Pub Date : 2024-01-12DOI: 10.1007/s11090-023-10444-6
Abstract
The effects of neutral gas heating along the direction of the gas flow inside the discharge channel of a parallel plate micro atmospheric pressure plasma jet, the COST-jet, on the spatio-temporal dynamics of energetic electrons are investigated by experiments and simulations. The plasma source is driven by a single frequency sinusoidal voltage waveform at 13.56 MHz in helium with an admixture (0.05–0.2%) of nitrogen. Optical emission spectroscopy measurements are applied to determine the spatio-temporally resolved electron impact excitation dynamics from the ground state into the He I (3s)(^3)S(_1) state and the rotational temperature of nitrogen molecules at different positions along the direction of the gas flow inside the 30 mm long discharge channel. The gas temperature, which is assumed to be equal to the N(_2) rotational temperature, is found to increase along the discharge channel. This effect is attenuated as the nitrogen concentration is increased in the gas mixture, leading to an eventually constant temperature profile. The experimental data also reveal a plasma operating mode transition along the discharge channel from the (Omega)- to the Penning-mode and show good agreement with the results of 1d3v kinetic simulations, which spatially resolve the inter-electrode space and use the gas temperature as an input value. The simulations demonstrate that the increase of the gas temperature leads to the observed mode transition. The results suggest the possibility of using the nitrogen admixture and the feed gas temperature as additional control parameters, (i) to tailor the plasma operating mode along the direction of the gas flow so that the production of specific radicals is optimized; and (ii) to control the final gas temperature of the effluent. The latter could be particularly interesting for biological applications, where the upper gas temperature limit is dictated by the rather low thermal damage threshold of the treated material.
摘要 通过实验和模拟,研究了沿平行板微大气压等离子体射流(COST-jet)放电通道内气体流动方向的中性气体加热对高能电子时空动力学的影响。等离子体源由 13.56 MHz 的单频正弦电压波形驱动,在氦气中掺入(0.05-0.2%)氮气。光学发射光谱测量用于确定从基态进入 He I (3s) (^3) S (_1)态的时空分辨电子碰撞激发动力学,以及氮分子在 30 毫米长放电通道内沿气流方向不同位置的旋转温度。假定气体温度等于 N (_2)旋转温度,发现气体温度会沿着放电通道上升。随着气体混合物中氮气浓度的增加,这种效应逐渐减弱,最终形成恒定的温度曲线。实验数据还揭示了沿放电通道从(Omega) - 到潘宁模式的等离子体工作模式转变,并与 1d3v 动力学模拟结果显示出良好的一致性,该模拟对电极间空间进行了空间解析,并使用气体温度作为输入值。模拟结果表明,气体温度的升高会导致观察到的模式转换。结果表明,可以使用氮气混合物和进料气体温度作为额外的控制参数,(i) 沿气体流动方向调整等离子体运行模式,从而优化特定自由基的产生;(ii) 控制流出物的最终气体温度。后者对生物应用特别有意义,因为在生物应用中,气体温度的上限是由被处理材料相当低的热损伤阈值决定的。
{"title":"Mode Transition Induced by Gas Heating Along the Discharge Channel in Capacitively Coupled Atmospheric Pressure Micro Plasma Jets","authors":"","doi":"10.1007/s11090-023-10444-6","DOIUrl":"https://doi.org/10.1007/s11090-023-10444-6","url":null,"abstract":"<h3>Abstract</h3> <p>The effects of neutral gas heating along the direction of the gas flow inside the discharge channel of a parallel plate micro atmospheric pressure plasma jet, the COST-jet, on the spatio-temporal dynamics of energetic electrons are investigated by experiments and simulations. The plasma source is driven by a single frequency sinusoidal voltage waveform at 13.56 MHz in helium with an admixture (0.05–0.2%) of nitrogen. Optical emission spectroscopy measurements are applied to determine the spatio-temporally resolved electron impact excitation dynamics from the ground state into the He I (3s)<span> <span>(^3)</span> </span>S<span> <span>(_1)</span> </span> state and the rotational temperature of nitrogen molecules at different positions along the direction of the gas flow inside the 30 mm long discharge channel. The gas temperature, which is assumed to be equal to the N<span> <span>(_2)</span> </span> rotational temperature, is found to increase along the discharge channel. This effect is attenuated as the nitrogen concentration is increased in the gas mixture, leading to an eventually constant temperature profile. The experimental data also reveal a plasma operating mode transition along the discharge channel from the <span> <span>(Omega)</span> </span>- to the Penning-mode and show good agreement with the results of 1d3v kinetic simulations, which spatially resolve the inter-electrode space and use the gas temperature as an input value. The simulations demonstrate that the increase of the gas temperature leads to the observed mode transition. The results suggest the possibility of using the nitrogen admixture and the feed gas temperature as additional control parameters, (i) to tailor the plasma operating mode along the direction of the gas flow so that the production of specific radicals is optimized; and (ii) to control the final gas temperature of the effluent. The latter could be particularly interesting for biological applications, where the upper gas temperature limit is dictated by the rather low thermal damage threshold of the treated material.</p>","PeriodicalId":734,"journal":{"name":"Plasma Chemistry and Plasma Processing","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139459802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-12DOI: 10.1007/s11090-023-10443-7
D. Reiser, A. von Keudell
Experimental investigations of n-butane oxidation under atmospheric-pressure plasma conditions and in He-dilution have provided detailed information on the power-dependence of the conversion of (text {C}_{4}text {H}_{10}) into CO and (text {CO}_{2}) at 450 K surface temperature. The rf-plasma discharge has been equipped with a (text {MnO}_{2})-catalyst, and a significant impact on the reaction chain due to the presence of the catalyst surface could be observed. We report on ongoing data-based model development. Recently, a reaction kinetic model has been published, which agrees well with the experimental data (Stewig et al. in Plasma Sources Sci Technol 32:105006, 2023). However, that model could not clearly identify the main mechanisms in the interaction of plasma and catalyst. We show that various models can be found that explain the data similarly well. Detailed sensitivity analysis shows that only a maximum of three parameters can be identified in all the models considered for the currently limited data. Despite this limitation, we intend to continue the data analysis using more general models and introduce possible surface effects. Such unified models simultaneously describe the experimental data from both measurements with and without catalyst using a single set of physical parameters. To evaluate the hypotheses, we present numerical results for certain ranges of experimental parameters, which, in a subsequent experimental verification, allows to exclude or confirm one or another model.
在大气压等离子体条件和氦稀释条件下进行的正丁烷氧化实验研究,提供了在 450 K 表面温度下 (text {C}_{4}text {H}_{10}) 转化为 CO 和 (text {CO}_{2}) 的功率依赖性的详细信息。rf-等离子体放电配备了一个(text {MnO}_{2})催化剂,可以观察到催化剂表面的存在对反应链的显著影响。我们报告了正在进行的基于数据的模型开发。最近发表的反应动力学模型与实验数据十分吻合(Stewig 等人,等离子体源科学与技术 32:105006, 2023)。但是,该模型无法明确等离子体与催化剂相互作用的主要机制。我们的研究表明,各种模型都能很好地解释数据。详细的敏感性分析表明,针对目前有限的数据,所有模型最多只能确定三个参数。尽管存在这种局限性,我们仍打算使用更通用的模型继续进行数据分析,并引入可能的表面效应。这样的统一模型可以同时描述使用和不使用催化剂时的实验数据,只需一组物理参数。为了评估假设,我们给出了某些实验参数范围内的数值结果,以便在随后的实验验证中排除或确认一种或另一种模型。
{"title":"Reaction Mechanisms and Plasma-Catalyst Interaction in Plasma-Assisted Oxidation of n-Butane: A Data-Driven Approach","authors":"D. Reiser, A. von Keudell","doi":"10.1007/s11090-023-10443-7","DOIUrl":"https://doi.org/10.1007/s11090-023-10443-7","url":null,"abstract":"<p>Experimental investigations of n-butane oxidation under atmospheric-pressure plasma conditions and in He-dilution have provided detailed information on the power-dependence of the conversion of <span>(text {C}_{4}text {H}_{10})</span> into CO and <span>(text {CO}_{2})</span> at 450 K surface temperature. The rf-plasma discharge has been equipped with a <span>(text {MnO}_{2})</span>-catalyst, and a significant impact on the reaction chain due to the presence of the catalyst surface could be observed. We report on ongoing data-based model development. Recently, a reaction kinetic model has been published, which agrees well with the experimental data (Stewig et al. in Plasma Sources Sci Technol 32:105006, 2023). However, that model could not