EXPERIMENTAL STUDIES OF COMBUSTION CHAMBER AND FEED SYSTEM STABILITY DURING THROTTLING OF A REGENERATIVELY COOLED LIQUID HYDROGEN - FLUORINE ROCKET ENGINE

Experimental data are presented for the stability and noise characteristics of the combustion chamber at oxidant-fuel ratios of 9.0 and 15.67 while thrust was varied over a 6:1 range by means of throttle valves in the propellant lines. The predominant frequency of the chamber pressure oscillation throughout the throttling range is approximately 200 cps with the exception that, at chamber pressures near 100 psia and an oxidant-fuel ratio of 15.67, an apparent combustion instability occurs with a frequency of oscillation of approximately 75 cps. The amplitude of the oscillation as a percent of combustion-chamber pressure varies from approximately 2% at the higher chamber pressures (390 to 250 psia) through a peak of approximately 12% at chamber pressures between 80 and 100 psia to under 4% below 60 psia. Data for an engine startup from essentially zero flow conditions to a final chamber pressure of 100 psia and an oxidant-fuel ratio of 9.0 are also included.