High-throughput generation of aircraft-like soot

Abstract

High-throughput, laboratory units for generation of aircraft-like soot are needed to quantify and understand the impact of such emissions on public health and climate change due to the high costs and limited access to aircraft engines. Enclosed spray combustion of jet fuel is used here to generate high soot concentrations, up to 255 mg/m3, three orders of magnitude higher than those typically obtained by widely used soot generators that use vapor-fed flames. This is attributed mostly to the use of real jet fuels. The large mass concentrations enable routine characterization of the soot specific surface area (SSA) and pore size distribution (PSD) by N2 adsorption. The geometric mean mobility diameter, overline(d)m, of soot agglomerates was systematically varied from 15 to 180 nm by varying the equivalence ratio (EQR) at constant fuel feed rates, while the organic to total carbon (OC/TC) ratio is low (<20%) at all conditions. The geometric mean primary particle (PP) diameter, overline(d)p, standard deviation, σ(g,p), and mass-mobility exponent, Dfm, were hardly altered in that EQR range. These measured D(fm) and σ(g,p) indicate that soot PPs were sinter-bonded by surface growth, in agreement with aircraft emissions literature. Most importantly, soot made at EQR ≤ 1.34 has mainly small pores (<2 nm) and similar morphology (D(fm) = 2.52 ± 0.17), SSA (160 − 239 m2/g), OC/TC (< 20%), overline(d)m (15 − 61 nm) and overline(d)p (14 nm) with those from high-thrust aircraft emissions.