NO x emissions from high swirl turbulent spray flames with highly oxygenated fuels Myles D. Bohon ⇑ , William L. Roberts Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC 27695, USA Clean Combustion Research Center, King Abdullah University of Science and Technology (KAUST), Thuwal 23955, Saudi Arabia Available online 26 August 2012 Abstract Combustion of fuels with fuel bound oxygen is of interest from both a practical and a fundamental viewpoint. While a great deal of work has been done studying the effect of oxygenated additives in diesel and gasoline engines, much less has been done examining combustion characteristics of fuels with extre- mely high mass fractions of fuel bound oxygen. This work presents an initial investigation into the very low NO x emissions resulting from the combustion of a model, high oxygen mass fraction fuel. Glycerol was chosen as a model fuel with a fuel bound oxygen mass fraction of 52%, and was compared with emis- sions measured from diesel combustion at similar conditions in a high swirl turbulent spray flame. This work has shown that high fuel bound oxygen mass fractions allow for combustion at low global equiva- lence ratios with comparable exhaust gas temperatures due to the significantly lower concentrations of diluting nitrogen. Despite similar exhaust gas temperatures, NO x emissions from glycerol combustion were up to an order of magnitude lower than those measured using diesel fuel. This is shown to be a result not of specific burner geometry, but rather is influenced by the presence of higher oxygen and lower nitrogen con- centrations at the flame front inhibiting NO x production. Ó 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved. Keywords: NO x ; Oxygenated fuel; Glycerol combustion; Emission characterization 1. Introduction The combustion of and emissions from fuels with high fractions of bound oxygen in diffusion flames are problems of both fundamental and practical interests. Biofuels (alcohols and fatty acid methyl esters) contain fuel bound oxygen in addition to serving as oxygenated additives to tra- ditional fuels as a means of pollution control. Bio- fuels are composed of bioderivatives such as ethanol from cellulose or biodiesel from triglycer- ides. These fuels innately have oxygen bound in their molecule. Oxygenated additives, such as dimethyl ether (DME), have high mass fractions of oxygen and are added to more traditional fuels for improved emissions. Often short alkyl chain alcohols (methanol and ethanol) are included in this category. Because the oxygenated additive is mixed into traditional fuel and not all of the fuel molecules contain oxygen, it becomes difficult to isolate the influence of the fuel bound oxygen on emissions. A number of researchers have 1540-7489/$ - see front matter Ó 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.proci.2012.07.064 ⇑ Corresponding author. Address: 2003 Candelar Dr., High Point, NC 27265, USA. E-mail address: mdbohon@gmail.com (M.D. Bohon). Available online at www.sciencedirect.com Proceedings of the Combustion Institute 34 (2013) 1705–1712 www.elsevier.com/locate/proci Proceedings of the Combustion Institute