共查询到20条相似文献,搜索用时 0 毫秒
1.
《Journal of Electrostatics》2005,63(6-10):657-663
In this paper, a needle–plane electrode system and polypropylene (PP) films were used to study the DC corona charging of polymers. It was found that the charges injected into the PP films sometimes show different polarity to the applied DC voltage, called polarity reversal charging, which may results in invalidation charging. The pulsed electro-acoustic (PEA) space charge measurement showed that charges of different polarities have been injected into the PP films’ bulk, simultaneously. From these results, a mechanism of two charging processes of high-field injection and return-stroke injection has been introduced here. We presumed that the return-stroke injection can be boosted with the increase of corona voltages and thus reduces the net charge as well as even change the polarity of charges injected. 相似文献
2.
Belaid Tabti Lucian Dascalescu Marius Plopeanu Angela Antoniu Mohamed Mekideche 《Journal of Electrostatics》2009,67(2-3):193-197
Corona discharge has a wide range of industry applications, such as charging the photosensitive layer and the toner particles in photocopying machines, modifying the wet-ability of plastic films, and conditioning the electrets for air filters. In all these situations, it is important to evaluate the surface charge density and compare it to the dielectric rigidity of atmospheric air. Experiments were carried out on 0.3 mm and 0.8 mm thick non-woven polypropylene fibrous media (average diameter of the fibres: 20 μm) that were exposed to positive corona discharges from a wire–grid–plate electrode system. The electrode system was powered from a continuously-adjustable DC high-voltage supply, employed as constant current generator. The monitored variable was the surface potential detected by the probe of an electrostatic voltmeter. The controlled variables were the potential of the grid electrode and the pre-conditioning temperature of the samples. The results of the experiments enabled a crude evaluation of each factor effect. Research should continue, using the experimental design methodology, in order to establish the optimum operating conditions. 相似文献
3.
Experimental results concerning the influence of the homogeneous magnetic field on the positive corona discharge between coaxial cylinders are presented. The change of the corona current due to axial magnetic field 0·6 T was observable at pressures below 4000 Pa in dry air. The influence on the initial and spark voltages has been investigated as well. 相似文献
4.
E. Ya. Zlotnik 《Radiophysics and Quantum Electronics》1994,37(7):533-542
Some ways of identifying magnetic fields in the solar corona using the observed properties of solar radio emissions are discussed. Examples are given for measuring the magnetic field in the active region atmosphere (in the chromosphere-corona transition region) based on spectral observations of microwave radiation from local sources associated with sunspots. Ways of determining the magnetic field in hot coronal loops in the case of recording cyclotron lines in solar microwave radiation are considered. It is shown that polarization of the second harmonic in Type III bursts testifies to a magnetic field on the track of electrons accelerated in the flare region and moving outward.Institute of Applied Physics, Russian Academy of Sciences, Nizhnii Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 7, pp. 821–835, July, 1994. 相似文献
5.
《Journal of Electrostatics》2006,64(12):836-842
Positive and negative current–voltage characteristics of a needle-grid electrostatic precipitator were measured for different electrode geometries and aerosols. Besides the well-known effect of corona quenching, additional findings show an interaction of fluid aerosols with the active electrode. A shift of the current–voltage characteristics was observed towards lower as well as higher voltages, as a function of the electrode geometry and the conductivity of the fluid aerosol. 相似文献
6.
A crossed-field cold-hollow-cathode arc is stable at low working gas pressures of 10−2–10−1 Pa, magnetic-field-and gas-dependent arcing voltages of 20–50 V, and discharge currents of 20–200 A. This is because electrons
come from a cathode spot produced on the inner cathode surface by a discharge over the dielectric surface. The magnetic field
influences the arcing voltage and discharge current most significantly. When the plasma conductivity in the cathode region
decreases in the electric field direction, the magnetic field increases, causing the discharge current to decline and the
discharge voltage to rise. The discharge is quenched when a critical magnetic field depending on the type of gas is reached.
Because of the absence of heated elements, the hollow cathode remains efficient for long when an arc is initiated in both
inert and chemically active gases. 相似文献
7.
We report a study on the magnetic nature of the two hyperfine fields observed in α-Mn by PAC. Both of the field sites behave
completely differently under the influence of an external field ranging from zero to 4 Tesla. The so-called high field originates
from the local moment antiferromagnetism of the matrix, while the low field should be associated with an itinerant magnetism. 相似文献
8.
