Rotating Valve for Velocity Coupled Combustion Response Measurements.
Annual technical rept. 1 Jan 78-9 Jan 79,
UNITED TECHNOLOGIES CORP SUNNYVALE CALIF CHEMICAL SYSTEMS DIV
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Coupling between the combustion process and the acoustics of the combustion chamber are important factors determining combustion stability of a solid propellant rocket. This coupling results from the response of the combustion process to both the local acoustic pressure and the local acoustic velocity. Because of the complexity of both processes, they cannot be totally characterized analytically therefore, laboratory test data are needed in making analytical combustion stability predictions. Analytical studies accomplished under this contract have developed a mathematical analysis of the transient ballistics. The solution of the transient mass, momentum, and energy equations incorporates both linear and nonlinear velocity coupling, as well as pressure coupling, particle damping, flow turning, and nozzle losses in the analysis. The analysis shows that velocity coupling dominates the system response when the two valves operate 180 deg. out of phase. Combustion tests were conducted using two nonaluminized propellants. Analysis of the data, using the linear velocity response model, indicates the imaginary part of the response increases from approximately -10 at 150 Hz to approximately 1.6 at 570 Hz. Amplitude spectrum analyses of the pressure traces show significant harmonic content. Since the area wave form contains very low harmonic content, this suggests the nonlinear velocity coupling may provide a more realistic framework for data interpretation. Combustion tests were also conducted with a formulation containing 21 aluminum. With the exception of one slot insert, the apparatus operated satisfactorily.
- Test Facilities, Equipment and Methods
- Combustion and Ignition
- Solid Rocket Propellants