Corona discharge ignition of premixed flames

1. Corona discharge ignition of premixed flames Jian-Bang Liu, Paul Ronney, Martin Gundersen University of Southern California Los Angeles, CA 90089-1453 USA

2. Flame ignition by pulsed corona discharges Characteristics Initial phase of spark discharge (< 100 ns) - highly conductive (arc) channel not yet formed Multiple streamers of electrons High energy (10s of eV) electrons - couple efficiently with cross-section for ionization, electron attachment, dissociation More efficient use of energy deposited into gas Enabling technology: USC-built discharge generators having high wall-plug efficiency (>50%) - far greater than arc or laser sources Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

3. Pulse detonation engine concept Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

4. Pulse detonation engines - initiation Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

5. Transient plasma (corona) discharge Not to be confused with “plasma torch” Initial phase of spark discharge (< 100 ns) - highly conductive (arc) channel not yet formed High field strength Multiple streamers of electrons Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

6. Corona vs. arc discharge Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

7. Transient plasma (corona) discharge Not to be confused with “plasma torch” Initial phase of spark discharge (< 100 ns) - highly conductive (arc) channel not yet formed High field strength Multiple streamers of electrons High energy (10s of eV) electrons - couple efficiently with cross-section for ionization, electron attachment, dissociation Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

8. Corona vs. arc discharges for ignition Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

9. Transient plasma (corona) discharge Not to be confused with “plasma torch” Initial phase of spark discharge (< 100 ns) - highly conductive (arc) channel not yet formed High field strength Multiple streamers of electrons High energy (10s of eV) electrons - couple efficiently with cross-section for ionization, electron attachment, dissociation Electrons not at thermal equilibrium with ions/neutrals Ions are good chain branching agents Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

10. Ions are energy-efficient chain-branching agents Rates Reaction Pre-exponential Activation energy H + O2 ? OH + O 3.1 x 10-10 s/cm3mol 16.81 kcal/mol H + O2- ? OH- + O 1.2 x 10-9 0 Rate ratio at 1000K: 1/18,000 Energy cost of O2- higher than H, but not 18,000x higher! Reaction Energy CH4 ? CH3 + H 4.6 eV vs. O2 + e- ? O2+ + e- + e- 12.1 eV N2 + O2 + e- ? N2 + O2- Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

11. Transient plasma (corona) discharge Not to be confused with “plasma torch” Initial phase of spark discharge (< 100 ns) - highly conductive (arc) channel not yet formed High field strength Multiple streamers of electrons High energy (10s of eV) electrons - couple efficiently with cross-section for ionization, electron attachment, dissociation Ions are good chain branching agents Electrons not at thermal equilibrium with ions/neutrals Ions stationary - no hydrodynamics Low anode & cathode drops, little radiation & shock formation - more efficient use of energy deposited into gas USC-built discharge generators have high wall-plug efficiency (>50%) - far greater than arc or laser sources Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

12. Comparison with conventional arc Single unnecessarily large, high current conductive path Low field strength (like short circuit) Large anode & cathode voltage drops - large losses Low energy electrons (1s of eV) Flow effects due to ion motion - gasdynamic losses Less efficient coupling of energy into gas Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

13. Experimental apparatus for corona ignition (constant volume) Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

14. Experimental apparatus for corona ignition Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

15. USC corona discharge generator "Inductive adder" circuit Pulse shaping to minimize duration, maximize peak power Parallel placement of multiple MOSFETs (thyratron replacement) all referenced to ground potential > 40kV, < 100 ns pulse

16. Images of corona discharge & flame Axial (left) and radial (right) views of discharge Axial view of discharge & flame (6.5% CH4-air, 33 ms between images) Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

17. Characteristics of corona discharge Arc leads to much higher energy consumption with little increase in energy deposited in gas Corona has very low noise & light emission compared to arc with same energy deposition

18. Characteristics of corona discharges “Optimal” energy above which ignition properties are nearly constant Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

