Thermal and Pressure Loads at Deflagration-to-Detonation Transition

10 Thermal and Pressure Loads at Deflagration-to-Detonation Transition 

Mechanical load values depend on the combustion regime. In the case of slow combustion, when flame propagation velocity is much less than the sound speed, a quasi-static pressure rise is observed. Overpressure values depend on the mixture composition and the initial conditions. Resultant pressure values can be estimated by Aicc - maximal pressure at adiabatic combustion in a confined volume. 

In a system of connected structures, before distribution of the gas throughout the structures is complete, local pressures can exceed or be less than Paicc- Quasi-static pressure rise characterizes, in general, the process of combustion. Local overpressures in a multi-structure configuration are functions of time even for slow flames. These overpressures are determined by competition of two processes the pressure rise caused by combustion and the pressure fall resulting from the gas venting to the neighboring structures. 

The rarefaction phase is a characteristic of slow combustion in unconfined and ventilated volumes. The rarefaction phase amplitude may be comparable with the compression phase amplitude. When the flame propagation velocity and the sound speed in the mixture are comparable, pressure waves are generated. The pressure wave amplitude depends on the mixture composition, initial conditions, the geometry and the combustion regime. Gas dynamics of the process must be taken into 

An increase in flame velocity causes significant combustion wave overpressure rise. A supersonic combustion wave, with respect to the laboratory coordinate system, forms compression and shock waves propagating ahead of the flame front. The pressure wave profile is determined by the flame acceleration, the resulting flame velocity and the geometry. 

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