Research on aging characteristics of epoxy resin （EP） under repetitive microsecond pulses is important for the design of insulating materials in high power apparatus. It is because that very fast transient overvolta...Research on aging characteristics of epoxy resin （EP） under repetitive microsecond pulses is important for the design of insulating materials in high power apparatus. It is because that very fast transient overvoltage always occurs in a power system, which causes flashover and is one of the main factors causing aging effects of EP materials. Therefore, it is essential to obtain a better understanding of the aging effect on an EP surface resulting from flashover. In this work, aging effects on an EP surface were investigated by surface flashover discharge under repetitive microsecond pulses in atmospheric pressure. The investigations of parameters such as the surface micro-morphology and chemical composition of the insulation material under different degrees of aging were conducted with the aid of measurement methods such as atomic force microscopy （AFM）, scanning electron microscopy （SEM）, and X-ray photoelectron spectroscopy （XPS）. Results showed that with the accumulation of aging energy on the material surface, the particles formed on the material surface increased both in number and size, leading to the growth of surface roughness and a reduction in the water contact angle; the surface also became more absorbent. Furthermore, in the aging process, the molecular chains of EP on the surface were broken, resulting in oxidation and carbonisation.展开更多
By means of a coaxial apparatus, high electrical breakdown experiments are carried out in the rest state and the low speed rolling state with microsecond charging and the experimental results are analyzed. The conclus...By means of a coaxial apparatus, high electrical breakdown experiments are carried out in the rest state and the low speed rolling state with microsecond charging and the experimental results are analyzed. The conclusions are： （1） the breakdown stress of water dielectric in the rolling state is in good agreement with that in Martin formula, and so is that in the rest state; （2） the breakdown stress of water dielectric in the rolling state is about 5% higher than that in the rest state; （3） the results simulated with ANSYS demonstrate that the breakdown stress of water dielectric decreases when the bubbles appear near the surface of electrodes; （4） the primary mechanism to increase the breakdown stress of water dielectric in the rolling state is that the bubbles are driven away and the number of bubbles near the surface of electrodes is decreased by rolling movement.展开更多
Propylene carbonate （PC） has a great potential to be used as an energy storage medium in the compact pulsed power sources due to its high dielectric constant and large resistivity. We investigate both the positive a...Propylene carbonate （PC） has a great potential to be used as an energy storage medium in the compact pulsed power sources due to its high dielectric constant and large resistivity. We investigate both the positive and negative breakdown characteristics of PC. The streamer patterns are obtained by ultra-high-speed cameras. The experimental results show that the positive breakdown voltage of PC is about 135% higher than the negative one, which is abnormal compared with the common liquid. The shape of the positive streamer is filamentary and branchy, while the negative streamer is tree-like and less branched. According to these experimental results, a charge layer structure model at the interface between the metal electrode and liquid is presented. It is suggested that the abnormal polarity effect basically arises from the electric field strength difference in the interface between both electrodes and PC. What is more, the recombination radiation and photoionization also play an important role in the whole discharge process.展开更多
Plasma flow control technology has broad prospects for application.Compared with conventional dielectric barrier discharge plasma actuators(DBD-PA),the sliding discharge plasma actuator(SD-PA)has the advantages of a l...Plasma flow control technology has broad prospects for application.Compared with conventional dielectric barrier discharge plasma actuators(DBD-PA),the sliding discharge plasma actuator(SD-PA)has the advantages of a large discharge area and a deflectable induced jet.To achieve the basic performance requirements of light weight,low cost,and high reliability required for UAV(Unmanned Aerial Vehicle)plasma flight experiments,this work designed a microsecond pulse plasma supply that can be used for sliding discharge plasma actuators.In this study,the topology of the primary circuit of the microsecond pulse supply is determined,the waveform of the output terminal of the microsecond pulse plasma supply is detected using the Simulink simulation platform,and the design of the actuation voltage,the pulse frequency modulation function and the construction of the hardware circuit are achieved.Using electrical diagnosis and flow field analysis,the actuation characteristics and flow characteristics of sliding discharge plasma under microsecond pulse actuation are studied,the optimal electrical actuation parameters and flow field characteristics are described.展开更多
