Predicted Nonsteady Internal Ballistics of Cylindrical-Grain Motor

In the design of solid-propellant rocket motors, the ability to understand and predict the expected behavior of a given motor under transient conditions is important. Research towards predicting and quantifying undesirable transient axial combustion instability symptoms necessitates a comprehensive numerical model for internal ballistic simulation under dynamic flow and combustion conditions. An updated numerical model incorporating recent developments in predicting negative and positive erosive burning, and transient, frequency-dependent combustion response, is applied to the investigation of instability-related behavior in a cylindrical-grain motor. Pertinent key factors, like the initial pressure disturbance magnitude and the propellant’s net surface heat release, are varied and evaluated with respect to identifiable trends for prediction of instability symptoms in actual motors. Results show that acceleration-related burning, tied to structural vibration, remains a key factor on symptom strengths, with or without the modifying influence of frequency-dependent combustion response.