A visualization study on the effect of forcing amplitude on tone-excited isothermal jets and jet diffusion flames

Mixing characteristics in strongly forced non-premixed methane jet flames

“…In this case, the flame becomes completely blue, much shorter and wider at the base, and much more turbulent looking than the unpulsed and non-resonantly pulsed flames. There is more than 50% reduction in flame length, which is consistent with the results of Oh and Shin [6] who operated at a much smaller mean Reynolds number of 650.…”

“…The focus of the current study is also on highly modulated jet flames but where the frequencies of forcing are considerably higher than in the puff-flames (e.g., hundreds to thousands of hertz) [4][5][6][7][8]. A few previous studies have investigated this type of flow in which the forcing was achieved by using a loudspeaker to drive a nozzle directly [8], or alternatively by exciting the organ-pipe resonance of the fuel delivery tube/nozzle [4][5][6][7]9,10].…”

“…A few previous studies have investigated this type of flow in which the forcing was achieved by using a loudspeaker to drive a nozzle directly [8], or alternatively by exciting the organ-pipe resonance of the fuel delivery tube/nozzle [4][5][6][7]9,10]. In these studies, the amplitude of the fuel flow modulation can be as high as 10 times the mean flow rate and significant reverse flow back into the fuel nozzle can occur.…”

“…Kim et al [5] and Oh and Shin [6] studied HFHA jet flames by forcing the fuel delivery tube at an acoustic resonant frequency and achieved amplitude ratios, AR = u max /u mean (where u max and u mean are the maximum and mean jet exit velocities, respectively) as high as 11. They observed a 50% reduction in flame length at a Reynolds number of about 650 and a 20% reduction in flame length at a Reynolds number of 2300.…”

Pulsed flow modulation of soot production in a laminar jet-diffusion flame

“…Lovett and Turns [5] measured pollutants and characteristics of high frequency forced transitional and turbulent jets. Kim et al [6] and Oh and Shin [7] studied enhanced mixing at the exit plane of acoustically driven non-premixed laminar and transitional jet flames. Various explanations are given for the enhanced or suppressed levels of soot measured in acoustically forced flames.…”