Computational characterization of ignition regimes in a syngas/air mixture with temperature fluctuations

Pal, Pinaki; Valorani, Mauro; Arias, Paul G.; Im, Hong G.; Wooldridge, Margaret S.; Ciottoli, Pietro Paolo; Galassi, Riccardo Malpica

doi:10.1016/j.proci.2016.07.059

Cited by 47 publications

(23 citation statements)

References 43 publications

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“…The ignition regimes were classified into three categories: (1) weak ignition with the dominant mode of deflagration, (2) reaction-dominant strong, and (3) mixing-dominant strong with the dominant mode of spontaneous ignition. A recent DNS study has been conducted to verify the ignition regime diagram using syngas [66]. The results were consistent with the predictions by the ignition regime diagram.…”

Section: Introductionsupporting

confidence: 73%

Prediction of Ignition Regimes in DME/Air Mixtures with Temperature and Concentration Fluctuations

Luong¹,

Pérez²,

Sow³

et al. 2019

AIAA Scitech 2019 Forum

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The objective of the present study is to establish a theoretical prediction of the autoignition behavior of a reactant mixture for a given initial bulk mixture condition. The ignition regime criterion proposed by Im and coworkers based on the Sankaran number (Sa), which is a ratio of the laminar flame speed to the spontaneous ignition front speed, is extended to account for both temperature and equivalence ratio fluctuations. The extended ignition criterion is then applied to predict the autoignition characteristics of dimethyl ether (DME)/air mixtures and validated by two-dimensional direct numerical simulations (DNS). The response of the ignition mode of DME/air mixtures to three initial mean temperatures of 770, 900 K, and 1045 K lying within/outside the NTC regime, two levels of temperature and concentration fluctuations at a pressure of 30 atm and equivalence ratio of 0.5 is systematically investigated. The statistical analysis is performed, and a newly developed criterion-the volumetric fraction of Sa < 1.0, F Sa,S , is proposed as a deterministic criterion to quantify the fraction of heat release attributed to strong ignition. It is found that the strong and weak ignition modes are well captured by the predicted Sa number and F Sa,S regardless of different initial mean temperatures and the levels of mixture fluctuations and correlations. Sa p and F Sa,S demonstrated under a wide range of initial conditions as a reliable criterion in determining a priori the ignition modes and the combustion intensity.

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Section: Introductionsupporting

confidence: 73%

Prediction of Ignition Regimes in DME/Air Mixtures with Temperature and Concentration Fluctuations

Luong¹,

Pérez²,

Sow³

et al. 2019

AIAA Scitech 2019 Forum

Self Cite

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“…In single-fuel (SF) constant-volume conditions, there is a body of literature available that scrutinize the importance of ignition and subsequent combustion modes, where effects of temperature [23,[27][28][29][30][31][32][33][34][35][36][37][38][39] , and/or composition [33][34][35]39,40] , and/or velocity [28,31,35,36,38] fluctuations are taken into account. For instance, Pal et al [28,38] proposed regime diagrams which specify different modes of combustion with velocity and temperature fluctuations. More recently, Luong et al [39] studied the role of temperature and composition fluctuations based on a theoretical analysis for dimethyl ether/air mixtures and validated it against two-dimensional (2d) direct numerical simulations (DNS).…”

Section: Introductionmentioning

confidence: 99%

A numerical study on combustion mode characterization for locally stratified dual-fuel mixtures

Karimkashi

Kahila

Kaario

et al. 2020

Combustion and Flame

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a b s t r a c tCombustion modes in locally stratified dual-fuel (DF) mixtures are numerically investigated for methanol/n-dodecane blends under engine-relevant pressures. In the studied constant-volume numerical setup, methanol acts as a background low-reactivity fuel (LRF) while n-dodecane serves as high-reactivity fuel (HRF), controlling local ignition delay time. The spatial distribution of n-dodecane is modeled as a sinusoidal function parametrized by stratification amplitude ( Y ) and wavelength (0.01 mm <λ< 15 mm). In contrast, methanol is assumed to be fully premixed with air at equivalence ratio 0.8. First, onedimensional setup is investigated by hundreds of chemical kinetics simulations in ( Y , λ) parameter space. Further, the concepts by Sankaran et al. (2005, Proceedings of the Combustion Institute ) and Zeldovich (1980, Combustion and Flame ) on ignition front propagation speed are applied to develop a theoretical analysis of the time-dependent diffusion-reaction problem. The theoretical analysis predicts two combustion modes, (1) spontaneous ignition and (2) deflagrative propagation, and leads to an analytical expression for the border curve called β-curve herein. One-dimensional chemical kinetics simulations confirm the presence of two combustion modes in ( Y , λ) parameter space while the β-curve explains consistently the position of phase border observed in the simulations. Finally, the role of convective mixing is incorporated to the theoretical expression for the β-curve. The effect of convection on combustion modeis assessed by carrying out two-dimensional fully-resolved simulations with different turbulence levels. Two-dimensional numerical simulation results give evidence on combustion mode switching, which is consistent with predictions of the modified β-curve for turbulent cases. The practical output of the paper is the β-curve which is proposed as a predictive tool to estimate combustion modes for various fuels or fuel combinations.

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“…As 3D DNS involving accurate models for chemical, diffusion and thermodynamic processes are still not practical for systematic studies, the present work is mainly focused on 2D configurations, as done also for instance in [20, 21, 23, 28–30]. Yu et al [31] compared 2D and 3D DNS of auto-ignition of a lean H 2 /air mixture, and concluded that 3D turbulence results in faster heat transfer rate than 2D.…”

Section: Introductionmentioning

confidence: 99%

Direct Numerical Simulations of Hotspot-induced Ignition in Homogeneous Hydrogen-air Pre-mixtures and Ignition Spot Tracking

Chi

Abdelsamie

Thévenin

2018

Flow Turbulence Combust

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A systematic study relying on Direct Numerical Simulations (DNS) of premixed hydrogen-air mixtures has been performed to investigate the hotspot ignition characteristics and ignition probability under turbulent conditions. An ignition diagram is first obtained under laminar conditions by a parametric study. The impact of turbulence intensity on ignition delays and ignition probability is then quantified in a statistically-significant manner by repeating a large number of independent DNS realizations. By tracking in a Lagrangian frame the ignition spot, the balance between heat diffusion and heat of chemical reaction is observed as function of time. The evolution of each chemical species and radicals at the ignition spot is checked and the mechanism leading to ignition or misfire are analyzed. It is observed that successful ignition is mostly connected to a sufficient build-up of a HO2 pool, ultimately initiating production of OH. Turbulence always delays ignition, and ignition probability goes to zero at sufficiently high turbulence intensity when keeping temperature and size of the initial hotspot constant.

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Computational characterization of ignition regimes in a syngas/air mixture with temperature fluctuations

Cited by 47 publications

References 43 publications

Prediction of Ignition Regimes in DME/Air Mixtures with Temperature and Concentration Fluctuations

Prediction of Ignition Regimes in DME/Air Mixtures with Temperature and Concentration Fluctuations

A numerical study on combustion mode characterization for locally stratified dual-fuel mixtures

Direct Numerical Simulations of Hotspot-induced Ignition in Homogeneous Hydrogen-air Pre-mixtures and Ignition Spot Tracking

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