Modeling and Active Control of Nonlinear Unsteady Motions in Combustion Chambers

摘要

This program is devoted to understanding fundamental process in actual combustionchambers through coordination of theory, analysis and experiment. Theoretical work has been carried out in the framework of an approach based on a form of Galerkin's method. General unsteady motions are synthesized of modes. Spatial averaging produces a representation of the unsteady behavior in a combustion chamber as the time evolution of a system of coupled nonlinear oscillators, one for each mode. Consequently, immediate advantage can be taken of the methods available in contemporary research on nonlinear dynamical systems. The experimental work has involved ties with a Rijke tube with the Caltech dump combustor developed and used in work funded by AFOSR over the past 12 years. Those tests have demonstrated that due the presence of hysteresis in the stability of oscillations in the dump combustor, suppression of the oscillations is possible over a wide range of equivalence ratio by pulsed injection of secondary fuel in the recirculation zone. We have shown that the behavior is related to a subcritical bifurcation in the dynamics of the recirculation zone and unsteady combustion associated with vortex shedding.