Effect of Flow Parameters and Injection Flow Area on Non-Premixed Methane/Oxygen Diffusion Flame Stability

The focus of this research was the design, fabrication, and testing of an experimental non-premixed flame burner to determine the effect of gaseous flow parameters and flow geometry on the stability of methane/oxygen combustion. The non-premixed burner consisted of a horizontally mounted, rectangular combustion chamber with a single coaxial injector, capable of introducing reactants at a specified impingement angle of 30° at the exit plane. Gaseous oxygen was the primary flow and gaseous methane was the secondary flow. The non-premixed burner was equipped with optical windows on both sides of the chamber parallel to the axis of the flame, which allowed for clear viewing of the product flame. Ignition of the reactants was achieved by a retractable spark plug. Stability maps of the resultant diffusion flame were created for three different injection flow areas based upon reactant equivalence ratio and primary reactant Reynolds numbers. The results showed that decreasing the primary flow area resulted in a more stable flame condition over a broader range of Reynolds numbers (laminar flow to over 40000) and equivalence ratios (fuel-lean 0.27 to fuel-rich 4.94). Increasing Reynolds number also resulted in a transition from a stable, anchored flame to a detached, unstable flame.