Dielectric Barrier Discharge Discharge Research Articles

Degradation performance and mechanism of microcystins in aquaculture water using low-temperature plasma technology

The eutrophication of aquaculture water bodies seriously restricts the healthy development of the aquaculture industry. Among them, microcystins are particularly harmful. Therefore, the development of technologies for degrading microcystins is of great significance for maintaining the healthy development of the aquaculture industry. The feasibility and mechanism of removing microcystins-LR by dielectric barrier discharge (DBD) plasma were studied. DBD discharge power of 49.6 W and a treatment time of 40 min were selected as the more suitable DBD parameters, resulting in microcystin-LR removal efficiency of 90.4%. Meanwhile, the effects of initial microcystin-LR concentration, initial pH value, turbidity, anions on the degradation effect of microcystin-LR were investigated. The removal efficiency of microcystin-LR decreased with the increase of initial microcystin-LR concentration and turbidity. The degradation efficiency of microcystin-LR at pH 4.5 and 6.5 is significantly higher than that at pH 8.5 and 3.5. HCO3− can inhibit the removal efficiency of microcystin-LR. Furthermore, five intermediates products (m/z = 1029.5, 835.3, 829.3, 815.4, 642.1) were identified in this study, and the toxicity analysis of these degradation intermediates indicated that DBD treatment can reduce the toxicity of microcystin-LR. e－aq, •OH, H2O2, and O3 have been shown to play a major role in the degradation of microcystin-LR, and the contribution ranking of these active species is e－aq > •OH > H2O2 > O3. The application of DBD plasma technology in microcystin-LR removal and detoxification has certain development potential.

Atmospheric–pressure DBD plasma modifying photoemission, optical and electrical properties of polycarbonate films

In this study, the DBD plasma reactor has been constructed, characterized, and tested to be employed in material treatment for use in different applications. A neon power source with an output of 10 kV, 30 mA, with a frequency of 20 kHz is used to drive the DBD reactor in an atmospheric-pressure environment. The investigation covered the analysis of many parameters of the dielectric barrier discharge (DBD) reactor, including its discharge voltage, current, capacitance, consumption energy, and the light emission of the produced plasma. Also, to examine the generated DBD plasma effect, the photoemission, optical, and electrical characteristics of untreated/treated polycarbonate films were investigated using photoluminescence spectroscopy, UV/Vis spectroscopy, and electrical spectroscopy. The results demonstrated the appearance of two modes in the DBD discharge: filamentary and homogeneous. Moreover, the DBD reactor's power consumption has been measured to be 20 mW at a supplied voltage of 6.5 kV peak-to-peak, operated in atmospheric–pressure. The photoluminescence emission results emphasized that the treated films are modified particularly with increasing DBD treatment time. The UV–Vis spectra demonstrated a notable displacement of the absorption edge towards higher wavelengths as the duration of DBD exposure increased. This is indicative of the reduction of the band gap energy, thus improving the electric conductivities. The optical parameters of the treated polycarbonate films were enhanced in comparison to the untreated sample. Through the used frequency range, measurements of dielectric loss, dielectric constant, as well as AC electrical conductivity, are sensitive parameters to the modifications in electrical behaviors due to DBD plasma treatment.

Ammonia synthesis using atmospheric pressure fluidized bed plasma

In recent years, extensive research has been conducted on ammonia synthesis using catalysts under mild conditions and by combining plasma with the catalysts. Increasing the contact area between the catalyst surface and atmospheric pressure dielectric barrier discharge (DBD) is crucial for improving the ammonia synthesis efficiency. In this study, we present a fluidized bed dielectric barrier discharge (FB-DBD) method that can be used to form FB-DBD plasma through the electrohydrodynamics of DBD discharge without a feed gas. We performed ammonia synthesis experiments using our FB-DBD reactor. The results indicate that the FB-DBD plasma can achieve an energy yield of 5.9 g-NH3/kWh, which is about twice higher than that of conventional DBD plasma. Consequently, it can be implemented in various applications as a new reaction field between solids and gases where surface reactions are predominant.

