Autoignition of n-Butanol/n-Heptane Blend Fuels in a Rapid Compression Machine under Low-to-Medium Temperature Ranges

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• 作者：Zheng Yang ; Yong Qian ; Xin Yang ; Yue Wang ; Ya Wang ; Zhen Huang ; Xingcai Lu
• 刊名：Energy & Fuels
• 出版年：2013
• 出版时间：December 19, 2013
• 年：2013
• 卷：27
• 期：12
• 页码：7800-7808
• 全文大小：585K
• 年卷期：v.27,no.12(December 19, 2013)
• ISSN：1520-5029

文摘

Ignition delay times of n-butanol/n-heptane mixtures (0%, 20%, 40%, 60% n-butanol in moles) were measured using a rapid compression machine at compressed pressures of 15, 20, and 30 bar, in the compressed temperature range of 650鈥?30 K, and with equivalence ratios of 0.4, 1.0, and 1.5. Sensitivity analysis and reaction fluxes analysis were performed using a detailed mechanism of blend fuels so as to evaluate the impact of n-heptane addition on the ignition and combustion process. Over the experimental conditions in this study, the blend fuels display apparent low and high temperature reactions and a negative-temperature-coefficient (NTC) behavior; with increasing n-butanol mole fraction in the mixtures, the ignition delay times increased; the pressure curves present two-stage heat release behavior at low temperature but one-stage behavior at high temperature. It is worth noting that the n-butanol mole fraction shows negligible effect on the ignition delay times for equivalence ratios of 1.5 at low temperature. Moreover, compressed pressure has a limited effect on the ignition of blend mixture at low temperature but certain influence at medium temperature range. The chemical analysis indicates that n-butanol also presents the NTC behavior because of the low temperature reactivity radicals pool produced by n-heptane. Sensitivity analysis shows that for the pure n-butanol fuel, H-abstraction from the 纬-carbon plays the dominant role in the reactions having the promoting effect on the low-temperature branching, while the major inhibiting reaction is H-abstraction from the 伪-carbon; for n-butanol/n-heptane mixtures, more reactions play the leading role. The major promoting reactions include some H-abstraction reactions from n-heptane, while the major inhibiting reactions add some elementary reactions of small radicals.