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Prediction of unsteady non-linear combustion instability in solid rocket motors

Abstract The influence of the surrounding motor structure on the appearance of unsteady non-linear axial combustion instability symptoms in a solid rocket motor internal combustion chamber is investigated. The numerical simulation model consists of three coupled physical components, including the combined propellant and motor casing structure, the motor core fluid flow, and the corresponding propellant combustion. A transient frequency-dependent burning-rate model and an updated erosive burning-rate component model are incorporated in the current overall numerical simulation model. The results of simulating a hot-flow unsteady motor firing indicate that structural vibrations directly affect the burning rate and the axial pressure wave development within the chamber that appears as a primary symptom of combustion instability. Comparison of the predicted results with the experimental test results indicates that a good correlation exists between the two, providing support for the present simulation model.