Physicochemical Characteristics and Antimicrobial Efficacy of Plasma-Activated Water Produced by an Air-Operated Coaxial Dielectric Barrier Discharge Plasma

In this study, Plasma-Activated Water (PAW) was synthesized using a coaxial Dielectric Barrier Discharge (DBD) reactor, benefiting from the elevated capacity of air-flow-assisted DBD discharges to enhance nitrogen-based species concentration. By manipulating operational parameters, including gas flow rate, activation time, and DI water volume, we achieved significant concentrations of reactive oxygen and nitrogen species (RONS). As a result, the PAW obtained displayed pronounced physicochemical attributes: a pH of 2.06, an ORP of 275 mV, conductivity of 3 mS/cm, and TDS of 1200 mg/L. A pivotal aspect of this research was the evaluation of the reactor’s efficiency, as indicated by metrics like the specific input energy and ozone efficiency yield. The antimicrobial potential of the PAW was also assessed against pathogenic microbes, with remarkable reductions in viability for both Staphylococcus aureus and Escherichia coli (99.99%) and a more moderate decrease for Candida albicans (37%). These findings underscore the capability of coaxial DBD reactors in crafting high-quality PAW with significant antimicrobial properties, necessitating further studies to validate its broad-spectrum and safe applications.

Simulation study of DBD discharge characteristics and active particle-assisted methane combustion

This paper established a model of the coaxial dielectric barrier discharge (DBD). Ar-CH4 is fed into the mixture as a working gas. Using 10.0 kHz as power research in different voltage and dielectric materials and medium thickness has influences on producing active particle mole fraction. The simulation results show that when the voltage increase, the molar concentration of O3 and H energetic particles increase obviously. When the thickness of the medium increases, the molar concentration of O3 and H decreases. When the dielectric constant of the dielectric material increases, the molar concentration of O3 and H also increases. The molar concentration of OH active particles also changed, but the law was unclear. At the same time, when the discharge voltage is 15 kV, the dielectric thickness is 2 mm, the dielectric constant is 3.75, and the DBD discharge is uniform and stable, the molar concentration of O3 and H is 0.069% and 0.056% respectively. The corresponding concentrations of O3 and H active particles were introduced into the established methane combustion reaction model. The study found that the joining of O3 and H energetic particles make the reaction begin to move significantly ahead of time. That has a promoting effect on the rate of the methane combustion reaction. In the methane combustion reaction model with different equivalence ratios, O3 with a molar concentration of 0.069% and H with a molar concentration of 0.056% introduced, it is concluded that these two active particles also have a tremendous promoting effect on the expansion of the thin burning limit of methane.

Efficient deactivation of aerosolized pathogens using a dielectric barrier discharge based cold-plasma detergent in environment device for good indoor air quality

Air pollution is one of the top 5 risks causing chronic diseases according to WHO and airborne transmitted pathogens infection is a huge challenge in the current era. Long living pathogens and small size aerosols are not effectively dealt with by the available indoor air purifiers. In this work, a dielectric barrier discharge (DBD) based portable cold-plasma detergent in environment device is reported and its disinfection efficiency has been analyzed in the indoor environment of sizes up to 3 × 2.4 × 2.4 m3. The deactivation efficiency of total microbial counts (TMCs) and total fungal counts (TFCs) is found to be more than 99% in 90 min of continuous operation of the device at the optimized parameters. The complete inactivation of MS2 phage and Escherichia coli bacteria with more than 5 log reduction (99.999%) has also been achieved in 30 min and 90 min of operation of the device in an enclosed environment. The device is able to produce negative ions predominantly dominated by natural plasma detergent along with positive ions in the environment similar to mother nature. The device comprises a coaxial DBD geometry plasma source with a specially designed wire mesh electrode of mild steel with a thickness of 1 mm. The need for feed gas, pellets and/or differential pressure has been eliminated from the DBD discharge source for efficient air purification. The existence of negative ions for more than 25 s on average is the key advantage, which can also deactivate long living pathogens and small size aerosols.

Testing of Sr-Doped ZnO/CNT Photocatalysts for Hydrogen Evolution from Water Splitting under Atmospheric Dielectric Barrier Plasma Exposure.

