UNSTABLE COMBUSTION OF ADVANCED SOLID PROPELLANTS.

摘要

The report consists of several investigations of important problems regarding acoustic combustion instability in solid propellant rocket motors. The aims of these investigations were to understand limiting amplitudes of oscillation in motor cavities;to establish the relevance of various damping mechanisms in the nonlinear regime,and to find the conditions for coupling between orthogonal modes of oscillation that had been observed in solid-propellant motor research. The damping mechanisms considered in the nonlinear regime were the following: vent losses,particulate damping,wall losses,harmonic generation,and shock formation. The main conclusions are: (1) The limiting amplitudes of oscillation in resonant cavities can be explained in terms of gas nonlinearities. (2) In the nonlinear regime,shock dissipation may be the leading limiting mechanism for longitudinal oscillations. (3) Nonlinear wall losses may be equally important in small diameter cavities. (4) A new type of instability was found theoretically. This instability is due to coupling between longitudinal and transverse oscillations,and results in large amplitude instability. The theory for this nonlinear coupling yields conditions for its occurrence,and the conditions are in complete agreement with results obtained in solid-propellant motor research. (Author)