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- 2015
稀释气对高甲烷含量天然气燃烧特性的影响
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Abstract:
针对高甲烷含量天然气在实际发动机中燃烧温度过高、NOx排放过高的问题,利用定容燃烧弹实验和Chemkin软件模拟计算相结合的方法,对其预混层流燃烧特性进行研究,分析了不同稀释比和稀释气种类(N2和CO2)对混合气的层流火焰速度、NOx摩尔分数、燃烧压力和燃烧期等燃烧特性参数的影响。研究表明,层流火焰速度、质量燃烧率和热释放率均随稀释比的增加而减小,稀释气添加导致火焰温度下降,从而降低了NOx摩尔分数。Markstein长度和火焰厚度都随稀释比的增加而增加,火焰流动不稳定性得到抑制。添加稀释气导致燃烧压力峰值和压力升高率降低、燃烧期延长,与N2相比,CO2对混合气燃烧特性的稀释效果更加显著,从而为通过废气再循环技术路径降低高甲烷含量天然气发动机燃烧温度,控制NOx排放提供了理论指导。
The combustion characteristics of premixed laminar flames of natural gas with high methane content were studied to reveal the influences of dilution ratio and diluent kinds (N2 and CO2) on the combustion characteristics such as the laminar flame speed, NOx mole fraction, combustion pressure and combustion duration. The study results show that the laminar flame speed, the mass burning flux and the heat release rate all decrease with the increasing of dilution ratio; and with the addition of diluents, the flame temperature decreases, hence decreasing the NOx mole fraction. The Markstein length and flame thickness also increase with the dilution ratio, indicating that the flow instability of flame is suppressed. The combustion pressure peak and the pressure rising rate decrease while the combustion duration increases with the addition of diluents. Additionally, compared with N2, CO2 has more obvious dilution effect on the combustion characteristics of natural gas with high methane content
| [1] | ［1］HEFFEL J W. NOx emission reduction in a hydrogen fueled internal combustion engine at 3000 rpm using exhaust gas recirculation ［J］. International Journal of Hydrogen Energy, 2003, 28(11): 1285？？1292. |
| [2] | ［2］CHO G, MOON G, JEONG D, et al. Effects of internal exhaust gas recirculation on controlled auto？？ignition in a methane engine combustion ［J］. Fue1, 2009, 88(6): 1042？？1048. |
| [3] | ［4］TANG C L, ZHENG J J, HUANG Z H, et al. Study on nitrogen diluted propane？？air premixed flames at elevated pressures and temperatures ［J］. Energy Conversion and Management, 2010, 51(2): 288？？295. |
| [4] | ［5］LIAO S Y, JIANG D M, GAO J, et al. Measurements of Markstein numbers and laminar burning velocities for natural gas？？air mixtures ［J］. Energy and Fuels, 2004, 18(2): 316？？326. |
| [5] | ［8］HU E J, HUANG Z H, LIU B, et al. Experimental study on combustion characteristics of a spark？？ignition engine fueled with natural gas？？hydrogen blends combining with EGR ［J］. International Journal of Hydrogen Energy, 2003, 34(2): 1035？？1044. |
| [6] | ［9］TANG C L, ZHANG S, SI Z B, et al. High methane natural gas/air explosion characteristics in confined vessel ［J］. Journal of Hazardous Materials, 2014, 278: 520？？528. |
| [7] | ［10］TANG C L, HUANG Z H, JIN C, et al. Laminar burning velocities and combustion characteristics of propane？？hydrogen？？air premixed flames ［J］. International Journal of Hydrogen Energy, 2008, 33(18): 4906？？4914. |
| [8] | ［18］KEE R J, GRCAR J F, SMOOKE M D, et al. A Fortran program for modeling steady laminar one？？dimensional pre？？mixed flames, SNAD85？？8240 ［R］. Albuquerque, USA: Sandia National Laboratory, 1985. |
| [9] | ［19］THIERRY P, DENIS V. Theoretical and numerical combustion ［M］. Philadelphia, USA: R.T. Edwards, Inc., 2005. |
| [10] | ［20］ZHANG B, XIU G L, BAI C H. Explosion characteristics of argon/nitrogen diluted natural gas？？air mixtures ［J］. Fuel, 2014, 124(5): 125？？132. |
| [11] | ［3］ABD？？ALLA G H, SOLIMAN H A, BADR O A, et al. Effects of diluent admissions and intake air temperature in exhaust gas recirculation on the emissions of an indirect injection dual fuel engine ［J］. Energy Conversion and Management, 2001, 42(8): 1033？？1045. |
| [12] | ［7］STONE R, CLARKE A, BECKWITH P. Correlations for the laminar？？burning velocity of methane/diluent/air mixtures obtained in free？？fall experiments ［J］. Combustion and Flame, 1998, 114(3/4): 546？？555. |
| [13] | ［11］TANG C L, HUANG Z H, JIN C, et al. Explosion characteristics of hydrogen？？nitrogen？？air mixtures at ele？？vated pressures and temperatures ［J］. International Journal of Hydrogen Energy, 2009, 34(1): 554？？561. |
| [14] | ［12］BRADLEY D, GASKELL P H, GU X J. Burning velocities, Markstein lengths, and flame quenching for spherical methane？？air flames: a computational study ［J］. Combustion and Flame, 1996, 104(1/2): 176？？198. |
| [15] | ［13］TANG C L, HE J J, HUANG Z H, et al. Measurements of laminar burning velocities and Markstein lengths of propane？？hydrogen？？air mixtures at elevated |
| [16] | pressures and temperatures ［J］. International Journal of Hydrogen Energy, 2008, 33(23): 7274？？7285. |
| [17] | ［14］HUANG Z H, ZHANG Y, ZENG K, et al. Measurements of laminar burning velocities for natural gas？？hydrogen？？air mixtures ［J］. Combustion and Flame, 2006, 146(1/2): 302？？311. |
| [18] | ［15］蒋德明. 内燃机燃烧与排放学 ［M］. 西安: 西安交通大学出版社, 2001. |
| [19] | ［16］GIBAUD C, SNYDER J A, SICK V, et al. Laser？？induced fluorescence measurements and modeling of absolute CH concentrations in strained laminar methane/air diffusion flames ［J］. Proceedings of the Combustion Institute, 2005, 30(1): 455？？463. |
| [20] | ［17］EL？？ASRAG H, LU T, LAW C K, et al. Simulation of soot formation in turbulent premixed flames ［J］. Combustion and Flame, 2007, 150(1/2): 108？？126. |
| [21] | ［6］GU X J, HAQ M Z, LAWES M, et al. Laminar burning velocity and Markstein lengths of methane？？air mixtures ［J］. Combustion and Flame, 2000, 121(1/2): 41？？58. |
