Liquid Oxygen/Gaseous Methane Single-Element Shear Coaxial Flame Dynamics

An experimental study was conducted to visualize the dynamics and spectra of single-element shear coaxial liquid oxygen (LOX)/gaseous methane flames at high but still subcritical pressure for the LOX, and at supercritical temperature for the methane. High-speed shadowgraphs were employed to image and track the flame and jet dynamics close to the liquid oxygen’s post region. High-speed [Formula: see text] and [Formula: see text] chemiluminescence were also simultaneously collected along the same line of sight as the shadowgraphs. The results were compared to previous LOX/hydrogen results using the same injector at the same momentum flux ratios. The initial temperature of the methane was varied between 200 and 300 K. The LOX/methane flames were found to share many features in common with the LOX/hydrogen flames previously studied, but there were notable differences. The spreading rate of the LOX/hydrogen flames was larger than that of LOX/methane flames. The amplitude of the spreading rate fluctuations for hydrogen was also larger, although the relative spreading rate fluctuations normalized by the average spreading rates were about the same. Despite the differences, a wave amplification mechanism found previously to be active for shear coaxial LOX/hydrogen flames was found to also be active for LOX/methane flames. Overall, both the LOX/methane flames and the LOX/hydrogen were both found to be spectrally fairly quiet.