Double Dielectric Barrier Discharge Research Articles

Effects of Dielectric Barrier Discharge Plasma on the Combustion Performances of Reverse-Flow Combustor in an Aero-Engine

In order to apply plasma assisted combustion (PAC) into a reverse-flow aero-engine and verify the improvement of combustion performance, a feasible approach was proposed in this work. In this approach, based on the structure characteristics of the reverse-flow combustor, a parallel plate double dielectric barrier discharge (DBD) PAC actuator was designed to generate plasma. It was installed at the front of combustor. When the actuator is driven, the original air flow is not disturbed for the device's structure and installation. Using aviation kerosene as fuel, the effects of plasma on ignition boundary and outlet temperature of the combustor were experimentally investigated at atmosphere pressures. Through the dual high voltage differential power supply, the large gap, large area and uniform plasma discharge was achieved. The results of PAC actuator discharge indicate that inlet air temperature has a small increase of 4–9 K. After PAC is applied, the combustion performances of reverse-flow combustor in an aero-engine are remarkably improved. Experimental results indicate that ignition boundary is widened by 3.7%-12.5% because of the impact of plasma. Outlet highest temperature of combustor is raised by 19–75 K; outlet temperature distribution coefficient is reduced by 11.1%-26.6%. This research provides an effective and practicable way to implement the application of PAC in aero-engine combustor and has some engineering application significance.

A novel array of double dielectric barrier discharge combined with TiCo catalyst to remove high-flow-rate toluene: Performance evaluation and mechanism analysis.

A novel array double dielectric barrier discharge (ADDBD) combined with a TiO2/Al2O3-Co3O4/AC (TiCo) catalyst was applied to remove toluene. The effects of catalyst setting distance, catalyst combination mode, and process factors (including specific input energy, initial toluene concentration, and relative humidity) were investigated in terms of the toluene degradation efficiency (ηtoluene) and the selectivity of CO2 (SCO2). When the specific input energy was 65 J·L-1, the initial toluene concentration was 100 mg·m-3, and the relative humidity was 30%, the highest ηtoluene of 72% and SCO2 of 44% could be achieved with TiO2/Al2O3 10 cm and Co3O4/AC 20 cm downstream of the ADDBD. Based on the determination of active substances (e.g., O3, OH) and the catalyst activation mode, a synergistic effect of active substances and photon between the ADDBD and the TiCo catalyst was proposed for the removal of toluene. Finally, the biodegradability and toxicity of the outlet gas were evaluated, and the results showed that the outlet gas was more convenient for subsequent biopurification and less toxic to the surroundings after the treatment by the ADDBD combined with the TiCo catalyst.

Using non-thermal plasma for decomposition of toluene adsorbed on γ-Al2O3 and ZSM-5: Configuration and optimization of a double dielectric barrier discharge reactor

A novel hybrid system was established to degrade adsorbed toluene efficiently. A double dielectric barrier discharge (DDBD) reactor was filled with two common adsorbents, γ-Al2O3 and ZSM-5, in various combinations. Packing material, high-voltage electrode structure, and gas-flow mode were investigated to optimize this reactor. The reactor packed with a mixture of γ-Al2O3 and ZSM-5 provided a mineralization rate 6.1% to –14.1% greater than one using a single material. Specifically, the highest mineralization rate was obtained in a DDBD reactor packed with γ-Al2O3 in the inner tube and ZSM-5 in the outer tube. Using the optimal combination of packing material, two high-voltage electrodes were compared. A higher mineralization rate was observed in the reactor with a rod electrode (63.3%) than in one equipped with a coil electrode (53.7%), The total amounts of O3 and N2O generated were much less in the reactor with a rod electrode. The effect of gas-flow mode on toluene decomposition was investigated and the result showed that mode 1 (with the gas flowing from the inner tube into the outer tube during both adsorption and discharge phases) could not only improve the degradation of toluene, but could also suppress the generation of O3 and N2O. A possible mechanism for toluene decomposition in the packed-bed DDBD reactor was proposed based on the analysis of organic intermediates remaining in the adsorbents.

