Characteristics of laminar lifted flames of pure ethane in a non-premixed jet under various pressures

Abstract

Recent studies have discovered that laminar lifted flames (LLFs) can be stabilized within a triangular stabilization regime (TSR), defined by the parameters of normalized lift-off height and Reynolds number. The stabilization mechanism of an LLF could be explained by using an effective Schmidt number over an extended pressure range. In this study, the existence of LLFs of pure ethane was confirmed for the first time, and their characteristics were investigated. However, the corresponding TSR was significantly shrunk compared to propane and butane. The reasons were discussed in relation to the effective Schmidt number. The variation in effective Schmidt number depending on lift-off height and fuel type was theoretically predicted by considering the relative influence of the volume expansion on flow velocity and fuel concentration. Two additional stabilization modes near the turbulent transition were examined. One is the pathway from LLFs within the TSR to turbulent lifted flames at higher Reynolds numbers, and the criteria for this transition were explained. The other is an additional stabilization mode having much larger lift-off heights near the blowout conditions, and its stabilization mechanism was discussed.