AN EXPERIMENTAL INVESTIGATION OF THE BLOWOUT LIMITS OF A JET DIFFUSION FLAME IN CO-FLOWING STREAMS OF DIFFERENT VELOCITY AND COMPOSITION

The blowout limits of a methane diffusion flame in a co-flowing air-fu el or air-diluent stream were determined for a range of surrounding co -flow stream velocities, both laminar and turbulent, up to approximate ly 1.50 m/s. Methane, ethylene, propane and hydrogen were used as the fuels in the surrounding co-flow stream while nitrogen and carbon diox ide were used as diluents. The experimental results show that the velo city of the surrounding stream affects the blowout phenomena significa ntly. An increase in the stream velocity has a detrimental effect on t he blowout limits at very low velocities up to 0.30 m/s (essentially l aminar flow) and at velocities higher than 1.50 m/s (turbulent flow). The addition of a fuel to the air stream in most cases enhances the bl owout limit of a methane diffusion flame. However, different trends in the variation of the blowout limits with the surrounding fuel concent ration were observed, depending on the type of fuel used and on whethe r the surrounding co-flow stream was laminar or turbulent. The additio n of nitrogen or carbon dioxide to the air stream results in decreasin g the blowout limits. The effect is more severe at the higher velociti es.