Oscillatory response of leading edge flames in heterogeneous propellant combustion

The leading edge flame (LEF) anchored in the vicinity of the interface between the solid oxidizer and solid fuel of a heterogeneous propellant is subjected to externally imposed oscillations in pressure and velocity normal to the burning surface of the propellant. The problem is investigated by means of numerical simulation. When the flame is anchored close to the surface, its oscillations exhibit a mild hysteresis, but the flame does not undergo any significant changes in its structure during the oscillatory cycle. However, when the flame is anchored close to a blow-off condition, hysteresis behavior is prominently observed, under conditions favorable to the prevalence of stable oscillations. The flame is blown off for large amplitude and/or time period of the imposed oscillations. The flame exhibits a large response, in terms of its total chemical heat release, for large time periods of the imposed oscillations, in a non-linear manner. It appears that these features involve the merger of adjacent LEFs into a premixed flame as they move away from the burning surface, and vice versa, as postulated in some of the earlier studies.