Nonthermal plasma is a well-recognized environmentally advantageous method for producing green fuels. This work used different photocatalysts, including PZO, SxZO, and SxZCx for hydrogen production using an atmospheric argon coaxial dielectric barrier discharge (DBD)-based light source. The photocatalysts were produced using a sol-gel route. The DBD discharge column was filled with water, methanol, and the catalyst to run the reaction under argon plasma. The DBD reactor was operated with a 10 kV AC source to sustain plasma for water splitting. The light absorption study of the tested catalysts revealed a decrease in the band gap with an increase in the concentration of Sr and carbon nanotubes (CNTs) in the Sr/ZnO/CNTs series. The photocatalyst S25ZC2 demonstrated the lowest photoluminescence (PL) intensity, implying the most quenched recombination of charge carriers. The highest H2 evolution rate of 2760 μmol h-1 g-1 was possible with the S25ZC2 catalyst, and the lowest evolution rate of 56 μmol h-1 g-1 was observed with the PZO catalyst. The photocatalytic activity of S25ZC2 was initially high, which decreased slightly over time due to the deactivation of the photocatalyst. The photocatalytic activity decreased from 2760 to 1670 μmol h-1 g-1 at the end of the process.

Supported bimetallic hydrogenation catalysts treated by non-thermal plasmas

Non-thermal plasma (NTP) may be an effective and clean way for enhancing catalyst performance. The paper aims to treat the surface of catalysts by different NTP techniques. Here, radio-frequency (RF) plasma jet, dielectric barrier discharge (DBD), and spark discharge are used to treat supported bimetallic hydrogenation catalysts (i.e., Mo-Ni sulfide/γ-Al2O3 and Mo-Co oxide/γ-Al2O3) in ambient air. Surface representations of the virgin and NTPs treated catalysts show that the surface morphology, chemical states and functional groups change remarkably after NTPs treatment. The catalyst’s surface become smoother after RF plasma jet treatment, but rougher after DBD or spark discharge treatment, compared with the virgin case. The heavy particles (i.e., Ar metastable states) in RF plasma jet, high-energy electrons in DBD, and heat in spark discharge play major roles in the plasma-catalyst interactions, respectively. The evident promotion of Mo chemical valence by the oxidation of O atoms happens after DBD treatment, which indicates that DBD may be an effective way to regulate Mo chemical valence. The MoS2 layers of the Mo-Ni sulfide/γ-Al2O3 catalyst are severely destroyed as the MoS2 Raman spectrum disappear after RF plasma jet treatment. The paper provides guidance for structure regulation of catalyst surfaces by NTPs.

A SIMPLE STUDY OF JOULE HEATING EFFECT IN ARGON DBD REACTOR

Study of the gas heating phenomenon due to the heat joule effect in plasma created by an argon dielectric barrier discharge (DBD) reactor operating under treatment surface and medical sterilization conditions is essential to find the optimum of DBD discharge functioning. The present investigation of the influence of gas heating on argon discharge characteristics was executed by a one-dimensional fluid model. The gas temperature development in the DBD discharge was determined by the heat conduction equation. To consider the joule heating effect, the heat transport equation was solved along the gap distance of discharge. The results obtained from the coupling of a 1D fluid model with the heat conduction equation allowed us to calculate the gas temperature profile of argon in the DBD and plasma physical characteristics such as the densities of charged particles, the voltages, the electric field, and the coefficient rate of the ionization, attachment, and recombination in order to analyze the gas temperature development in argon DBD.

Flow control performance evaluation of a tri-electrode sliding discharge plasma actuator

Tri-electrode sliding discharge (TED) plasma actuators are formed by adding a direct current (DC) exposed electrode to conventional dielectric barrier discharge (DBD) plasma actuators. There are three TED modes depending on the polarity and amplitude of the DC supply: DBD discharge, extended discharge and sliding discharge. This paper evaluates the electrical, aerodynamic and mechanical characteristics of a TED plasma actuator based on energy analysis, particle image velocimetry experiments and calculations using the Navier–Stokes equation. The flow control performances of different discharge modes are quantitatively analyzed based on characteristic parameters. The results show that flow control performance in both extended discharge and sliding discharge is more significant than that of DBD, mainly because of the significantly higher (up to 141%) body force of TED compared with DBD. However, conductivity loss is the primary power loss caused by the DC polarity for TED discharge. Therefore, power consumption can be reduced by optimizing the dielectric material and thickness, thus improving the flow control performance of plasma actuators.

