Application of Electric Field Induced Second Harmonic Technique to the Study of Plasma Assisted Combustion

The Electric Field Induced Second Harmonic (E-FISH) technique has been developed for measuring electric fields in plasma, and applied to studies of nanosecond pulsed discharges sustained in a counterflow diffusion flame. A self-calibration method has been used for nanosecond discharges, and the results show that the breakdown occurs across the flame when the applied electric field reaches a threshold. After the breakdown, the electric field measured by E-FISH will drop, instead of following the voltage increase, due to self-shielding of the plasma. In the dielectric-barrier-discharge sustained across the flame, a weak DC electric field offset has been detected, presumably due to the residual charges on the dielectric surface. The dielectric materials will extend the effective time scales of pulsed discharges and generate efficient hydrodynamic (EHD) forces and ion winds, thereby causing flame oscillations.