Extinction Limits of Swirl Nonpremixed Methane Flames and CH4/CxHy/N2 Mixtures: Experimental Evaluation and Thermodynamic Calculations

Abstract

In this study, we aimed to evaluate the extinction limits of fuel-rich and fuel-lean flames created in non-premixed coaxial swirl burner of combustion substrates. The experiments were performed with three types of fuels: methane and two mixtures of CH4/CxHy/N2. The analyzed fuels reflected varied composition of the natural gas containing methane, ethane, propane, butane, and nitrogen. The examination of the extinction limits of flames isolated from the surroundings with a quartz tube was based on the limit ratios of equivalence (Φ). Results showed that an increase in the stream of methane directed toward the burner improves blowout limits as determined by the equivalence ratios. However, this pattern was not observed for the other studied fuels. A concurrent increase in the content of CxHy and N2 in natural gas implies worsening of extinction limits of fuel-lean flames and improvement of extinction limits for fuel-rich flames. Also performed thermodynamic calculations using the FactSage 6.3 software packa...