Blow-off of Fuel Jet Flames in the Atmosphere

Further data from experiments with the atmospheric burning of jet fuels, particularly their blow-off and flame quenching characteristics, have been collected and interpreted. These are characterised in terms of both their dimensionless Flow Number and Flame Thickness. Regimes of Lifted Flames, Flame Blow-off, Choked Flow and Flame Quench have been defined by these Dimensionless Groups. New data are presented for a variety of hydrocarbon and ammonia-hydrogen fuels. New techniques are required for the assessment of the latter, including derivation of their acoustic velocities and the characterisation of their laminar flames, including burning velocity and flame thickness. It is possible to create NH3+H2 jet flow blends with burning rates and blow-off velocities closer to those of hydrocarbons than of H2. The properties of individual fuels are displayed in terms of the fuel velocities at which blow-off occurs for different pipe diameters. The properties of individual fuels displayed in this way show a greater diversity than is evident from the dimensionless groups. Similarities are drawn between premixed and jet flow flame quenching. Blow-off velocities from a pipe of 3 mm diameter display an approximate correlation with the heat release rates of the flames just prior to blow-off.