Double dielectric barrier discharge cells for promoting the catalytic degradation of volatile organic compound released by industrial processes.

In this study, the recycling of gas flow was added to oxidize mixture (toluene and xylene) in the post-plasma catalysis (PPC) system, and the MnOx catalysts using impregnation method were used to further oxidize the VOC mixture. The circulation and catalysts were of enhancement for the plasma degradation on both toluene and xylene. The improvement of CO2 selectivity and the reduction of NO, NO2, and O3 were 64.4%, 92.0%, 62.2%, and 51.9%, respectively. The fresh and used catalysts were characterized for the ozone decomposition and mixture degradation in the NTP-REC-CATAL system with the 15wt% loading amount of catalysts. The results showed that OH groups, lattice oxygen, and manganese sites were potential and significant for the catalytic ability for O3 and mixture conversion. Aldehyde was detected from FT-IR characterization after treating, which indicates that it is the main intermediate NTP-REC-CATAL process. The air plasma was employed to reactive catalytic activity.

DDBD ozone plasma reactor generation: the proper dose for medical applications

Double Dielectric Barrier Discharge (DDBD) ozone plasma reactor generation are presented in this paper. The generation of this reactor generates ozone concentration which can be arranged upon the proper dose for medical applications. AC high voltage is applied to the range of 0-3 kV and the frequency of 50 Hz. Pure oxygen gas was piped into the DDBD reactor with flow rate variations of 2, 4 and 6 L/min. The results showed that current as a function of voltage where the current is increased with the increasing of voltage. Ozone productivity is shown by the significant increase of current. Ozone concentration is increasing as the increase of the voltage provided, but rather the concentration of ozone is decreasing as the increasing of flow rate. The Ozone capacity is affected by ozone concentration and flow rate, and can be used to determine the ozone dose. The proper dose of ozone can be ozone therapy for various kinds of diseases.

Electrical model and experimental analysis of a double spiral structure surface dielectric barrier discharge

A surface dielectric barrier discharge (SDBD) can discharge at atmospheric pressure and produce a large area of low-temperature plasma. An SDBD plasma reactor based on the double spiral structure is introduced in this paper. To study the discharge mechanism of SDBD, an equivalent circuit model was proposed based on the analysis of the micro-discharge process of SDBD. Matlab/Simulink is used to simulate and compare the voltage–current waves, Lissajous and discharge power with the experimental results. The consistency of the results verifies the validity of the SDBD equivalent circuit model. Maxwell software based on the finite elements method is used to analyze the electrostatic field distribution of the device, which can better explain the relationship between the discharge image and the electrostatic field distribution. The combination of equivalent circuit simulation and electrostatic field simulation can provide better guidance for optimizing a plasma generator. Finally, the device is used to treat PM2.5 and formaldehyde. The test results show that the degradation rate of PM2.5 can reach 78% after 24 min, and formaldehyde is about 31.5% after 10 min of plasma treatment.

Characteristics and mechanism of toluene removal from gas by novelty array double dielectric barrier discharge combined with TiO2/Al2O3 catalyst

A new reactor of array double dielectric barrier discharge (DDBD) combined with catalysis was prepared, and the effect of different factors on removal efficiency of toluene at pilot scale were investigated. The possible degradation mechanism was explored. The results indicate that the removal efficiency of toluene in the exhaust gas decreases with the increasing of the toluene initial concentration and the gas flow rate, but increases with the increasing of the specific energy density. When the air relative humidity is 55%, the removal efficiency of toluene is higher than that of the relative humidity by 85%. The results of XPS, FT-IR and GC-MS analysis show that the main intermediate products of removing toluene by DDBD combined with TiO2/Al2O3 catalyst are phenol, benzaldehyde, benzyl alcohol, benzoic acid, N-benzyl formamide, dimethyl terephthalate, dimethyl isophthalate and other substances. There are five possible pathways to degrade toluene by DDBD combined with TiO2/Al2O3.

