Ensemble Combustion of Liquid Oxygen/ Gaseous Hydrogen Coaxial Flames

Abstract

ABSTRACT Experiments were performed to investigate the ensemble combustion of a linear array of three coaxial liquid oxygen/gaseous hydrogen turbulent non-premixed jet flames. The experimental conditions were carefully controlled to duplicate those of a previous single element experiment as closely as possible, so that the single element flame could be closely compared with the present three element flame. All ensemble and inter-element effects were due to the turbulent combustion only; acoustic effects were intentionally suppressed. Abundant interactions were found both in the time averaged sense as well as in the dynamics of the larger scale motions. The multielement flames were found to be axially longer, and dominant frequencies were found to emerge for the multielement flames that were not present for the single element flames. A dynamic wave amplification mechanism previously identified for single element flames was found to remain present for multielement flames. However, the mechanism did not operate independently for each element in the ensemble, but instead entered into phase relationships with the neighboring elements. The phase relationship possibly encouraged the dynamics between jet flames that allowed the dominant frequencies to emerge. Several indications of such a phase relationship were found, but not all indications were observed to occur all of the time. It is possible that the coordination of the wave amplification mechanism between the flames was weak or intermittent. Other simultaneous processes probably also contributed to the overall flame behavior.