在大气压介质阻挡放电的实际应用中,空气介质阻挡放电具有极其广泛的工业化应用前景。目前,空气均匀放电的获得仍比较困难,且诊断均匀性的依据缺乏可信的依据。文章采用粒子云网格法(Particle in Cell,PIC)与蒙特卡罗碰撞(Monte Carlo C...在大气压介质阻挡放电的实际应用中,空气介质阻挡放电具有极其广泛的工业化应用前景。目前,空气均匀放电的获得仍比较困难,且诊断均匀性的依据缺乏可信的依据。文章采用粒子云网格法(Particle in Cell,PIC)与蒙特卡罗碰撞(Monte Carlo Collision,MCC)方法模拟了放电过程中粒子的运动情况,研究大气压下空气介质阻挡放电的发展过程,然后讨论介质厚度、电源频率对形成均匀放电的影响,并研究这两种因素对等离子体密度的影响。模拟结果表明:介质厚度在d≥1.5 mm时可获得没有放电细丝的电流波形;电源频率高于2.5 kHz时,放电细丝是难以避免的。在能够形成均匀放电的条件下,将介质厚度适当的调整在1.5 mm附近,提高电源频率,将产生更高的等离子体密度。展开更多
真空直流断路器弧后介质恢复过程是决定其开断是否成功的重要物理过程,因而受到研究者的广泛关注。该文的主要目标是采用粒子模拟的方法研究真空断路器弧后金属蒸气击穿阶段的发展过程及影响因素,并基于粒子云网格(Particle in Cell)和...真空直流断路器弧后介质恢复过程是决定其开断是否成功的重要物理过程,因而受到研究者的广泛关注。该文的主要目标是采用粒子模拟的方法研究真空断路器弧后金属蒸气击穿阶段的发展过程及影响因素,并基于粒子云网格(Particle in Cell)和蒙特卡罗碰撞(Monte Carlo Collision)相结合的PIC-MCC方法,建立弧后金属蒸气击穿模型,对金属蒸气击穿的发展过程进行空间2维速度3维的仿真模拟,然后讨论触头表面温度、金属蒸气密度、触头开距、电压等重要因素对击穿的影响。模拟结果表明:在一定范围内,增大金属蒸气的密度,击穿发生的更迅速;触头温度越高,击穿更容易发生;暂态恢复电压峰值越高,击穿发生更快。另外,当场强不变时,对于较小开距,击穿反而不太容易发生,当开距较大时,击穿发生的时间几乎不受开距的影响。展开更多
A two-dimensional PIC/MCC model is developed to simulate the nitrogen radio frequency hollow cathode discharge（rf-HCD）.It is found that both the sheath oscillation heating and the secondary electron heating together...A two-dimensional PIC/MCC model is developed to simulate the nitrogen radio frequency hollow cathode discharge（rf-HCD）.It is found that both the sheath oscillation heating and the secondary electron heating together play a role to maintain the rf-HCD under the simulated conditions.The mean energy of ions（N＋_2,N＋）in the negative glow region is greater than the thermal kinetic energy of the molecular gas（N2）,which is an important characteristic of rf-HCD.During the negative portion of the hollow electrode voltage cycle,electrons mainly follow pendulum movement and produce a large number of ionization collisions in the plasma region.During the positive voltage of the rf cycle,the axial electric field becomes stronger and its direction is pointing to the anode（substrate）,therefore the ions move toward the anode（substrate）via the axial electric field acceleration.Compared with dc-HCD,rf-HCD is more suitable for serving as a plasma jet nozzle at low pressure.展开更多
Numerical simulations by the code of Object-Oriented PIC （Particle-in-Cell） and the Monte Carlo Collision （MCC） method were carried out in order to obtain an insight into the characteristics of plasmas generated b...Numerical simulations by the code of Object-Oriented PIC （Particle-in-Cell） and the Monte Carlo Collision （MCC） method were carried out in order to obtain an insight into the characteristics of plasmas generated by glow discharges in low pressure helium in a four-anode DC glow discharge device. The results show that, the pressure, the external mirror magnetic field, and the virtual breadth of the annular electrode affect the radial distribution of the plasma density and temperature. The simulations are instructive for further experiments.展开更多
地球同步轨道航天器在地磁亚暴环境下处于向光面和背光面的两侧会产生电位差。本文利用高能电子和高能离子的双麦克斯韦分布拟合同步轨道环境等离子体并加入二次电子和光电子的影响,建立了航天器的三维计算模型,利用基于PIC(Particle In...地球同步轨道航天器在地磁亚暴环境下处于向光面和背光面的两侧会产生电位差。本文利用高能电子和高能离子的双麦克斯韦分布拟合同步轨道环境等离子体并加入二次电子和光电子的影响,建立了航天器的三维计算模型,利用基于PIC(Particle In Cell)方法的仿真程序,计算了航天器表面各材料的充电电位及其附近的等离子体的电位分布,以及低能电子、高能电子、二次电子和光电子的密度分布和充电电流分布,最后探讨了航天器不同表面材料电势随时间的变化情况。展开更多