A review on application of dielectric barrier discharge plasma technology on the abatement of volatile organic compounds

Volatile organic compounds (VOCs) released from the waste treatment facilities have become a significant issue because they are not only causing odor nuisance but may also hazard to human health. Non-thermal plasma (NTP) technologies are newly developed methods and became a research trend in recent years regarding the removal of VOCs from the air stream. Due to its unique characteristics, such as rapid response at room temperature, bulk homogenized volume, high reaction efficiency, dielectric barrier discharge (DBD) plasma technology is considered one of the most promising techniques of NTP. This paper reviews recent progress of DBD plasma technology for abatement of VOCs. The principle of plasma generation in DBD and its configurations (electrode, discharge gap, dielectric barrier material, etc.) are discussed in details. Based on previously published literature, attention has been paid on the effect of DBD configuration on the removal of VOCs. Effect of various process parameters such as initial concentration, gas feeding rate, oxygen content and input power on VOCs removal are also considered. Moreover, the role of catalysis and inhibitors in VOCs removal by DBD system are presented. Finally, a modified configuration of the DBD reactor, i.e. double dielectric barrier discharge (DDBD) for the abatement of VOCs is discussed. It was suggested that the DDBD plasma reactor could be used for higher conversion efficiency as well as for avoiding solid residue deposition on the electrode. These depositions can interfere with the performance of the reactor.

Development of DDBD and plasma jet reactors for production reactive species plasma chemistry

A novel Double Dielectric Barrier Discharge (DDBD) and an atmospheric pressure plasma jet (APPJ) was generated with a dielectric barrier discharge (DBD) column by AC high voltage have been developed. This reactor can produce cold atmospheric plasmas (CAP) that formed in air reactive oxygen species (ROS). These species among others are O3, H2O2, was quantified in the outlet of reactors. The analysis for ROS has been conducted by using medium that we call Plasma-Activated Medium (PAM). Some analysis conducted including variation of exposure times by ROS to the plasma-activated medium. In addition, concentration-voltage characteristics of ozone production. Peroxide Value, Acid Value and Viscosity of virgin coconut oil (VCO, as PAM) increased with increasing exposure time of O3. The concentration of hydrogen peroxide in water (as PAM) has been measured. The concentration of H2O2 179 μM with exposure time for 1 minute. The concentration of H2O2 in the study is quite high when compared with some other research results. The results showed that increased exposure time resulted in increased concentrations of ozone and hydrogen peroxide.

New development of double dielectric barrier discharge (DBD) plasma reactor for medical

Effect of gas source and flowrate to ozone concentration and capacity was investigated using double DBD plasma reactor with cylinder-cylinder configuration. The high AC voltage was applied in the range of 200-500 Volts and the frequency of 50 Hz. Gas sources; i.e. free air and pure oxygen; flowed into the reactor with several variations in flow rate, i.e. 2 to 24 L/min. The results showed that the ozone concentration decreased with increasing gas flow rate. Free air sources produced smaller ozone concentration and capacity compared to those produced using a pure oxygen source (O2). While the ozone capacity increases with increasing gas flow rate. The pure oxygen (O2) with a flow rate of 24 L/min had produced ozone concentration of 2.2 mg/liter and ozone capacity of 52.8 mg/min. A number of further studies need to be conducted related to the effect of voltage, diameter, and length of the electrode to obtain lower ozone concentration and capacities, for ozone applications in medical therapy. The suitable dose of ozone therapy for medical can be used for wound healing and chronic disease.

Ar plasma jet generation and its application for water and surface sterilization

Microorganisms are widely distributed in the living environment of human, animals and plants. Some of the microorganisms are harmful for their pathogenic effects. Non-thermal plasma technology, especially, the atmospheric pressure plasma jet, is considered to be one of the promising technologies for sterilization. This work proposes a double-dielectric barrier discharge reactor for Ar plasma jet generation. Charteristics of discharge and temperature thermogram of plasma jet are investigated by the means of U-P curve and infrared image, respectively. Performance of the plasma jet is evaluated by surface and water sterilization. The results show that, Ar plasma jet is generated stable with double-dielectric barrier discharge. The length of plasma jet increases as the applied voltage, frequency or gas flow increased, but the plasma jet generation can be restricted in high frequency or gas flow. For E. coli in the water and surface, high sterilization efficiency is observed for a short time treatment by Ar plasma jet.

