Temperature perturbations evolution as a possible mechanism of exothermal reaction kernels formation in shock tubes

31st International Conference on Equations of State for Matter

Drakon, A.V.^1 ; Kiverin, A.D.^1 ; Yakovenko, I.S.^1

Joint Institute for High Temperatures, Russian Academy of Sciences, Izhorskaya 13, Moscow

125412, Russia^1

关键词: Exothermal reaction;    Experimental techniques;    Possible mechanisms;    Reflected shock waves;    Reflected shocks;    Shock tube experiment;    Spontaneous ignition;    Temperature perturbations;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/774/1/012092/pdf
DOI  :  10.1088/1742-6596/774/1/012092

来源: IOP

【 摘 要 】

The basic question raised in the paper concerns the origins of exothermal reaction kernels and the mechanisms of detonation onset behind the reflected shock wave in shock-tube experiments. Using the conventional experimental technique, it is obtained that in the certain diapason of conditions behind the reflected shocks a so-called "mild ignition" arises which is characterized by the detonation formation from the kernel distant from the end-wall. The results of 2-D and 3-D simulations of the flow evolution behind the incident and reflected shocks allow formulation of the following scenario of ignition kernels formation. Initial stage during and after the diaphragm rupture is characterized by a set of non-steady gasdynamical processes. As a result, the flow behind the incident shock occurs to be saturated with temperature perturbations. Further evolution of these perturbations provides generating of the shear stresses in the flow accompanied with intensification of velocity and temperature perturbations. After reflection the shock wave interacts with the formed kernels of higher temperature and more pronounced kernels arise on the background of reactivity profile determined by moving reflected shock. Exothermal reaction starts inside such kernels and propagates into the ambient medium as a spontaneous ignition wave with minimum initial speed equal to the reflected shock wave speed.