Lifted Turbulent Jet Flames
Abstract
Experiments were conducted on lifted, turbulent jet diffusion flames. A linear photodiode array was used to measure the temporal history of the liftoff height bar-h. Measurements of the mean liftoff height bar-h under a wide range of flow conditions, including several fuels, nozzle diameters, and exit velocities U (sub s), showed an approximately linear relationship between bar-h and U (sub s), with a slight dependence on Reynolds number. A strain-rate model was developed for liftoff, based on far-field scaling of turbulent jets; it provides an explanation for the linear dependence of bar-h on U (sub s). When the nozzle fluid was diluted with varying amounts of air it was found that the slope of the bar-h vs. U (sub s), line increases faster than predicted by the far-field scaling. The discrepancy is attributed to near-field effects. The amplitudes of the fluctuations in bar-h were found to be of the order of the local large scale of the jet but the time scales were found to be much larger than the local large-scale time of the turbulence tau delta. By using fuels of different chemical times to vary tau delta, the measured correlation time tau 1/ 2 normalized by tau delta was found to collapse with Richardson number xih.... Flame stability, Burning fuel jets, Flame models.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 14, 1993
- Accession Number
- ADA267911
Entities
People
- Jay A. Hammer
Organizations
- California Institute of Technology