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An experimental study of the stability of natural gas and propane turbulent non-premixed flame under diluting condition

Kashir Babak (Aerospace Engineering Department, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran)
Tabejamaat Sadegh (Aerospace Engineering Department, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran)
Baig Mohammadi Mohammadreza (Aerospace Engineering Department, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran)

The stability behavior of a jet diffusion flame developing in a co-flowing stream is studied experimentally, using natural gas and propane as fuel gases. Effects of oxidant and fuel stream velocities and oxidant stream dilution have been studied. The results of experiments showed that with increasing fuel jet Reynolds number, there appears along the flame a point that is accompanied by reaction zone sudden expansion. Flame becomes turbulent downstream from this point. This point is called transition point. More increment of fuel jet Reynolds number moves the transition point to the upstream. Furthermore, two types of stability limits are observed. Blow-off of the rim-stabilized flame is the first stability limit. The second one is the break-off or extinction of the turbulent portion of the flame at the transition point from laminar to turbulent flow. The oxidant and fuel streams are in environmental temperature. In dilution experiments, the oxidant primary stream is oxygen that is diluted with nitrogen or carbon dioxide. In the other experiments oxidant is environmental air.

Keywords: experimental, stability, turbulent, non-premixed flame, diluting