Experimental and numerical studies on interactions of a spherical flame with incident and reflected shocks

Abstract

Observations are presented from experiments and calculations where a laminar spherical CH 4 /air flame is perturbed successively by incident and reflected shock waves. The experiments are performed in a standard shock tube arrangement, in which a high-speed shadowgraph imaging system is used to record evolutions of the flame. Numerical simulations are conducted by using second-order wave propagation algorithms, based on two-dimensional axisymmetric Navier-Stokes equations with detailed chemical reactions. Qualitative agreements are obtained between the experimental and numerical results. Under actions of incident shock waves, Richtmyer-Meshkov instability responsible for the flame deformation is induced in the flame, and the distorted flame takes a barrel shape. Then, under subsequent actions of the shock wave reflected from a planar wall, the flame takes an inclined non-symmetrical kidney shape in a symmetric cross section, which means a mushroom-like shape of the flame comes finally into being. The vorticity direction in the ring cap has been altered by the reflected shock's action, which makes the head of the mushroom-like flame extend quickly to the side wall.

Effect of chemical reactivity on the detonation initiation in shock accelerated flow in a confined space

“…When a shock wave interacts with a flame in an unburned fuel/oxide mixture, it produces baroclinic effects on the surface of flame and results in the latter's Richtmyer-Meshkov (RM) instability [1][2][3][4]. The RM instability greatly promotes the mixing of fuel/oxide and therefore leads to the acceleration of flame.…”