Effects of H2O and NO on extinction and re-ignition of vortex-perturbed hydrogen counterflow flames

Lee, Uen Do; Yoo, Chun Sang; Chen, Jacqueline H.; Frank, Jonathan H.

doi:10.1016/j.proci.2008.06.150

Cited by 16 publications

(4 citation statements)

References 28 publications

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“…In contrast, there are multiple physical processes involved in the re-ignition of a locally extinguished flame, including mixing, edge flame propagation, independently burning flame parcels, autoignition, and the contact of reactants with hot combustion products [49,[66][67][68][69].…”

Section: Flame Leading Edge Location and Velocitymentioning

confidence: 99%

Near-lean blowoff dynamics in a liquid fueled combustor

Rock

Emerson

Seitzman

et al. 2020

Combustion and Flame

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This paper describes an analysis of the near-lean blow off(LBO) dynamics of spray flames, including the influence of fuel composition upon these dynamics. It is motivated by the fact that, while reasonable correlations exist for predicting blowoffconditions, the fundamental reasons for why flames supported by flow recirculation actually blow offare not well understood. Prior work on gaseous systems has shown that the blowoffevent is a culmination of several intermediate processes, initiating with local extinction of reactions ("stage 1"), followed by large scale changes in flame and flow dynamics ("stage 2"), finally leading to blowoff. In this study, near-LBO dynamics were characterized for ten liquid fuels with widely varying kinetic and physical properties. Results were compared at two air inlet temperatures, 450 and 300 K, as this influences the relative importance of physical and kinetic properties in controlling LBO. Extinction, re-ignition, and recovery of the flame are evident from these data, and grow in frequency as blowoffis approached. Results show that after a near-blowoffevent, the flame can move upstream at velocities much faster than the flow velocity, corresponding to re-ignition. Nonetheless, the majority of the flame recovery events appear to be associated with convection of hot products back upstream, not re-ignition. In contrast, downstream motion of the flame faster than the flow, which would correspond to bulk flame extinction, was never observed. This indicates that "extinction events"actually correspond to convection of the flame downstream by the flow when it loses its stabilization point. The dependence of the equivalence ratio when these events appear, their frequency, and event duration were quantified as a function of fuel composition and air inlet temperature. For example, the data shows a higher percentage of recovery from near-blowoffevents through re-ignition for high DCN fuels at the 450 K air temperature condition. These extinction/re-ignition results suggest that high DCN fuels are harder to blow offthan low DCN fuels through two mechanisms: (1) by delaying the onset of LBO precursor events, and (2) because they are able to recover from these precursor events through re-ignition more often.

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Section: Flame Leading Edge Location and Velocitymentioning

confidence: 99%

Near-lean blowoff dynamics in a liquid fueled combustor

Rock

Emerson

Seitzman

et al. 2020

Combustion and Flame

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“…The increased OH species enhances the auto-ignition process in the quenched zone thus favouring re-ignition, whereas additives such as water inhibit the process due to their large specific heats and third-body efficiencies promoting chain termination reactions. 61,62 Most of the studies on flame vortex interactions have been limited to atmospheric pressure conditions and simple H 2 or methane/air flames. However, in actual reactors, the flames would be subjected to adverse pressure conditions as well as to a variety of multi-component fuels.…”

Section: Flame-vortex Interactionmentioning

confidence: 99%

Advances in understanding combustion phenomena using non-premixed and partially premixed counterflow flames: A review

Ravikrishna

Sahu

2017

International Journal of Spray and Combustion Dynamics

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Counterflow flames provide an ideal platform for understanding the flame structure and as a model to study the effect of physical and chemical perturbations on the flame structure. This article reviews the advances made in the understanding of combustion dynamics and chemistry through experimental and numerical studies in counterflow non-premixed and partially premixed flames. Key contributions on fundamental aspects such as extinction, ignition and effect of perturbations on the stability of diffusion flames are first summarized and analysed. The review then focuses on the progress made in the understanding of the effect of inert particles and flame suppressants on the flame characteristics. A review of detailed studies on edge flames facilitates further understanding of local quenching and re-ignition phenomena in highly turbulent flames. The influence of radiation model and unsteady flow-conditions on the flame kinetics and dynamics along with work on NO x kinetics has been discussed. The review also outlines that specific experiments need to be carried out over a wide range of conditions for further understanding and validation of numerical models.

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“…32 In addition to dilution from CO 2 and H 2 O, combustion product minor species have an impact on the ignition delay. The addition of small amounts of NO and NO 2 , as low as 1 ppm, to the composition was reported to reduce the ignition delay, the magnitude of which is dependent upon temperature and pressure conditions, while being most significant at temperatures less than 1200 K. [33][34][35] Kinetic pathways that yield this ignition delay enhancement are believed to be through the HO 2 and RO 2 (R = alkyl group) radicals reacting with NO. 36 In this work, a single-zone perfectly stirred reactor with heattransfer and detailed chemistry is applied to model the premixed burn and cool-down within the CV.…”

Section: ' Introductionmentioning

confidence: 99%

Minor Species Production from Lean Premixed Combustion and Their Impact on Autoignition of Diesel Surrogates

et al. 2011

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Formation of minor species, including NO, NO2, and OH, during the premixed burn and cool-down in a constant-volume combustion vessel (CV) was modeled to investigate the effect of these species on the chemical kinetics portion of the ignition delay of n-heptane used as a diesel surrogate. Control parameters included ambient temperature, pressure, and diluent level (EGR) matched to typical diesel engine conditions. For the preburn model, the GRI 3.0 mechanism was used with experimentally determined heat loss from the CV. Subsequently, the cool-down premixed burn products served as reactant inputs and were mixed stoichiometrically with n-heptane, modeled using a reduced reaction mechanism modified to include NO and NO2. Results computed with premixed burn constituents were compared to those using dry air and air plus ideal combustion residuals with the impact of dilution on ignition delay examined. A sensitivity analysis was performed to characterize the influence of OH and NO x levels on ignition delay. The preburn kinetics simulation showed OH concentrations above equilibrium; however, OH was below 100 ppb during the cool-down when fuel spray and ignition would occur. In contrast, the slow chemistry due to the low temperature (1750 K) prevents NO formation from reaching equilibrium levels; rather, levels are frozen in the 10−30 ppm range as the cool-down proceeded. This NO level is of the same order for cylinder charge concentrations in modern diesels when using 20−50% EGR rates producing 100−200 ppm in the exhaust. The ignition delay predictions showed that minor species of NO, NO2, and OH shorten the ignition delay by 3% relative to dry air, while being 6% longer when compared with the simulated dilution of 7.6% residuals (19% O2), typical of internal residuals in an engine. These kinetics effects are small in comparison to changes in oxygen concentration (from 21 to 15%) associated with EGR, which show a 170% increase in ignition delay.

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Effects of H2O and NO on extinction and re-ignition of vortex-perturbed hydrogen counterflow flames

Cited by 16 publications

References 28 publications

Near-lean blowoff dynamics in a liquid fueled combustor

Near-lean blowoff dynamics in a liquid fueled combustor

Advances in understanding combustion phenomena using non-premixed and partially premixed counterflow flames: A review

Minor Species Production from Lean Premixed Combustion and Their Impact on Autoignition of Diesel Surrogates

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