Analytical Model and Experimental Study of a Cylindrical DBD Discharge Operating in the Filamentary Mode

In this work, we present an experimental and theoretical study of a cylindrical atmospheric pressure dielectric barrier discharge (DBD) operating in the filamentary mode. An analytical model that takes into account the nonuniformity of the charge distributions on the dielectrics was developed. Using the model, it is possible to estimate important characteristics of a DBD device, like breakdown voltage, mean power consumption, and circuital parameters, directly from the geometry and physical characteristics of the device. The model also helps to understand and quantify some aspects of the behavior of the DBD discharge, like the decrease of breakdown voltage as the amplitude of the applied voltage increases, and how the fraction of area of dielectric covered with deposited charge determines the device performance. The theory was tested with experiments performed with a DBD operated in atmospheric air, with voltages from 14 to 22 kV peak to peak, and a frequency of 10 kHz.

New in situ superlow-friction method for nitrogen-containing diamond-like carbon coatings using dielectric barrier discharge treatment in ambient air

In the present paper, we develop a new in situ surface treatment technology for diamond-like carbon (DLC) coatings using dielectric barrier discharge (DBD) in ambient air. The friction coefficient dropped from 0.33 to 0.02–0.008 (low to superlow friction) shortly after DBD irradiation. Especially, when the gas containing humidity and oxygen was blew to DBD discharge position, a superlow friction of 0.008 was observed. Only nitrogen-containing DLC coatings developed a liquid film with DBD irradiation, and this film exhibited superlow friction. Surface analysis revealed that the low friction was due to the interaction of developed soft organic material and highly acidic liquid.

Deflected Synthetic Jet due to Vortices Induced by a Tri-Electrode Plasma Actuator

A tri-electrode dielectric barrier discharge (DBD) plasma actuator, which consists of a traditional DBD plasma actuator and an additional direct current (dc) electrode, is proposed to achieve a deflected synthetic jet ranging from 0 deg to 180 deg by only changing the polarity and magnitude of the dc component. Depending on the polarity of dc voltage, the tri-electrode plasma actuator can be operating in three discharge modes: traditional DBD discharge, extended discharge, and sliding discharge. The characteristics of three discharge modes are revealed and analyzed. The evolution of vortices induced by the tri-electrode plasma actuator under burst-mode actuation is investigated by particle image velocimetry (PIV) measurement and schlieren visualization. Results show that in DBD discharge mode, the vortices induced by the tri-electrode plasma actuator is symmetrical and a vertical synthetic jet forms. However, a deflected synthetic jet forms due to the asymmetrical vortices induced by extended discharge and sliding discharge. The deflection mechanism is analyzed from the viewpoint of body force induced by the tri-electrode plasma actuator. The deflected angle of the synthetic jet is identified from PIV measurement and schlieren visualization and found to be nearly linear with , which probably will be a promising result for further flow control applications.

Deposition of CeO2 on TiO2 nanorods electrode by dielectric barrier discharge plasma to enhance the photoelectrochemical performance in high chloride salt system

• One-step deposition and synthesis of CeO 2 /TiO 2 -NRs electrode by DBD plasma. • A bond combined CeO 2 (1 1 1) with TiO 2 was formed in CeO 2 /TiO 2 -NRs electrode. • The proportion of Ce 3+ /Ce 4+ was increased by plasma modification to enhance oxygen vacancy. • Heterojunction was formed between TiO 2 and CeO 2 to have a narrower band gap. • DBD plasma promotes PEC performance of CeO 2 /TiO 2 -NRs in high chloride salt system. In this study, cerium oxide (CeO 2 ) was deposited on TiO 2 nanorods (TiO 2 -NRs) through the one-step deposition by using dielectric barrier discharge (DBD) plasma treatment, where this was a simple and efficient means of synthesizing a CeO 2 /TiO 2 -NR electrode. The results of X-ray diffraction indicated that CeO 2 (1 1 1) was successfully loaded on the TiO 2 -NRs, and the peak shifted in the positive direction after DBD discharge-induced modification, indicating that a bond between CeO 2 and TiO 2 had been formed in the CeO 2 /TiO 2 -NR electrode. Based on X-ray photoelectron spectroscopy, the ratio of Ce 3+ /Ce 4+ increased due to plasma modification to enhance the oxygen vacancy of the CeO 2 /TiO 2 -NRs in the lattice structure. The CeO 2 /TiO 2 -NR composite electrode delivered the best photoelectrochemical (PEC) performance at a modified input voltage of 45 V and a deposition time of 10 min due to DBD discharge. The efficiency of removal of phenol from simulated seawater with a high salt system yielded the highest value of 97.1% for the CeO 2 /TiO 2 -NR electrodes through the PEC process at 3 V and UV–visible irradiation. A mechanism of the PEC performance of the CeO 2 /TiO 2 -NRs electrode was proposed, whereby a heterojunction was formed between TiO 2 and CeO 2 to increase the effect of oxygen storage, and active chlorine ions were produced in the high chloride salt system to enhance the degradation of pollutants.