An experimental device is used to study the characteristics of dielectric barrier discharge(DBD)plasma excited by high voltage sub-microsecond pulse power in atmospheric air.Glass,polytetrafluoroethene(PTFE)and plexig...An experimental device is used to study the characteristics of dielectric barrier discharge(DBD)plasma excited by high voltage sub-microsecond pulse power in atmospheric air.Glass,polytetrafluoroethene(PTFE)and plexiglass are used as dielectric barrier materials.Comparatively homogeneous discharge is obtained within 130 mm diameter area in atmospheric air using the three dielectric materials with gap distances of 4.5 mm,6.5 mm and 6.5 mm,respectively.There is no filamentary discharge observed by naked eyes or by camera with the exposure time of 0.25 s.Gas gap voltage,discharge current,discharge power density,etc.are calculated by using Liu’s equivalent circuit model for pulsed DBD.These parameters are used to study the DBD characteristics.Typically,current varies from tens of amperes to hundreds of amperes in atmospheric air DBD excited by sub-microsecond pulses.The peak power can reach to MW order of magnitude.The average power surface density of 1.0 W/cm2and the average electron density of 1011cm 3can also be obtained in the discharge.Rotational and vibrational temperatures,approximately 400 K and 2 650 K,respectively,are obtained by using the emission spectrum of the discharge.This is the basic work performed for a better understanding of the characteristics of atmospheric air DBD plasma excited by high voltage sub-microsecond pulsed power source.展开更多
Real-time thermal sensing through flexible temperature sensors in extreme environments is critically essential for precisely monitoring chemical reactions,propellant combustions,and metallurgy processes.However,despit...Real-time thermal sensing through flexible temperature sensors in extreme environments is critically essential for precisely monitoring chemical reactions,propellant combustions,and metallurgy processes.However,despite their low response speed,most existing thermal sensors and related sensing materials will degrade or even lose their sensing performances at either high or low temperatures.Achieving a microsecond response time over an ultrawide temperature range remains challenging.Here,we design a flexible temperature sensor that employs ultrathin and consecutive Mo1−xWxS2 alloy films constructed via inkjet printing and a thermal annealing strategy.The sensing elements exhibit a broad work range(20 to 823 K on polyimide and 1,073 K on flexible mica)and a record-low response time(about 30μs).These properties enable the sensors to detect instantaneous temperature variations induced by contact with liquid nitrogen,water droplets,and flames.Furthermore,a thermal sensing array offers the spatial mapping of arbitrary shapes,heat conduction,and cold traces even under bending deformation.This approach paves the way for designing unique sensitive materials and flexible sensors for transient sensing under harsh conditions.展开更多
Thermoacoustic instabilities,frequent in a wide range of combustors,arise from the intricate coupling between the flame's unsteady heat release and the combustor acoustic.The application of plasma,characterized by...Thermoacoustic instabilities,frequent in a wide range of combustors,arise from the intricate coupling between the flame's unsteady heat release and the combustor acoustic.The application of plasma,characterized by its substantial local energy addition and radical generation,has demonstrated potential in disrupting this coupling and thereby mitigating thermoacoustic oscillations.Notably,open-loop control using discharge plasma has been successfully implemented to suppress self-excited oscillations in a Rijke tube setup.Considering the broader context of a complex system that integrates both thermoacoustic systems and discharge plasma,experiments were done to see its performance in stability under different arrangement and discharge repetition rates of discharge plasma.These experimental