Observations on Upstream Flame Propagation in Ignited Hydrocarbon Jets

Abstract

Studies are presented that examine the development of combustion in an initially non-reacting methane jet after ignition at a downstream location. Image measurements depicting the axial location of a fixed energy ignition source that permits transient flame propagation back to the nozzle are presented. The results from the experimental investigations are discussed. Nine different cases were investigated in order to determine the major parameters that impact the axial location of the ignition source at which flame propagation back to the burner was permitted. When the ignition source was located at larger axial distances than those indicated, flame propagation upstream to the burner was not possible and, instead, the flame blew out. The Reynolds number of the jet, the scalar field and the air co-flow magnitude were investigated for their contributions. A standard digital video camera was used in order to film the ignition of the jet and to determine the farthest axial location from the burner at which upstream flame propagation was possible. With the aid of computer software, the height for each case was determined. Conclusions to the effect these parameters had on the axial location are discussed as well as the implications for the physics governing the process.