Rotating Gliding Arc Research Articles

The Role of CH4 in Plasma-Assisted CO2 and CH4 Conversion in a Rotating Gliding Arc Plasma: Insights Revealed by Experiments and Modeling

The Role of CH₄ in Plasma-Assisted CO₂ and CH₄ Conversion in a Rotating Gliding Arc Plasma: Insights Revealed by Experiments and Modeling

Experimental study on the discharge characteristics of an air rotating gliding arc

In this study, the discharge characteristics of an air rotating gliding arc (RGA) are investigated by synchronous measurements of a digital oscilloscope and a high-speed camera, and the emission spectrum measurement. The discharge evolution in one complete motion cycle exhibits a ‘breakdown-elongation-extinction’ process accompanied by a jump phenomenon of the arc root and a back-breakdown phenomenon. The discharge evolves from the unstable breakdown mode (U-B), to the transition mode and finally to the stable gliding mode (S-G) by increasing the input voltage or decreasing the tangential and axial gas flow rates. The U-B mode at an input voltage of 120 V is featured by the large reduced electric field and high electron temperature of 1.90 eV, but the arc length and existence time are very short. The S-G mode at an input voltage of 270 V has a relatively low breakdown frequency of 0.33 kHz and an average breakdown current of 1.31 A, implying that the arc steadily glides and rotates along the spiral electrode. The average electron temperature is 0.64 eV in the S-G mode, while the arc length and existence time are longer. The rotational and vibrational temperatures of the N2(C3∏u) state are respectively measured at 2200 K and 4400 K in the U-B mode, and in the S-G mode are 2600 K and 4820 K. From the evolution of emission intensities of measured excited species, it is found that the NOγ band emission intensity generally rises from the U-B mode to the S-G mode since the gas temperature and arc existence time rise, indicating that the S-G mode may be beneficial for the vibrationally promoted Zeldovich reactions. This study could deepen the understanding of arc characteristics in air RGA for selecting a suitable mode to achieve better plasma performance in practical applications.

The Influence of Vortex Formation on the Electrical Characteristics of Argon Plasma in a Rotating Gliding Arc Discharge

The Influence of Vortex Formation on the Electrical Characteristics of Argon Plasma in a Rotating Gliding Arc Discharge

A Novel Lumped Parameter Approach Toward Understanding Rotating Gliding Arc

A Novel Lumped Parameter Approach Toward Understanding Rotating Gliding Arc

Characteristics of an AC rotating gliding arc discharge in NH3 and air atmospheres

Plasmas have emerged as a promising technology for the utilization of NH3 as a carbon-free fuel for direct plasmas-assisted combustion and hydrogen production. This study aims to explore the electrical and optical emission characteristics of the rotating gliding arc (RGA) discharge in NH3 and air swirling flows over a wide range of nominal power inputs. The electrical characteristics were measured using voltage–current probes, while a spectrometer was employed to assess the spectral characteristics. Additionally, a synchronized high-speed camera equipped with a dual-scope objective was utilized to capture transient phenomena of the arc in the optical emission spectrum. Both the spark-type and glow-type discharges were observed in RGA. Interestingly, the spark-type discharge frequency exhibited a non-monotonic variation with increasing nominal power inputs for both NH3 and air, while the glow-type discharge frequency displayed a monotonous upward trend. Regarding the spectral emission characteristics in NH3, a dramatic transition of the arc emission spectrum from Hα to NH2* was observed as nominal power inputs increased. The Hα and NH2* emissions that are dominated in the spark-type and glow-type discharges, respectively, and the intensity ratio of Hα and NH2* emission shows evident correlations with discharge current and electric field strength. In summary, this study represents the first investigation into the electrical and spectral characteristics of RGA in NH3.

