Transport issues when impinging laminar premixed flame jets on a rotating cylinder
✍ Scribed by Neal P. Sullivan; Melvyn C. Branch; Mark Strobel; Michael Ulsh
- Publisher
- Elsevier Science
- Year
- 2000
- Tongue
- English
- Weight
- 295 KB
- Volume
- 28
- Category
- Article
- ISSN
- 1540-7489
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✦ Synopsis
The impingement of flame jets against cooled surfaces has widespread applications in areas ranging from pollution control to materials processing. Premixed flames are commonly employed to treat the surface of polymer films; the polymer is oxidized when briefly exposed to the products of combustion, thereby increasing polymer surface energy and improving wettability. In this study, the transport issues in this process were investigated using a pilot-scale treatment facility. Arrays of laminar premixed methane/air flame jets impinged upon a water-cooled rotating cylinder. Color bulls-eye Schlieren imaging and temperature measurements were used to experimentally investigate the flow field that develops between the hot products of combustion, the rotating cylinder, and the ambient environment. The effects of strain on the impinging flame-jet structure were modeled using the SPIN application of the CHEMKIN software. The temperature measurements and flow visualization suggest the source of non-homogeneous film surface treatment. To produce a uniform treatment zone, a significant separation distance between the burner and rotating cylinder is required to complete interjet mixing of gases prior to impingement. In addition, entrainment of ambient air at high roller-rotational speed results in an imbalance in the flow field that magnifies the problems caused by insufficient jet mixing. Chemical kinetics modeling reveals that the species that are likely to participate in surface oxidation are H, OH, O 2 , HO 2 , and H 2 O 2 . Atomic oxygen, previously considered important in polymer surface oxidation, is shown to be in low concentration (3 ppm) at the stagnation surface. Cold-wall quenching consumes atomic hydrogen, hydroxyl radicals, and atomic oxygen, while producing hydroperoxy radicals and hydrogen peroxide. The concentrations of these species at the stagnation surface correlate with improvements in wettability observed as a function of flame equivalence ratio.