clearly identify the main mechanisms in the interaction of plasma and catalyst. We show that various models can be found that explain the data similarly well. Detailed sensitivity analysis shows that only a maximum of three parameters can be identified in all the models considered for the currently limited data. Despite this limitation, we intend to continue the data analysis using more general models and introduce possible surface effects. Such unified models simultaneously describe the experimental data from both measurements with and without catalyst using a single set of physical parameters. To evaluate the hypotheses, we present numerical results for certain ranges of experimental parameters, which, in a subsequent experimental verification, allows to exclude or confirm one or another model.</p>","PeriodicalId":734,"journal":{"name":"Plasma Chemistry and Plasma Processing","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139459898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-11DOI: 10.1007/s11090-023-10439-3
Bhavadharini Boopathy, Debapriya Mukherjee, V. Nishanth, Atish Roy Chowdhury, Dipshikha Chakravortty, Lakshminarayana Rao
Understanding the individual effects of species in plasma activated water (PAW) is indeed necessary for its selective application as an antimicrobial agent. The current study describes a setup and a methodology to generate species-specific high strength PAW at neutral pH. Three types of PAW i.e., ROS-rich PAW (Reactive Oxygen Species-rich Plasma Activated Water), RNS-rich PAbW (Reactive Nitrogen Species- Rich Plasma Activated buffer Water) and hs-PAbW (High strength Plasma Activated buffer Water) were generated in the developed set-up, the concentration of species was measured, shelf-life studies under ambient condition were carried out and each water type was studied for its antimicrobial activity. Results show that, after 60 min of activation, hs-PAbW had ROS and RNS concentrations of 215 mg/l and 650 mg/l respectively. The ROS-rich PAW had ROS and RNS concentration of 218 mg/l and 0 mg/l respectively. The RNS-rich PAbW had ROS and RNS concentration of 16 mg/l and 858 mg/l respectively after 60 min of activation. Antimicrobial studies showed that individual species i.e., high concentrations of ROS alone and high concentrations of RNS alone, were ineffective in achieving microbial degradation, whereas hs-PAbW containing high concentrations of both ROS and RNS showed significant antimicrobial effect. This study marks an important step in generating high concentrations of species-specific PAW, which is crucial to understand the mechanistic pathways of bacterial death in PAW systems.
{"title":"Generation of Species-Specific High-Strength Plasma Activated Water at Neutral pH and its Antimicrobial Characteristics","authors":"Bhavadharini Boopathy, Debapriya Mukherjee, V. Nishanth, Atish Roy Chowdhury, Dipshikha Chakravortty, Lakshminarayana Rao","doi":"10.1007/s11090-023-10439-3","DOIUrl":"https://doi.org/10.1007/s11090-023-10439-3","url":null,"abstract":"<p>Understanding the individual effects of species in plasma activated water (PAW) is indeed necessary for its selective application as an antimicrobial agent. The current study describes a setup and a methodology to generate species-specific high strength PAW at neutral pH. Three types of PAW i.e., ROS-rich PAW (Reactive Oxygen Species-rich Plasma Activated Water), RNS-rich PAbW (Reactive Nitrogen Species- Rich Plasma Activated buffer Water) and hs-PAbW (High strength Plasma Activated buffer Water) were generated in the developed set-up, the concentration of species was measured, shelf-life studies under ambient condition were carried out and each water type was studied for its antimicrobial activity. Results show that, after 60 min of activation, hs-PAbW had ROS and RNS concentrations of 215 mg/l and 650 mg/l respectively. The ROS-rich PAW had ROS and RNS concentration of 218 mg/l and 0 mg/l respectively. The RNS-rich PAbW had ROS and RNS concentration of 16 mg/l and 858 mg/l respectively after 60 min of activation. Antimicrobial studies showed that individual species i.e., high concentrations of ROS alone and high concentrations of RNS alone, were ineffective in achieving microbial degradation, whereas hs-PAbW containing high concentrations of both ROS and RNS showed significant antimicrobial effect. This study marks an important step in generating high concentrations of species-specific PAW, which is crucial to understand the mechanistic pathways of bacterial death in PAW systems.