19. Ignition delay & rise time (methane-air) Both ignition delay time (0 - 10% of peak P) & rise time (10% - 90% of peak P) ˜ 3x smaller with corona ignition Rise time more significant issue Longer than delay time Unlike delay time, can’t be compensated by “spark advance” “Brush” electrode provides localized field strength enhancement with minimal increase in surface area (? drag, heat loss) Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

20. Peak pressures Peak pressure higher with corona discharge Radial propagation (corona) vs. axial propagation (arc) Corona: more combustion occurs at higher pressure (smaller quenching distance) Corona: lower fraction of unburned fuel Consistent with measurements of residual pressure (need GC verification) Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

21. Modified electrode “Brush” electrode provides localized field strength enhancement with minimal increase in surface area (? drag, heat loss) ˜ 5x faster rise time than arc Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

22. Pressure effects Results similar at reduced pressure - useful for high-altitude ignition Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

23. Pressure effects Results similar at higher pressure Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

24. Pressure & fuel effects - propane-air Results similar with other fuels (e.g. propane) Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

25. Fuel effects n-butane and iso-butane exhibit similar trends but greater difference between corona and arc for n-butane (more weaker secondary C-H bonds?) Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

26. PDE testing at U.S. Naval Postgraduate School 1 day facility time Ethylene-air, 1 atm, 2 inch diameter tube, no obstacles Initial results promising - ˜ 3x shorter time to reach peak pressure than with arc ignition, much higher peak pressure (17 psig vs. ˜ 1 psig) Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.Flame spread over solid fuels is a useful model for simple 2 phase spreading flames, like building fires. It has well defined properties which can easily be quantified, like the spread rate which relates to CO production. And it is highly dependant on the fuel and environment. Downward, opposed flow flame spread at 1g is generally well understood. However, opposed flow flame spread at microgravity is less understood but important in manned spacecraft. upward, concurrent flow flame spread, which is especially important in a building fire, is also less understood.

27. Prior work: Diesel Emission NO – Plasma Interactions Energy efficient: ˜ 10 eV/molecule or less possible Transient plasma provides dramatically improved energy efficiency - by 100x compared to prior approaches employing quasi-steady discharges 10 eV/molecule corresponds to 0.2 % of fuel energy input per 100 ppm NO destroyed Applicable to propulsion systems, unlike catalytic post-combustion treatments

28. NO removal by corona discharge Diesel engine exhaust Needle/plane corona discharge (20 kV, 30 nsec pulse) Lower left: before pulse Lower right: 10 ms after pulse Upper: difference, showing single-pulse destruction of NO (˜ 40%)

29. Conclusions Corona ignition is promising for ignition delay reduction More energy efficient than arc discharges More rapid ignition & transition to detonation Higher peak pressures Reasons for improvements not yet fully understood Geometrical - more distributed ignition sites? Chemical effects - more efficient use of electron energy? (Radical ignition courses similar minimum ignition energies to thermal sources, but shorter ignition delays) Enabling technology: corona generators - require sophisticated approach to electronics

30. Potential applications PDE-related Integration into PDE test facility NPS (Brophy) WPAFB (Schauer) Coaxial geometry easily integrated into PDEs Multiple parallel electrodes to create “imploding” flame Electrostatic sprays charged with corona discharges Pipe dream: integration of electrostatic fuel dispersion, ignition & NOx remediation Others Flameholding Quasi-steady, constant pressure jet flames - USC Cavity-stabilized ramjet-like combustor - WPAFB (Jackson) High altitude relight Cold weather ignition Endothermic fuels Lean-burn internal combustion engines

31. Future work - science-related Transient plasmas are a new area for applications Quantitative understanding of physics needed for applications, but theory almost nonexistent Temporal, spatial behavior of electron energy distribution Need integration of plasma into CFD codes (add field subroutine, radical generator, spatial distribution of energetic electrons relative to streamer head) Modeling of chemical reactions between ions / electrons / neutrals (no “GRI Mech” for ionized species!)