A Mathematical Model of Flare Plume Combustion and Radiation

Abstract

GZVT ACCESSION NO,. RECIPINNT'S CATALOG NUMBER F-INWSC CRDT9 4,TL ES(An Sublil) s. TYPE OF REA'ORT & PERIOD COVERED ITLE(aidSubitf.

Microwave-assisted modulation of light emission intensity in alkali-pyrotechnic plumes

“…The emission region grows to 3 to 4 cm in height from the burning surface. The emission enhancement of the flame is expected, in part, from the high alkali metal content of the formulations, which results in emission from low-lying electronic states [8][9][10][11][12] . For all formulations tested, microwave field application increased both the visible flame volume and emission intensity.…”

“…By inspection of Eqs. 7and (9) , it is apparent that without substantial electron-alkali excitation or continual heat transfer to maintain plume temperature, sustaining nonequilibrium excited-state alkali population N 2 is not possible. The long-duration sustained emission is therefore strong evidence that WMIP is directly responsible for generating increased excited-state alkali species, especially for post-combustion periods where the ratio of intensities is nearly infinite.…”

“…Herein, we refer to this approach as weak microwave induced plasma (WMIP), which is similar to conventional MIP but generated by relatively plume complex index of refraction n 0 , n amb total number density, plume and ambient T 0 , T amb gas temperature, plume and ambient weak (sub-breakdown) electric fields. For alkali-pyrotechnics, early research confirmed that visible and near-infrared (VIS/NIR) emission is dominated by spontaneous emission from electronically excited alkali atoms [8][9][10][11][12] , making the WMIP approach relevant for these systems. While direct electron collisions are thought to be the primary pathway for producing excess alkali emitters, indirect production by collisions with other excited molecules, like electronically-excited metastable nitrogen, may play a role [13] .…”

“…Modeling of emission in alkali-magnesium pyrotechnics has been performed, but only under the strict conditions of Boltzmann (electronic), Saha (ionic), and Planck (optical) equilibrium [8][9][10][11] . Still, relaxing these assumptions has become commonplace in plasma modeling [26] , and provides a framework for inclusion in pyrotechnic emission models.…”