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ON THE OSCILLATORY BEHAVIOR OF LIQUID PROPELLANT ROCKETS

2008; Begell House; Volume: 7; Issue: 4 Linguagem: Inglês

10.1615/intjenergeticmaterialschemprop.v7.i4.40

2150-7678

Gary Flandro,

Combustion and flame dynamics

Despite many decades of intense study the combustion instability problem remains a major issue in liquid rocket design and development. Similar difficulties are frequently experienced in turbojet thrust augmenters and are anticipated in hypersonic propulsion systems, and especially in scramjets as their development cycle matures. The apparent lack of progress is largely the outcome of an incomplete understanding of the dynamics of the flow field in an injection-driven combustor. What is missing is a self-consistent theoretical framework capable of providing clear physical interpretations of the available experimental data. Of concern is the incomplete and often poorly understood set of energy gain/loss mechanisms used in formulating the unsteady behavior in the analytical models in current use. A fresh approach is described in this paper that provides nonlinear extensions to generalized models representing unsteady energy transport in compressible, rotational flows with viscosity, heat transfer, and distributed combustion heat release. A tightly integrated treatment of coupled acoustic, vortical, and entropic disturbances is employed. In addition to reliable linear stability prediction, the resulting algorithm can accurately represent: 1) time-evolution of the pressure oscillations; 2) wave system limit cycle amplitude; and 3) shifts in the mean field properties coupled to the oscillating flow. The calculations provide information regarding the sensitivity of these features to the geometry and physical parameters describing the engine and injector configuration. This is accomplished with no limitation on the Mach number of the compressible quasi-steady mean flow field. Predicted waveforms in high-amplitude limit cycle oscillations closely approximate those observed experimentally. These capabilities are demonstrated by comparison to measurements from actual systems that have exhibited high-amplitude pressure fluctuations; examples include the well-remembered Rocketdyne F-1 (Saturn V, first stage engine).