Fuel and Combustion

Fuel and Combustion

Investigation of the Effect of Chain Initiation on Direct Initiation of Detonation

Authors
Seyed Abdolmahdi Hashemi
Masuod Afrand
Faculty of Engineering, Department of Mechanical Engineering, University of Kashan, Kashan, Iran
Abstract
In this paper, the role of reaction mechanism in direct initiation of detonation is studied numerically. The combustion mechanism is presented using a three-step kinetics model, which consists of chain initiation, chain branching and chain termination. In this research, the role of chain initiation on the blast initiation is studied. To investigate the role of chemical mechanism, a characteristic time (τ) is defined for each step, which contains the effect of various kinetics parameters. Numerical simulation shows that extending the initiation characteristic time (tI) causes an increase in the critical energy of direct initiation. To demonstrate the role of chain initiation on detonation initiation, shock pressure diagrams are presented for different values of tI, and also for various initiation energies (E0). These diagrams show that for smaller tI's, kinetics has a more important effect than for larger values of tI's. Also, it is shown that by increasing the initiation energy, dependence of minimum value of the shock pressure on tI is decreased. For large values of tI's, the behavior of the wave in the critical initiation is almost independent of tI; thus, detonation behavior for a given E0 nearly coincides with the respective tI's. The relationship between a tI and E0 depends on the value of tI. For small tI, this relationship is linear with a small slope, whereas for large tI, it is linear with a large slope.
Keywords
Chain initiation
Characteristic time of reaction
Direct initiation
Detonation
Initiation energy
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