Laser Diagnostic Imaging of Energetically Enhanced Flames Using Direct Microwave Plasma Coupling

Quantitative images of temperature and hydroxyl (OH) concentrations are presented in plasma-enhanced flames, where a nonthermal microwave plasma discharge is coupled directly with the reaction zone of the flame. The plasma jet is generated through a novel microwave (2.45 GHz) waveguide based a coaxial reactor system. Planar laser-induced fluorescence is used to generate the OH fields, and planar Rayleigh scattering thermometry is used for the temperature. Plasma-enhanced flames present new possibilities for ignition and flame holding under harsh operating conditions, including stabilization of combustion in hypersonic flame conditions.