Published online by Cambridge University Press: 02 August 2021
Shock-flame interactions are fundamental problems in many combustion applications ranging from flame acceleration to flame control in supersonic propulsion applications. The present paper seeks to quantify the rate of deformation of the flame surface and burning velocity caused by the interaction and to clarify the underlying mechanisms. The interaction of a single shock wave with a cellular flame in a Hele-Shaw shock tube configuration was studied experimentally, numerically and theoretically. A mixture of stoichiometric hydrogen-air at sub-atmospheric pressure was chosen such that large cells can be isolated and their deformation studied with precision subsequent to the interaction. Following passage of the incident shock and vorticity deposition along the flame surface, the flame cusps are flattened and reversed backwards into the burned gas. The reversed flame then goes through four stages. At times significantly less than the characteristic flame burning time, the flame front deforms as an inert interface due to the Richtmyer–Meshkov instability with nonlinear effects becoming noticeable. At times comparable to the laminar flame time, dilatation due to chemical energy release amplifies the growth rate of the Richtmyer–Meshkov instability. This stage is abruptly terminated by the transverse burnout of the resulting flame funnels, followed by a longer front re-adjustment to a new cellular flame evolving on the cellular time scale of the flame. The proposed flame evolution model permits us to predict the evolution of the flame geometry and burning rate for arbitrary shock strength below the shock-induced auto-ignition point and flames with unit Lewis number in two dimensions.
The experimental result of the Interaction of a Ms = 1.9 incident shock wave with stoichiometric hydrogen-air flame
The experimental result of the Interaction of a Ms = 1.75 incident shock wave with stoichiometric hydrogen-air flame
The experimental result of the Interaction of a Ms = 1.53 incident shock wave with stoichiometric hydrogen-air flame
Density profiles illustrating the numerical result of flame evolution subsequent to the interaction with the Ms=1.9 shock
Density profiles illustrating the numerical result of inert interface evolution subsequent to the interaction with the Ms=1.9 shock
Density profiles illustrating the numerical result of flame evolution subsequent to the interaction with the Ms=2.5 shock
Density profiles illustrating the numerical result of flame evolution subsequent to the interaction with the Ms=1.75 shock