Experimental study of ultraviolet irradiation for aerospace applications

• Main Author: Lee, Alvin Jia Jun
• Other Authors: Li King Ho Holden
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Aeronautical engineering
• Online Access: https://hdl.handle.net/10356/150656
• Institution: Nanyang Technological University

A novel Ultraviolet C Band (UVC) device was developed for the purpose of disinfection of the aircraft lavatory when grounded. For reduction of exposure to UVC, an acrylic test cell of 5mm wall thickness was used to determine the radiation characteristics of a UVC Light Emitting Diode (LED) from OSRAM. The radiation characteristics were then compared with simulated radiation characteristics. After confirmation of the radiation characteristics from the simulation and experiment, the simulated parameters that reflected the experimental radiation characteristics were repeated on a 3D modelled aircraft lavatory. The results determined if the UVC LED could achieve 99.9% sterility in specific lavatory structures within a certain timeframe. Sterilisation within 30 minutes was set as a boundary condition as 30 minutes is the minimum stopover time for most aircrafts. The radiation characteristics generated from the simulation were observed to follow a slightly different trend as compared to the characteristics observed from the LEDs provided by OSRAM. The simulated LED parameters, however, were still used on the 3D model due to the difference being marginal. Previous studies have suggested that the minimum safe dosage for 99.9% sterility of SARS-CoV-2 is 10mJ/cm2. Given the time limit of 30 minutes, the required intensity from the UVC LEDs equated to 0.006mW/cm2, which corresponded to a maximum distance of 500mm at a view angle of 50°. The LEDs were placed on non-essential lavatory structures in the traditional aircraft lavatory model of 34 inches (Width) by 48 inches (Length) by 72 inches (Height) and the updated aircraft lavatory model of 24 inches (Width) by 48 inches (Length) by 72 inches (Height). The simulation suggested that modern aircraft lavatories would highly benefit from employment of UVC devices as most frequently touched structures achieved a UVC dose of 10mJ/cm2 within 30 minutes. However, it was observed on traditional lavatories that most of the toilet seat did not achieve 99.9% sterilisation within 30 minutes.