Thermo-acoustic instabilities driven by fuel droplet lifetime oscillations

Abstract

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Model for Acoustic Induced Aluminum Combustion Fluctuations in Solid Rocket Motors

“…This motion essentially takes place in the radial direction, whereas the acoustic mode is controlled by an axial oscillation of the flow. It has recently been shown that this motion originates from droplet lifetime oscillations [26]. Figure 4a shows the heat release rate distribution _ q^η 0 without acoustic forcing (η 0).…”

“…The oscillation level chosen to excite the system corresponds to half the pressure level observed at the limit cycle of unstable cases studied in Refs. [25,26], and the selected forcing frequency is defined by the frequency of the limit cycle of a close unstable case [25,26] of D r 60 μm.…”

“…A series of numerical simulations [24][25][26] made in a generic SRM helped for a better understanding of the combustion dynamics of aluminum droplets during thermoacoustic instabilities. These simulations revealed that the dynamics of the burning aluminum droplets released from the solid propellant can couple with one of the low-frequency acoustic modes of the motor chamber.…”

“…The numerical model was described in Refs. [24][25][26]. Simulations are made with CPS, which is an in-house ArianeGroup flow solver [54].…”

“…This peak results from the motion of the combustion volume boundary and is not reproduced by the analytical models. It has, however, been shown that this motion largely contributes to the thermoacoustic source [25,26].…”