The Characteristics of CF₃I Dielectric Barrier Discharge

The high global warming potential (GWP) of sulfur hexafluoride (SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> ) pushed the researcher to find an alternative environmentally friendly gas for high voltage applications. Trifluoroiodomethane (CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> I) has attracted a great deal of attention as new insulation gases. This article has investigated the use of CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> I in dielectric barrier discharge (DBD) based on a 1-D model. Three symmetric waveforms named sinusoidal, triangular, and the clipped waveform was used as a feeding voltage with a frequency of 5 kHz and amplitude of 5 kV. The obtained results revealed that the discharge current consists of many sequential current pulses at each half of the applied voltage and the number of these pulses depends on the waveform of the applied voltage. The discharge current pulses are identical during the positive and negative halves of the applied voltage which refer to the CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> I providing a stable DBD discharge regardless of the polarity of the applied voltage. The first discharge current peak moment, for each waveform and during each half of the cycle, has been selected as the characteristic parameter to investigate the discharge characteristics. At the moment of the first current peak, for all tested waveforms, the results showed that the spatial distribution of the electric field across the gap takes a shape of the letter V referring to the minimum point of the electrical field inside the discharge gap dividing the gap to electronegative and electropositive parts.

The exploration of discharge efficiency and uniformity improvement with pre-ionized bipolar pulse method in DBD device

An exploration of discharge efficiency and uniformity improvement by using pre-ionized bipolar pulse method in dielectric barrier discharge (DBD) device under atmospheric pressure is conducted. Through utilizing the pre-ionized charged particles on the dielectric surface, the amplitude of the applied pulses for sustaining discharge can be significantly decreased. By analyzing the influence of “built-in” electric field from surface charges on discharge efficiency and uniformity, a scheme of pre-ionized bipolar pulse method is proposed. Since the property of “built-in” field is closely dependent with pre-ionized pulse parameters, such as amplitude, pulse number, and polarity, the discharge uniformity and efficiency under different combinations of pre-ionized pulse parameters are investigated. According to experimental results, the discharge efficiency of the proposed method is increased by 11.8% and 17.4%, and the production efficiency of active species of N2(C3Πu→ B3Πg) is increased by 10.4% and 89.5% compared with a conventional bipolar pulse and positive pulse method, respectively, in ambient air. Moreover, the uniformity of DBD discharge is improved, and the maximum intensity difference between discharge regions is decreased from ∼20% to ∼5% compared with the one driven by the conventional positive pulse.

Tube-Based DBD Plasma Treatment for Improving the Performance of the Slippery Coating Layers on Medical Catheters

This work develops a tube-based dielectric barrier discharge (DBD) plasma treatment for improving the performance of the slippery coating layers on medical catheters. The raw materials of the polymer catheters usually exhibit hydrophobic surface property and need a hydrophilic slippery coating layer for reducing the friction during catheter insertion. However, the high friction force may cause an uncomfortable feeling or even the infective or thrombosis injuries on the epithelium. This study develops an atmospheric tube-based DBD plasma for treating the surface of the plastic catheter for enhancing the coating performance of the slippery layer coating on medical catheters. The tube-based DBD plasma system is a semiclose and co-axial concentric circles system composed of a glass tube as the DBD layer and the inner supporting hook for catheter production as the center electrode for DBD discharges. The treatment for the inner and outer catheter tube can be achieved simultaneously with a small carrier flow rate of 30–100 sccm. Results show that the contact angles of these catheter tubes are significantly reduced after plasma treatment and the hydrophilicity of the treated surface maintains 57% for more than 30 min after the treatments. The catheters with different plasma treatments are coated with the commercial slippery layer and tested the kinetic friction under the ASTM D1894 standard. The kinetic friction test indicates that the catheters with plasma treatment exhibit lower kinetic friction force, indicating that lower friction during catheter medical insertion operations. The experimental results have shown that the medical catheter treated by the developed tube-based DBD plasma can be effectively modified and facilitated in the subsequent coating process.

