Opening diameter: | m | |

Molecular weight of fuel: | kmol/kg | |

Gas specific heat ratio (gamma): | ||

Upstream pressure at the opening: | Pa bar psi | |

Ambient pressure : | Pa bar psi |

Distance from the orifice to the visible flame tip (L) minus the lift-off distance (s): | m |

Release type : | |

Lift-off distance : | m |

L : | m |

diameter (m) | |

axial distance from the orifice (m) | |

At x : | m |

flame diameter : | m |

In practice a fire resulting from a high-pressure gas release will have a shape of a frustum of a cone with an opening angle of 20-25

The first thing this calculator does is to calculate the effective Mach number, M

where

The lift-off distance, s, is then determined from the following equation by Kent:

γ = isentropic exponent (heat ratio) of the actual gas = c _{p}/c_{v}(-)p _{v}= upstream pressure at the event orifice (bar) p _{o}= atmospheric pressure (bar)

where

The effective exit velocity which is the effective exit Mach number,M

u _{e}= exit velocity (m/s) u _{a}= the average jet velocity (m/s) ≈ 0.4⋅u _{e}D _{e}= the orifice or exit diameter (m)

The well known model of Hawthorne et al., Ref. /6-12/, is then used to predict the distance, L, from the orifice to the visible flame tip: where

C _{t}= mole ratio of fuel to reactants α = mole ratio of reactants to products (-) T _{ad}= adiabatic flame temperature (K) T _{v}= temperature of the fuel before it is released (K) M _{0}= molecular weight of air = 29 (kmol/kg) M _{f}= molecular weight of fuel (kmol/kg)

Since α ≈ 1, C

McCaffrey et al., Ref. /6-13/, state that for choked releases(i.e. releases with an effective Mach number, M

The diameter of the jet flame plume (shown in the graph) is determined from the following equation by Baron, Ref. /6-15/:

where x = the axial distance from the orifice (m).