CFD Modeling of Oxygen Generation System Operation Effect on the Rack Air Composition

The goal of the study is to analyze the airflow and oxygen transport in the regenerative International Space Station (ISS) Environmental Control and Life Support System (ECLSS) rack of the U.S. Laboratory in case of the Oxygen Generation System (OGS) operation. The rack was proposed to be a location of new equipment that makes difficulties for air circulation. To review on rack internal airflow structure and oxygen content, a detailed three-dimensional (3D) Computational Fluid Dynamics (CFD) analysis for ventilation characteristics in the ISS ECLSS rack has been developed. Air velocity fields and oxygen concentration distributions were numerically predicted on the basis of the 3D Reynolds-Averaged Navier-Stokes (RANS) approach using ANSYS Fluent software. The computational results gave a conclusion that air jets from the avionics equipment exhausts form airflow characteristics sufficient air circulation throughout the rack volume, and the concern on the high-oxygen-content bubble formation within the rack is presented. A sensitivity study of the influence of OGS performance on oxygen content within the rack will present whether there is any risk of flammable limit excess for the oxygen flow rate range considered. The computational data obtained could serve as the basis for verification of the new rack equipment arrangement.