Chemical Flame Length of a Methane Jet into Oxidant Stream

The present paper reports a systematic study on different methods of obtaining the chemical length of a turbulent non-premixed CH (4) jet flame. The study is performed based on numerical simulations by the RANS modeling over wide ranges of the fuel jet velocity (25 similar to 100 m/s), the coflow oxygen concentration (6 similar to 100 % by volume) and the coflow temperature (300 similar to 2000 K). To validate the modeling, some calculations are compared with previous measurements of Dally et al. (Proc. Combust. Inst. 29, 1147-1154, 2002) and Kim et al. (Energy Fuels 21, 1459-1467, 2007). Primary results reveal that, among seven different definitions of chemical flame length, the best performance is made by those defined from the yield ratio of CO to CO (2) at y (C O) / y (C O2)= 0.02 and the carbon monoxide ratio at R (C O) = X (C O) /X (C O m a x) = 0.01. It is also found that only use of these two definitions exhibit the flame lift-off behavior and to gain the lift-off height properly. Besides, this paper explains the importance of taking the near-zero contour of the CO concentration as the base on which the border of the complete combustion region is defined for chemical flame length.