《Journal of Electrostatics》2014,72(2):99-106
Numerical modeling of corona discharges has followed the same set of procedures for many years. Corona discharges on large scales are modeled only for ion drift, neglecting ionization. Studies of the ionization zone are often conducted in uniform axisymmetric configurations. However, in configurations that induce non-uniform electric fields, a combination of the two procedures is necessary to accurately capture the discharge physics and ion distribution. The present study conducts numerical simulations of a wire-cylinder corona using both the models and demonstrates the necessity of including the ionization physics to obtain improved accuracy, particularly in the presence of non-uniform electric fields. 相似文献
9.
Ulrich Kinkel 《Zeitschrift fur Physik C Particles and Fields》1992,54(4):573-575
The phenomenological two-state model usually used to describe the influence of external fields on neutron oscillations is illustrated and extended in order to take into account the vector character of magnetic fields. It is shown that, for sufficiently weak fields, the solution of the extended model can be reduced to the solution of three independent two-state models, one for each vector component. This result is useful for the calculation of antineutron losses in neutron oscillation experiments.Supported by the Bundesministerium für Forschung und Technologie under contract number 06 HD 983 I 相似文献
10.
Mukkavilli S. Lee C.K. Varghese K. Tavlarides L.L. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1988,16(6):652-660
A model is presented for the electrostatic corona discharge reactor (ECDR) in a pin-plate configuration. The main objective is to describe the fundamental chemistry and physics governing the discharge behavior and to predict the ECDR performance under various operating conditions. The electric field strength is estimated assuming a space-charge-free field. A two-term spherical harmonic expansion is used to solve the Boltzmann equation for the electron energy distribution function (EEDF) and calculate the electron-molecule reaction rates using collision cross-section data. Species continuity equations are solved for the dry and wet air systems to predict ozone and NOx at various feed flow rates (1630, 4890, 14, 670 cm/s) and an applied voltage of 10 kV. Among the various results reported, it is noted that the calculations indicate the Maxwell EEDF cannot be used because it overpredicts the electron-molecule rate coefficients by several orders of magnitude 相似文献
11.
S. B. Afanas’ev D. S. Lavrenyuk I. N. Petrushenko Yu. K. Stishkov 《Technical Physics》2008,53(7):848-852
The results of a comprehensive experimental study of the positive and negative corona discharges and their accompanying processes
are reported. It is shown that specific features of the corona in air under atmospheric pressure are related to the electric
wind. 相似文献
12.
S. Pekárek 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,61(3):657-662
The processes of ozone generation in non-thermal plasma produced by an
electrical discharge in air at atmospheric pressure are burdened by the
presence of nitrogen oxides, which on the one hand contribute to ozone
generation and on the other hand are responsible for unpleasant discharge
poisoning. The term discharge poisoning refers to the situation when the
discharge ozone formation completely breaks down. Discharge poisoning can be
affected by placing a catalyst in the discharge chamber. For the dc hollow
needle to mesh corona discharge enhanced by the flow of air through the
needle electrode we studied the effect of titanium dioxide TiO2, ZSM-5
zeolite or Cu++ZSM-5 zeolite on discharge poisoning by monitoring the
ozone, nitrogen monoxide and nitrogen dioxide discharge production. We found
that placing globules of any of these catalysts on the mesh decreases the
energy density of the onset of discharge poisoning, and this energy density
is smallest for a discharge with globules of a TiO2 on the mesh. 相似文献
13.
We have shown experimentally that the application of an electric field to an air stream blowing over a corona point has the additional effect of increasing the air velocity. This result is derived from the interaction of two factors. We have developed a model of the phenomenon which is based on electrostatic and hydrodynamic equations. The model provides an equation which relates the additional air velocity to the basic corona discharge parameters. The resulting function agrees with the experimental results. 相似文献
14.
《Physics letters. A》1997,228(3):182-186
A bifurcation analysis of the cylindrically symmetric solution obtained in the framework of the steady-state model of the negative corona discharge in air at atmospheric pressure has been carried out. No bifurcations have been found, which indicates that current contraction probably does not occur in the considered model. It follows that the current-free stripes on the corona cathode surface, observed by previous authors in two- and three-dimensional computer simulation and in experiment, are due to the specific discharge geometry rather than current contraction. 相似文献
15.
