Preprints
https://doi.org/10.5194/egusphere-2023-1264
https://doi.org/10.5194/egusphere-2023-1264
13 Jun 2023
 | 13 Jun 2023

Jet aircraft lubrication oil droplets as contrail ice-forming particles

Joel Ponsonby, Leon King, Benjamin Murray, and Marc Stettler

Abstract. The radiative characteristics and lifetime of contrails are dependent on the number concentration of ice-forming particles in the engine exhaust plume. Aircraft gas turbine engines produce a variety of particles, yet it is understood that non-volatile black carbon aggregates are the dominant source of ice-forming particles with typical, fossil-derived jet fuel. However, with cleaner combustion technologies and the adoption of alternative fuels (e.g., hydrogen or synthetic aviation fuel), non-volatile black carbon particle emissions are expected to decrease or even be eliminated. Under these conditions, contrail properties will depend upon the concentration and characteristics of particles other than black carbon. Ultrafine (<100 nm) jet lubrication oil droplets constitute a significant fraction of the total organic particulate matter released by aircraft, however their ability to form contrail ice crystals is hitherto unexplored. In this work, we experimentally investigate the activation and freezing behaviour of lubrication oil droplets using an expansion chamber, assessing their potential as ice-forming particles. We generate lubrication oil droplets with a geometric mean mobility diameter of (100.9 ± 0.6) nm and show that these activate to form water droplets despite their hydrophobicity. These subsequently freeze when the temperature is below ~235 K. We find that nucleation on lubrication oil droplets should be considered in future computational studies - particularly under soot-poor conditions - and that these studies would benefit from particle size distribution measurements at cruise altitude. Overall, taking steps to reduce lubrication oil number emissions would help reduce the climate impact of contrail cirrus.

Joel Ponsonby et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1264', Anonymous Referee #1, 05 Sep 2023
  • RC2: 'Comment on egusphere-2023-1264', Anonymous Referee #2, 06 Sep 2023
  • AC1: 'Comment on egusphere-2023-1264 - response to RC1 and RC2', Marc Stettler, 18 Oct 2023

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1264', Anonymous Referee #1, 05 Sep 2023
  • RC2: 'Comment on egusphere-2023-1264', Anonymous Referee #2, 06 Sep 2023
  • AC1: 'Comment on egusphere-2023-1264 - response to RC1 and RC2', Marc Stettler, 18 Oct 2023

Joel Ponsonby et al.

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Latest update: 10 Dec 2023
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Short summary
Aerosol emissions from aircraft engines contribute to the formation of contrails, which have a climate impact as important as that of aviation’s CO2 emissions. For the first time, we experimentally investigate the freezing behaviour of water droplets formed on jet lubrication oil aerosol. We show that they can activate to form water droplets and discuss their potential impact on contrail formation. Our study has implications for contrails produce by future aircraft engine and fuel technologies.