Effect of Oxygenation on the Liftoff, Stabilization, and Blowout Characteristics of Laminar Co-flow Jet Flames

Abstract

AbstractThis chapter summarizes the results of a computational study that examined the effects of a new oxygenation strategy on the flame structure, liftoff height, stabilization, and blowout characteristics in non-premixed laminar co-flow jets. Oxygenated ethylene–air flames were established by employing an innovative strategy of using \({\mathrm{N}}_{2}\)-diluted fuel jet along with O2-enriched oxidizer jet such that the stoichiometric mixture fraction (fst) is varied but the adiabatic flame temperature is not materially changed. For each case, the flame liftoff and blowout processes were examined by using CO2 dilution in the fuel jet. A time accurate, implicit, axisymmetric CFD code that uses a detailed description of transport and chemistry (111 species and 784 reactions) and that includes radiation effects was adopted. The computational model and chemical mechanism were validated using published measurements of the flame length, temperature, and species profiles of ethylene/air jet flames. Simulations indicated burner attached flames for all levels of oxygen enrichment, without CO2 dilution. The flame stabilization mechanism in the near-field region can be described by a balance between the reaction rate and local scalar dissipation rate. Further, as the oxygen enrichment is increased, it becomes more difficult to get lifted flames. However, once a flame is lifted, its liftoff height increases rapidly with the increase in CO2 dilution, i.e., a lifted oxygenated flame exhibited a greater sensitivity to CO2 dilution.KeywordsOxygenationDilutionLiftoffBlowout