- Author
-
Ratner, A.
- Title
- Highly Turbulent Combustion: Lifted and Shredded Flames. BFRL Fire Research Seminar. VHS Video.
- Coporate
- Michigan Univ., Ann Arbor
- Report
-
Video
May 8, 2000
- Keywords
-
turbulent combustion
|
fluid mechanics
|
flame research
- Abstract
- Highly turbulent combustion is a regime of fluid mechanics and chemistry that is difficult to investigate experimentally, computationally, and theoretically. Under commonly seen circumstances, the regime is hard to probe due to large spatial and temporal changes, natural luminescence, small scales, and a multitude of chemical species. The approach taken in this work is to modify both the chemical and fluid mechanical conditions in two different experimental geometries to achieve states that are both measurable while still remaining in the highly turbulent combustion regime. With this achieved, several measurement techniques were applied in each case. While some of the results confirmed current understanding, others showed novel and surprising behavior. The first study is of a lifted flame produced in a model of a supersonic combustor. Sonic hydrogen is injected axially from a bluff body fuel tube while Mach 2.5 air produces a high-speed co-flow. The flame produced has a lift-off height of 5 cm, which allows imaging of this premixed zone with both PIV and acetone (as fuel marker) PLIF. Downstream measurements were made with OH PLIF and gas sampling. Surprisingly, downward flow reached speeds of 200 m/s in the recirculation zone. The second study is of a specialized high turbulence burner. Using a 19 m/s swirled, co-flowing oxidizer (air doped with oxygen) and a 7 m/s axially injected fuel jet (methane doped with nitrogen), a flame environment was created that produced a significant number of flame segments and a turbulence intensity of 3.6 (compared with 0.6 for a turbulent jet flame). This flame region was measured with simultaneous CH and OH PLIF and with simultaneous OH PLIF and PIV. We confirmed that the flamelet concept is valid in this highly turbulent regime.