</p>","PeriodicalId":734,"journal":{"name":"Plasma Chemistry and Plasma Processing","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139459923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-08DOI: 10.1007/s11090-023-10442-8
Abstract
We study the bactericidal efficacy of surface dielectric barrier discharge low-temperature plasma treatments, powered by nanosecond high voltage pulses. We achieve (sim )4-log reduction in Escherichia coli population, after 10 min treatments, at a distance of 1.5 cm from the plasma surface. To investigate the reactive oxygen and nitrogen species (RONS) responsible for the bactericidal effect, we employ in-situ fourier transform infrared (FTIR) spectroscopy to measure a selection of relevant species, such as O(_3), NO(_2), N(_2)O and N(_2)O(_5). The measurements are taken under various relative humidity conditions to replicate the bacteria treatment environment. While RONS originating from nitrogen chemistry are detected, nitric oxide (NO), a pivotal molecule in nitrate production, is absent due to the sensitivity limitations of FTIR detection. To overcome this limitation, we employ laser induced fluorescence utilizing a picosecond-pulsed laser to measure the kinetics of NO produced by the plasma. Our results show that the NO concentration is smaller than 1 ppm and primarily localized near the plasma surface, with concentrations increasing proportionally with relative humidity. Notably, at a distance of 1.5 cm from the plasma surface, at which the E. coli is treated, the concentration of NO falls below 50 ppb. Although NO is pivotal in generating secondary reactive species within the plasma, our results suggest that it does not directly contribute to the bacteria inactivation process. Instead, other molecules, such as O(_3), NO(_2), and N(_2)O, which are found in higher concentrations, may be responsible for the bactericidal properties observed in indirect plasma treatments.
摘要 我们研究了纳秒高压脉冲驱动的表面介质阻挡放电低温等离子体的杀菌效果。在距离等离子体表面 1.5 厘米处,经过 10 分钟处理后,我们发现大肠杆菌的数量减少了 4 个菌落。为了研究造成杀菌效果的活性氧和氮物种(RONS),我们采用了原位傅立叶变换红外(FTIR)光谱来测量一些相关物种,如 O (_3)、NO (_2)、N (_2)O 和 N (_2)O (_5)。测量是在各种相对湿度条件下进行的,以复制细菌处理环境。虽然检测到了源于氮化学的 RONS,但由于傅立叶变换红外检测的灵敏度限制,没有检测到硝酸盐生成过程中的关键分子一氧化氮(NO)。为了克服这一限制,我们利用皮秒脉冲激光诱导荧光来测量等离子体产生一氧化氮的动力学。我们的结果表明,氮氧化物的浓度小于 1 ppm,主要集中在等离子体表面附近,浓度随相对湿度成比例增加。值得注意的是,在距离等离子体表面 1.5 厘米处,即处理大肠杆菌的地方,NO 的浓度低于 50 ppb。虽然氮氧化物在等离子体内产生二次反应物方面起着关键作用,但我们的研究结果表明,它并不直接参与细菌的灭活过程。相反,在间接血浆处理中观察到的杀菌特性可能是由其他分子造成的,如浓度较高的 O (_3)、NO (_2)和 N (_2)O。
{"title":"In-Situ FTIR and Laser Induced Fluorescence RONS Characterization of Atmospheric Pressure Nanosecond-Pulsed Surface DBD Plasma for Indirect Treatments of E. Coli","authors":"","doi":"10.1007/s11090-023-10442-8","DOIUrl":"https://doi.org/10.1007/s11090-023-10442-8","url":null,"abstract":"<h3>Abstract</h3> <p>We study the bactericidal efficacy of surface dielectric barrier discharge low-temperature plasma treatments, powered by nanosecond high voltage pulses. We achieve <span> <span>(sim )</span> </span>4-log reduction in <em>Escherichia coli</em> population, after 10 min treatments, at a distance of 1.5 cm from the plasma surface. To investigate the reactive oxygen and nitrogen species (RONS) responsible for the bactericidal effect, we employ in-situ fourier transform infrared (FTIR) spectroscopy to measure a selection of relevant species, such as O<span> <span>(_3)</span> </span>, NO<span> <span>(_2)</span> </span>, N<span> <span>(_2)</span> </span>O and N<span> <span>(_2)</span> </span>O<span> <span>(_5)</span> </span>. The measurements are taken under various relative humidity conditions to replicate the bacteria treatment environment. While RONS originating