Jet Flame Size

Once the fuel flow rate is determined, the heat release rate is calculated as  

In relatively still air, the flame length, L (m), of most jet flames can be estimated as  

The base of the jet flame is usually not attached to the release point, due to the high velocity and richness of the fuel near the heat source. This lift-off distance has been measured on flares to be 20% of jet length. This effect is important in reducing the predicted radiation level on the leak source, which might otherwise cause a small leak to escalate to a full-bore failure. 

A jet flame in the presence of a crosswind has been addressed (Brzustowski et al., 1975a Gollahalli et al., 1975 Kalghatki, 1983). Generally, the flame can be considered as the frustum of a cone, with increasing flame diameters further from the nozzle. Calculation methods and the effects of wind on the jet flame diameter and lift-off distance are presented in the literature (Beyler, 2002 SINTEF, 1997). 

When a jet fire impinges on an object, its shape may be very distorted compared to the free-field shapes modeled. If the jet fire impinges perpendicularly on a flat object such as a fire-wall or deck, it will produce a thin circular flame over the object s surface. 

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