Structure of hydrogen-rich transverse jets in a vitiated turbulent flow

Abstract

This paper reports the results of a joint experimental and numerical study of the flow characteristics and flame structure of a hydrogen rich jet injected normal to a turbulent, vitiated crossflow of lean methane combustion products. Simultaneous high-speed stereoscopic PIV and OH PLIF measurements were obtained and analyzed alongside three-dimensional direct numerical simulations of inert and reacting JICF with detailed H 2 /CO chemistry. Both the experiment and the simulation reveal that, contrary to most previous studies of reacting JICF stabilized in low-to-moderate temperature air crossflow, the present conditions lead to a burner-attached flame that initiates uniformly around the burner edge. Significant asymmetry is observed, however, between the reaction zones located on the windward and leeward sides of the jet, due to the substantially different scalar dissipation rates. The windward reaction zone is much thinner in the near field, while also exhibiting significantly higher local and global heat release than the much broader reaction zone found on the leeward side of the jet. The unsteady dynamics of the windward shear layer, which largely control the important jet/crossflow mixing processes in that region, are explored in order to elucidate the important flow stability implications arising in the inert and reacting JICF. The paper concludes with an analysis of the ignition, flame characteristics, and global structure of the burner-attached flame. Chemical explosive mode analysis (CEMA) shows that the entire windward shear layer, and a large region on the leeward side of the jet, are highly explosive prior to ignition

High-repetition-rate planar measurements in the wake of a reacting jet injected into a swirling vitiated crossflow

“…For applications such as secondary injection of fuel into a vitiated gas stream in a gas turbine combustor, rapid mixing and chemical reaction in the near-field of jet injection plane are desirable. In a recent study based on high-speed CH* and OH* chemiluminescence imaging, vitiated crossflow, it was 6 observed that the flame stabilizes just downstream of the injector [23] [24]. The H2/CO jet flames remained attached to the injector for all observed conditions.…”

Simulation of the Self-Ignition of a Cold Premixed Ethylene-Air Jet in Hot Vitiated Crossflow

“…The problem of ignition has also been studied with direct numerical simulations (DNS) (Lapointe et al 2015;Krisman et al 2017). For instance, Lyra et al (2015) investigated a rich hydrogen RJICF configuration using joint DNS and experiments observing significant differences between the structure and stability mechanism of windward and leeward flames. Kolla et al (2012) simulated by DNS a RJICF and studied the blowout phenomenon dynamics due to kinematic imbalance between flame propagation speed and flow normal velocity.…”

Assessing the relative importance of flame regimes in Raman/Rayleigh line measurements of turbulent lifted flames

“…Much of the current knowledge of fundamental structures in turbulent partially premixed flames has come from direct numerical simulation (DNS) [7][8][9][10]. In these numerical studies, several flame indices and regime identifiers have been developed for describing local reaction zones as premixed or non-premixed [4,5,[11][12][13][14][15].…”

“…All of those indices and identifiers require the knowledge of 3D gradients of multiple scalars, so they are not directly applicable to experimental data. Chemical explosive mode analysis (CEMA), which relies only on the knowledge of the local thermochemical state, has also been used in analysis of DNS data to identify premixed reaction zones [16,17] and extinction and ignition processes [8,18]. However, the analysis of experimental data in terms of the combustion regime has been conducted mostly in connection with simulations, e.g.…”