from nitrogen chemistry are detected, nitric oxide (NO), a pivotal molecule in nitrate production, is absent due to the sensitivity limitations of FTIR detection. To overcome this limitation, we employ laser induced fluorescence utilizing a picosecond-pulsed laser to measure the kinetics of NO produced by the plasma. Our results show that the NO concentration is smaller than 1 ppm and primarily localized near the plasma surface, with concentrations increasing proportionally with relative humidity. Notably, at a distance of 1.5 cm from the plasma surface, at which the <em>E. coli</em> is treated, the concentration of NO falls below 50 ppb. Although NO is pivotal in generating secondary reactive species within the plasma, our results suggest that it does not directly contribute to the bacteria inactivation process. Instead, other molecules, such as O<span> <span>(_3)</span> </span>, NO<span> <span>(_2)</span> </span>, and N<span> <span>(_2)</span> </span>O, which are found in higher concentrations, may be responsible for the bactericidal properties observed in indirect plasma treatments.</p>","PeriodicalId":734,"journal":{"name":"Plasma Chemistry and Plasma Processing","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139397227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-08DOI: 10.1007/s11090-023-10441-9
Marcin Buchowiecki, Péter Szabó
New collision integrals and transport cross sections for O((^{3})P)–O((^{3})P) interaction are reported in the 300–30000 K range. Those values are based on a new set of potential energy curves (PECs) calculated with the multireference configuration interaction method. The results of the classical and semiclassical WKB (Wentzel–Kramers–Brillouin) methods are compared, excellent performance of the classical approach is shown (discrepancy much lower than 1% even at room temperature). In particular, the classical and WKB methods agree very well for the repulsive potentials effectively reducing overall uncertainty.
{"title":"Transport Cross Sections and Collision Integrals for O( $$^{3}$$ P)–O( $$^{3}$$ P) Interaction","authors":"Marcin Buchowiecki, Péter Szabó","doi":"10.1007/s11090-023-10441-9","DOIUrl":"https://doi.org/10.1007/s11090-023-10441-9","url":null,"abstract":"<p>New collision integrals and transport cross sections for O(<span>(^{3})</span>P)–O(<span>(^{3})</span>P) interaction are reported in the 300–30000 K range. Those values are based on a new set of potential energy curves (PECs) calculated with the multireference configuration interaction method. The results of the classical and semiclassical WKB (Wentzel–Kramers–Brillouin) methods are compared, excellent performance of the classical approach is shown (discrepancy much lower than 1% even at room temperature). In particular, the classical and WKB methods agree very well for the repulsive potentials effectively reducing overall uncertainty.</p>","PeriodicalId":734,"journal":{"name":"Plasma Chemistry and Plasma Processing","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139397229","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-03DOI: 10.1007/s11090-023-10440-w
Abstract
The use of fused silica material is crucial in various scientific applications; however, its chemical inertness and brittle nature pose challenges to machining and fabrication processes. The present study introduced a dynamic plasma flow system for medium-pressure plasma processing of fused silica substrate to address this issue. The results indicate that the new plasma flow system can significantly enhance the material removal rate compared to existing systems, with a 300% increase in material removal rate. Importantly, this process enables a sustained linear material removal rate, essential for long process durations. Despite the higher material removal rate, there is no deterioration in surface finish observed, and in fact, an improvement in surface integrity is noted after plasma processing. Confocal Raman microscopy characterization further confirms this improvement, revealing reduced stress-induced defect peaks compared to a confined plasma system.
