Effects of acoustic oscillations on flame dynamics of homogeneous propellants in rocket motors

The interactions between acoustic waves and gas-phase flame dynamics of a double-base homogeneous propellant in a rocket motor has been studied by means of a comprehensive numerical analysis. The formulation treats the complete conservation equations of mass, momentum, energy, and species concentration, and accounts for finite rate chemical kinetics in the gas phase and subsurface reactions. The model has been implemented to examine the detailed flow structures and heat-release mechanisms in various parts of the motor, including microscale motions near the propellant surface and macroscale motions in the bulk of the chamber. Results indicate that strong interactions between exothermic reactions and acoustic waves occur in regions with steep temperature gradients due to the large activation energy of the associated chemical kinetics. The dynamic behavior of the luminous flame plays a decisive role in determining the motor stability characteristics. Distributed combustion response in the gas phase provides the energy for driving flow oscillations, and can be treated correctly as a combination of monopole and dipole sources based on acoustic theory.