The influence of fuel type and partial premixing on the structure and behaviour of turbulent autoigniting flames

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

“…The occurrence of these structures is largely dependent on the combination of fuel/oxidant composition and temperatures (Medwell et al, 2008(Medwell et al, , 2016Medwell and Dally, 2012a;Evans et al, 2016a,b), which dictates both the stoichiometric and most-reactive mixture fractions, and the underlying flow-field, which governs the local strain-field between the fuel and oxidant streams (Ye et al, 2016). Of these mechanisms, ignition kernel formation and autoignitive triple flames have been examined at significant length, and a full discussion is not provided here (Gordon et al, 2008;Mastorakos, 2009;Yoo et al, 2011;Arndt et al, 2012Arndt et al, , 2019Sidey and Mastorakos, 2015;Macfarlane et al, 2017Macfarlane et al, , 2018Macfarlane et al, , 2019Ramachandran et al, 2019). Observations from OH-PLIF (Medwell et al, 2008), and resulting numerical studies (Medwell et al, 2009b;Evans et al, 2016bEvans et al, , 2017a suggest that the least studied of these mechanisms-the "weak-to-strong transition"anchors as a weakly reacting diffusion flame close to the jet exit, in ≈ 0.2 (Evans et al, 2016a) under temperature and flowfield conditions almost identical to the laminar coflow stream.…”

“…Planar images of the OH radical in flames stabilized in hot coflows can be used to provide insight into the flame-front (Medwell et al, 2007(Medwell et al, , 2008Gordon et al, 2008Gordon et al, , 2009Ye et al, 2016Ye et al, , 2017Ye et al, , 2018Macfarlane et al, 2017Macfarlane et al, , 2018Macfarlane et al, , 2019 and, in combination with simultaneous PIV, its interaction with the underlying flow-field (Lyons et al, 2005;Oldenhof et al, 2011;Oldenhof et al, 2012). This latter approach is not available simultaneously with Rayleigh scattering measurements of temperature, due to the overwhelming Mie scattering signal from PIV seed particles.…”

“…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.…”

MILD Combustion: Modelling Challenges, Experimental Configurations and Diagnostic Tools

“…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.).…”