Experiments and simulations of NOx formation in the combustion of hydroxylated fuels

Handle URI:
http://hdl.handle.net/10754/565977
Title:
Experiments and simulations of NOx formation in the combustion of hydroxylated fuels
Authors:
Bohon, Myles ( 0000-0002-6724-0805 ) ; Rachidi, Mariam El ( 0000-0001-7392-6777 ) ; Sarathy, Mani ( 0000-0002-3975-6206 ) ; Roberts, William L. ( 0000-0003-1999-2831 )
Abstract:
This work investigates the influence of molecular structure in hydroxylated fuels (i.e. fuels with one or more hydroxyl groups), such as alcohols and polyols, on NOx formation. The fuels studied are three lower alcohols (methanol, ethanol, and n-propanol), two diols (1,2-ethanediol and 1,2-propanediol), and one triol (1,2,3-propanetriol); all of which are liquids at room temperature and span a wide range of thermophysical properties. Experimental stack emissions measurements of NO/NO2, CO, and CO2 and flame temperature profiles utilizing a rake of thermocouples were obtained in globally lean, swirling, liquid atomized spray flames inside a refractory-lined combustion chamber as a function of the atomizing air flow rate and swirl number. These experiments show significantly lower NOx formation with increasing fuel oxygen content despite similarities in the flame temperature profiles. By controlling the temperature profiles, the contribution to NOx formation through the thermal mechanism were matched, and variations in the contribution through non-thermal NOx formation pathways are observed. Simulations in a perfectly stirred reactor, at conditions representative of those measured within the combustion region, were conducted as a function of temperature and equivalence ratio. The simulations employed a detailed high temperature chemical kinetic model for NOx formation from hydroxylated fuels developed based on recent alcohol combustion models and extended to include polyol combustion chemistry. These simulations provide a qualitative comparison to the range of temperatures and equivalence ratios observed in complex swirling flows and provide insight into the influence of variations in the fuel decomposition pathways on NOx formation. It is observed that increasing the fuel bound oxygen concentration ultimately reduces the formation of NOx by increasing the proportion of fuel oxidized through formaldehyde, as opposed to acetylene or acetaldehyde. The subsequent oxidation of formaldehyde contributes little to the formation of hydrocarbon (HC) radicals. Ultimately, by reducing the contributions to the HC radical pool, NOx can be effectively reduced in these fuels through suppression of non-thermal NOx formation pathways. © 2015 The Combustion Institute.
KAUST Department:
Clean Combustion Research Center
Publisher:
Elsevier BV
Journal:
Combustion and Flame
Issue Date:
Jun-2015
DOI:
10.1016/j.combustflame.2015.01.022
Type:
Article
ISSN:
00102180
Appears in Collections:
Articles; Clean Combustion Research Center

Full metadata record

DC FieldValue Language
dc.contributor.authorBohon, Mylesen
dc.contributor.authorRachidi, Mariam Elen
dc.contributor.authorSarathy, Manien
dc.contributor.authorRoberts, William L.en
dc.date.accessioned2015-08-12T08:57:47Zen
dc.date.available2015-08-12T08:57:47Zen
dc.date.issued2015-06en
dc.identifier.issn00102180en
dc.identifier.doi10.1016/j.combustflame.2015.01.022en
dc.identifier.urihttp://hdl.handle.net/10754/565977en
dc.description.abstractThis work investigates the influence of molecular structure in hydroxylated fuels (i.e. fuels with one or more hydroxyl groups), such as alcohols and polyols, on NOx formation. The fuels studied are three lower alcohols (methanol, ethanol, and n-propanol), two diols (1,2-ethanediol and 1,2-propanediol), and one triol (1,2,3-propanetriol); all of which are liquids at room temperature and span a wide range of thermophysical properties. Experimental stack emissions measurements of NO/NO2, CO, and CO2 and flame temperature profiles utilizing a rake of thermocouples were obtained in globally lean, swirling, liquid atomized spray flames inside a refractory-lined combustion chamber as a function of the atomizing air flow rate and swirl number. These experiments show significantly lower NOx formation with increasing fuel oxygen content despite similarities in the flame temperature profiles. By controlling the temperature profiles, the contribution to NOx formation through the thermal mechanism were matched, and variations in the contribution through non-thermal NOx formation pathways are observed. Simulations in a perfectly stirred reactor, at conditions representative of those measured within the combustion region, were conducted as a function of temperature and equivalence ratio. The simulations employed a detailed high temperature chemical kinetic model for NOx formation from hydroxylated fuels developed based on recent alcohol combustion models and extended to include polyol combustion chemistry. These simulations provide a qualitative comparison to the range of temperatures and equivalence ratios observed in complex swirling flows and provide insight into the influence of variations in the fuel decomposition pathways on NOx formation. It is observed that increasing the fuel bound oxygen concentration ultimately reduces the formation of NOx by increasing the proportion of fuel oxidized through formaldehyde, as opposed to acetylene or acetaldehyde. The subsequent oxidation of formaldehyde contributes little to the formation of hydrocarbon (HC) radicals. Ultimately, by reducing the contributions to the HC radical pool, NOx can be effectively reduced in these fuels through suppression of non-thermal NOx formation pathways. © 2015 The Combustion Institute.en
dc.publisherElsevier BVen
dc.subjectAlcoholen
dc.subjectHydroxylateden
dc.subjectNOxen
dc.subjectPrompten
dc.subjectSwirlen
dc.subjectThermalen
dc.titleExperiments and simulations of NOx formation in the combustion of hydroxylated fuelsen
dc.typeArticleen
dc.contributor.departmentClean Combustion Research Centeren
dc.identifier.journalCombustion and Flameen
kaust.authorSarathy, Manien
kaust.authorRoberts, William L.en
kaust.authorBohon, Mylesen
kaust.authorRachidi, Mariam Elen
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