Experimental Investigation of Aerosol Particle Loss from Sampling Tube Surface Roughness for Aviation nvPM Regulatory Measurements
FERGUS LIDSTONE-LANE, Paul Williams, Amanda Lea-Langton, Mark Johnson,
University of Manchester Abstract Number: 688
Working Group: Combustion
AbstractIt is estimated that 16,000 premature deaths are caused by aviation emissions annually (Quadros et al, 2020). Further to this, aviation emissions are thought to cause significant negative impacts on the environment, as they are the main source of anthropogenic particulate sources in the upper atmosphere (Jonsdottir et al, 2019).
In response to the growing aforementioned concerns, the ICAO has introduced a global nvPM emissions reporting standard to regulate the emitted concentrations of nvPM. The standard is relevant for all in-production and new gas turbine engines above 26.7 kN (ICAO, 2017).
Due to the harsh environment at the aircraft engine exit, long sampling tubing is used to transport the exhaust sample to the measurement systems. Transporting the nvPM sample through the long sampling tubes results in large nvPM losses that can be described by many aerosol loss mechanisms, the dominate aerosol loss mechanism is caused from diffusional deposition (Hinds, 1998).
One parameter that can enhance aerosol diffusional deposition is the sampling tube surface roughness (El-Shobokshy, 1982) through increasing the losses caused by eddy-diffusion (Hussein et al, 2012). This loss mechanism become more prevalent when sampling in turbulent regimes.
For regulatory nvPM measurements, a specified correction factor is applied to account for nvPM losses (ICAO, 2017). This correction factor does not account for any losses caused by the surface roughness, and only stipulates that a significantly smooth tube should be used.
This study provides a thorough analysis quantifying the relative effect of aerosol particle loss for a variety of sampling tube surface roughness’s – from 0.25 µm to 8 µm. This study also includes an investigation of aerosol particle loss on convoluted tubes – which represent an exaggerated surface roughness. Further to this, the flow regime and sampling tube diameters will be varied to understand a range of sampling situations.