Application of a Generalized Instability Model to a Longitudinal Mode Combustion Instability

An analytic model is used to study combustion insta bilities via the solution of an inhomogeneous pressure wave equation by a modified Galerkin method. This generalized instability model (GIM) is part of a testbed develo ped to study combustion instabilities in liquid rocket engines and augmentors. This model represents the lower fidelity spectrum of the testbed, and is compared with its higher order counterparts to asses its accuracy as well as its limitations. The model is used to study spec ial problems in acoustics, such as ducts with discontinuous changes in flow properties, continuous and discontinuous changes in mean flow Mach numbers, as well as their coupling with unsteady heat addition. The model is then used to determine the longitudinal stability charac teristics of a model rocket combustor and compared with relevant experimental results.