investigations identified critical operating conditions essential for complete suppression:(A)the optimal location of discharge actuations,and(B)the minimum energy required for complete suppression.Moreover,the impact of discharge plasma,particularly when tuned to the eigenfrequencies of oscillations within the thermoacoustic system.was thoroughly examined.The insights gained from these successful suppression trials are instrumental in guiding the strategic design of both physical arrangement and electrical configurations for the control of combustion instabilities via discharge plasma.Furthermore,through the photographing of the swinging arcs and their thermal disturbances by high-speed camera and highspeed schlieren,the characteristics of arcs'thermal disturbances and the reasons affecting its suppression effectiveness were determined.展开更多
SI:Agentic AI for 6G Networks.Introduction.6G networks are poised to provide full coverage across air,land,and sea,deliver terabit-per-second data rates,and achieve microsecond-level latency.They promise comprehensive...SI:Agentic AI for 6G Networks.Introduction.6G networks are poised to provide full coverage across air,land,and sea,deliver terabit-per-second data rates,and achieve microsecond-level latency.They promise comprehensive upgrades across industries through embedded intelligence,ushering in an era of intelligent interconnection of all things.However,managing real-time interactions among devices,infrastructure,and services in 6G networks is much more complex than in previous generations.Massive data streams from terrestrial nodes(e.g.,edge devices,sensors,distributed computing)and non-terrestrial nodes(LEO/MEO/GEO satellites)demand more intelligent and efficient processing.展开更多
为了获得常压条件下绝缘支撑材料环氧树脂的沿面闪络特性,通过微秒脉冲下连续沿面放电对环氧树脂表面造成老化损伤,获得老化前后的环氧树脂沿面闪络特性数据。在脉冲电压幅值为18 k V、频率为100 Hz、电极间距为10 mm的情况下,对环氧树...为了获得常压条件下绝缘支撑材料环氧树脂的沿面闪络特性,通过微秒脉冲下连续沿面放电对环氧树脂表面造成老化损伤,获得老化前后的环氧树脂沿面闪络特性数据。在脉冲电压幅值为18 k V、频率为100 Hz、电极间距为10 mm的情况下,对环氧树脂表面进行沿面放电老化处理,对不同放电老化时间下的表面形貌、粗糙度及水接触角进行测量,分析放电对材料表面的老化影响。结果发现,放电老化后环氧树脂表面疏松,且有大量突起颗粒形成,表面极易吸水。此外对老化前后的环氧树脂表面进行闪络实验,结果发现,表面闪络电压随老化时间出现先降低后升高的现象。相关实验结果及分析为研究环氧树脂的沿面耐压性能提供了一定的参数数据。展开更多
基金supported by the Natural Science Foundation of Hebei Province(No.E2015502081)National Natural Science Foundation of China(Nos.51222701,51307060)the National Basic Research Program of China(No.2014CB239505-3)
文摘Research on aging characteristics of epoxy resin （EP） under repetitive microsecond pulses is important for the design of insulating materials in high power apparatus. It is because that very fast transient overvoltage always occurs in a power system, which causes flashover and is one of the main factors causing aging effects of EP materials. Therefore, it is essential to obtain a better understanding of the aging effect on an EP surface resulting from flashover. In this work, aging effects on an EP surface were investigated by surface flashover discharge under repetitive microsecond pulses in atmospheric pressure. The investigations of parameters such as the surface micro-morphology and chemical composition of the insulation material under different degrees of aging were conducted with the aid of measurement methods such as atomic force microscopy （AFM）, scanning electron microscopy （SEM）, and X-ray photoelectron spectroscopy （XPS）. Results showed that with the accumulation of aging energy on the material surface, the particles formed on the material surface increased both in number and size, leading to the growth of surface roughness and a reduction in the water contact angle; the surface also became more absorbent. Furthermore, in the aging process, the molecular chains of EP on the surface were broken, resulting in oxidation and carbonisation.
基金supported by the National 863 Project of China(No. 807-2020, 803-5051)
文摘By means of a coaxial apparatus, high electrical breakdown experiments are carried out in the rest state and the low speed rolling state with microsecond charging and the experimental results are analyzed. The conclusions are： （1） the breakdown stress of water dielectric in the rolling state is in good agreement with that in Martin formula, and so is that in the rest state; （2） the breakdown stress of water dielectric in the rolling state is about 5% higher than that in the rest state; （3） the results simulated with ANSYS demonstrate that the breakdown stress of water dielectric decreases when the bubbles appear near the surface of electrodes; （4） the primary mechanism to increase the breakdown stress of water dielectric in the rolling state is that the bubbles are driven away and the number of bubbles near the surface of electrodes is decreased by rolling movement.
