Parametric study of jet fires simulation in FDS using a spray-of-particles approach

Lifted turbulent jet flames are observed in industry accidental scenarios and can lead to undesirable consequences. The results from a lifted, horizontal, sonic, propane jet fire experiment were used in this study to compare against simulation results obtained using FDS. The release was first simulated as a leak using FLACS software to determine the velocity within the lift-off region. Then, the jet fire was simulated considering release at a lift-off location along the nozzle axis where the Mach number was valid for FDS application. The horizontal jet fire was simulated in FDS as a spray of particles, and the effects of two input variables required for the spray approach (i.e. spray angle and particle diameter) were assessed in relation to the total flame reach, flame height, flame area, and flame temperature profile. It was observed that the best result considering all output variables of interest was obtained using a spray angle of 5° and a particle diameter of 500 µm. Additionally, it was corroborated that FDS, even with flow velocities corresponding to low Mach numbers, cannot capture lifted flames. Further work should be done to investigate if a finite-rate chemistry model should be considered and if the time integration approach for mixing and reaction in FDS should be modified.