@article{BUTTERWORTH2020,
title = {Electric field measurement in electric-field modified flames},
journal = {Proceedings of the Combustion Institute},
year = {2020},
issn = {1540-7489},
doi = {https://doi.org/10.1016/j.proci.2020.08.019},
url = {https://www.sciencedirect.com/science/article/pii/S1540748920306039},
author = {Thomas D. Butterworth and Min Suk Cha},
keywords = {Electric field, E-FISH, Space charge, Electron attachment, Nonpremixed flame},
abstract = {The application of an electric field to a flame modifies the flame characteristics due to the collective motion of charged particles generated within the flame. The applied field mobilises electrons and ions depending on their polarity, leading to localised regions of space charge with sufficient density to either locally amplify or shield the applied electric field. A fundamental understanding of the local electric field is essential for both electrically and plasma-assisted combustion, because it determines electric body force as well as electron temperature. In this work, we propose a method, which is independent of gas composition and temperature, to measure the local electric field using electric field induced second harmonic generation (E-FISH). We successfully apply this method to a laminar nonpremixed counterflow flame by applying modulated direct current (DC) electric field with a microsecond duration zero volt pulse. Electric potential and space charge distribution are also deduced from the measured electric field. Furthermore, we show the importance of electron attachment to O2 forming O2− by changing the polarity of the applied DC electric field. When the anode is in the oxygen stream, a region of negative charge is obtained near the anode, whereas, when the anode is in the fuel stream, no region of negative charge is found. We also find the qualitative trends of the measured electric fields reasonably agree with previously reported one-dimensional modelling results. The limitations of the methodology are addressed, and we show that the ability to modulate the DC voltage on sub-microsecond timescales is required for accurate quantitative measurements.}
}
However, this calculation is not straightforward due to ambiguity in the direction of the field vector, Eoff, since E-FISH signal only represents the magnitude of the electric field
The high voltage is DC (±2.5 kV) with a brief off pulse (duty cycle > 99.7%), where the off period is typically set to be between 10 and 100 µs, at a frequency of 50 Hz or 1000 Hz
The 1064 nm pump beam is from a picosecond Nd:YAG laser (Ekspla, PL2251A), which emits 30-ps pulses at 50 Hz and ∼10 mJ/pulse.
@article{BUTTERWORTH2020, title = {Electric field measurement in electric-field modified flames}, journal = {Proceedings of the Combustion Institute}, year = {2020}, issn = {1540-7489}, doi = {https://doi.org/10.1016/j.proci.2020.08.019}, url = {https://www.sciencedirect.com/science/article/pii/S1540748920306039}, author = {Thomas D. Butterworth and Min Suk Cha}, keywords = {Electric field, E-FISH, Space charge, Electron attachment, Nonpremixed flame}, abstract = {The application of an electric field to a flame modifies the flame characteristics due to the collective motion of charged particles generated within the flame. The applied field mobilises electrons and ions depending on their polarity, leading to localised regions of space charge with sufficient density to either locally amplify or shield the applied electric field. A fundamental understanding of the local electric field is essential for both electrically and plasma-assisted combustion, because it determines electric body force as well as electron temperature. In this work, we propose a method, which is independent of gas composition and temperature, to measure the local electric field using electric field induced second harmonic generation (E-FISH). We successfully apply this method to a laminar nonpremixed counterflow flame by applying modulated direct current (DC) electric field with a microsecond duration zero volt pulse. Electric potential and space charge distribution are also deduced from the measured electric field. Furthermore, we show the importance of electron attachment to O2 forming O2− by changing the polarity of the applied DC electric field. When the anode is in the oxygen stream, a region of negative charge is obtained near the anode, whereas, when the anode is in the fuel stream, no region of negative charge is found. We also find the qualitative trends of the measured electric fields reasonably agree with previously reported one-dimensional modelling results. The limitations of the methodology are addressed, and we show that the ability to modulate the DC voltage on sub-microsecond timescales is required for accurate quantitative measurements.} }