为了考察亲电子效应(包含斥电子效应)对等离子体中尘埃带电的影响,建立了基于粒子网格(particle in cell,PIC)技术的尘埃带电计算方法.在物理上使用表面附加电荷来表征亲电子效应,并在计算方法中增加了相应的数学描述.基于该方法,开展...为了考察亲电子效应(包含斥电子效应)对等离子体中尘埃带电的影响,建立了基于粒子网格(particle in cell,PIC)技术的尘埃带电计算方法.在物理上使用表面附加电荷来表征亲电子效应,并在计算方法中增加了相应的数学描述.基于该方法,开展了多个场景例的计算,结果表明:亲电子效应越强,尘埃平衡电荷量就越大,且其平衡电荷量增幅与表面附加电荷面密度有着近似的正比关系;类似地,斥电子尘埃同样具有这种正比关系,但与亲电子尘埃不同的特点是,斥电子尘埃达到平衡电荷量的用时更长;此外,尘埃的粒径越大,亲电子效应所带来的平衡电荷量提升效果就越显著.该方法实现了对等离子体中亲电子尘埃带电的计算能力.通过该方法的计算表明,亲电子材质对等离子体中尘埃带电可以造成影响,且当亲电子效应足够强时,影响效果将不可忽视.展开更多
Radio frequency capacitively coupled plasma source(RF-CCP)with a hollow electrode can increase the electron density through the hollow cathode effect(HCE),which offers a method to modify the spatial profiles of the pl...Radio frequency capacitively coupled plasma source(RF-CCP)with a hollow electrode can increase the electron density through the hollow cathode effect(HCE),which offers a method to modify the spatial profiles of the plasma density.In this work,the variations of the HCE in one RF period are investigated by using a two-dimensional particle-in-cell/Monte-Carlo collision(PIC/MCC)model.The results show that the sheath electric field,the sheath potential drop,the sheath thickness,the radial plasma bulk width,the electron energy distribution function(EEDF),and the average electron energy in the cavity vary in one RF period.During the hollow electrode sheath's expansion phase,the secondary electron heating and sheath oscillation heating in the cavity are gradually enhanced,and the frequency of the electron pendular motion in the cavity gradually increases,hence the HCE is gradually enhanced.However,during the hollow electrode sheath's collapse phase,the secondary electron heating is gradually attenuated.In addition,when interacting with the gradually collapsed hollow electrode sheaths,high-energy plasma bulk electrons in the cavity will lose some energy.Furthermore,the frequency of the electron pendular motion in the cavity gradually decreases.Therefore,during the hollow electrode sheath's collapse phase,the HCE is gradually attenuated.展开更多
文摘在大气压介质阻挡放电的实际应用中,空气介质阻挡放电具有极其广泛的工业化应用前景。目前,空气均匀放电的获得仍比较困难,且诊断均匀性的依据缺乏可信的依据。文章采用粒子云网格法(Particle in Cell,PIC)与蒙特卡罗碰撞(Monte Carlo Collision,MCC)方法模拟了放电过程中粒子的运动情况,研究大气压下空气介质阻挡放电的发展过程,然后讨论介质厚度、电源频率对形成均匀放电的影响,并研究这两种因素对等离子体密度的影响。模拟结果表明:介质厚度在d≥1.5 mm时可获得没有放电细丝的电流波形;电源频率高于2.5 kHz时,放电细丝是难以避免的。在能够形成均匀放电的条件下,将介质厚度适当的调整在1.5 mm附近,提高电源频率,将产生更高的等离子体密度。
文摘真空直流断路器弧后介质恢复过程是决定其开断是否成功的重要物理过程,因而受到研究者的广泛关注。该文的主要目标是采用粒子模拟的方法研究真空断路器弧后金属蒸气击穿阶段的发展过程及影响因素,并基于粒子云网格(Particle in Cell)和蒙特卡罗碰撞(Monte Carlo Collision)相结合的PIC-MCC方法,建立弧后金属蒸气击穿模型,对金属蒸气击穿的发展过程进行空间2维速度3维的仿真模拟,然后讨论触头表面温度、金属蒸气密度、触头开距、电压等重要因素对击穿的影响。模拟结果表明:在一定范围内,增大金属蒸气的密度,击穿发生的更迅速;触头温度越高,击穿更容易发生;暂态恢复电压峰值越高,击穿发生更快。另外,当场强不变时,对于较小开距,击穿反而不太容易发生,当开距较大时,击穿发生的时间几乎不受开距的影响。
基金supported by Natural Science Foundation of Hebei Province,China(No.A2012205072)
