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Flame ignition by pulsed corona discharges. CharacteristicsInitial phase of spark discharge (< 100 ns) - highly conductive (arc) channel not yet formedMultiple streamers of electronsHigh energy (10s of eV) electrons - couple efficiently with cross-section for ionization, electron attachment, diss
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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!)