CFD Study of Different Aircraft Cabin Ventilation Systems on Thermal Comfort and Airborne Contaminant Transport : A Study on Passenger Thermal Comfort and Indoor Cabin Air Quality.

Abstract: Aircraft Cabin Ventilation systems are crucial for not only maintaining a fresh supply of air but also help in proper air distribution control and reducing airborne pathogen contamination. Passenger thermal comfort is of vital importance for a comfortable cabin environment and thus the need to measure environmental parameters such as velocity and temperature stratification for different ventilation systems is paramount.  Experimental setups often lead to investigation uncertainties and limitations of measured data in a mock-up model when compared to a real cabin. This is due to simplifications either made in the geometry or air supply systems and thus a careful comparison of airflow differences due to the simplifications should be considered. Computational Fluid Dynamic (CFD) models of aircraft cabins can provide a virtual solution for a physical phenomenon (in this case, airflow distribution of an aircraft ventilation system) and thus, such simplifications can be studied and comprehended while reducing the cost and time associated with experimental setups. CFD studies, however, do require thorough verification and validation to avoid compromise on accuracy. This study investigates different aircraft cabin ventilation systems using CFD to analyze airflow distribution and its implications on the thermal comfort and contaminant transport in the cabin. The CFD study results are verified by conducting a mesh sensitivity study since there is no experimental investigation to validate against. This master thesis project was performed at Linköping University in the Applied Thermodynamics and Fluid Mechanics division at the Department of Management and Engineering. A generic single-aisle cabin of a regional jet aircraft is modelled and further implemented in a CFD solver to simulate different Aircraft ventilation systems. The aircraft cabin is modelled using the Autodesk Fusion 360 CAD tool and a CFD model is set up in ANSYS FLUENT using a RANS RNG K-epsilon turbulence model with Enhanced wall treatment. Human Manikins are also designed to represent passengers and are included as heat sources to study thermal distribution. The mouth is used to release CO2 to stimulate breathing through respiration. A tracer gas (CO2) used to represent a pathogen which is discharged from an occupant as a cough or sneeze to study its diffusion path and infection risk. The aircraft cabin is reduced to a cross-section of one row of four seats abreast with a periodic boundary condition which is used to imitate the entire length of the cabin to help reduce meshing as well as computational cost.