Singlet Oxygen Generation in a High Pressure Non-Self-Sustained Electric Discharge

Hicks, Adam; Norberg, Seth; Shawcross, Paul; Lempert, Walter R.; Rich, John Martin; Adamovich, Igor V.; Wehe, Swawn

doi:10.2514/6.2005-745

Cited by 5 publications

(4 citation statements)

References 8 publications

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“…This success stimulates the further studies of the energy efficiency and oxygen pressure scaling problems. It is obviously that the low reduced electric fields E/N (E-electric field, N-gas density), which are peculiar to the different types of non-self sustained discharge, are most favorable to optimal singlet oxygen (SO) excitation [2][3][4][5] . However the rather high specific energy input at high oxygen pressure needed for achieving the threshold SO yield in 15 % wasn't received yet at the optimal (E/N) value.…”

Section: Introductionmentioning

confidence: 99%

Pressure scaling of an electro-discharge singlet oxygen generator (ED SOG)

Рахимова

Kovalev

Lopaev

et al. 2006

XVI International Symposium on Gas Flow, Chemical Lasers, and High-Power Lasers

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This work is devoted to the experimental and theoretical study of rf frequency influence on the discharge structure and the O 2 (a 1 ∆ g ) yield in a rf discharge in the tubes with HgO coating for removing atomic oxygen to avoid fast O 2 (a 1 ∆ g ) quenching. Two series of experiments were carried in two discharge sets up: 1 -tube of large diameter of 14 mm, electrode length of 30 cm; 2 -tube of small diameter of 7 mm, electrode length of 10 cm. In the first series, the increase of rf frequency from 13.56 MHz to 81 MHz resulted in the singlet oxygen (SO) yield Y >15% at such high oxygen pressure as 10 Torr. 2D self-consistent model was developed to simulate the rf discharges in gas flow in a wide rage of discharge parameters both with and without HgO coating. Results of the simulation agreed very well with the experimental data. It is shown that at the high rf frequency the discharge operates in a mode of the normal current density so that the energy absorbed by electrons from the rf field increases with the frequency. In the second series we scaled up the rf discharge on the pd parameter (p-pressure, d-tube diameter) to increase the oxygen pressure. The pd discharge scaling at the high rf frequency allowed to reach the O 2 (a 1 ∆ g ) yield Y > 15% at oxygen pressure up to ~17 Torr. The effect of NO admixture on the O 2 (a 1 ∆ g ) production has been studied in series 2 at rf frequency of 160 MHz. NO admixture (5÷20%) results in the noticeable increase in the O 2 (a 1 ∆ g ) yield in comparison with the discharge tube without HgO coating. It is shown that combination of O 2 + NO mixture with HgO coating of the discharge tube walls provides the most optimal O 2 (a 1 ∆ g ) production with the efficiency up to 7-10 % and allows to reach the threshold yield in 15 % at oxygen pressure even above ~20 Torr.

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Section: Introductionmentioning

confidence: 99%

Pressure scaling of an electro-discharge singlet oxygen generator (ED SOG)

Рахимова

Kovalev

Lopaev

et al. 2006

XVI International Symposium on Gas Flow, Chemical Lasers, and High-Power Lasers

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“…For higher temperatures, this difference becomes smaller and reaches a factor of ≈17 at T = 1500 K. Therefore, even the elementary theory predicts that introduction of fairly small amounts of excited O 2 (a 1 Δ g ) molecules into the original hydrogen-air mixture (≈5% of non-excited O 2 molecules) is expected to increase the laminar flame velocity. Note that the calculations [23] and experiments [24,25] yield rather high mole fractions of singlet oxygen molecules in the oxygen discharge plasma. Thus, more than 5% of O 2 (a 1 Δ g ) molecules were detected in experiments [24] performed at a gas pressure p 0 ≈ 0.25 atm.…”

Section: Flame Propagation With O 2 (A 1 δ G ) Molecules Present In Tmentioning

confidence: 99%

“…Note that the calculations [23] and experiments [24,25] yield rather high mole fractions of singlet oxygen molecules in the oxygen discharge plasma. Thus, more than 5% of O 2 (a 1 Δ g ) molecules were detected in experiments [24] performed at a gas pressure p 0 ≈ 0.25 atm. The calculations [23] and measurements [25] demonstrate that significant concentrations of O 2 (a 1 Δ g ) and O 2 (b 1 + g ) molecules can be reached in a non-self-sustained discharge at the atmospheric pressure as well.…”

Section: Flame Propagation With O 2 (A 1 δ G ) Molecules Present In Tmentioning

confidence: 99%

Enhancement of combustion of a hydrogen-air mixture by excitation of O2 molecules to the a 1Δ g state

Kozlov

Starik

Титова

2008

Combust Explos Shock Waves

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The possibility of increasing the laminar flame velocity in a hydrogen-air mixture by excitation of O 2 molecules into the a 1 Δ g singlet state. The presence of 10% of O 2 (a 1 Δ g ) molecules in oxygen is demonstrated to result in noticeable (up to 50%) enhancement of mixture burning. The temperature of combustion products and also the concentrations of H 2 O, NO, and other constituents increase. The greatest effect of O 2 (a 1 Δ g ) molecules is manifested in combustion of lean mixtures; the least pronounced effect is observed in rich mixtures. These effects are caused by intensification of the chain mechanism in the presence of a super-equilibrium amount of excited O 2 (a 1 Δ g ) molecules in a hydrogen-air mixture.

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“…O 2 (b 1 Σ + g ) molecules. Recent theoretical and experimental studies of physical and chemical processes in oxygen plasma generated by a non-self-sustained discharge [10][11][12][13][14][15] showed that significant amounts of singlet oxygen O 2 (a 1 Δ g ) and O 2 (b 1 Σ + g ) molecules (≈4%) can be obtained even at pressures close to the atmospheric value. In contrast to excitation of O 2 molecules by laser radiation, the plasma in the electric discharge always contains small amounts of atomic oxygen (O) and ozone molecules (O 3 ), as well as vibrationally excited O 2 molecules in the ground electronic state [10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Initiation of combustion of a CH4-O2 mixture in a supersonic flow with excitation of O2 molecules by an electric discharge

Starik

Lukhovitskii

Титова

2008

Combust Explos Shock Waves

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The possibility of intensification of ignition of a methane-oxygen mixture in a supersonic flow behind the front of an oblique shock wave by means of excitation of O 2 molecules to the states a 1 Δ g and b 1 Σ + g in an electric discharge is discussed. Through numerical simulations, activation of O 2 molecules by an electric discharge is demonstrated to speed up chain reactions in the CH 4 -O 2 mixture and to reduce the induction-zone length. Even a small amount of energy input to O 2 molecules in the discharge (≈3 ·0 −2 J/cm 3 ) can reduce the ignition-delay length by a factor of hundreds and initiate combustion at distances of ≈1 m from the discharge zone at comparatively low temperatures of the gas behind the front (≈1000 K) and moderate pressures (≈10 5 Pa). Excitation of O 2 molecules by an electric discharge is much more efficient than simple heating of the mixture.

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Singlet Oxygen Generation in a High Pressure Non-Self-Sustained Electric Discharge

Cited by 5 publications

References 8 publications

Pressure scaling of an electro-discharge singlet oxygen generator (ED SOG)

Pressure scaling of an electro-discharge singlet oxygen generator (ED SOG)

Enhancement of combustion of a hydrogen-air mixture by excitation of O2 molecules to the a 1Δ g state

Initiation of combustion of a CH4-O2 mixture in a supersonic flow with excitation of O2 molecules by an electric discharge

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