Characteristics of rotating gliding arc induced thermal ignition of lean methane-air mixtures

The rotating gliding arc discharge (RGA) induced methane-air ignition process under the lean conditions is investigated by the high-speed videography and the numerical simulation, with the focus on the effects of dynamic discharge characteristics. The experimental and numerical results both indicate that the ignition process in the burner can be divided into two stages, including the waiting stage and the rapid flame propagation stage. The effective ignition time (τburner) including both stages decreases nonlinearly as the effective input ignition power (i.e. Pig/Pcomb) increases, following the exponential law, i.e. τburner=2.98 × 10−9(Pig/Pcomb)−7.299+81.75. It is because of that as the input power is relatively low τburner is governed by the duration of the waiting stage to decrease notably with the increment of the input power. However, as the input power is too large τburner becomes determined by the rapid flame propagation stage to be insensitive to the input power. The rotation frequency of the plasma sources can impact the τburner with that too low or too high frequency is detrimental to the ignition. The flame quenching is less likely to occur with the increase of the plasma volume. Based upon the experimental and numerical results, an RGA-induced ignition mechanism is proposed. It indicates that the two-staged ignition process is largely determined by the waiting stage, where multiple flame kernels are frequently initialized by the RGA to be locally quenched or propagate downstream/upstream with flow. Due to the recirculating flow, the energy released by the plasma and the ignited flame kernels can be accumulated upstream to reduce the local Ka number and enhance the flame propagation at the waiting stage. As Ka is lower than a critical value, the flame kernels can propagate rapidly to complete the ignition.

Rotating gliding arc discharge induced flame oscillation near the lean blowout limit

This work investigates the rotating gliding arc (RGA) assisted swirling methane combustion characteristics near the lean blowout limit by utilizing the high-speed videography. As the flow rate and the global equivalence ratio were varied, four flame modes, namely self-sustained flame, RGA-sustained stable flame, RGA-induced oscillating flame, and RGA anchored flame modes were detected. In particular, the oscillating flame mode with an oscillating frequency of 2∼4 Hz occurs with the air flow rates above 13 L/min and the equivalence ratio between 0.52 and 0.56. It is an RGA-induced low-frequency flame oscillation phenomenon. The RGA discharge characteristics can impact the oscillating behaviors that with the increase of the transformer input voltage, the flame oscillation frequency is enhanced and the averaged flame area becomes larger to result in a higher combustion efficiency. Besides, increasing the wall temperature of the combustion chamber promotes the combustion during the oscillating stage. Based upon the experimental and numerical results this RGA-induced low-frequency oscillating flame are further interpreted by a three-staged mechanism. It implies that the first stage, during which the fuel/oxidant mixture is refreshed in the chamber and the temperature increases through recirculating flow gradually, determines the oscillating frequency. The fast accumulation of released energy from plasma discharge and partial fuel burning by recirculation can accelerate the temperature growth in the recirculation zone to increase the oscillation frequency. In all, this unique oscillating phenomenon and related explanations indeed broaden our knowledge of oscillating combustion behaviors and GA assisted combustion.

Dry reforming of methane in a rotating gliding arc plasma: Improving efficiency and syngas cost by quenching product gas

Rotating gliding arc (GA) plasma has attracted increasing interest in dry reforming of methane (DRM) for CO2 utilization. Most DRM studies using GA plasma are conducted to improve energy efficiency by increasing the conversion of reactants. This study aimed to improve energy efficiency by increasing the selectivity of products, particularly that of H2. To increase the selectivity of H2, a quenching device (i.e., a quenching rod (QR)) was developed to protect H2 from being consumed by suppressing the reverse water–gas shift (RWGS) reaction that is dominant in CO2 and H2 consumption in DRM processes. When the QR was applied, the conversion of CH4 and CO2 was reduced, while the selectivity and yield of H2 and H2O changed significantly, i.e., the yield of H2 increased, and the yield of H2O decreased. Owing to the increased yield of H2, the energy efficiency and syngas cost were improved. At an SEI of 4.2 kJ/L with a CH4/CO2 ratio of 5/7, the conversion of CH4 and CO2 was 51.1% and 40.2%, respectively; the highest energy efficiency was 55.3% with syngas costs of 10.9 kJ/L. Moreover, compared with the results of other DRM studies, syngas with the highest H2/CO ratios of 0.95 and 1.26 at CH4/CO2 ratios of 5/7 and 1 was produced with the reactor applied in this study, respectively. In conclusion, optimizing the quenching process will probably further improve the DRM performance. Moreover, the quenching method will be applied to dry reforming processes for syngas with high H2/CO ratios.

