On the effect of injection timing on the ignition of lean PRF/air/EGR mixtures under direct dual fuel stratification conditions

Luong, Minh Bau; Sankaran, Ramanan; Yu, Gwang Hyeon; Chung, Suk Ho; Yoo, Chun Sang

doi:10.1016/j.combustflame.2017.05.023

Cited by 56 publications

(37 citation statements)

References 72 publications

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“…Note that the prediction of F Sa,S for the previous n-heptane and other fuels under various conditions [25][26][27][28][29][30][31][32][33][34] is validated by comparing F Sa,S with F S of the previous DNS studies that shows a satisfactory agreement between F Sa,S and F S (not shown here). For example, with T = 15 K, both F Sa,S and F S are approximately equal to unity for T 0 of 850 K, 934 K, and 1008 K, confirming a purely spontaneous ignition for all these three cases [25].…”

Section: A Temperature Fluctuationsmentioning

confidence: 53%

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: A Temperature Fluctuationsmentioning

confidence: 53%

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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“…However, the study was limited to specific initial conditions, including fixed turbulence and stratification levels. Other 2d DNS studies [42][43][44] highlighted influences of mixing time-scales, temperature, fuel stratification, and turbulence on ignition characteristics, and reported existence of both deflagrative and spontaneous ignition, specifically, at early phases of ignition. More recently, Liu et al [45] carried out an experimental study to examine effects of different fuel stratification levels on the ratio of flame front propagation and autoignition in RCCI, where increased port injection mass fractions resulted in observable flame front propagation.…”

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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“…Achieved also was high thermal efficiency of 48.7% with a very low NOx and soot emissions. Utilizing a considerable quantity of the fuel during the first injection timing enables effective control of the combustion by maximizing evaporative cooling in the squish region as similarly reported in [9]. Despite the achievement of the DDI technique, an unacceptable rise in the CO and UHC emission still manifested at low load [10].…”

Section: Introductionmentioning

confidence: 92%

An Experimental Investigation on the Influence of Port Injection at Valve on Combustion and Emission Characteristics of B5/Biogas RCCI Engine

et al. 2020

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High unburned hydrocarbon (UHC) and carbon monoxide (CO) emissions, on account of the premixed air-fuel mixture entering the crevices and pre-mature combustion, are setbacks to reactivity-controlled compression ignition (RCCI) combustion at a low load. The influence of direct-injected B5 and port injection of biogas at the intake valve was, experimentally, examined in the RCCI mode. The port injection at the valve was to elevate the temperature at low load and eliminate premixing for reduced pre-mature combustion and fuel entering the crevices. An advanced injection timing of 21° crank angle before top dead centre and fraction of 50% each of the fuels, were maintained at speeds of 1600, 1800 and 2000 rpm and varied the load from 4.5 to 6.5 bar indicated mean effective pressure (IMEP). The result shows slow combustion as the load increases with the highest indicated thermal efficiency of 36.33% at 5.5 bar IMEP. The carbon dioxide and nitrogen oxides emissions increased, but UHC emission decreased, significantly, as the load increases. However, CO emission rose from 4.5 to 5.5 bar IMEP, then reduced as the load increases. The use of these fuels and biogas injection at the valve were capable of averagely reducing the persistent challenge of the CO and UHC emissions, by 20.33% and 10% respectively, compared to the conventional premixed mode.

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On the effect of injection timing on the ignition of lean PRF/air/EGR mixtures under direct dual fuel stratification conditions

Abstract: CS (2017) On the effect of injection timing on the ignition of lean PRF/air/ EGR mixtures under direct dual fuel stratification conditions. Combustion and Flame 183: 309-321.

Cited by 56 publications

References 72 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

An Experimental Investigation on the Influence of Port Injection at Valve on Combustion and Emission Characteristics of B5/Biogas RCCI Engine

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