Study of Dielectric Barrier Discharge in Air and Estimation of Electron Density and Energy Deposition

This paper reports the electrical behaviors of atmospheric pressure plasma reactor with Dielectric Barrier Discharge (DBD) in air medium. The DBD discharge was generated in air at atmospheric pressure using Disc Electrode Geometry (DEG) reactor powered by ac voltage (0-7kV) at a frequency of 24kHz. The glass plates of thickness 1.0mm and 3.0mm were used as dielectric. The current-voltage characteristics were studied for two air gap of 2.0mm and 3.0mm by varying the applied voltages. The numbers of filamentary micro discharges were found as increased in each half cycle with increase in power. The observations of Lissajous figure of applied voltage versus electric current was used for measuring energy deposited by discharge and also compared with calculated value. Lissajous figures clearly show that the energy deposited by discharge was dependent on applied voltage. The electron density of discharge was measured by power balance method. Electron density was found in the order of 1017 per cubic meter.

Dielectric barrier discharge-coupled Fe-based zeolite to remove ammonia nitrogen and phenol pollutants from water

In this work, dielectric barrier discharge (DBD) coupled with Fe-based zeolite catalyst was used to treat ammonia nitrogen and phenol wastewater. This experiment mainly investigated the effects of discharge voltage, discharge frequency, zeolite dosage, initial solution concentration and pH on ammonia nitrogen or phenol removal. Results showed that the removal rate of ammonia nitrogen increased with increased discharge voltage, discharge frequency, zeolite dosage, and initial pH and decreased with increased initial ammonia nitrogen concentration. The best removal rate of ammonia nitrogen reached 75.11%, which was higher than removal rates of the solutions treated with zeolite adsorption alone (10.93%) and DBD discharge alone (9.67%). However, the removal rate of phenol increased with discharge voltage, discharge frequency, and zeolite dosage and decreased with increased initial phenol concentration and initial solution pH. After 20 min of reaction, the removal rate of phenol reached 56.67%, which was higher than the removal rates of the solutions treated with zeolite adsorption alone (20.61%) and DBD discharge alone (3.54%).Therefore, a DBD-coupled metal zeolite catalyst system has a good treatment effect on inorganic and organic wastewater. In addition, DBD-coupled Fe-based zeolite catalyst was used to simultaneously treat mixed ammonia nitrogen and phenol wastewater. The degradation process and mechanism of mixed ammonia nitrogen and phenol wastewater in the system were studied to reflect the synergistic effect of the system.

Modeling of a Dielectric-Barrier Discharge-Based Cold Plasma Combustion Ignition System

We present a computational modeling study of plasma phenomena in a dielectric-barrier discharge (DBD) for automotive combustion ignition applications. The study was performed using a self-consistent, two-temperature plasma model with finite-rate plasma chemical kinetics for methane-air combustion mixture. The structure of a DBD discharge and the yield of active combustion enhancing radicals from the discharge is quantified for positive and negative pulsing, and a comparison is made with a single electrode corona discharge. The DBD plasma develops as a streamer discharge with individual streamers preferentially emerging from sharp features on the bare electrode of DBD which quickly propagates to the opposite dielectric surface where it is quenched. The dielectric barrier therefore self-limits the discharge resulting in a total radical yield that saturates in time. The corona on the other hand provides a radical yield that can continuously increase in time. The negative polarity pulsing of the DBD results in a more intense plasma with a higher radical yield compared to a positive polarity pulse. Simulations are also performed for a long 1-μs duration afterglow period once the active pulse is terminated. The active combustion enhancing radicals are found to remain relatively stable in density over this duration, indicating that ~100-kHz pulse repetition rates can sustain or even gradually increase the radical densities over long durations of transient time.