CFD studies of tanks draining : how to enlarge the qualification field of ESC-A Lox tank anti-vortex ?

Paper number

IAC-06-C4.3.06

Author

Mr. Jerome Lacapere, Air Liquide DTA, France

Year

2006

Abstract

Developments are performed at Air Liquide to model with CFD tool the thermo-hydraulic behaviour of cryogenic propellants during all phases of a space launch (from tank pressurization on the pad up to the end of draining of upper stage tank, including future ballistic phases).
Validation of this tool is now in progress at Air Liquide.

In this paper, we will present numerical investigations of “diphasic residuals” of ESC-A liquid oxygen tank. These are the small amount of cryogenic liquid remaining in the nearly empty tank at the end of the engine feeding process. When this point is reached, external perturbations and the very high flow rate of ingestion could cause bubble ingestion, which must be avoided. We will show that these residuals can be predicted using complex 3D simulations.

The quantity of “diphasic residual” mass depends on the dynamic conditions during the draining process.
In quiet conditions, perturbations in the liquid surface are minimal, so gas ingestion is small. However, rolling can be imposed to the stage and transmitted to the drained propellants by the launcher attitude control system, and sloshing can occur. A vortex can form with an associated residual mass that increases with the intensity of these disturbances. To compensate for this, anti-vortex devices have been added to LOX tanks since the development of the Ariane 4 upper stage in order to delay the ingestion of bubbles in the collector and reduce the mass of the diphasic residuals. The impact of these devices is now being computed for a number of different flight configurations with different degrees of rolling associated with different lateral perturbations. These computations are being performed with the complete 3D geometry, starting from the very beginning of the launch phase and finishing at the end of the upper stage thrust phase, when the tank is draining. 

Preliminary studies included a comparison of numerical and experimental results, with tests performed on sub-scale tanks filled with water and conditions with a similar Froude number. Very good agreement was achieved, from quantitative and qualitative points of view. Following the validations, further computations were carried out using an actual flight configuration.

Abstract document

IAC-06-C4.3.06.pdf

Manuscript document

IAC-06-C4.3.06.pdf (🔒 authorized access only).

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