Experimental study on ozone generation from oxygen in double surface dielectric barrier discharge

Double surface dielectric barrier discharge (DSDBD) can simultaneously form two uniform plasma zones for ozone synthesis with an AC power supply, thus exhibiting great advantages in achieving high energy yield at high ozone concentration. However, effects of the experimental parameters on DSDBD is urgently to be investigated to optimize the discharge reactor and provide references for high-efficiency ozone generator design. Here we present a systematical experimental study of the DSDBD in oxygen for ozone generation. The effects of important parameters (gas-flow mode, dielectric, discharge gap, etc.) on DSDBD in oxygen were studied, and the optimal DSDBD reactor was screened out. The optimal DSDBD reactor can achieve ozone energy yield of 317.7–130.0 g/kWh within ozone concentration of 12.7–56.2 g/Nm3 and exhibit an excellent stability during a 2-h continuous test, demonstrating its much better performance in ozone synthesis than other conventional DBDs. The discharge characteristics and the optimization results suggest that the superior performance of the optimal DSDBD reactor lies in its complete interaction of oxygen and plasma, large numbers of reactive species and electrons as well as favorable energy distribution of the reactive species.

Process for Chloroform Decomposition: Nonthermal Plasma Polymerization with Methane and Hydrogen

This paper describes an alternative process for chloroform decomposition via nonthermal plasma polymerization at atmospheric pressure and investigates the effect of methane and hydrogen addition on the process. The effect of both additives was assessed separately, where experiments were conducted in a double dielectric barrier discharge reactor under nonoxidative conditions. The most profound impact of the additives was a significant increase in the yield of non-cross-linked polymer produced compared to that in their absence. The addition of methane resulted in a 120% increase in polymer yield, while in hydrogen the increase was 31%. Critical parameters such as effect of the methane and hydrogen concentration on the conversion of chloroform at various applied voltages, the product distribution, mass balance, and polymer characterization are elucidated in this paper. Single pass conversions of 61% and 68% (with corresponding mass balances of 98% and 95%, respectively) were achieved for CHCl3 + CH4 and CHCl3 + H2 feed scenarios, respectively. Furthermore, a polymerization mechanism which explains the formation of major chain structures as well as structural defects in the polymer is expounded upon in the paper.

Effects of Reduced Electric Field on Sulfur Hexafluoride Removal for a Double Dielectric Barrier Discharge Reactor

Sulfur hexafluoride (SF6) is a greenhouse gas with very high global warming potential. This paper investigated the effects of reduced electric field, E/N, on SF6 abatement by using a coaxial double-layer dielectric barrier discharge (DBD) reactor. The concentration of SF6 was 2%, and the remaining 98% of the feed gas is He/water vapor. The reduced electric field of the discharge region was calculated. The effects of different reduced electric fields on SF6 removal and the mechanisms were studied in terms of the removal efficiency and energy yield (EY). The experimental results showed that higher removal efficiency was achieved when the reduced electric field was higher than 126 Td and as the E/N increased; the time for removing SF6 completely was shortened. However, the EY at different reduced electric fields did not change much. SO2F2, SOF4, SOF2, and SO2 were the main products after the plasma removal process.

Volatile organic compounds (VOCs) removal in non-thermal plasma double dielectric barrier discharge reactor

Non-thermal plasma (NTP) an emerging technology to treat volatile organic compounds (VOCs) present in unhygienic point source air streams. In present study, double dielectric barrier discharge (DDBD) reactors were used for the first time to evaluate the removal efficiency of VOCs mixture of different nature at constant experimental conditions (input power 16–65.8 W, VOCs mixture feeding rate 1–6 L/min, 100–101 ppm inlet concentration of individual VOC). Reactor A and B with discharge gap at 6 mm and 3 mm respectively, were used in current study. When treated at an input power of 53.7 W with gas feeding rate of 1 L/min in DDBD reactor A, removal efficiency of the VOCs were: tetrachloroethylene (100%), toluene (100%), trichloroethylene (100%), benzene (100%), ethyl acetate (100%) and carbon disulfide (88.30%); whereas in reactor B, the removal efficiency of all VOCs were 100%. Plasma-catalyst (Pt-Sn/Al2O3, BaTiO3 and HZSM-5) synergistic effect on VOCs removal efficiency was also investigated. Highest removal efficiency i.e 100% was observed for each compound with BaTiO3 and HZSM-5 at an input power 65.8 W. However, integrating NTP with BaTiO3 and HZSM-5 leads to enhanced removal performance of VOCs mixture with high activity, increase in energy efficiency and suppression of unwanted byproducts.