Effects of environmental temperature on the spectral characteristics of RGA plasma-assisted combustion actuator for aero-engines

Using rotating gliding arc (RGA) discharge, a plasma-assisted combustion actuator was designed and used in aero-engines. To study the spectral characteristics of the actuator at the changed environmental temperature, an experimental system for the spectral characteristics of the RGA plasma-assisted combustion actuator was established. The optical emission spectroscopy (OES) of the actuator discharge was measured with an emission spectrometer. It was discovered to primarily include the emission spectroscopy of N2∗ (C3Πu→ B3Πg), N+, N, and O atom. As the environmental temperature increased, OES of N2∗ (C3Πu→ B3Πg) has a fluctuating change rising of first at less than 313K, then falling between 313 K and 353 K, and rising again between 353 K and 373 K. Simultaneously, the emission intensity of N+, N, and O atoms decreased. In addition, the vibrational temperature was calculated by the second positive system (SPS) N2∗ (C3Πu→ B3Πg) and Boltzmann plots. The vibrational temperature decreased by 363–492 K with the increase in environmental temperature. These results are valuable for understanding RGA’s application in aero-engines.

(Invited, Digital Presentation) Eco-Friendly and Sustainable Ammonia Production with Atmospheric Pressure Rotating Gliding Arc Discharge

Increasing fossil-free global energy demands have motivated the scientific community to investigate new clean and sustainable techniques that can meet global energy demands. The production of green and sustainable fuel, such as ammonia, from base molecules like water and nitrogen using electricity from renewable sources shows great potential to solve energy issues. Non-thermal atmospheric pressure plasma-based ammonia synthesis has great potential for carbon-free fertilizer production powered by renewable electricity. We developed an atmospheric pressure rotating gliding arc discharge reactor coupled with a catalyst for a higher ammonia production rate. Here we reported two-step ammonia production, including 1) facile production of NOx and hydrogen from nitrogen discharge in water, and 2) highly selective catalytic reduction of NOx to ammonia in the presence of hydrogen. The studied plasma technique offers ~0.84 % ammonia concentration with ~95 % selectivity and a 120 µmol/s production rate by integrating a catalytic reduction system with plasma. Compared with previous studies on ammonia synthesis from nitrogen, the remarkable ammonia yield (300–400-fold higher). These promising results provide a breakthrough in the transition toward sustainable and environmentally friendly ammonia production.

플라즈마 버너를 활용한 노후건설기계의 백연(white smoke) 배출 저감 기술

White smoke emission from decrepit construction vehicles is one of the main causes of fine dust production. In particular, despite the fact that a large amount of white smoke is occurring in the vehicles such as decrepit construction machinery equipped with DPF (Diesel Particulate Filter), no technical solution has been found yet. This study aims to analyze the causes of white smoke emission that occurs in DPF system and propose technical solutions to resolve the issues. The performance and operational characteristics of the burner mounted to thermally manage the DPF performance are the main causes of the occurrence of white smoke. The fundamental ignition mechanism of the diesel burners was investigated depending on the types of ignition sources; the rotating gliding arc for plasma burner and glow plug for conventional diesel burner. It was verified that plasma burner can be applied to drastically reduce the occurrence of white smoke.

Chemical Kinetics Simulation of Hydrogen Generation in Rotating Gliding Arc Plasma

This work reports hydrogen (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) formation using methane nitrogen gas mixture as a feed stream in a rotating gliding arc (RGA) reactor. The H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> formation in the RGA was quantified by experimental studies, and the results were validated by simulating plasma chemical kinetics using the Chemical Workbench software. The simulation was performed for an experimental condition, where methane (1%) and nitrogen (99%) gas mixture was fed to an RGA at 5, 10, 25, and 40 lpm. For these flow rates, the simulation predicted 1417, 802, 299, and 67 ppm of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , respectively. Also, the results show that at these flow rates, the reduced electric field (E/N) of the discharge was 78, 83, 92, and 101 Td and the gas temperature was 3800, 4108, 4590, and 4975 K respectively. The simulation result was in reasonable agreement with the experimental data, which shows 1276, 717, 213, and 61 ppm of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> in the product gas, respectively, at 5, 10, 25, and 40 lpm. This work marks the first step toward process optimization through the simulation approach.

