Rotating Valve for Velocity Coupled Combustion Response Measurements.

Abstract
Quanitative measurement of the velocity coupled response function is required for quantitative predictions of the combustion stability characteristics of rocket motors. Velocity oscillations of controlled frequency and magnitude can be generated in a test motor by simultaneously operating a rotating valve at each end of the motor, 180 deg out of phase. Analytical studies have developed a transient ballistics model for the one dimensional flow in the test motor. The analysis incorporates velocity coupling, pressure coupling, and particle damping effects. The model reduces to previously developed approximate solutions of the mass, momentum, and energy equations. In addition, the analysis predicts the stability characteristics for one dimensional acoustic oscillations. Approximate solutions were developed for deriving velocity coupled response functions and potentially particle parameters from experimental pressure measurements. Experimental tests have shown cold flow ballistics are concurrently modeled by the analysis when the two valves are in phase. Thus, the internal geometries are ballistically sound. Velocity coupled cold flow tests show significant pressure amplitude modulations which were traced to mechanical tolerance buildups. Methods are under study for reducing this buildup and for eliminating residual tolerance effects by appropriate cold flow calibrations. (Author)

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