R. Benocci M. Urbano L. Mauri 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,37(1):115-122
The corona discharge in argon at atmospheric pressure has been studied by
means of a 2D model. The reduced characteristic derived from the
experimental data has been described by linear regressions for the different
pressures and the two studied inter-electrode distances thus confirming the
validity of Townsend's approximation also in case of point to plane
configuration and argon as process gas. The model validated this hypothesis
which has been attributed to the minor influence of space charge in the
ionization zone. Its effect is, on the other hand, more significant in the
drift zone where the electric field is greatly enhanced, leading, for higher
currents, to the formation of a spark gap. Electron and ion distributions
allow the influence of structural (electrode configurations and distance)
and operative (pressure and discharge current) parameters to be evaluated
including the current loss due to diffusion through different confining
boundaries. 相似文献
16.
利用自编1D3V PIC程序,数值研究了不同外加磁场方式对次级电子倍增抑制的物理过程,给出了次级电子数目、平均能量、密度、运动轨迹、渡越时间、介质表面静电场及沉积功率等物理量时空分布关系。模拟结果表明:不同方向外加磁场抑制次级电子倍增的机理有所不同。轴向外加磁场利用电子回旋运动干扰微波电场对电子加速过程,使其碰壁能量降低以达到抑制二次电子倍增的效果;横向外加磁场利用电子回旋漂移过程中,电子半个周期被推离介质表面(不发生次级电子倍增),半个周期被推回介质表面(降低电子碰撞能量)的作用机理,达到抑制二次电子倍增的效果。讨论了横向磁场在回旋共振下,电子回旋同步加速导致回旋半径增大,电子能量持续增加的特殊过程。两种外加磁场方式都可以通过增加磁场达到进一步抑制次级电子倍增的目的。轴向外加磁场加载容易,但对磁场要求较高;横向外加磁场需要磁场较低,但加载较为困难。 相似文献
17.
18.
在常压空气中,利用OES技术检测到负直流电晕放电等离子中激发态N原子发射光谱,并利用相对谱峰强度最大的674.5nm N原子激发跃迁谱线研究了相关空气参数和电参数对其相对密度的影响。结果表明,电离区内N原子相对密度随注入功率的升高呈增加趋势;随电极间距和相对湿度的增加,其相对密度逐渐减小;随N2流量增加,其相对密度呈先增加再减小趋势。在实验条件下,当针尖轴向距离r=1mm时,N原子相对密度出现最大值。 相似文献
19.
Marcela Morvová 《Czechoslovak Journal of Physics》1999,49(12):1703-1719
The plasmochemical and/or electrocatalytical reactions of carbon monoxide with water vapour were studied. Dc corona discharge
of both polarities at room temperature and temperatures enhanced up to 70°C was applied at pressures close to atmospheric.
The reaction products were analysed by IR absorption spectrometry. The main products in the gas phase were CO2 and CH4. The reactions are influenced by the formation of a catalytically active surface layer on electrodes. The composition of
this layer depends on the polarity of electrode. 相似文献
20.
In this paper we deal with the derivation of dynamic localization conditions for electrons on the one-dimensional (1D) lattice under the influence of ac electric and magnetic fields of the same frequency. We resort, for convenience, to a tight-binding single-band Hamiltonian. Our emphasis is on a more fundamental theoretical understanding by investigating interplays between such fields and the nearest-neighbor hopping interactions characterizing the Hamiltonian. In general, such conditions get expressed in terms of infinite sums of binary products of Bessel functions of the first kind. These sums are hardly tractable, but we found that selecting in a suitable manner the phases of time-dependent modulations leads to controllable frequency-mixing effects providing appreciable simplifications. Such mixings concern competitions between the number of flux quanta and the quotients of field amplitudes and field frequencies. More exactly, tuning one of the mixed frequencies to zero opens the way to establishing the simplified dynamic localization conditions. By resorting again to the zeros of the Bessel function of zeroth order. This results in quickly tractable relationships between the amplitudes of electric and magnetic fields, the field frequency, and the zeros referred to just above. Pure field limits and superpositions between uniform electric and time-dependent magnetic fields are also discussed. Comments concerning the role of disorder and of the Coulomb interaction are also made. 相似文献