{"title":"Medium Pressure Plasma Processing of Fused Silica: A Comparative Study for Material Removal Rate","authors":"","doi":"10.1007/s11090-023-10440-w","DOIUrl":"https://doi.org/10.1007/s11090-023-10440-w","url":null,"abstract":"<h3>Abstract</h3> <p>The use of fused silica material is crucial in various scientific applications; however, its chemical inertness and brittle nature pose challenges to machining and fabrication processes. The present study introduced a dynamic plasma flow system for medium-pressure plasma processing of fused silica substrate to address this issue. The results indicate that the new plasma flow system can significantly enhance the material removal rate compared to existing systems, with a 300% increase in material removal rate. Importantly, this process enables a sustained linear material removal rate, essential for long process durations. Despite the higher material removal rate, there is no deterioration in surface finish observed, and in fact, an improvement in surface integrity is noted after plasma processing. Confocal Raman microscopy characterization further confirms this improvement, revealing reduced stress-induced defect peaks compared to a confined plasma system.</p>","PeriodicalId":734,"journal":{"name":"Plasma Chemistry and Plasma Processing","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139102060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-03DOI: 10.1007/s11090-023-10438-4
E. Cejas, L. Prevosto, F. O. Minotti
The glow-to-arc transition of a convection-stabilized atmospheric pressure air discharge is numerically investigated. Two separate models are considered: a one-dimensional axisymmetric time-dependent fluid model of the positive column, describing the thermal-instability, and a sheath model of a cold cathode describing the field-emission instability, which must then be properly matched together. The fluid model considers the most important chemical reactions in air plasma, including thermal ionization in atomic collisions. The radial electric field in the plasma is obtained from the Poisson equation. The voltage–current characteristic of the discharge is simulated for a time-varying current up to 300 mA. It is found that at some critical value slightly above 200 mA, the contraction of the positive column arises from a vibrational–translational energy relaxation. The subsequent increases in the discharge current density in the positive column drive in turn a field-emission instability in the cathode, which is accompanied by a large voltage drop. Simulation results are validated against available experimental data.
对对流稳定的大气压空气放电的辉光到电弧的转变进行了数值研究。研究考虑了两个独立的模型:描述热不稳定性的正柱一维轴对称随时间变化的流体模型,以及描述场发射不稳定性的冷阴极鞘模型。流体模型考虑了空气等离子体中最重要的化学反应,包括原子碰撞中的热电离。等离子体中的径向电场由泊松比方程求得。模拟了高达 300 mA 的时变电流的放电电压-电流特性。结果发现,在略高于 200 mA 的临界值时,正极柱的收缩是由振动-翻译能量弛豫引起的。正极柱中放电电流密度的增加反过来又推动了阴极的场发射不稳定性,并伴随着巨大的电压降。模拟结果与现有实验数据进行了验证。
{"title":"Numerical Simulation of the Voltage–Current Characteristic of an Atmospheric Pressure Discharge: The Glow-to-Arc Transition","authors":"E. Cejas, L. Prevosto, F. O. Minotti","doi":"10.1007/s11090-023-10438-4","DOIUrl":"https://doi.org/10.1007/s11090-023-10438-4","url":null,"abstract":"<p>The glow-to-arc transition of a convection-stabilized atmospheric pressure air discharge is numerically investigated. Two separate models are considered: a one-dimensional axisymmetric time-dependent fluid model of the positive column, describing the thermal-instability, and a sheath model of a cold cathode describing the field-emission instability, which must then be properly matched together. The fluid model considers the most important chemical reactions in air plasma, including thermal ionization in atomic collisions. The radial electric field in the plasma is obtained from the Poisson equation. The voltage–current characteristic of the discharge is simulated for a time-varying current up to 300 mA. It is found that at some critical value slightly above 200 mA, the contraction of the positive column arises from a vibrational–translational energy relaxation. The subsequent increases in the discharge current density in the positive column drive in turn a field-emission instability in the cathode, which is accompanied by a large voltage drop. Simulation results are validated against available experimental data.