Influence of flow regime on the decomposition of diluted methane in a nitrogen rotating gliding arc

This work reports the operation of rotating gliding arc (RGA) reactor at a high flow rate and the effect of flow regimes on its chemical performance, which is not explored much. When the flow regime was changed from transitional to turbulent flow (5rightarrow 50~hbox {SLPM}), operation mode transitioned from glow to spark type; the average electric field, gas temperature, and electron temperature raised (106rightarrow 156~hbox {V}cdot hbox {mm}^{-1}, 3681rightarrow 3911~hbox {K}, and 1.62rightarrow 2.12~hbox {eV}). The decomposition’s energy efficiency (eta _E) increased by a factor of 3.9 (16.1rightarrow 61.9~hbox {g}_{{text{CH}}_{4}}cdot hbox {kWh}^{-1}). The first three dominant methane consumption reactions (MCR) for both the flow regimes were induced by text {H}, CH, and text {CH}_3 (key-species), yet differed by their contribution values. The MCR rate increased by 80–148% [induced by e and singlet—text {N}_2], and decreased by 34–93% [CH, text {CH}_3, triplet—text {N}_2], due to turbulence. The electron-impact processes generated atleast 50% more of key-species and metastables for every 100 eV of input energy, explaining the increased eta _E at turbulent flow. So, flow regime influences the plasma chemistry and characteristics through flow rate. The reported RGA reactor is promising to mitigate the fugitive hydrocarbon emissions energy efficiently at a large scale, requiring some optimization to improve conversion.

Destruction of biomass tar model compound in a rotating gliding arc plasma catalytic system: Contribution of typical transition metals in Ni-based bimetallic catalyst

In this work, the destruction of toluene as a biomass tar model compound has been investigated in a rotating gliding arc (RGA) plasma catalytic system focusing on understanding the contribution of typical transition metals (Fe, Co, Cu) in Ni-based bimetallic catalyst. Investigations were conducted to elucidate their synergy with plasma under simulated gasifier gas (SGG) to destruct toluene and their effect on value-added benefits such as the enhanced heat content of the reacted producer gas. Results showed that the N2 environment offered better performance than the SGG environment, especially at high tar concentration, due to a more abundance of N2 excited species. The loading of Ni on the Al2O3 catalyst remarkably enhanced the tar conversion from 80.7% to 93.1%. Except for the NiFe, the bimetallic catalysts improved conversion and reduced specific energy consumption (SEC). Primarily, the NiCu catalyst provided a maximum tar conversion of up to 94.3% and significantly enhanced the heat content of the producer gas by 29% from that of the SGG. The minimum SEC of 64.5 kWh/kg was achieved by the NiCo, which also showed the best sintering resistance. In the 24-hour plasma-catalytic operation, NiCu and NiCo showed excellent stability with only a slight drop in the tar conversion (∼94% to ∼ 91%) after 10–12 h. Analysis of by-products indicated back spillover of OH and O, which could help clean the metal surface. Thermogravimetric analysis of the spent catalyst indicated that the coke deposited is likely composed of the aromatic compounds of boiling point in the range of 100 °C to 300 °C.

Effusion nozzle for energy-efficient NOx production in a rotating gliding arc plasma reactor

Plasma-based NOx production is of interest for sustainable N2 fixation, but more research is needed to improve its performance. One of the current limitations is recombination of NO back into N2 and O2 molecules immediately after the plasma reactor. Therefore, we developed a novel so-called “effusion nozzle”, to improve the performance of a rotating gliding arc plasma reactor for NOx production, but the same principle can also be applied to other plasma types. Experiments in a wide range of applied power, gas flow rates and N2/O2 ratios demonstrate an enhancement in NOx concentration by about 8%, and a reduction in energy cost by 22.5%. In absolute terms, we obtain NOx concentrations up to 5.9%, at an energy cost down to 2.1 MJ/mol, which are the best values reported to date in literature. In addition, we developed four complementary models to describe the gas flow, plasma temperature and plasma chemistry, aiming to reveal why the effusion nozzle yields better performance. Our simulations reveal that the effusion nozzle acts as very efficient heat sink, causing a fast drop in gas temperature when the gas molecules leave the plasma, hence limiting the recombination of NO back into N2 and O2. This yields an overall higher NOx concentration than without the effusion nozzle. This immediate quenching right at the end of the plasma makes our effusion nozzle superior to more conventional cooling options, like water cooling In addition, this higher NOx concentration can be obtained at a slightly lower power, because the effusion nozzle allows for the ignition and sustainment of the plasma at somewhat lower power. Hence, this also explains the lower energy cost. Overall, our experimental results and detailed modeling analysis will be useful to improve plasma-based NOx production in other plasma reactors as well.

