Dynamic responses of combustion to acoustic waves in porous chambers with transpiration.

摘要

An integrated analysis has been conducted to study the premixed and diffusion flame dynamics in a porous chamber under steady and oscillatory conditions. The formulation is based on the complete conservation equations of mass, momentum, energy, and species concentration, with considerations of finite-rate chemical kinetics and variable properties. Research attention is focused primarily on the internal flow structure, the transport of acoustic, vorticity, and entropy waves, and the effect of heat release on the acoustic field. The analysis consists of two sections: the dynamic responses of premixed and diffusion flames to acoustic waves are investigated. A dual-time stepping integration procedure with preconditioning is used for the simulations. The results from the reacting-flow simulations indicate that a strong tendency toward driving the acoustic waves in the combustion zone is observed in both the premixed and the diffusion flame cases. The dipole arising from the unsteady displacement of the flamelets has a greater effect on driving or damping acoustic oscillations than does that arising from oscillatory premixed flame dynamics, mainly because of its directional preference.; A comprehensive numerical analysis of the combustion and flame response to the acoustic wave of AP/HTPB composite propellant in a rocket motor was also conducted. The global chemical kinetics for AP monopropellants proposed by Guirao and Williams is employed to simulate the deflagration process of the premixed flame over the oxidizer section. The pyrolysis law established by Seleznev is employed to estimate the mass flux leaving the melting layer. For the gas phase, the formulation is based on the conservation equations of mass, momentum, energy and species concentration, with variable thermodynamic and transport properties. A quasi-steady state approach is proposed to simulate the flame response to the acoustic waves. Results show complicated flame structures, involving both premixed and diffusion flames in the near field. A velocity coupling mechanism plays a crucial factor in the gaseous flame dynamic.