(71f) Eliminating Soot Emissions from Jet Fuel Combustion

Soot from jet fuel combustion in aircraft engines contributes to global warming through the formation of contrail cirrus clouds that make up to 60 % of the total radiative forcing from aviation. Here, the elimination of such emissions is explored through gas injection (containing 0 - 25 vol % O₂) at the exhaust of enclosed spray combustion of jet fuel that emulates nicely aircraft soot emissions (Trivanovic et al., 2022). It is shown that injecting gas containing 5 vol % of O₂ enhances the formation of polyaromatic hydrocarbons that adsorb on the surface of soot. This increases its number density and volume fraction by 25 and 80 %, respectively. Further increasing the O₂ concentration to 20 or 25 vol %, however, enhances oxidation (Kelesidis & Pratsinis, 2019) and nearly eliminates soot emissions from jet fuel spray combustion, reducing their total number density and volume fraction by 87.3 or 95.4 and 98.3 or 99.6 %, respectively (Fig. 1)! The reduction of soot emissions attained here is up to 60 % higher than that by blending jet fuel with alternative ones. So, injection of air just after the aircraft engine exhaust can reduce the radiative forcing from their emissions by 50 %.

References:

Kelesidis, G.A., Trivanovic, U., and Pratsinis, S.E. 2022. High-throughput generation of aircraft-like soot. Aerosol Sci. Technol. 56:732–743, doi.org/10.1080/02786826.2022.2070055.

Kelesidis, G. A., and Pratsinis, S. E. 2019. Estimating the internal and surface oxidation of soot agglomerates. Combust. Flame 209: 493-499, doi.org/10.1016/j.combustflame.2019.08.001.

Figure 1. Volume fraction of aviation surrogate soot as a function of the O₂ concentration in the gas injected at the exhaust of jet fuel combustion.