文摘A two-dimensional PIC/MCC model is developed to simulate the nitrogen radio frequency hollow cathode discharge（rf-HCD）.It is found that both the sheath oscillation heating and the secondary electron heating together play a role to maintain the rf-HCD under the simulated conditions.The mean energy of ions（N＋_2,N＋）in the negative glow region is greater than the thermal kinetic energy of the molecular gas（N2）,which is an important characteristic of rf-HCD.During the negative portion of the hollow electrode voltage cycle,electrons mainly follow pendulum movement and produce a large number of ionization collisions in the plasma region.During the positive voltage of the rf cycle,the axial electric field becomes stronger and its direction is pointing to the anode（substrate）,therefore the ions move toward the anode（substrate）via the axial electric field acceleration.Compared with dc-HCD,rf-HCD is more suitable for serving as a plasma jet nozzle at low pressure.
文摘Numerical simulations by the code of Object-Oriented PIC （Particle-in-Cell） and the Monte Carlo Collision （MCC） method were carried out in order to obtain an insight into the characteristics of plasmas generated by glow discharges in low pressure helium in a four-anode DC glow discharge device. The results show that, the pressure, the external mirror magnetic field, and the virtual breadth of the annular electrode affect the radial distribution of the plasma density and temperature. The simulations are instructive for further experiments.
文摘地球同步轨道航天器在地磁亚暴环境下处于向光面和背光面的两侧会产生电位差。本文利用高能电子和高能离子的双麦克斯韦分布拟合同步轨道环境等离子体并加入二次电子和光电子的影响,建立了航天器的三维计算模型,利用基于PIC(Particle In Cell)方法的仿真程序,计算了航天器表面各材料的充电电位及其附近的等离子体的电位分布,以及低能电子、高能电子、二次电子和光电子的密度分布和充电电流分布,最后探讨了航天器不同表面材料电势随时间的变化情况。
文摘为了考察亲电子效应(包含斥电子效应)对等离子体中尘埃带电的影响,建立了基于粒子网格(particle in cell,PIC)技术的尘埃带电计算方法.在物理上使用表面附加电荷来表征亲电子效应,并在计算方法中增加了相应的数学描述.基于该方法,开展了多个场景例的计算,结果表明:亲电子效应越强,尘埃平衡电荷量就越大,且其平衡电荷量增幅与表面附加电荷面密度有着近似的正比关系;类似地,斥电子尘埃同样具有这种正比关系,但与亲电子尘埃不同的特点是,斥电子尘埃达到平衡电荷量的用时更长;此外,尘埃的粒径越大,亲电子效应所带来的平衡电荷量提升效果就越显著.该方法实现了对等离子体中亲电子尘埃带电的计算能力.通过该方法的计算表明,亲电子材质对等离子体中尘埃带电可以造成影响,且当亲电子效应足够强时,影响效果将不可忽视.
文摘Radio frequency capacitively coupled plasma source(RF-CCP)with a hollow electrode can increase the electron density through the hollow cathode effect(HCE),which offers a method to modify the spatial profiles of the plasma density.In this work,the variations of the HCE in one RF period are investigated by using a two-dimensional particle-in-cell/Monte-Carlo collision(PIC/MCC)model.The results show that the sheath electric field,the sheath potential drop,the sheath thickness,the radial plasma bulk width,the electron energy distribution function(EEDF),and the average electron energy in the cavity vary in one RF period.During the hollow electrode sheath's expansion phase,the secondary electron heating and sheath oscillation heating in the cavity are gradually enhanced,and the frequency of the electron pendular motion in the cavity gradually increases,hence the HCE is gradually enhanced.However,during the hollow electrode sheath's collapse phase,the secondary electron heating is gradually attenuated.In addition,when interacting with the gradually collapsed hollow electrode sheaths,high-energy plasma bulk electrons in the cavity will lose some energy.Furthermore,the frequency of the electron pendular motion in the cavity gradually decreases.Therefore,during the hollow electrode sheath's collapse phase,the HCE is gradually attenuated.
