Experimental and kinetic studies of ignition processes of the methane–n-heptane mixtures

Liang, Junjie; Zhang, Zunhua; Li, Gesheng; Wan, Qing; Li, Xu; Fan, Shidong

doi:10.1016/j.fuel.2018.08.041

Cited by 40 publications

(28 citation statements)

References 31 publications

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“…While numerous experimental data on ignition are available for methane- [28,29,30] and nhexane-based [31,32,33,34,35] mixtures, experimental data for dual-fuel methanen-alkane mixtures are scarce. Liang et al [36] studied the ignition delay-time of n-heptane-methane-based mixtures in a shock tube. The present study differs from that of Liang et al in the approach used to prepare the mixtures.…”

Section: Introductionmentioning

confidence: 99%

Ignition characteristics of dual-fuel methane-n-hexane-oxygen-diluent mixtures in a rapid compression machine and a shock tube

Wang

Grégoire

et al. 2019

Fuel

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Ignition delay times of methane-n-hexane-oxygen mixtures were studied experimentally and numerically in a wide temperature range (640-2335 K) using both a rapid compression machine (RCM) and a shock tube (ST). The RCM results demonstrated a two-stage ignition and negative temperature coefficient (NTC) behavior. Increasing n-hexane concentration, pressure and equivalence ratio shortened the ignition delay time. For the ST experiments, the addition of 10% n-hexane (relative to methane) can reduce the ignition delay time dramatically. However, no further reduction effect can be achieved with increasing addition of n-hexane from 10% to 20%. In addition, increasing equivalence ratio reduces the effect of n-hexane addition on ignition delay time. Three detailed chemical mechanisms, CaltechMech, GalwayMech and LLNLMech, were evaluated based on a quantitative error analysis. LLNLMech and CaltechMech demonstrated the best performance in the RCM and ST temperature ranges, respectively. Chemical kinetic analyses showed that the addition of n-hexane to methane provides some chemical pathways not available for methane oxidation which result in the production of active radicals and eventually accelerate the ignition of the methane-oxygen mixtures. The crucial intermediate species for the ignition process are H 2 O 2 and H under RCM and ST conditions, respectively.

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Section: Introductionmentioning

confidence: 99%

Ignition characteristics of dual-fuel methane-n-hexane-oxygen-diluent mixtures in a rapid compression machine and a shock tube

Wang

Grégoire

et al. 2019

Fuel

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“…Figure 1 shows the comparison between the experimental values and the CSU mechanism of n-heptane [34], methane [35], methane/n-heptane [36], methane/H 2 [37,38], and H 2 /CO [39] in different operating conditions (temperature, pressure, equivalence ratio, and gas component content). It can be seen that the predicted values of ignition delay agree well with the experimental values in different temperature, pressure, and equivalence ratio ranges, which indicates that the current CSU mechanism can reproduce the ignition characteristics of n-heptane, methane, H 2 , and syngas.…”

Section: Mechanism Selection and Validationmentioning

confidence: 99%

“…Compared with the ignition delay time of H 2 , methane, and carbon monoxide, the ignition delay time of carbon monoxide is the shortest. For n-heptane, the negative coefficient temperature (NCT) behavior usually occurs in the middle-temperature [34], methane [35], methane/n-heptane [36], methane/H 2 [37,38], and H 2 /CO [39]. Solid line: simulation; symbols: experiment.…”

Section: Mechanism Selection and Validationmentioning

confidence: 99%

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A Numerical Study of the Effects of Using Reformer Gas on Ignition Characteristics under Dual-Fuel Engine-Relevant Conditions

