Instability Characteristics of a Gaseous-Oxygen/Methane Pentad Injector

摘要

This experimental research characterized the modes of combustion instability produced by an impinging-jetnpentad injector burning in an open cylindrical chamber. The device is being explored as a laboratory analog fornunsteady mixing processes in supercritical rocket injectors. The injector burned gaseous oxygen and gaseousnmethane at equivalence ratios from0.5 to 2.0 and totalmass flow rates from0.33 to 4.9 grams per second. The radialnposition of the injector was also varied from 0 to 76% of the chamber radius. Six high-frequency pressurentransducers located around the circumference and end of the chamber simultaneously recorded pressurenfluctuations at each operating point. A detailed phase analysis among the transducers allowed determination of thenmodes of instability. Fast Fourier transforms determined the amplitude and frequency of the primary instability atneach operating point. The results show that this single-element injector exhibits spontaneous first radial, first radial-nfirst tangential, or second tangential modes at fluctuation amplitudes up to 17%of chamber pressure. Changing thenradial location of the injector changed the operating points at which maximum instability occurred. The tangentialninstability modes occurred with only one injector element operating under the conditions described and thereforenwere not driven by injector-to-injector interactions.