Abstract. In this article, a model which examines the formation and evolution of chemiions in an aircraft engine is proposed. This model which includes chemiionisation, electron thermo-emission, electron attachment to soot particles and to neutral molecules, electron-ion and ion-ion recombination, ion-soot interaction, allows the determination of the ion concentration at the exit of the combustor and at the nozzle exit of the engine. It also allows the determination of the charge of the soot particles. A comparison of the model results with the available ground-based experimental data obtained on the ATTAS research aircraft engines during the SULFUR experiments (Schumann, 2002) shows an excellent agreement.
A modelling study of the formation of volatile particles in a combustor exhaust has been carried out in the frame of the PartEmis European project. A kinetic model has been used in order to investigate nucleation efficiency of the H 2 O−H 2 SO 4 binary mixture in the sampling system. A value for the fraction ε of the fuel sulphur S(IV) converted into 5 S(VI) has been indirectly deduced from comparisons between model results and measurements. In the present study, ε ranges between roughly 2.5% and 6%, depending on the combustor settings and on the microphysical approach used. Soot particles hygroscopicity has also been investigated as their activation is a key parameter for contrail formation. Growth factors of monodisperse particles exposed to high relative humidity 10 (95%) have been calculated and compared with experimental results. The modelling study confirms that the growth factor increases as the soot particle size decreases. Abstract Introduction Conclusions ReferencesTables 20The exhaust was sampled close to the combustor exit by a probe (4 mm inner diameter), laterally moved to eleven traverse positions (position 6 was central). This allowed the lateral distribution of gaseous and particles to be measured. After exiting the probe, the sample temperature was rapidly quenched to minimise post sampling reactions, by a water cooling system, bringing its temperature to about 420 K avoiding 25 any condensation of water and unburnt hydrocarbons in particular. The exhaust was then split and delivered to a diluted and to an undiluted sampling line which supplied 5806 ACPD 3, 2003 Abstract Introduction Conclusions ReferencesTables 25 the cold diluting air. Indeed, volatile particles were detected at the end of the sampling line, in the 4-7 nm size range but only for the high fuel sulphur case (FSC = 1270 ppm). Model calculations described below confirm that only for this high FSC volatile particles are 5807 ACPD 3, 2003 Abstract Introduction Conclusions ReferencesTables 25 magnitude) it is assumed that, between the incorporation of sulfuric acid molecules in a cluster, a cluster is in quasi-equilibrium with respect to exchange of water molecules 5808 ACPD 3, 2003 Abstract Introduction Conclusions ReferencesTables 25 mean value of about 5.2% for old and 5.7% for modern cruise conditions. However, if the CE is reduced to 50% (still a rather high value), ε mean values translate to 2.5% and 2.8%, respectively. These last values provide very reasonable agreement both with the measured concentration of volatile particles and ε values deduced by the MPI 5812 ACPD 3, 2003 Abstract Introduction Conclusions ReferencesTables 25 the wall losses for gases and particles, as calculated by Eqs. (1-2). The sulphur conversion ε and the collision efficiency on walls are not the only parameters which have an influence on particles growth. Chemi-ion concentrations, which were measured during PartEmis, may play also a major role. As already noted, we 5813 ACPD 3, 2003 Abstract Introduction Conclusions ReferencesTables 20...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.