Experimental Evaluation Of Particle Transmission Risk In A Single-aisle Aircraft Cabin

Transmission of COVID-19 in cabin has been a significant concern.According to records,some cases of COVID-19 infection are probably caused by the spread of virus aerosol in the cabin.Currently,the mixed ventilation with upper air supply and lower air exhaust is commonly used in the commercial aircraft.In the cabin,especially in the same row,the air is mixed evenly,and the cross transport of expired aerosols among passengers may exist.But the transmission is different due to different air supply inlets.It should be noted that although the air in the cabin is highly mixed,the particle exposure might still vary from seat to seat.Therefore,it is of great significance to clarify the exposure risk of inhalable particles at different positions around the suspicious passengers for controlling the epidemic and improving the ventilation of the cabin.In this study,we built a single-aisle cabin as an experimental platform that can accommodate seven rows of seats.By testing the particle concentration distribution,the risk of particle exposure in different seat respiratory zones in the cabin was evaluated.The ventilation system of the cabin adopted the mixed ventilation widely used in aircraft in service.The thermal manikins with precise surface temperature control were used to simulate the passengers on board,and the surface temperature was controlled within 1℃.The velocity fields and air temperatures were measured to delve into a better understanding of the particle transport.During the experiment,the three-dimensional ultrasonic anemometer and T-thermocouple were used to measure the airflow pattern and temperature field in the cabin,and APS-3321 was used to measure the particle concentration at different locations.In order to analyze the particle exposure risk of passengers at different seats,the particle transmission experiments in both a cross section and a longitudinal section under the mixed ventilation were carried out.In addition,leaving the middle seat vacant to reduce particle exposure was also addressed.In the experiment,the release of single or dual particle source was carried out in different seats to represent the exhaled particles from passengers.In order to improve the mixed ventilation,the cabin air ducts were equipped with valves,so as to switch to the displacement ventilation mode for research.Under the displacement ventilation mode,the particle concentration distribution in the stable cabin was tested and compared with the traditional mixed ventilation.The results of particle exposure experiments under mixed ventilation show that:(1)No matter where the particles are released,the particle concentration in the respiratory zone of the window seat is always the lowest.Under the current mixing ventilation,particles can’t be confined to the half cabin on the same side as the particle source.The half cabin on the same side as the particle release source has high particle concentration,while the other is low.(2)For the three adjacent seats,vacating the middle seat is an effective way to reduce the exposure.If not,when the middle passenger releases particles,these particles together with those from any of the adjacent passengers can result in a particle concentration in the respiratory zone that is more than twice that of a single-source release when the middle seat is left vacant.(3)The released particles can be transported away at least four rows of seats in the longitudinal direction.Besides,compared with the mixed ventilation,the displacement ventilation mode can form a stable displacement airflow in the cabin,which can play a better role in controlling the transmission of pollutants.