Influence of transitional and turbulent flow on electrical, optical, morphological and chemical characteristics of a nitrogen rotating gliding arc

The work reports the effect of flow regime on plasma characteristics of an atmospheric rotating gliding arc (RGA). When changed from transitional (5 SLPM) to turbulent (50 SLPM) flow, operation mode transitioned from glow to spark discharge due to frequent reignition events; the average reduced electric field () and electron temperature raised (3892 Td, 0.842.2 eV); and gas temperature (T g ) slightly cooled (29732807 K). Molecules generated for 100 eV of energy input (G–factor) increased by a factor of 20 and 65, for the chemically active singlet and triplet metastable states of , respectively—a promising feature for chemical applications. A sudden three fold increase in the energy efficiency, achieving a destruction of g·kWh−1 of dilute toluene ( ppmV) at highly turbulent flow corroborated the enhancement of the G–factor, and T g ; and indicated the sensitivity of plasma properties to the flow regime. Interestingly, for flows having Reynolds number , the bandhead of shifted from 0–0 at 391.4 nm to 3–3 at 383.3 nm attributed to higher-level perturbations, showing again the sensitivity. The smallest eddies (m) is less than the discharge diameter ( 220±90 µm), and thermal/mass Péclet number 1. The eddies of size advected the plasma species, wrinkled/distorted the discharge, and increased the reignition events, eventually affected the plasma properties including the chemical performance (energy efficiency), which is observed in this work.

Plasma Effects on Swirl Flames in a Scaled Dry Low Emission Burner

The effect of a rotating gliding arc (RGA) plasma discharge on the flame in a downscaled Siemens Energy dry low emission, SGT-750, burner was experimentally investigated under atmospheric combustion conditions. The central pilot section of the burner, named RPL (rich-pilot-lean), was redesigned with an integrated high-voltage electrode to generate an RGA. The exhaust gas was sampled and analyzed in terms of CO and emissions, and the CO emission data show that the RGA extends the lean blowout limit. High-speed OH chemiluminescence imaging was employed to understand the transient behavior of the flame in both conditions, with and without RGA, and also to study the process of flame restabilization by the assistance of the RGA. A flame kernel, initiated around the RGA channel, was observed to play an important role in the restabilizing process of the flame. Although the emission for the flame with RGA was found to be higher than that without RGA, it was still less than what previous data show for operating conditions with the RPL flame.

Experimental Investigation on Kerosene Cracking Driven by Nanosecond Pulsed Rotating Gliding Arc Discharge Plasma

As an advanced technology that could achieve excellent cracking effects, nanosecond pulsed discharge plasma has attracted a lot of interest in recent years. In this article, nanosecond pulsed gliding arc discharge (GAD) plasma was developed for kerosene cracking. The influence of applied voltage, pulse repetition frequency (PRF), pulsewidth, and carrier gas flow rate on the cracking effects of the nanosecond pulse GAD plasma was investigated. Experimental results indicated that C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> had the highest production rate in all experimental conditions. The increase in applied voltage, PRF, and pulsewidth enlarges the SIE, which drops with greater carrier gas flow rate. Higher applied voltage promotes the secondary cracking of C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sub> , C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> , and C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> but influences the primary cracking (cracking of macromolecular hydrocarbons) slightly. Higher PRF and longer pulsewidth promote both the primary cracking and the secondary cracking of the gaseous light hydrocarbon. However, higher PRF could intensify the production of coke while longer pulsewidth inhibits it. Greater carrier gas flow rate would suppress the secondary cracking of gaseous light hydrocarbons while promoting the cracking of macromolecular hydrocarbons significantly.

Stability and Emission Characteristics of Ammonia/Air Premixed Swirling Flames with Rotating Gliding Arc Discharge Plasma

Stability and Emission Characteristics of Ammonia/Air Premixed Swirling Flames with Rotating Gliding Arc Discharge Plasma

Dry Reforming of Methane in a Rotating Gliding Arc Plasma: Improving Efficiency and Syngas Cost by Quenching Product Gas

Dry Reforming of Methane in a Rotating Gliding Arc Plasma: Improving Efficiency and Syngas Cost by Quenching Product Gas