scholarly journals Effect of DC Electric Fields on Flame Spread Over Twin Electrical Wires

2019 ◽  
Author(s):  
Jeong Park ◽  
Sun Ho Park ◽  
Min Suk Cha ◽  
Suk Ho Chung
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Flame Spread ◽  
Wind Effect ◽  
Spread Rate ◽  
Dc Voltage ◽  
Positive Voltage ◽  
Transient Period ◽  
Dc Electric Field ◽  
Flame Behavior

Abstract The effect of DC electric field on the behaviors of spreading flame over polyethylene (PE)-insulated twin electrical wires was investigated by varying the wire gap (S) and voltage (VDC). The twin flame spreads with the same flame spread rate (FSR) independently when no electric field is applied. With an applied DC electric field, the twin flame interacts such that FSR, flame width, and the leaning direction of interacting twin flames vary appreciably. The spread rate for wire flame with negative voltage (SF–) was larger than that with positive voltage (SF+) during transient period and then the two became the same in a developed region (a quasi-steady spread). Such a flame behavior could be grouped into two: twin flame spread (regime I) and single flame spread (regime II) after the extinction of SF+. Each regime could be categorized into three sub-regimes depending on S and VDC. For small VDC, the flame leaned toward the burnt wire, reducing FSR. With further increasing VDC, FSR increased due to the ionic wind effect and then decreased via the mass loss of molten PE. These non-monotonic behavior of FSR with DC voltage can be attributed the behaviors of molten PE, exhibiting dripping, electrospray, and di-electrophoresis phenomena. For further increased voltage, the flames were extinguished by streamer generation and an electrical short occurred at excessive voltages.

Study on Electric Field Characteristics of Converter Transformer on Valve Side Winding

2011 ◽  
Vol 130-134 ◽  
pp. 1413-1417
Author(s):  
You Hua Gao ◽  
Guo Wei Liu ◽  
Yan Bin Li ◽  
You Feng Gao
Keyword(s):  
Electric Field ◽  
Field Distribution ◽  
Electric Fields ◽  
High Voltage ◽  
Electric Field Distribution ◽  
Influence Factors ◽  
Calculation Model ◽  
Dc Voltage ◽  
Voltage Polarity ◽  
Transient Electric Field

Numerical calculation model with compound insulation of transient electric field is given. The insulation is more prominent due to complication for voltage applied on valve side winding of the converter transformer. So the simplied structure for electric calculation on the valve side winding of the converter transformer is established. The electric field distribution characteristics on the valve side winding of the converter transformer is analyzed and electric fields in different resistivity and permittivity are calculated under AC high voltage, DC high voltage, AC superimposed DC voltage, polarity reversal voltage. The maximum electric field intensity is calculated and analyzed under kinds of high voltage. Some important influence factors for electric field distribution are also discussed in this paper.

scholarly journals External-Electric-Field-Enhanced Uniformity and Deposition Rate of a TiO2 Film Prepared by the Sparking Process

2018 ◽  
Vol 63 (6) ◽  
pp. 531 ◽  
Author(s):  
W. Thongpan ◽  
T. Kumpika ◽  
E. Kantarak ◽  
A. Panthawan ◽  
P. Pooseekheaw ◽  
...  
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Electric Fields ◽  
Deposition Rate ◽  
Tio2 Films ◽  
Dc Voltage ◽  
External Electric Fields ◽  
Deposited Film ◽  
Field Area ◽  
Scanning Electron

We have used an external electric field to increase both the uniformity and deposition rate of TiO2 films. The experiment is carried out by sparking-off titanium wires with a high dc voltage of 1 kV (field Eint = 10 kV/cm) and a limited current of 3 mA. The external electric fields (Eext) of 3, 6, and 9 kV/cm were applied to the sparking system for 1–5 hours. The as-deposited film morphology was characterized by scanning electron microscopy. The results clearly show that the films are only deposited on the external electric field area. Furthermore, the deposition rate of the films increased from 40.7% to 77.8% in the presence of the external electric field of 9 kV/cm. The effects of an external electric field on both the deposition rate and uniformity of films are investigated and described.

