PREDICTION AND VALIDATION OF BLOWOUT LIMITS OF CO-FLOWING JET DIFFUSION FLAMES - EFFECT OF DILUTION

The blowout limits of a co-flowing turbulent methane jet diffusion fla me with addition of diluent in either jet fuel or surrounding air stre am is studied both analytically and experimentally Helium, nitrogen, a nd carbon dioxide were employed as the diluents. Experiments indicated that an addition of diluents to the jet fuel or surrounding air strea m decreased the stability limit of the jet diffusion flames. The stron gest effect was observed with carbon dioxide as the diluent followed b y nitrogen and then by helium. A model of extinction based on recogniz ed criterion of the miring time scale to characteristic combustion tim e scale ratio using experimentally derived correlations is proposed. I t is capable of predicting the large reduction of the jet blowout velo city due to a relatively small increase in the co;Row stream velocity along with an increase in the concentration of diluent in either the j et fuel or surrounding air stream. Experiments were carried out to val idate the model. The predicted blowout velocities of turbulent jet dif fusion flames obtained using this model are in good agreement with the corresponding experimental data.