Pulsed Instabilities in Combustion Chambers

Abstract

A pulsed or "triggered" instability occurs when pressure oscillations develop in a linearly stable combustion system after being subjected to a sufficiently large disturbance. Such true nonlinear instabilities usually occur as subcritical bifurcations in dynamical systems theory. Understanding which nonlinear processes can lead to subcritical bi~urcations is the focus of this work. Earlier work with the approximate analysis used here has shown convincingly that nonlinear acoustics alone does not contain the phenomenon of pulsed instabilities; evidently some other nonlinear contribution must also be included. An extensive experimental and numerical investigation conducted by Baum and Levine strongly suggests that nonlinear combustion is required. Using models of pressure and velocity coupling, the current work studies the effect of nonlinear combustion on the behavior of the system.