The deconvolution of the thermal, dilution, and chemical effects of exhaust gas recirculation (EGR) on the reactivity of engine and flame soot

Al-Qurashi, Khalid; Lueking, Angela D.; Boehman, André L.

doi:10.1016/j.combustflame.2011.02.006

Cited by 88 publications

(40 citation statements)

References 47 publications

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“…They found that EGR addition retards the autoignition timing for all five fuels studied, and the amount of retardation is dependent on the specific fuel type. Al-Qurashi et al [5] successfully isolated and examined the thermal, chemical, and dilution effects of the CO2 (approximately simulate EGR) on soot reactivity in a diesel engine and a laminar co-flow ethylene diffusion flame. The authors reported that the magnitudes of three effects on the soot reactivity rank thermal effect (45%) as most important, dilution effect (35%) second, and chemical effect (20%) as the least important.…”

Section: Introductionmentioning

confidence: 99%

Effects of Buffer Gas Composition on Autoignition of Dimethyl Ether

et al. 2015

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Abstract:Experimental and numerical studies are conducted on the thermal, chemical and dilution effects of buffer gas composition on autoignition of dimethyl ether (DME). The buffer gases considered are nitrogen (N2), a mixture of N2 and argon (Ar) at a mole ratio of 50%/50% and a mixture of Ar and carbon dioxide (CO2) at a mole ratio of 61.2%/38.8%. Experiments are performed using a rapid compression machine (RCM) at compressed pressure of 10 bar, equivalence ratio (φ) of 1, and compressed temperature from 670 K to 795 K. The N2 dilution ratio considered ranges from 36.31% to 55.04%. The experimental results show that buffer gas composition has little impact on the first-stage ignition delay. However, significant differences in the total ignition delay as a function of buffer gas composition are observed in the negative temperature coefficient (NTC) region. Compared to N2, N2/Ar (50%/50%) mixture decreases the total ignition delay by 31%. The chemical effects of buffer gas composition on the first-stage and total ignition delays are negligible. With increasing N2 dilution ratio, the first-stage ignition delay slightly increases, while a significant increase in the total ignition delay is observed. Moreover, the NTC behavior of total ignition delay is noted to become more pronounced at high N2 dilution ratio. The heat release during the first-stage ignition decreases as N2 dilution ratio increases. Results of OPEN ACCESSEnergies 2015, 8 10199 numerical simulations with the Zhao DME mechanism over a wider range of temperature show good agreement with that of experiments. Further numerical simulations are conducted using pure N2, Ar and CO2 as buffer gases. Results indicate that the thermal effects are the dominant factor in low temperature and NTC regions. The chemical effects become pronounced in the NTC region, and the chemical effect of CO2 exceeds the thermal effect at the compressed temperature higher than 880 K.

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Section: Introductionmentioning

confidence: 99%

Effects of Buffer Gas Composition on Autoignition of Dimethyl Ether

et al. 2015

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“…Radiation and transport effects were found to be negligible in this flame configuration. As concerns soot reactivity [23], these three effects account for 45% (thermal), 35% (dilution) and 20% (chemical) in a CO 2 -diluted ethylene flame. It has been shown at room temperature [24,25] that when induced by dilution, flame lifting is controlled by the critical flow rate ratio (Q diluent /Q air ) lifting .…”

Section: Introductionmentioning

confidence: 99%

On preheating and dilution effects in non-premixed jet flame stabilization

Lamige

Min

Galizzi

et al. 2013

Combustion and Flame

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The impact of preheating and dilution on methane/air non-premixed flame stability are studied experimentally. Six preheating levels are considered for initial reactant temperature between 295 K and 850 K in a round jet configuration. Four diluent gases are added on the air-side, either CO 2 , N 2 , Ar or a (CO 2 + Ar) mixture having the same molar heat capacity as N 2. For undiluted flames, jet transition velocities between attached and lifted states are investigated depending on initial reactant temperature. The hysteresis zone defined by these stability limits is shifted towards higher jet velocities with preheating. Whereas jet and coflow temperatures were identical in similar previous experiments, the present work allows examination of the thermal effects from either fuel or oxidizer streams. Flame stability is described based on the propagative aspects of the flame leading-edge, by analogy with the temperature dependency of the laminar burning velocity of a stoichiometric mixture. Results show that the jet temperature has a major influence on the lifting of an attached flame, whereas the coflow temperature remains important for the reattachment of a lifted flame. In addition, flame stability experiments have been performed at high levels of both preheating and dilution. Stability maps of critical dilution ratios at lifting have been obtained with preheating. It appears that the ability of a diluent to break flame stability keeps the same relative order as at ambient temperature. It is even enhanced with preheating because higher temperature widens the gap between diluent molar heat capacities Cp. The Cp approach is however not sufficient to interpret the temperature dependency of the relative influence of the different dilution effects. Furthermore, the role played by the jet flow regime on attached flame stability in dilution-induced lifting experiments is highlighted when dilution is coupled with preheating.

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“…Besides of the emissions, EGR may also influence engine performance, carbon deposits, and wear of various parts of a diesel engine (Al-Qurashi et al 2011;Agarwal et al 2011;Ghazikhani et al 2010). EGR displaces oxygen in the intake air by exhaust gas recirculated to the combustion chamber.…”

Section: Exhaust Gas After Treatmentmentioning

confidence: 99%