Analytical Prediction of Motor Component Vibrations Driven by Acoustic Combustion Instability.

摘要

A detailed investigation has been conducted on the structural dynamic response of solid rocket motors. The study was particularly concerned with estimating the structural response to unstable acoustic combustion oscillations that often occur in solid motors during motor firing time. Detailed finite element analyses were performed on the Poseidon C-3 second stage motor and on the Minuteman III third stage motor using a NASTRAN computer program. In addition, the response of an inert second stage Poseidon C-3 motor to internal acoustic excitation was measured during an experimental task. A significant new analysis tool became available when the MacNeal-Schwendler Company incorporated the cyclic symmetry option into the NASTRAN frequency response rigid format using resources from this project. Results from the analyses were evaluated by comparing them with test data (from the inert Poseidon C-3 motor) and with actual firing data. Several special analyses were conducted on parts of the motor structure, such as separate grain or dome models, to better define expected overall motor response and to investigate possible modeling simplifications. Mechanical Impedance methods were used in the detailed motor analyses to account for components that are not symmetric about the motor centerline. Results from the AFRPL Component Vibration program that are given in the final report provide a considerable amount of detail on typical measured and predicted rocket motor response to acoustic combustion oscillations. (Author)