Effects of fuel-air mixing on flame structures and NOx emissions in swirling methane jet flames

T. S. Cheng, Y. C. Chao, D. C. Wu, T. Yuan, C. C. Lu, C. K. Cheng, J. M. Chang

研究成果: Conference article同行評審

66 引文 斯高帕斯(Scopus)

摘要

An experimental investigation is performed to study the effects of initial fuel-air mixing on NOx and CO emissions in swirling methane jet flames. The major parameters used to modify the initial fuel-air mixing ahead of the swirling flame are the swirl number, the fuel-air momentum flux ratio, and the fuel injection location. Two characteristic swirling combustion modes, the fuel jet-dominated (type-1) and the strongly recirculating (type-2) flames, are identified from flame visualization and 2-D laser-induced predissociative fluorescence imaging of OH by varying the fuel-air momentum flux ratio. Laser Doppler velocimetry (LDV) measurements show that the shear layer between the edge of the swirling recirculation zone and the external flow is a highly turbulent and rapid mixing region. The maximum mean flame temperature is located at the edge of the recirculation zone, indicating violent combustion and strong mixing of fuel, air, and hot products in this region. Strong and rapid mixing of the strongly recirculating flame, which increases mixture homogeneity and shortens the characteristic time for NOx formation, results in a lower NOx emission index than that in the fuel jet-dominated flame. Excess cold air entrained by the swirling flow may quench the combustion and the hot products, resulting in an increase of CO emission, indicating poor combustion efficiency. By modifying the fuel injection pattern with the annular fuel injector, which changes the fuel-air mixing pattern and properly smooths the rapid mixing leading to a higher flame temperature, the NOx emission level can further be reduced with a significant decrease in CO emission.

原文English
頁(從 - 到)1229-1237
頁數9
期刊Symposium (International) on Combustion
27
發行號1
DOIs
出版狀態Published - 1998
事件27th International Symposium on Combustion - Boulder, CO, United States
持續時間: 1998 八月 21998 八月 7

All Science Journal Classification (ASJC) codes

  • 化學工程 (全部)
  • 燃料技術
  • 能源工程與電力技術
  • 機械工業
  • 物理與理論化學
  • 流體流動和轉移過程

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