| An experimental study of a laboratory natural gas-fired radiant heating tube with quartz walls and a practical burner geometry reveals that confinement of a jet flame in a tube affects its behavior dramatically. Qualitative observations, colors, and visible flame heights demonstrate that the flame burns either as a long, luminous, orange flame or as a very short, blue flame. Wall temperature profiles, global radiation measurements, and an overall energy balance delineate differences in the radiant tube performance between the orange and the blue modes. Measurements of local species concentrations reveal that the confined flame transitions from non-premixed behavior through various levels of partial premixing, affecting exhaust NO;In particular, hydrocarbon-nitrogen chemistry was explored as a possible explanation for a previously observed NO... |