Electro-Hydrodynamic Control of Premixed Turbulent Methane Flames at Pressures Above 1 ATM

2005 ◽  
Author(s):  
T. Hammer ◽  
G. Lins ◽  
D. W. Branston ◽  
F. Dinkelacker ◽  
A. Sakhrieh ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Gas Flow ◽  
Thermal Power ◽  
Combustion Process ◽  
Optical Emission ◽  
Experimental Conditions ◽  
Reaction Zones ◽  
Co Reduction ◽  
Flame Behavior

Electric field control of combustion offers the potential of stabilizing flames and reducing emissions with comparatively little effort. Previous investigations of the effects of electric fields on flames were restricted to atmospheric pressure and the question whether field effects persist at higher pressures remained open. In the present work effects of electric fields on flame behavior are established for pressures up to 10 bar without any indication that this should be an upper limit. Voltage-current measurements and optical emission spectroscopy gave clear evidence that at all experimental conditions under investigation electric field induced ionization and dissociation reactions were negligible with regard to the combustion process. Thus it is concluded that all observed effects are due to electro-hydrodynamic distortions of the gas flow caused by electrostatic forces acting on the ions generated in the reaction zones of the flames. The concentration of pollutants such as CO, NO and NO2 in the presence of an electric field depends on the ratio U/p of electrode voltage U and pressure p which implies that the electric field strength required to obtain a given effect increases linearly with pressure. In an electric field directed towards the burner CO emissions could be reduced by about 90%, irrespective of pressure. The decrease of CO was accompanied by an increase of NOx by about 20%. The electric power required for a CO reduction of 90% amounted to 0.1% of the thermal power. The improvement of the lean blow-off limit upon application of an electric field observed so far ranges from 1 to 3% and increases with pressure.

scholarly journals Meteor plasma trails: effects of external electric field

2009 ◽  
Vol 27 (1) ◽  
pp. 279-296 ◽  
Author(s):  
Y. S. Dimant ◽  
M. M. Oppenheim ◽  
G. M. Milikh
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Electrostatic Interaction ◽  
Geomagnetic Field ◽  
Dense Plasma ◽  
Dc Electric Field ◽  
E Region ◽  
Flow Through ◽  
Short Circuits ◽  
Meteor Plasma

Abstract. Meteoroids traversing the E-region ionosphere leave behind extended columns of elevated ionization known as the meteor plasma trails. To accurately interpret radar signals from trails and use them for diagnostics, one needs to model plasma processes associated with their structure and evolution. This paper describes a 3-D quantitative theory of the electrostatic interaction between a dense plasma trail, the ionosphere, and a DC electric field driven by an external dynamo. A simplified water-bag model of the meteor plasma shows that the highly conducting trail efficiently short-circuits the ionosphere and creates a vast region of currents that flow through and around the trail. We predict that the trail can induce electric fields reaching a few V/m, both perpendicular and parallel to the geomagnetic field. The former may drive plasma instabilities, while the latter may lead to strong heating of ionospheric electrons. We discuss physical and observational implications of these processes.

Effect of Microstructure on Lifetime Performance of Barium Titanate Ceramics Under DC and AC Electric Fields

2010 ◽  
Author(s):  
Jay Shieh
Keyword(s):  
Fatigue Strength ◽  
Barium Titanate ◽  
Electric Field ◽  
Electric Fields ◽  
Time To Failure ◽  
Electrical Loading ◽  
Ac Electric Fields ◽  
Lifetime Performance ◽  
Weibull Statistical Analysis ◽  
Dc Electric Field

Bulk barium titanate (BaTiO3 ) ceramic specimens with bimodal microstructures are prepared and their dielectric and fatigue strengths are investigated under an alternating current (AC) electric field and a direct current (DC) electric field. It is found that under AC electrical loading, both the dielectric and fatigue strengths decrease with increasing amount of coarse abnormal grains. The scatter of the AC fatigue strength is characterized with the Weibull statistics. The extent of scatter of the AC fatigue strength data correlates strongly with the size distribution of the coarse grains. Such correlation is resulted from the presence of intrinsic defects within the microstructure. For DC electrical loading, the time to failure of the specimens with coarse abnormal grains is significantly shorter than the lifetimes of the specimens with only small normal grains. It is found that under a DC electric field of 6 MVm−1, the BaTiO3 specimens would fail within 200 h when abnormal grains are present in the microstructure. However, the lifetimes of the specimens containing abnormal grains vary significantly from one to another. The Weibull statistical analysis indicates that the amount of abnormal grains has little influence on the lifetime performance of bulk BaTiO3 ceramics under large DC electric fields. In most of the failed BaTiO3 specimens under DC electrical loading, regardless of their lifetimes, large through-thickness round holes with recrystallization features are present. A mixed failure mode consisting of avalanche and thermal breakdowns is proposed for the failed specimens.

