- 2015 by Princeton University. Repetitively pulsed, sub breakdown field strength microwave energy is efficiently coupled into laminar methane-air flames leading to significant increase in flame speed and a factor of two reduction in the lean combustion limit. The energy is deposited into the flame zone through microwave coupling to free electrons created by the combustion process and produces a local increase in temperature. Commensurate increase in NO production is below the level associated with the peak temperature increase. Laser guided microwave energy deposition creates ignition along a line and provides opportunities for volumetric ignition. Filtered Rayleigh Scattering provides quantitative images of local temperature, Radar REMPI yields NO concentrations, and Femtosecond Laser Electronic Excitation Tagging (FLEET) gives velocity and temperature profiles.