Properties of jet engine combustion particles during the PartEmis experiment: Hygroscopicity at subsaturated conditions

Abstract

Hygroscopic properties of combustion particles were measured online with a Hygroscopicity Tandem Differential Mobility Analyzer (H‐TDMA) during PartEmis jet engine combustor experiments. The combustor was operated at old and modern cruise conditions with fuel sulfur contents (FSC) of 50, 410 and 1270 μg g−1, and hygroscopic growth factors (HGF) of particles with different dry diameters were investigated at relative humidities RH ≤ 95%. HGFs increased strongly with increasing FSC (HGF[95% RH, 50 nm, modern cruise] = 1.01 and 1.16 for low and high FSC, respectively), and decreased with increasing particle size at fixed FSC, whereas no significant difference was detected between old and modern cruise. HGFs agreed well with a two‐parameter theoretical model which provided an estimate of the sulfuric acid content of dry particles, indicating a nearly linear dependence on FSC.

Volatile particles formation during PartEmis: a modelling study

“…At the end of the sampling line, when the sample enters the H-TDMA the sudden increase of relative humidity, up to 95% brings about a sudden growth of soot particles. As noted by Gysel et al (2003), the smaller the particles, the larger the growth factors are and no significant difference was detected between old and modern conditions (especially if error bars are included). These observations were confirmed by our modelling study since the calculated growth factors (independent of the flight conditions: old or modern cruise) are 1.14, 1.11 and 1.07 respectively for particles having initial diameters of 30, 40 and 50 nm before extraction.…”

“…end of the sampling line, and then exposed to a rather high relative humidity (up to 95%). Although soot activation has recently been observed to occur even with sulphur free kerosene (Popovicheva, personal communication), Gysel et al (2003) have shown a clear dependence between the fuel sulphur content and the growth factor defined as the ratio between the wet and the dry (initial) diameter of soot particles, calculated once they have been exposed to high humidity conditions. As volatile and soot particles undergo scavenging processes, soot particles have gained a sulphuric acid-water coating as they have been transported in the sampling line.…”

“…Soot particles have been taken into account in our calculations and we have studied the ability of the model to reproduce soot particles growth measurements, as they have been carried out by Gysel et al (2003). Actually, studies of soot hygroscopicity are of main importance as soot activation is a key process for their subsequent growth and transformation into contrails.…”

“…This mainly indicates that using a different CI emission index in the range proposed by MPI should not affect a lot our estimate of ε (for the probe position 5 -old cruise -and CE=50%, to fit measurements, ε should be increased from 2.7% to 2.9% to com- . Soot particles growth factor evolution in the sampling line and after Gysel et al (2003) sampling. Note that the growth factor presented here is different from the one presented in Table 2 as it refers to an initial dry diameter at the tip of the probe and not just before the sampling point (at t ∼0.9 s).…”

Ambient black carbon particle hygroscopic properties controlled by mixing state and composition

“…A variety of laboratory studies have been conducted to investigate how coatings or chemical reactions occurring on the soot particle could modify its initial low hygroscopicity to the point where eventually the soot particle could exhibit CCN activity. These experiments include investigations on soot from diesel engines (Weingartner et al, 1997;Gysel et al, 2003;Petzold et al, 2005;Tritscher et al, 2011), wood burning Snider et al, 2010) and a variety of flame generators using different chemical fuels (Zuberi et al, 2005;Zhang et al, 2008;Koehler et al, 2009).…”