank repressurization. The new method is applied to predict evaporation and the consequent ullage collapse in an upper-stage propellant tank undergoing simulated orbital maneuvers at microgravity levels.