基金Supported by the National Natural Science Foundation of China under Grant No 51677190the Hunan Provincial Natural Science Foundation of China under Grant No 2017JJ1005
文摘Propylene carbonate （PC） has a great potential to be used as an energy storage medium in the compact pulsed power sources due to its high dielectric constant and large resistivity. We investigate both the positive and negative breakdown characteristics of PC. The streamer patterns are obtained by ultra-high-speed cameras. The experimental results show that the positive breakdown voltage of PC is about 135% higher than the negative one, which is abnormal compared with the common liquid. The shape of the positive streamer is filamentary and branchy, while the negative streamer is tree-like and less branched. According to these experimental results, a charge layer structure model at the interface between the metal electrode and liquid is presented. It is suggested that the abnormal polarity effect basically arises from the electric field strength difference in the interface between both electrodes and PC. What is more, the recombination radiation and photoionization also play an important role in the whole discharge process.
基金supported by National Natural Science Foundation of China(No.61971345)the Foundation for Key Laboratories of National Defense Science and Technology of China(No.614220120030810)Shaanxi Provincial Key R&D Program General Project(No.2021GY-044)。
文摘Plasma flow control technology has broad prospects for application.Compared with conventional dielectric barrier discharge plasma actuators(DBD-PA),the sliding discharge plasma actuator(SD-PA)has the advantages of a large discharge area and a deflectable induced jet.To achieve the basic performance requirements of light weight,low cost,and high reliability required for UAV(Unmanned Aerial Vehicle)plasma flight experiments,this work designed a microsecond pulse plasma supply that can be used for sliding discharge plasma actuators.In this study,the topology of the primary circuit of the microsecond pulse supply is determined,the waveform of the output terminal of the microsecond pulse plasma supply is detected using the Simulink simulation platform,and the design of the actuation voltage,the pulse frequency modulation function and the construction of the hardware circuit are achieved.Using electrical diagnosis and flow field analysis,the actuation characteristics and flow characteristics of sliding discharge plasma under microsecond pulse actuation are studied,the optimal electrical actuation parameters and flow field characteristics are described.
基金Project supported by National Natural Science Foundation of China（11035004）, Double Hundred Talent Fotmdation of CAEP （ 2009R0102）, Key Laboratory of Pulsed Power of CAEP Science and Technology Development Foundation （2008B0402037）.
文摘An experimental device is used to study the characteristics of dielectric barrier discharge(DBD)plasma excited by high voltage sub-microsecond pulse power in atmospheric air.Glass,polytetrafluoroethene(PTFE)and plexiglass are used as dielectric barrier materials.Comparatively homogeneous discharge is obtained within 130 mm diameter area in atmospheric air using the three dielectric materials with gap distances of 4.5 mm,6.5 mm and 6.5 mm,respectively.There is no filamentary discharge observed by naked eyes or by camera with the exposure time of 0.25 s.Gas gap voltage,discharge current,discharge power density,etc.are calculated by using Liu’s equivalent circuit model for pulsed DBD.These parameters are used to study the DBD characteristics.Typically,current varies from tens of amperes to hundreds of amperes in atmospheric air DBD excited by sub-microsecond pulses.The peak power can reach to MW order of magnitude.The average power surface density of 1.0 W/cm2and the average electron density of 1011cm 3can also be obtained in the discharge.Rotational and vibrational temperatures,approximately 400 K and 2 650 K,respectively,are obtained by using the emission spectrum of the discharge.This is the basic work performed for a better understanding of the characteristics of atmospheric air DBD plasma excited by high voltage sub-microsecond pulsed power source.