</p>","PeriodicalId":734,"journal":{"name":"Plasma Chemistry and Plasma Processing","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139105488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, we present a plasma rapid heater (PRH) designed to uniformly heat methane with electric arc thermal plasma and reduce loss rate. Our model uses a simplified and detailed mechanism to analyze the rapid and intense mixing process between a plasma mainstream and circumferential cold jets of methane in a hydrogen environment. The research focuses on three areas: the plasma mainstream section, the circumferential jet mixing chamber, and the reaction chamber. We investigate the characteristics of the mainstream and explore the impact of the jet momentum ratio on the mixing process and the losses from methane heating. We explain these phenomena using Damkohler numbers to demonstrate the relationship from a time-scale perspective. The findings indicate that an increased momentum ratio improves mixing, reduces temperature and material non-uniformity, and minimizes losses from pyrolysis during methane heating. Additionally, we provide a formula for calculating the penetration depth of the jet. The examination of Damkohler numbers also suggests that the momentum ratio primarily reduces methane losses by extending the reaction time scale. This work offers guidance on extending the usage of plasma heaters and integrating them into other industry processes in the future.
{"title":"Numerical Simulation Study on Plasma Rapid Heater of Methane","authors":"Shaopeng Wang, Defu Kong, Xianhui Chen, Cheng Wang, Weidong Xia","doi":"10.1007/s11090-023-10433-9","DOIUrl":"https://doi.org/10.1007/s11090-023-10433-9","url":null,"abstract":"<p>In this paper, we present a plasma rapid heater (PRH) designed to uniformly heat methane with electric arc thermal plasma and reduce loss rate. Our model uses a simplified and detailed mechanism to analyze the rapid and intense mixing process between a plasma mainstream and circumferential cold jets of methane in a hydrogen environment. The research focuses on three areas: the plasma mainstream section, the circumferential jet mixing chamber, and the reaction chamber. We investigate the characteristics of the mainstream and explore the impact of the jet momentum ratio on the mixing process and the losses from methane heating. We explain these phenomena using Damkohler numbers to demonstrate the relationship from a time-scale perspective. The findings indicate that an increased momentum ratio improves mixing, reduces temperature and material non-uniformity, and minimizes losses from pyrolysis during methane heating. Additionally, we provide a formula for calculating the penetration depth of the jet. The examination of Damkohler numbers also suggests that the momentum ratio primarily reduces methane losses by extending the reaction time scale. This work offers guidance on extending the usage of plasma heaters and integrating them into other industry processes in the future.</p>","PeriodicalId":734,"journal":{"name":"Plasma Chemistry and Plasma Processing","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2023-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139051688","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The epoxidation reaction of propylene (C3H6) for propylene oxide (PO) production was, for the first time of its kind, investigated in a low-temperature parallel-plate dielectric barrier discharge system with two frosted glass plates and a separate C3H6 feed under ambient condition. For the mixed feed experiments, the maximum PO selectivity was found at a feed molar air-to-C3H6 ratio of 0.5:1, an applied voltage of 7 kV, an input of 550 Hz, and a feed flow rate of the mixed gas of 100 cm3/min (corresponding to a residence time (RT) of 12.1 s). At the optimum operational conditions, a separate C3H6 feed position fraction of 1 (complete separation of C3H6) with total reactant feed flow rate of 100 cm3/min (corresponding to an O2 residence time (RT) of 24.1 s), the greatest propylene oxide selectivity of 16.40% was achevied. The relatively high PO selectivity with very low selectivities for all other products and with the absence of both CO and CO2 obseved in this studied resulted from less active of C3H6 due to the separate feed of C3H6. The C3Hseparate feed is fundamentally responsible for the reduction in all the undesired reactions including cracking, dehydrogenation, coupling, and oxidations of C3H6.