Study on the carbon dioxide lockup phenomenon in aircraft cabin by computational fluid dynamics

As one of the commonly found tracer gas to evaluate the air quality, high concentration of carbon dioxide (CO₂) can cause exhaustion and drowsiness in enclosed spaces, especially those environments with very limited spaces, such as aircraft cabins. The phenomenon that CO₂ concentration keeps high due to the eddy airflow in some certain zones is named the CO₂ lockup phenomenon in this study. This CO₂ lockup phenomenon has not been clearly identified in previous research in relation to air quality in aircraft cabins. This paper presents the numerical study on the CO₂ lockup phenomenon in aircraft cabins. Firstly, the airflow, temperature and sulfur hexafluoride (SF₆) concentration fields in a simulated aircraft cabin mock-up with seven rows were numerically calculated by computational fluid dynamics (CFD) approach and then the results were compared with the experimental data to verify the reliability of the numerical methods. Secondly, the air velocity and CO₂ concentration distribution were further calculated in two aircraft cabin mock-ups (i.e. Boeing 737-200 and Airbus A330-300) to investigate the CO₂ lockup phenomenon. Finally, different ventilation strategies were numerically tested by changing air supply velocity and direction to optimize the ventilation scheme for the purpose of reducing the impact of the CO₂ lockup phenomenon and improving air quality in aircraft cabins.