基金supported by the National Natural Science Foundation of China(62304182,62371397,and 62288102)the Natural Science Foundation of Shaanxi Province(2023-JC-YB-495)+1 种基金the Fundamental Research Funds for the Central Universitiesthe start-up funds from Northwestern Polytechnical University(G2022WD01001 and 23GH02021).
文摘Real-time thermal sensing through flexible temperature sensors in extreme environments is critically essential for precisely monitoring chemical reactions,propellant combustions,and metallurgy processes.However,despite their low response speed,most existing thermal sensors and related sensing materials will degrade or even lose their sensing performances at either high or low temperatures.Achieving a microsecond response time over an ultrawide temperature range remains challenging.Here,we design a flexible temperature sensor that employs ultrathin and consecutive Mo1−xWxS2 alloy films constructed via inkjet printing and a thermal annealing strategy.The sensing elements exhibit a broad work range(20 to 823 K on polyimide and 1,073 K on flexible mica)and a record-low response time(about 30μs).These properties enable the sensors to detect instantaneous temperature variations induced by contact with liquid nitrogen,water droplets,and flames.Furthermore,a thermal sensing array offers the spatial mapping of arbitrary shapes,heat conduction,and cold traces even under bending deformation.This approach paves the way for designing unique sensitive materials and flexible sensors for transient sensing under harsh conditions.
基金supported by the Fundamental Research Funds for the Central Universities,China(No.501XTCX2023146001).
文摘Thermoacoustic instabilities,frequent in a wide range of combustors,arise from the intricate coupling between the flame's unsteady heat release and the combustor acoustic.The application of plasma,characterized by its substantial local energy addition and radical generation,has demonstrated potential in disrupting this coupling and thereby mitigating thermoacoustic oscillations.Notably,open-loop control using discharge plasma has been successfully implemented to suppress self-excited oscillations in a Rijke tube setup.Considering the broader context of a complex system that integrates both thermoacoustic systems and discharge plasma,experiments were done to see its performance in stability under different arrangement and discharge repetition rates of discharge plasma.These experimental investigations identified critical operating conditions essential for complete suppression:(A)the optimal location of discharge actuations,and(B)the minimum energy required for complete suppression.Moreover,the impact of discharge plasma,particularly when tuned to the eigenfrequencies of oscillations within the thermoacoustic system.was thoroughly examined.The insights gained from these successful suppression trials are instrumental in guiding the strategic design of both physical arrangement and electrical configurations for the control of combustion instabilities via discharge plasma.Furthermore,through the photographing of the swinging arcs and their thermal disturbances by high-speed camera and highspeed schlieren,the characteristics of arcs'thermal disturbances and the reasons affecting its suppression effectiveness were determined.
文摘SI:Agentic AI for 6G Networks.Introduction.6G networks are poised to provide full coverage across air,land,and sea,deliver terabit-per-second data rates,and achieve microsecond-level latency.They promise comprehensive upgrades across industries through embedded intelligence,ushering in an era of intelligent interconnection of all things.However,managing real-time interactions among devices,infrastructure,and services in 6G networks is much more complex than in previous generations.Massive data streams from terrestrial nodes(e.g.,edge devices,sensors,distributed computing)and non-terrestrial nodes(LEO/MEO/GEO satellites)demand more intelligent and efficient processing.
文摘为了获得常压条件下绝缘支撑材料环氧树脂的沿面闪络特性,通过微秒脉冲下连续沿面放电对环氧树脂表面造成老化损伤,获得老化前后的环氧树脂沿面闪络特性数据。在脉冲电压幅值为18 k V、频率为100 Hz、电极间距为10 mm的情况下,对环氧树脂表面进行沿面放电老化处理,对不同放电老化时间下的表面形貌、粗糙度及水接触角进行测量,分析放电对材料表面的老化影响。结果发现,放电老化后环氧树脂表面疏松,且有大量突起颗粒形成,表面极易吸水。此外对老化前后的环氧树脂表面进行闪络实验,结果发现,表面闪络电压随老化时间出现先降低后升高的现象。相关实验结果及分析为研究环氧树脂的沿面耐压性能提供了一定的参数数据。
