Structural differences of ethanol and DME jet flames in a hot diluted coflow

Abstract

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Understanding and Interpreting Laser Diagnostics in Flames: A Review of Experimental Measurement Techniques

“…This relationship becomes important when selecting excitation transitions for LIF experiments, and may be used to determine temperatures from comparative measurements of atomic, such as indium (Medwell et al, 2009a) or gallium (Borggren et al, 2017), and simplemolecular species, such as NO or OH (McMillin et al, 1994;Richardson et al, 2016). Similarly, the change in temperature across the reaction zone can introduce additional uncertainties in qualitative measurements (Sidey and Mastorakos, 2015;Kruse et al, 2019), or semi-quantitative measurements which do not include corrections to temperature (Medwell et al, 2007(Medwell et al, , 2008(Medwell et al, , 2009bYe et al, 2018). The latter approach may be considered valid following careful selection of excitation wavelength, to ensure little variation (e.g., 10% Medwell et al, 2007) in the Boltzmann fraction across the reaction zone.…”

“…It is therefore possible to estimate mole fractions from simultaneous species and temperature measurements, however, this introduces a dependency on accurate temperature measurements. Accordingly, species measurements may be reported in units of number density (Medwell et al, 2007(Medwell et al, , 2008Ye et al, 2018). This coupling has promoted the use of iterative solution processes for calculating the mole fraction of species such as OH simultaneously with temperature (Gordon et al, 2008(Gordon et al, , 2009.…”

“…Particle seeding must be ensured in the both the jet and hot coflow streams to ensure even and unbiased measurements in the mixing region. This requirement to seed particles into the coflow has restricted velocity measurements in JHC burners which generate hot and diluted coflows on porous bed burners (Dally et al, 2002;Medwell et al, 2007Medwell et al, , 2008Ye et al, 2017Ye et al, , 2018Evans et al, 2019b;Kruse et al, 2019). Particle image velocimetry is a planar technique using Mie scattering from particles illuminated by a pair of pulsed lasers separated by a known time interval.…”

“…Fundamental studies of these flames have not only provided significant insight into autoignition processes, but have been used to generate extensive datasets in simplified configurations for validating turbulence-chemistry interaction models for numerical modeling of combustion systems. Fundamental studies of laminar and turbulent jet flames issuing into high temperature, low oxygen environments have been undertaken in jet in hot coflow (JHC) burners (Dally et al, 2002;Medwell et al, 2007Medwell et al, , 2008Oldenhof et al, 2010Oldenhof et al, , 2011Oldenhof et al, 2012;Medwell and Dally, 2012a;Sepman et al, 2013;Ye et al, 2016Ye et al, , 2017Ye et al, , 2018Evans et al, 2017bEvans et al, , 2019aKruse et al, 2019), hot cross-flow burners (Sidey and Mastorakos, 2017), vitiated coflow burners (VCBs) (Cabra et al, 2002(Cabra et al, , 2005Gordon et al, 2008Gordon et al, , 2009Macfarlane et al, 2018Macfarlane et al, , 2019Ramachandran et al, 2019), and partially premixed jet burners (PPJBs) (Dunn et al, 2007a;Dunn et al, 2009), as have spray flames in hot coflow burners (Correia Rodrigues et al, 2015a,b;Wang et al, 2019b). In each case, fresh fuel issues from a jet into a stream of hot gas generated by lean premixed flames, resulting in 15% O 2 (by vol.).…”

“…Such improved understanding these transitions-and the structure of the upstream flames leading to their formation-may be achieved through targeted laser-diagnostics studies and subsequently validated, complementary numerical modeling. The high fidelity data that laser diagnostics can provide allows for the detailed study of reactive structures across the broad range of spatial and temporal scales in different optically-accessible JHC burners and reactors (Plessing et al, 1998;Cabra et al, 2002Cabra et al, , 2005Dally et al, 2002;Medwell et al, 2007Medwell et al, , 2008Gordon et al, 2008Gordon et al, , 2009Oldenhof et al, 2010Oldenhof et al, , 2011Oldenhof et al, 2012;Medwell and Dally, 2012a;Sepman et al, 2013;Sorrentino et al, 2015Sorrentino et al, , 2016Ye et al, 2016Ye et al, , 2017Ye et al, , 2018Evans et al, 2017bEvans et al, , 2019aSidey and Mastorakos, 2017;Macfarlane et al, 2018Macfarlane et al, , 2019Kruse et al, 2019;Ramachandran et al, 2019). Laser diagnostics a provide means to investigate the small-scale and distributed reaction zones in macroscopically-near-homogeneous MILD combustion conditions.…”