Soot-free Emissions from Jet Fuel Combustion: Oxidation Dynamics of Aircraft-like Soot

UNA TRIVANOVIC, Sotiris Pratsinis, ETH Zurich, Switzerland

     Abstract Number: 745
     Working Group: Combustion

Abstract
Aircrafts are a significant source of combustion related pollutants which can harm human health and the environment. New restrictions are currently being phased in to limit the permissible number concentrations of non-volatile particulate matter (soot) from aircrafts. So, efficient strategies to meet these increasingly stringent regulations are needed. In this regard, judicious injection of oxygen downstream of aircraft-like soot generators [1] is explored to eliminate soot emissions from spray combustion of jet fuel [2]. Fundamental understanding of the soot oxidation dynamics [3,4] in such a generator is essential for designing and operating aircraft engines to meet competing goals of emission reduction of various pollutants as well as safety and performance. Here, enclosed spray combustion of jet fuel is used to produce aircraft-like soot [1] and a torus ring is used to inject various oxygen concentrations downstream of the spray to remove the soot through oxidation [2]. Using a steel tube with sealable sampling ports for the enclosure allows for a study of the evolution of particles and temperature throughout the soot generator [5]. Injecting oxygen/nitrogen mixtures early on in the flame, at a height above the burner (HAB) = 10 cm, is most efficient at removing soot but does not allow for complete combustion of jet fuel. Late injection (HAB = 50 cm) has little effect on the final soot concentration. Early injection of oxygen/nitrogen increased slightly the OC/TC ratio of soot but had no apparent impact on its nanostructure as quantified by Raman spectroscopy. At HAB = 30 cm, most soot particles were removed by oxidation while still allowing for complete hydrocarbon combustion. At HAB = 35 cm, just after oxygen/nitrogen injection, soot number concentrations were drastically reduced with slightly higher concentrations near the tube wall than at its centerline. Concentrations continued to decrease downstream till the exit of the burner. Temperatures were measured along the centerline of the flame and radially, 1 cm from the wall and ranged from about 300 to 1050 C.

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