Modeling and Simulation of Indoor Aerosol Particle Behavior under Needle-Point Bipolar Ionization Air Cleaning

Particle removal has been demonstrated to be enhanced under needle-point bipolar ionization air cleaning technologies. With bipolar ion generation, aerosol particles acquire electrical charges, leading to agglomeration and subsequent deposition. Understanding the ion transport and particle decay in room-scale turbulence is essential for evaluating the overall effectiveness of ionization in indoor environments. Our previous single-zone modeling study built the ion-particle species interaction model and was validated with full-scale chamber experimental tests. In this study, a computational fluid dynamics (CFD) framework was developed to explore airflow characteristics, ion transport, and particle decay under ionization conditions. The Eulerian approach was applied to simulate particle behaviors, as it facilitates detailed tracking of species concentrations by charge and size, while explicitly accounting for ion-particle interactions. A deposition model was incorporated for each species as a permanent sink to indoor surfaces. The CFD framework was constructed based on a species transport model that emphasized particle charging, agglomeration, and deposition processes in previous work. The CFD results revealed that blower-induced recirculation dominated chamber mixing, disrupted inlet jet development, and governed ion and particle transport pathways. Ion concentrations were strongly coupled to the flow field, with enhanced transport along recirculation routes driven by the blower fan. Particle decay was primarily controlled by the room mixing, which influences species reaction processes and deposition. The simulated total particle concentration exhibits the particle decay with a fitted rate of 0.244 Ir1, indicating that reduced turbulence condition leads to weaker effective particle removal compared with experimental conditions. This work is expected to support the optimization of ionizer design, placement, and operation for improved indoor air quality.