Baker-Strehlow method, vapor cloud

Application of the Baker-Strehlow method for evaluating blast effects from a vapor cloud explosion involves defining the energy of the explosion, calculating the scaled distance (/ ), then graphically reading the dimensionless peak pressure (Ps) and dimensionless specific impulse (i ). Equations (4.41) and (4.42) provide the means to calculate incident pressure and impulse based on the dimensionless terms. 

The energy term E must be defined to calculate energy-scaled standoff R. The energy term represents the sensible heat that is released by that portion of the cloud contributing to the blast wave. Any of the accepted methods of calculating vapor cloud explosive energy are applicable to the Baker-Strehlow method. These methods include ... 

The TNT model is well established for high explosives, but when applied to flammable vapor clouds it requires the c3q>losion yield, T), determined from past incidents. There are several physical differences between TNT detonations and VCE deflagrations that limit the theoretical validity. The TNO multi-energy method is directly correlated to incidents and has a defined efficiency term, but the user is required to specify a relative blast strength from 1 to 10. The Baker-Strehlow method uses flame speed data correlated with relative reactivity, obstacle density and geometry to replace the relative blast strength in the TNO method. Both methods produce relatively close results in examples worked. 

The TNT equivalence, TNO multi-energy and Baker-Strehlow methods require the mass of flammable material in the vapor cloud, and the lower heat of combustion for the vapor. 

Calculation of blast overpressure parameters There are three major methods in use today. One is the TNT Equivalency Methbd which gives inaccurate results for vapor cloud explosions. The other two methods are the Strehlow Curves from Baker 1983 and the Multi-Energy Method from TNO 1985. Both provide a family of curves based on flame speed or explosion strength. These curves are used to select dimensionless parameters which are then unsealed to determine the actual overpressures. 

---