SIMULATIONS OF CRYOGEN EXPULSION FROM A SPACE DEPOT UNDER ZERO-GRAVITY

With an increasing number of missions in space, cryogenic fluid supply systems become necessary as mission duration is extended. Most of the system operations involve multiple-phase phenomena. Accurate simulati on of the operations is needed to predict the physics and efficiency o f these systems. One operation of interest is the expulsion of liquid cryogens from a partially filled depot; the challenge concerns finding ways to expel the liquid while preventing vapour from entering the tr ansfer line. The problem involves tracking the motion of a floating, m obile and expanding vapour ullage as fluid is expelled from a tank. Th e simulation of the interface movement of the vapour ullage in a volum e of confined liquid under zero gravity is carried out by solving the Navier-Stokes equations in the transformed boundary-fitted curvilinear co-ordinate system using a finite difference approach. An alternating expulsion and pressurization scheme is presented for the operation ba sed on mass and momentum conservation.