The Effect of Growth, Migration and Bacterial Cellulose Synthesis of Gluconacetobacter xylinus in Presence of Direct Current Electric Field Condition

2012 ◽  
Vol 550-553 ◽  
pp. 1108-1113 ◽  
Author(s):  
Lin Yan ◽  
Shi Ru Jia ◽  
Xin Tong Zheng ◽  
Cheng Zhong ◽  
Miao Liu ◽  
...  
Keyword(s):  
Electric Field ◽  
Bacterial Cellulose ◽  
Electric Fields ◽  
Direct Current ◽  
Cellulose Fiber ◽  
Sem Analysis ◽  
Cellulose Synthesis ◽  
Gluconacetobacter Xylinus ◽  
Growth State ◽  
Dc Electric Field

In this study, the movement and orientation of bacteria cells were controlled by direct current(DC) electric fields, result in altering alignment of bacterial cellulose nanofiber and further changing the 3-dimensional network structure of bacterial cellulose. A modified swarm plate assay was performed to investigate the migration of Gluconacetobacter xylinus cells which exposed in DC electric field. It suggested that the cells moved toward to negative pole and with the increasement of the electric field strength the velocity will also increase. The SEM analysis demonstrated that the cellulose fiber bundles which synthesized at 1V/cm have lager diameter and a trend toward one direction. Meanwhile the growth state of G.xylinus in the presence of DC electric field was also being observed.

Effects of AC/DC Electric Fields on Stretching DNA Molecules

NANO ◽  
2020 ◽  
Vol 15 (05) ◽  
pp. 2050065
Author(s):  
Ying Wang ◽  
Mingyan Gao ◽  
Yingmin Qu ◽  
Jun Hu ◽  
Ying Xie ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Dna Molecules ◽  
Dna Interactions ◽  
Biophysical Properties ◽  
Voltage Range ◽  
Atomic Force ◽  
Ac Electric Field ◽  
Dc Electric Field ◽  
Dc Electric Fields

The effects of AC/DC electric fields on stretching DNA molecules were discussed in this work. In the experiments of stretching DNA molecules with AC/DC electric fields, the voltage range was changed from 0[Formula: see text]V to 10[Formula: see text]V, and the frequency of AC electric field was kept at 50[Formula: see text]kHz. An atomic force microscope (AFM) was used to obtain DNA distributions under different electric fields. DNA molecules were curved and randomly distributed in solution if there was not any force applied to them. When an AC electric field was applied to the DNA sample, the curvature of DNA molecules was decreased gradually, and the stretching result was more obvious with the increase of voltage from 0.1[Formula: see text]V to 5[Formula: see text]V. The DNA molecules were broken when the voltage was increased to 6[Formula: see text]V. However, under the DC electric field, the stretching result of DNA molecules reached to their optimum state when the voltage was 2[Formula: see text]V, and they kept their steady state even though larger electric field intensities applied to the electrodes. The results can be used for the study of DNA–DNA, protein–DNA and quantum dot–DNA interactions and for the exploration of DNA biophysical properties.

scholarly journals Electron Acceleration by Strong DC Electric Fields in Extragalactic Jets

2000 ◽  
Vol 195 ◽  
pp. 311-312
Author(s):  
Y. E. Litvinenko
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Magnetic Reconnection ◽  
Current Sheet ◽  
Electric Fields ◽  
Electron Acceleration ◽  
Acceleration Time ◽  
Extragalactic Jets ◽  
Dc Electric Field ◽  
The Magnetic Field

Fast magnetic reconnection in extragalactic jets leads to electron acceleration by the DC electric field in the reconnecting current sheet. The maximum electron energy (γ > 106) and the acceleration time (< 106 s) are determined by the magnetic field dynamics in the sheet.

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