First-stage ignition delay in the negative temperature coefficient behavior: Experiment and simulation

Zhang, Peng; Ji, Weiqi; He, Tanjin; He, Xin; Wang, Zhi; Yang, Bin; Law, Chung K.

doi:10.1016/j.combustflame.2016.03.002

Cited by 87 publications

(34 citation statements)

References 24 publications

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“…Plots are on log-scale, and the evolution of OH/HO 2 radicals closely follow any heat release in the Low temperature regime. The mechanism involved has been described in detail in previous literature [59,60,61,62]. Briefly, PRF mixtures display significant LTHR and 2-stage ignition characteristics due to the low temperature radical chain branching pathways that lead to formation of ketohydroperoxides and eventually OH radical production.…”

Section: Resultsmentioning

confidence: 99%

Simulating HCCI Blending Octane Number of Primary Reference Fuel with Ethanol

Singh¹,

Waqas²,

Johansson³

et al. 2017

SAE Technical Paper Series

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The blending of ethanol with primary reference fuel (PRF) mixtures comprising n-heptane and iso-octane is known to exhibit a non-linear octane response; however, the underlying chemistry and intermolecular interactions are poorly understood. Well-designed experiments and numerical simulations are required to understand these blending effects and the chemical kinetic phenomenon responsible for them. To this end, HCCI engine experiments were previously performed at four different conditions of intake temperature and engine speed for various PRF/ethanol mixtures. Transfer functions were developed in the HCCI engine to relate PRF mixture composition to autoignition tendency at various compression ratios. The HCCI blending octane number (BON) was determined for mixtures of 2-20 vol % ethanol with PRF70. In the present work, the experimental conditions were considered to perform zerodimensional HCCI engine simulations with detailed chemical kinetics for ethanol/PRF blends. The simulations used the actual engine geometry and estimated intake valve closure conditions to replicate the experimentally measured start of combustion (SOC) for various PRF mixtures. The simulated HCCI heat release profiles were shown to reproduce the experimentally observed trends, specifically on the effectiveness of ethanol as a low temperature chemistry inhibitor at various concentrations. Detailed analysis of simulated heat release profiles and the evolution of important radical intermediates (e.g., OH and HO 2 ) were used to show the effect of ethanol blending on controlling reactivity. A strong coupling between the low temperature oxidation reactions of ethanol and those of n-heptane and iso-octane is shown to be responsible for the observed blending effects of ethanol/PRF mixtures.

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Section: Resultsmentioning

confidence: 99%

Simulating HCCI Blending Octane Number of Primary Reference Fuel with Ethanol

Singh¹,

Waqas²,

Johansson³

et al. 2017

SAE Technical Paper Series

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“…As the pressure increases, the NTC region moves to the higher temperature region. As indicated in the literatures, the competition between the low‐temperature chain‐branching reactions and chain‐propagation reactions leads to the NTC behavior of fuels, and the low temperature chain‐branching reactions of alkane fuels as follows:

RH + normalX < = > HX + normalR

normalR + normalO 2 < = > RO 2

RO 2 < = > QOOH

QOOH + normalO 2 < = > normalO 2 QOOH

normalO 2 QOOH < = > OH + KOOH

KOOH < = > OH + KO

wherein R is the alkyl, X is OH or HO 2 radical, QOOH is the hydroperoxyalkyl, and KOOH is the ketohydroperoxide. In the NTC region, the forward reactions (2) and (4) are inhibited, and the competition of the chain‐propagation reactions is enhanced as the temperature increases.…”

Section: Resultsmentioning

confidence: 99%

“…Furthermore, the rest of C 4 H 8 OOH isomers abstract the HO 2 radicals to form 1‐butene (20.69%) and 2‐butene (25.99%). As we know, 1‐butene and 2‐butene formed above undergo a chain propagation process, which reduces the overall reactivity …”

Section: Resultsmentioning

confidence: 99%

“…As the pressure increases, the NTC region moves to the higher temperature region. As indicated in the literatures, [42][43][44] the competition between the lowtemperature chain-branching reactions and chainpropagation reactions leads to the NTC behavior of fuels, and the low temperature chain-branching reactions of alkane fuels as follows:…”

Section: Effect Of Initial Pressurementioning

confidence: 99%

“…As we know, 1-butene and 2-butene formed above undergo a chain propagation process, which reduces the overall reactivity. [42][43][44]47 Figure 10B shows the reaction pathway of n-butane and TBHP in the n-butane/TBHP fuel with R TBHP = 10% at 750 K and 0.1 MPa. It can be seen that the proportion of the reaction channels combining with OH radicals increases greatly compared with the pathway of pure n-butane and that of the reaction channel combining with HO 2 radicals decreases greatly.…”

Section: Reaction Pathway Analysismentioning

confidence: 99%

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Numerical investigation on ignition intensification of n‐butane with tert‐butyl hydroperoxide (TBHP) addition

et al. 2019

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Summary Aimed to intensify the ignition and combustion process of n‐butane fuel in micro internal combustion (IC) engines, ignition delay characteristics of n‐butane/air mixtures with tert‐butyl hydroperoxide (TBHP) addition ratios below 10% were investigated numerically by CHEMKIN‐PRO software. Results show that ignition delay times of n‐butane can be shortened nonlinearly with TBHP addition at initial temperatures of 650 K to 1000 K, namely, the reduction rate of ignition delay times rises slowly as the TBHP addition ratio increases. In addition, the negative temperature coefficient (NTC) behavior can be weakened significantly with TBHP addition at 650 K to 1000 K. Especially, the ignition delay time of n‐butane can be reduced about 32 times with 10% TBHP addition at 750 K. However, the ignition intensification effect of TBHP addition is slight when the initial temperature is above 1000 K. The acting mechanism of TBHP addition was investigated in detail by the rate of production and consumption (ROP), sensitivity, and reaction pathway analysis. The ROP analysis shows that the released and quickly consumed OH radicals with TBHP addition play an important role in promoting n‐butane ignition at the lower initial temperature. However, the relatively slow consumption rate of OH radicals at higher temperature weakens the intensification effect. Furthermore, the sensitivity analysis and reaction pathway analysis indicate that the dominated elemental reactions and reaction pathway vary significantly with TBHP addition at lower initial temperature.

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Detailed Kinetics in Combustion Simulation: Manifestation, Model Reduction, and Computational Diagnostics

Zhao

2017

Energy, Environment, and Sustainability

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First-stage ignition delay in the negative temperature coefficient behavior: Experiment and simulation

Cited by 87 publications

References 24 publications

Simulating HCCI Blending Octane Number of Primary Reference Fuel with Ethanol

Simulating HCCI Blending Octane Number of Primary Reference Fuel with Ethanol

Numerical investigation on ignition intensification of n‐butane with tert‐butyl hydroperoxide (TBHP) addition

Detailed Kinetics in Combustion Simulation: Manifestation, Model Reduction, and Computational Diagnostics

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