Tailoring the wettability of glass using a double-dielectric barrier discharge reactor

A double dielectric barrier discharge reactor operated at a low power frequency of 400 Hz and atmospheric pressure was utilized for regulating the wettability of glass surface. The hydrophobic treatment was performed by plasma polymerization of tetramethylsilane (TMS, in argon gas). The obtained results showed that the TMS coatings formed on the glass substrates without oxygen addition were smooth, uniform films with the maximum water contact angle (WCA) of about 106°, which were similar to those obtained by low pressure, high power frequency plasmas reported in the literature. The addition of oxygen into TMS/Ar plasma gas decreased the WCA and induced the formation of SiOSi and/or SiOC linkages, which dominated the existence of Si(CH2)nSi network formed in TMS/Ar (without oxygen) plasma.

Measurements and kinetic modeling of atomic species in fuel-oxidizer mixtures excited by a repetitive nanosecond pulse discharge

This work presents the results of number density measurements of metastable Ar atoms and ground state H atoms in diluted mixtures of H2 and O2 with Ar, as well as ground state O atoms in diluted H2–O2–Ar, CH4–O2–Ar, C3H8–O2–Ar, and C2H4–O2–Ar mixtures excited by a repetitive nanosecond pulse discharge. The measurements have been made in a nanosecond pulse, double dielectric barrier discharge plasma sustained in a flow reactor between two plane electrodes encapsulated within dielectric material, at an initial temperature of 500 K and pressures ranging from 300 Torr to 700 Torr. Metastable Ar atom number density distribution in the afterglow is measured by tunable diode laser absorption spectroscopy, and used to characterize plasma uniformity. Temperature rise in the reacting flow is measured by Rayleigh scattering. H atom and O atom number densities are measured by two-photon absorption laser induced fluorescence. The results are compared with kinetic model predictions, showing good agreement, with the exception of extremely lean mixtures. O atoms and H atoms in the plasma are produced mainly during quenching of electronically excited Ar atoms generated by electron impact. In H2–Ar and O2–Ar mixtures, the atoms decay by three-body recombination. In H2–O2–Ar, CH4–O2–Ar, and C3H8–O2–Ar mixtures, O atoms decay in a reaction with OH, generated during H atom reaction with HO2, with the latter produced by three-body H atom recombination with O2. The net process of O atom decay is O + H → OH, such that the decay rate is controlled by the amount of H atoms produced in the discharge. In extra lean mixtures of propane and ethylene with O2–Ar the model underpredicts the O atom decay rate. At these conditions, when fuel is completely oxidized by the end of the discharge burst, the net process of O atom decay, O + O → O2, becomes nearly independent of H atom number density. Lack of agreement with the data at these conditions is likely due to diffusion of H atoms from the partially oxidized regions near the side walls of the reactor into the plasma. Although significant fractions of hydrogen and hydrocarbon fuels are oxidized by O atoms produced in the plasma, chain branching remains a minor effect at these relatively low temperature conditions.

