An investigation of methane and propane vertical flares

Flame lengths, temperature, species and lift-off heights have been experimentally and numerically investigated and compared for buoyant methane and propane jet diffusion flames at Reynolds number of 5700. The flow field has been modeled using the Reynolds-Averaged Navier-Stokes equation incorporating the k-ε realizable turbulence closure model. Combustion was modeled using the unsteady Eulerian-flamelet model based on the mixture fraction approach and the heat loss by radiation was accounted for using the Discrete Ordinates Method. The GRI mech. 3.0 and the CRECK reaction mechanisms were used to model the kinetics of the methane and propane reactions, respectively. Comparison of the predicted flame length and temperature revealed good agreement with experimental data. Post-flame measurements of NOx and CO revealed greater quantities of both pollutants in the methane flame. Furthermore, investigation of the effect of the burner nozzle thickness on the flame lift-off heights showed that the lift-off height decreased as the nozzle thickness was increased, with the methane flame displaying higher lift-off heights.