The experimental study of flame height and lift-off height of propane diffusion flames diluted by carbon dioxide

The flame height and lift-off height of the turbulent jet diffusion flame of gas mixture at ambient temperature and pressure were studied. Different diameter nozzles (2, 3 and 4 mm), heat release rates, and concentrations of carbon dioxide (CO2) were considered. The flow rates of propane (C3H8) and CO2 were controlled by two rotameters. The experimental results showed that the flame height firstly increased with an increase in the concentration of CO2 in the gas mixture under the same heat release rate, and then decreased with a further increase in the concentration of CO2. The flame height decreased with an increase in the concentration of CO2 when the heat release rate was sufficiently large. The lift-off height of the gas mixture increased with an increase in the concentration of CO2 under the same heat release rate and nozzle diameter. Considering the stoichiometric air fuel ratio and laminar flame speed, two correlations of flame height and lift-off height for a mixture of C3H8 and CO2 have been proposed, respectively.