Parameters of Fuel-Air Mixture Unconfined Deflagration Explosion

2 Parameters of Fuel-Air Mixture Unconfined Deflagration Explosion 

Experiments described in [1] and [7] have revealed the pressure load character in a space surrounding a burning HAM volume. In the experiments [1] a parallelepiped (see the diagram in Fig. 9.6) was filled with the most dangerous stoichiometric HAM mixture. The range of parallelepiped geometrical dimensions is given in Table 9.1. 

The HAM was ignited by an electric spark. Insignificant flame acceleration was recorded at combustion. The pressure wave front parameters in the surroundings did not change sharply. The shape of the pressure profiles along the whole measurement range 0.6 R/Ro 4 were close to profiles presented in Fig. 9.7. 

The dependence of the pressure wave profile on the HAM volume (Fig. 9.7) and the unavoidable transition from the compression phase to the rarefaction phase attract attention. For defiagration, the pressure wave amplitude depends on the HAM cloud linear dimensions, in the near zone it is ten times less than for detonation (Fig. 9.8). The reduced impulse value is less than that of the detonation and it is practically the same for different volumes. Such a result is important for expert assessments of targets behavior depending on a HAM explosion type. Assessments of the effects based only on a pressure amplitude level might contain subjective errors. 

Even in combustion of stoichiometric hydrogenous mixtures the obstructions in the test did not affect the pressure loads recorded or the blast products heat radiation level (Fig. 9.11). The heat radiation level caused by the deflagration is no less than that resulting from a detonation, but its duration is longer (see the radiation records in Fig. 9.12). This conclusion was drawn based on the comparison between the heat flows at 15.6 m distance (Fig. 9.5). 

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