Application of non-thermal plasma technology on fugitive methane destruction: Configuration and optimization of double dielectric barrier discharge reactor

Fugitive methane (CH4) from waste treatment facilities (landfill mining), power industries (oil and gas process plants) and coal mining etc. into atmosphere is an increasing environmental concern. In this study, CH4 conversion efficiency in double dielectric barrier discharge (DDBD) has been investigated at various operating parameters including input power, feed gas-mixture flow rate, CH4 initial concentrations, and discharge gap distance between two dielectrics. Increase in input power, decrease in the gas-mixture flow rate and discharge gap distance; results in increases of CH4 conversion efficiency. In plasma alone, maximum CH4 conversion efficiency of 76% was obtained using 3 mm plasma discharge gap distance at flow rates of 2 L/min, input power of 65.8 W and is limited by experimental conditions. In addition, CH4 conversion efficiency in plasma alone and plasma-catalytic is compared by introducing various catalysts includes Pt–Sn/Al2O3, BaTiO3 and HZSM-5 in single plasma discharge zone. Results revealed that plasma combined with Pt–Sn/Al2O3 showed higher CH4 conversion efficiency (84.93%) as compare to plasma alone (56.42%) using 6 mm plasma discharge gap distance at flow rates of 2 L/min, input power of 65.8 W. Moreover, maximum energy efficiency of CH4 conversion (limited by experimental conditions) was 27.24 × 10−12 mol/kJ at 32.6 W observed in plasma-catalyst. Analysis of the exhaust gas showed that DDBD is a promising alternative reactor not only to achieve high CH4 conversion efficiency, but also to overcome the drawbacks of formation of undesirable byproducts. Moreover, deposition of carbon residues on the surface of internal electrode is not observed, which is often occurred in single DBD reactors.

Analysis of Ar plasma jets induced by single and double dielectric barrier discharges at atmospheric pressure

The aim is the comparison of different plasma parameters of single and double dielectric barrier discharge plasma jet configurations (S-DBD and D-DBD) which are potentially usable in biomedical applications. Both configurations are studied in terms of electric field distribution, electrical discharge characteristics, plasma parameters (estimated by optical emission spectroscopy analysis), and hydrodynamics of the plasma jet for electrical parameters of power supplies corresponding to an applied voltage of 10 kV, pulse duration of 1 μs, frequency of 9.69 kHz, and Ar flow of 2 l/min. We observed that the D-DBD configuration requires half the electrical power one needs to provide in the S-DBD case to generate a plasma jet with similar characteristics: excitation temperature around 4700 K, electron density around 2.5 × 1014 cm−3, gas temperature of about 320 K, a relatively high atomic oxygen concentration reaching up to 1000 ppm, the presence of reactive oxygen and nitrogen species (nitric oxide, hydroxyl radical, and atomic oxygen), and an irradiance in the UV-C range of about 20 μW cm−2. Moreover, it has been observed that D-DBD plasma jet is more sensitive to short pulse durations, probably due to the charge accumulation over the dielectric barrier around the internal electrode. This results in a significantly longer plasma length in the D-DBD configuration than in the S-DBD one up to a critical flow rate (2.25 l/min) before the occurrence of turbulence in the D-DBD case. Conversely, ionization wave velocities are significantly higher in the S-DBD setup (3.35 × 105 m/s against 1.02 × 105 m/s for D-DBD), probably due to the higher electrostatic field close to the high voltage electrode in the S-DBD plasma jet.

Abatement of Gaseous Xylene Using Double Dielectric Barrier Discharge Plasma with In Situ UV Light: Operating Parameters and Byproduct Analysis

Ultraviolet (UV) light with a wavelength of 254 nm was applied to a double dielectric barrier discharge (DDBD) system to decompose of gaseous xylene. The results show that a significantly synergistic effect can be achieved with the introduction of UV light into the DDBD system. When UV light is applied, the system show a 21.8 % increase in its removal efficiency for xylene at 35 kV with an ozone concentration close to 971 ppmv. The COx (x = CO2 and CO) selectivity of outlet gas rises from 6.54 to 76.2 %. The optimal synergetic effect between UV light and DDBD can be obtained at a peak voltage of 30 kV. The system is robust for humidity, which only slightly reduces the xylene removal efficiency at a high peak voltage (30–35 kV). With the increase of gas flow rate, the removal efficiency for xylene decreases due to a reduced residence time. In addition, the products of xylene degradation were also analyzed. The major products of the degradation were found to be CO2 and H2O while byproducts such as O3 and HCOOH were observed as well.