An experimental study of well-defined turbulent nonpremixed spray flames
- Additional Document Info
- View All
An experiment system was designed for the study of well-defined turbulent nonpremixed spray flames. Particular emphasis was placed on minimizing the influence of the injector design and on maximizing turbulence within the spray flames. A comprehensive description of the structure of such flames was obtained by applying a variety of complementary diagnostic techniques, including: broadband chemiluminescence imaging, CH* emission imaging, phase Doppler interferometric techniques, and spontaneous Raman spectroscopy. Two methanol spray flames were examined in detail, with Reynolds number ranging from 2.1 x 104 to 2.8 x 104. Flame appearance and detailed measurements confirmed the occurrence of group combustion. Near the burner mouth, a dense column of drops enveloped by a common flame was observed. Further up, large corrugated structures were visualized which eventually developed into separate “islands.” A significant fraction of the spray escaped unburned, which implies that droplet evaporation is slow in this configuration. Detailed scanning of the flames provided an extensive database of average and fluctuating components of gas velocity and temperature, as well as spray and droplet size-classified properties. Key conclusions from such measurements include: the evidence of two-way coupling between the two phases along the centerline near the burner mouth; a velocity acceleration in the densest areas of the spray flames, as a result of momentum addition through vaporization, followed by deceleration farther downstream as the jet spreading predominates; and the droplet inertial behavior, especially for the large size classes, as confirmed by estimates of some relevant Stokes numbers. The average flame height was found to correlate with an overall equivalence ratio and with the initial concentration of droplets at the burner mouth. © 2000 by The Combustion Institute.
author list (cited authors)
Karpetis, A. N., & Gomez, A.