Evaluation of flame geometry of horizontal turbulent jet fires in reduced pressures: A numerical approach

Accidental releases of hydrocarbons can result in jet fires, which have the potential to escalate accidental events to catastrophes. The geometry and size of a jet flame are vital parameters deciding the potential of the flames to trigger such a series of accidental events called domino effects. In this study, Computational Fluid Dynamics (CFD) simulations on horizontal turbulent jet fires are carried out using Fire Dynamics Simulator (FDS (R)). The results are validated with previous experimental results. Eight different fuel exit velocities ranging between 27.5 and 125 m/s, and 5 different ambient pressures: 0.6, 0.7, 0.8, 0.9 and 1 atm, are used for studying two main flame geometrical parameters: jet flame length and flame area. The simulation results obtained for the flame lengths are found to be higher in reduced pressure cases. In the present study, the classic correlation proposed by Quintiere and Grove is extended to reduced pressure conditions by refining the 'air entrainment strength (C)' values. These air entrainment strength constants were found to have a linear relationship with the ambient pressures. In addition, it is revealed that low ambient pressure conditions can also result in higher jet flame areas. The previously established relationship between the flame area and the non-dimensional heat release rate (i.e. AF similar to Q*4/5) is also verified with the present obtained results, with an introduced proportionality constant (k) showing linear variations with the ambient pressure.