Shock tube and kinetic study on ignition characteristics of lean methane/n-heptane mixtures at low and elevated pressures

Gong, Zhen; Feng, Liyan; Wei, Lai; Qu, Wenjing; Li, Lincheng

doi:10.1016/j.energy.2020.117242

Cited by 19 publications

(8 citation statements)

References 39 publications

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“…Shock tube data for methane/ n -heptane mixtures are available from Liang et al (1257–1763 K and 10 atm), Gong and co-workers , (1257–1825 K and 2 atm), and Schuh et al (785–1284 K and 60 atm). In this study, the methane/ n -heptane combined models are compared to the data from Schuh et al and Liang et al The data of Gong and co-workers , were deemed to be less relevant for this study due to the lower pressure.…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Evaluation of a Semiglobal Approach for Modeling Methane/n-Heptane Dual-Fuel Ignition

et al. 2021

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Because of the relatively high autoignition temperature of natural gas, its use in conventional diesel engines requires a pilot fuel, typically diesel oil, to promote ignition. To conduct computational fluid dynamics (CFD) simulations of the combustion in such engines, there is a need for dual-fuel combustion models that achieve a balance between computational efficiency and accuracy. This study investigates a semiglobal approach for modeling ignition of n-heptane/methane mixtures. In the semiglobal approach, the heptane oxidation is modeled by using a four-step global scheme from Müller, Peters, and Liñán (MPL) (1992), while the methane chemistry is described by a skeletal mechanism with 22 species, derived from a detailed reaction mechanism. The resulting semiglobal model includes 25 species and 138 reactions. Both the global heptane mechanism and the merged semiglobal dual-fuel model are validated against a wide range of ignition delay data from shock tubes as well as through comparison with predictions of the detailed heptane mechanism by Zhang et al. (2016). The MPL model cannot fully capture the ignition delay across the negative temperature coefficient (NTC) region for an n-heptane/air mixture. Despite this shortcoming, the ignition delay at high pressure (38–55 atm) is predicted typically within a factor of 2 compared to experiments. Under dual-fuel conditions with methane as the main fuel, the NTC behavior is less pronounced. Methane ignition is promoted by heat release from the n-heptane oxidation rather than by any direct chemical interaction. Predictions of ignition delays using the combined global/skeletal model are in good agreement with the n-heptane/methane measurements reported by Schuh et al. (2019; 60 atm, 785–1284 K), while at the higher temperatures and lower pressures of the experiments of Liang et al. (2019; 10 atm, 1257–1763 K), predictions are accurate within a factor of 2 for methane contents of 90% and higher. The present results indicate that it is possible with a small combined model to predict the ignition delay for methane/n-heptane mixtures with sufficient accuracy for practical use. The semiglobal model approach can thus be employed in CFD simulations, facilitating development of sustainable dual-fuel engines as well as identification of optimal fuel compositions and conditions.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Evaluation of a Semiglobal Approach for Modeling Methane/n-Heptane Dual-Fuel Ignition

et al. 2021

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“…It has been observed in engine experiments that the ignition of diesel spray is retarded if the ambient air contains methane [1,2]. This is confirmed by numerous experimental studies which were carried out in fundamental reactors, such as shock tube (ST) [3,4], rapid compression machine [2].…”

Section: Introductionmentioning

confidence: 89%

“…To gain a better understanding of the ignition process, numerical simulations are carried out. Zerodimensional (0-D) homogeneous reactor (HR) calculations were performed to have more insights on the role of each reactions during methane/n-heptane ignition [3,4,5,6]. In all cases, methane addition is shown to delay the ignition of n-heptane mixture.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Reduced n-Heptane Mechanisms in Dual-Fuel Combustion

Ong

Walther

Bai

et al. 2021

Preprint

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“…is is the complete oxidation process of n-heptane. On the basis of the above discussion, the first 16 representative reactions in Table 1 [43,44], which are also very important in the previous sensitivity analysis, are selected for sensitivity analysis under three different α values.…”

Section: Effect Of H 2 Additionmentioning

confidence: 99%

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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Shock tube and kinetic study on ignition characteristics of lean methane/n-heptane mixtures at low and elevated pressures

Cited by 19 publications

References 39 publications

Evaluation of a Semiglobal Approach for Modeling Methane/n-Heptane Dual-Fuel Ignition

Evaluation of a Semiglobal Approach for Modeling Methane/n-Heptane Dual-Fuel Ignition

Evaluation of Reduced n-Heptane Mechanisms in Dual-Fuel Combustion

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

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