Combustion and pressure wave interaction in enclosed mixtures initiated by temperature nonuniformities

Numerical simulation of the deflagration to detonation transition

“…The initial temperature of the high-temperature region has little influence on the DDT run-up length, since this region is much smaller than the tube length. Nevertheless, both the initial temperature of the cold gas mixture and the temperature gradient between the high-temperature region and the fresh mixture affect the DDT run-up length, as was shown in [15]. The present simulations were performed with the minimum temperature gradient necessary to provide the DDT.…”

“…It was also found that is necessary to establish a gradient in the temperature profile to provide a transition to detonation. Weber et al [15] estimated that 3000 K/m is the minimum temperature gradient for DDT development in a stoichiometric H 2 -O 2 mixture at an uniform pressure of 0.1 MPa.…”

“…It is an additional requirement to use a gridrefinement algorithm [15,21] to accurately track the converging compression waves and the interaction between the flame front and the pressure wave. In the calculations described here, we used an adaptive mesh to represent a confined domain 1.5 m long.…”

“…An interesting study of the DDT behavior as a function of the activation energy and the initial gas temperature was reported by Smirnov and Panfilov [12] who studied two distinct types of DDT initiation mechanisms: initiation of detonation from the flame zone and initiation along a contact discontinuity near the primary shock wave. Other aspects of gas-phase detonation recently reported include the study of unsteady detonation velocities compared with theoretical CJ velocities [11,14], detonation structures [10], DDT run-up length [8,9,15], and the influence of the initial temperature and temperature gradient on the DDT process [15]. Also of interest is the critical energy required for direct initiation [14] and the abundant data available for detonation velocities of gases with elevated initial pressures provided by Bauer et al [16].…”

Numerical simulation on detonation initiation and propagation in supersonic combustible mixtures with nonuniform species

“…Ishii et al [41] performed experiments on the behavior of detonations in non-uniform mixtures with concentration gradients normal to the propagation direction and showed that a tilted wave front was created, whose angle was consistent with the deflection angle of the detonation front obtained from trajectories of the triple point. Weber et al [42] studied numerically the formation and development of detonation waves stemming from temperature non-uniformity using detailed chemical kinetics. Kim et al [43] showed that the increase of the temperature gradient in a non-uniform temperature zone resulted in a decreasing mixture temperature in the unburned mixture zone, which could reduce the combustion wave speed.…”