Conditions of Spontaneous Blast Processes Initiation

Abnormally rapid explosion development has been reported in the experiments [38] with high-sensitivity mixtures (Ha + CI2, Ha + Oa with Cla additive) irradiated with ultraviolet rays causing an inhomogeneous distribution of free radical concentration. Existence of optimal radiation intensity causing a shock wave of the largest amplitude has been proved. The authors in [38] have proposed an alternative term for the gradient mechanism of shock wave amplification - SWACER (Shock Wave Amplification by Coherent Energy Release). 

There are experiments with mixtures in which parameter non-uniformity was created by a jet of hot combustion products [39]. Self-ignition of such a mixture leads to detonation wave generation. The experimental results obtained in free clouds of low-sensitivity air mixtures can also be an example of the SWACER -mechanism causing detonation initiation [40]. 

The literature provides cogent arguments, proved experimentally, for the existence of detonation initiation mechanisms caused by generation and fast amplification of a pressure wave in non-uniform mixtures. 

Let us study the DDT processes. In all cases a mixture region that serves as a source of detonation is distinctly differentiated. This self-initiation region is formed 

To assess the DDT conditions, it is proposed that the considered process be divided into two stages [41]. The first stage includes flame acceleration and flow mixing, which depend on combustion conditions and lead to formation of a selfinitiation region. Sufficient mixing may result from flame propagation in narrow tubes, combustion in a large volume or, by the effects of obstacles or the accumulation of solid or liquid particles etc. 

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