Junwu

Guo

2022

International Journal of Chemical Engineering

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Natural gas/diesel dual-fuel engine has become an urgent need to alleviate the energy crisis and reduce emissions. As an additive, reforming gas can improve the combustion process of dual-fuel engines because it improves the combustion rate and compensates for the low reactivity of natural gas. Therefore, it is of great significance to study the ignition characteristics of natural gas diesel blends by adding H2 and syngas. Based on ANSYS Chemkin 17.0 software, the ignition delay time was solved by a closed uniform model. The effects of H2 and syngas on the ignition performance of a natural gas/diesel engine were studied. The results showed that the ignition delay time of the methane/n-heptane mixture was prolonged after adding H2 in the range of medium and low temperatures. This was due to the fact that reaction R3 (OH + H2 = H + H2O) was an endothermic reaction, which consumed OH radicals and inhibited the ignition process. In the high-temperature range, adding H2 reduced the ignition delay time of the mixture system, which was because of the significant increase in the sensitivity coefficients of R1(H + O2 = O + OH) and R3 and the generation of OH radicals. Therefore, the reduction in ignition delay caused by H2 addition in the high-temperature regions was mainly attributed to R3 and R1. In syngas, CO reduced the ignition delay time of methane/syngas/n-heptane. However, the addition of CO could reduce the importance of R3 in the reaction process—resulting in the weakening of the influence of H2 on ignition delay. This study can expand the theoretical basis of ignition characteristics of methane/n-heptane mixture with H2 and syngas under dual-fuel engine-relevant conditions.

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“…For natural gas, which is primarily composed of methane and minimal fractions of hydrogen, ethane, propane, or other mixtures depended on the sources and refinement methods, researchers usually adopt methane to predict the combustion process of natural gas. Many efforts have been devoted to studying the ignition process of n-heptane and methane in laboratory devices such as shock tubes [2,[16][17][18][19][20][21][22], flow reactors [23][24][25], rapid compression machines [26][27][28][29], and engines [30][31][32].…”

Section: Introductionmentioning

confidence: 99%

Development of a simplified n-heptane/methane model for high-pressure direct-injection natural gas marine engines

Liu

et al. 2021

Front. Energy

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High-pressure direct-injection (HPDI) of natural gas is one of the most promising solutions for the future ship engines, for which the combustion process is mainly controlled by the chemical kinetics. However, the employment of detail chemical mechanisms for the multi-dimensional combustion simulation is significantly expensive due to the large scale of the marine engine. In the present study, a reduced n-heptane/methane mechanism consisted of 35-step reactions was constructed using multiple reduction approaches. Then this mechanism was further reduced to include only 27 reactions by the HyChem (Hybrid Chemistry) method. An overall good agreement with the experimentally measured ignition delay data of both nheptane and methane for these two reduced mechanisms was achieved and reasonable predictions for the measured laminar flame speeds were obtained for the 35-step mechanism. But the 27-step mechanism cannot predict the laminar flame speed very well. In addition, these two reduced mechanisms were both able to reproduce the experimentally measured in-cylinder pressure and heat release rate profiles for a HPDI natural gas marine engine, although the engine-out CO emission was overpredicted and the NOx emission was slightly underestimated. The predicted distributions of temperature and equivalence ratio by the 35-step and 27-step mechanisms are similar with those of the 334-step mechanism. However, the predicted distributions of OH and CH2O are significantly different from those of the 334-step mechanism. In short, the developed reduced chemical kinetic mechanisms provide a high-efficient and dependable method to simulate the characteristics of combustion and emissions in HPDI natural gas marine engines.

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Experimental and kinetic studies of ignition processes of the methane–n-heptane mixtures

Cited by 40 publications

References 31 publications

Ignition characteristics of dual-fuel methane-n-hexane-oxygen-diluent mixtures in a rapid compression machine and a shock tube

Ignition characteristics of dual-fuel methane-n-hexane-oxygen-diluent mixtures in a rapid compression machine and a shock tube

A Numerical Study of the Effects of Using Reformer Gas on Ignition Characteristics under Dual-Fuel Engine-Relevant Conditions

Development of a simplified n-heptane/methane model for high-pressure direct-injection natural gas marine engines

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