Transient combustion responses of homogeneous propellants to acoustic oscillations in axisymmetric rocket motors

摘要

A numerical analysis of unsteady motions in solidudrocket motors has been conducted. The formulationudconsiders a 2-D axisymmetric combustion chamber anduda choke nozzle, and treats the complete conservationudequations accounting for turbulence closure and finiterateudchemical kinetics in the gas phase and subsurface reactions.udA fully coupled implicit scheme based on a dualudtime-stepping integration algorithm has been adoptedudto solve the governing equations and associated boundaryudconditions. Results of the steady-state calculationsudindicate that the distributions of pressure in the motorudand Mach number in the nozzle are one-dimensionaludalong the axial direction. Vorticity contours show similarudpattern to those of Mach number in the combustionudchamber. The nozzle has an influence on the flow andudtemperature fields in the combustion chamber. A narrowudpressure pulse is imposed at the head end to simulateudunsteady acoustic oscillations in the combustionudchamber. When the front of the pulse reaches near theudnozzle throat, pressure near the nozzle throat increasesudand blocks the hot gas flow from passing through theudnozzle throat. Self-generated oscillations have similarudfrequencies to those of standing waves of the combustionudchamber. Large vorticity fluctuations are observedudin near surface region. The luminous flame zone respondsudto low-frequency pressure wave rather than highfrequencyudone. Temperature fluctuations in the primaryudflame zone of the head end oscillates independently ofudthe imposed pressure oscillations while temperature fluctuationsudin downstream region show pressure-dependentudoscillations.