甲烷-T425混合物的着火动力学研究
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摘要
基于CHEMKIN PRO软件研究了不同初始温度和甲烷掺混比例下甲烷-T425(摩尔比分别为57.5%,42.5%的正庚烷、甲苯混合物,简称T425)混合物的着火特性,并进行了反应动力学分析.结果表明,甲烷-T425混合物的着火延迟时间随甲烷掺混比例的变化规律因初始温度不同而存在一定的差异.在中温区(725～925 K),当甲烷掺混比例低于82.5%时,混合物的着火延迟时间存在NTC(negative temperature coefficient)现象,随着甲烷掺混比例的增加,NTC现象消失.此外,混合物的着火延迟时间与甲烷掺混比例之间呈现出非线性的关系.根据着火延迟时间的变化规律,对30 MPa、当量比1.0条件下不同甲烷掺混比例的甲烷-T425混合物着火过程进行了反应路径分析,结果表明,高甲烷掺混比例下,混合燃料着火延迟时间NTC现象的消失是正庚烷的负温度系数现象和甲烷、甲苯正温度系数现象综合作用的结果.
Based on CHEMKIN PRO software, the ignition characteristics of methane-T425 mixture at different initial temperatures and methane blending ratios were studied, and the reaction kinetics was analyzed.(mixture of n-heptane and toluene with molar ratios of 57.5 % and 42.5 %, respectively, i.e. T425). The results show that the ignition delay time of methane-T425 mixture varies with the methane blending ratio due to different initial temperatures. Within the medium temperature region(725～925 K), when the mixing ratio of methane is lower than 82.5 %, NTC(negative temperature coefficient) phenomenon exists in the ignition delay time of the mixture. With the increase of the mixing ratio of methane, NTC phenomenon disappears. In addition, there is a nonlinear relationship between the ignition delay time of the mixture and the methane blending ratio. According to the variation rule of ignition delay time, the ignition process of methane-T425 mixture with different methane blending ratios at 30 ATM and equivalence ratio of 1.0 was analyzed. The results show that at high methane blending ratio, the disappearance of NTC phenomenon of ignition delay time of mixed fuel is the combined effect of negative temperature coefficient phenomenon of n-heptane and positive temperature coefficient phenomenon of methane and toluene.
Based on CHEMKIN PRO software, the ignition characteristics of methane-T425 mixture at different initial temperatures and methane blending ratios were studied, and the reaction kinetics was analyzed.(mixture of n-heptane and toluene with molar ratios of 57.5 % and 42.5 %, respectively, i.e. T425). The results show that the ignition delay time of methane-T425 mixture varies with the methane blending ratio due to different initial temperatures. Within the medium temperature region(725～925 K), when the mixing ratio of methane is lower than 82.5 %, NTC(negative temperature coefficient) phenomenon exists in the ignition delay time of the mixture. With the increase of the mixing ratio of methane, NTC phenomenon disappears. In addition, there is a nonlinear relationship between the ignition delay time of the mixture and the methane blending ratio. According to the variation rule of ignition delay time, the ignition process of methane-T425 mixture with different methane blending ratios at 30 ATM and equivalence ratio of 1.0 was analyzed. The results show that at high methane blending ratio, the disappearance of NTC phenomenon of ignition delay time of mixed fuel is the combined effect of negative temperature coefficient phenomenon of n-heptane and positive temperature coefficient phenomenon of methane and toluene.
引文
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[3] LIANG J, ZHANG Z, LI G, et al. Experimental and kinetic studies of ignition processes of the methane-n-heptane mixtures[J]. Fuel, 2019(1):522-529.
[4] 姚春德,臧儒振,王建云,等.正庚烷-甲烷二元燃料着火特性的模拟研究[J].天津大学学报:自然科学与工程技术版,2015,48(2):119-125.
[5] 李永哲.低温燃烧柴油、汽油燃料替代物的试验研究[D].天津:天津大学,2011.
[6] CORCIONE F E, COSTA M, ALLOCCA L, et al. Study of multiple injections and auto-ignition of diesel sprays in a constant volume vessel[C].The Proceedings of the International Symposium on Diagnostics and Modeling of Combustion in Internal Combustion Engines, Tokyo, 2004.
[7] HERNANDEZ J J, SANZ-ARGENT J, BENAJES J, et al. Selection of a diesel fuel surrogate for the prediction of auto-ignition under HCCI engine conditions[J]. Fuel, 2008,87(6):655-665.
[8] HUANG J, HILL P G, BUSHE W K, et al. Shock-tube study of methane ignition under engine-relevant conditions: experiments and modeling[J]. Combustion and flame, 2004(1):25-42.
[9] HERZLER J, FIKRI M, HITZBLECK K, et al. Shock-tube study of the autoignition of n-heptane/toluene/air mixtures at intermediate temperatures and high pressures[J]. Combustion and Flame, 2007(1):25-31.
[10] ANDRAE J C G, BJORNBOM P, CRACKNELL R F, et al. Autoignition of toluene reference fuels at high pressures modeled with detailed chemical kinetics[J]. Combustion and Flame, 2007(1):2-24.
[11] ZHAO P, LAW C K. The role of global and detailed kinetics in the first-stage ignition delay in NTC-affected phenomena[J]. Combustion and Flame, 2013,160(11):2352-2358.
[12] POON H M, PANG K M, NG H K, et al. Development of multi-component diesel surrogate fuel models–part II: Validation of the integrated mechanisms in 0-D kinetic and 2-D CFD spray combustion simulations[J]. Fuel, 2016(1):120-130.
[13] MURPHY M J, TAYLOR J D, MCCORMICK R L. Compendium of experimental cetane number data[M]. Golden: National Renewable Energy Laboratory, 2004.
[14] MEHL M, PITZ W J, WESTBROOK C K, et al. Kinetic modeling of gasoline surrogate components and mixtures under engine conditions[J]. Proceedings of the Combustion Institute, 2011,33(1):193-200.
[15] ANDRAE J C G. Development of a detailed kinetic model for gasoline surrogate fuels[J]. Fuel, 2008,87(10):2013-2022.
[16] HARTMANN M, GUSHTEROVA I, FIKRI M, et al. Auto-ignition of toluene-doped n-heptane and iso-octane/air mixtures: high-pressure shock-tube experiments and kinetics modeling[J]. Combustion and Flame, 2011,158(1):172-178.
[17] PETERSEN E L, HALL J M, SMITH S D, et al. Ignition of lean methane-based fuel blends at gas turbine pressures[J]. Journal of Engineering for Gas Turbines and Power, 2007,129(4):937-944.
[18] 许汉君.柴油/甲醇二元燃料燃烧反应动力学研究[D].天津:天津大学,2012.