Numerical Analysis of Non-Uniform Pollutant Distribution in an Internal Space of Tank and the Efficacy of an Active Purification Strategy

Hazardous gas intrusion in tightly sealed and geometrically complex confined spaces, such as armored tanks, poses a critical threat to occupant health. The intricate internal structure of these systems may lead to non-intuitive pollutant transport pathways. However, the spatial and temporal evolution of these structures, as well as the intrinsic mechanisms of the purification systems, remain poorly elucidated. In this study, a high-fidelity, transient three-dimensional computational fluid dynamics (CFD) model was developed to simulate the leakage and dispersion of carbon monoxide (CO) and nitrogen dioxide (NO2) using the RNG k-ε turbulence model. Scenarios with and without an active purification system were systematically investigated under four leakage rate conditions: 0.33, 0.66, 1.32, and 2.64 m·s−1. Our results reveal that, flow recirculation driven by the compartment’s geometry leads to the formation of stable, high-concentration “hazard zones”. Following the activation of the purification system, decreases from 1 to 0.1, demonstrating that the primary value of the purification system lies in homogenizing the internal flow field and minimizing localized hazardous zones. At leakage rates below 1.32 m/s, the purification system ensures pollutant concentrations at all monitoring points are effectively controlled below limitation. When single-pass purification efficiency increases from 25% to 30%, pollutant concentrations at critical monitoring points decrease by approximately 30%. This work provides crucial mechanistic insights and a quantitative basis for the design of advanced ventilation systems in complex confined environments, advocating a design philosophy shift from simple air exchange to strategic flow-field management.