Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202861
A. Belevtsev
The approach is based on consideration of the time evolution of the electron energy distribution function and uses the analytical solutions of the unsteady Boltzmann kinetic equation for electrons in liquids, taking into account their elastic and inelastic collisions with liquid particles. Ionization delay time and characteristic time for avalanche ionization growth in liquids are determined. The mechanisms of ionization involving excitons are also considered. The theory can be applied to liquid rare gases, pure and with admixtures.<>
{"title":"The theory of development of impact ionization and excitation in liquids","authors":"A. Belevtsev","doi":"10.1109/ICDL.1990.202861","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202861","url":null,"abstract":"The approach is based on consideration of the time evolution of the electron energy distribution function and uses the analytical solutions of the unsteady Boltzmann kinetic equation for electrons in liquids, taking into account their elastic and inelastic collisions with liquid particles. Ionization delay time and characteristic time for avalanche ionization growth in liquids are determined. The mechanisms of ionization involving excitons are also considered. The theory can be applied to liquid rare gases, pure and with admixtures.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121059413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202915
P. Atten, B. Malraison
The turbulent electroconvective motion of an insulating liquid subjected to weak unipolar injection is examined in regimes of dominant viscous effects and dominant inertia effects. Order-of-magnitude analyses are developed which consider two boundary layers adjacent to the electrodes, a core and intermediate regions. The main features of the electroconvective regimes are derived and used to predict the heat transfer that can be achieved in conditions where buoyancy plays only a negligible role. Laws of variation of the typical turbulent velocity for weak injection electroconvection and of the Nusselt number with the electrical parameters for both viscous and inertially dominated regimes are derived. An experiment using oils of different viscosities was performed to test the obtained laws. For Reynolds number convection, the experimental results support the analysis.<>
{"title":"Turbulent convection induced by weak unipolar injection in plane parallel electrode geometry","authors":"P. Atten, B. Malraison","doi":"10.1109/ICDL.1990.202915","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202915","url":null,"abstract":"The turbulent electroconvective motion of an insulating liquid subjected to weak unipolar injection is examined in regimes of dominant viscous effects and dominant inertia effects. Order-of-magnitude analyses are developed which consider two boundary layers adjacent to the electrodes, a core and intermediate regions. The main features of the electroconvective regimes are derived and used to predict the heat transfer that can be achieved in conditions where buoyancy plays only a negligible role. Laws of variation of the typical turbulent velocity for weak injection electroconvection and of the Nusselt number with the electrical parameters for both viscous and inertially dominated regimes are derived. An experiment using oils of different viscosities was performed to test the obtained laws. For Reynolds number convection, the experimental results support the analysis.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116250757","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202925
V. S. Teslenko
The kinetics of a laser breakdown in liquids taking into account stimulated scattering has been studied theoretically and experimentally. It has been shown that optical breakdown directions coincide with those of stimulated Brillouin scattering and stimulated Raman scattering. It is concluded that the description of the kinetics of extended optical breakdown should be based on the assumption that extended laser breakdown in pure media is a 'catastrophe' in the process of development of absolute and convective instability, which initially corresponds to the processes of cascade stimulated scattering generation.<>
{"title":"Initial stage of extended laser breakdown in liquids","authors":"V. S. Teslenko","doi":"10.1109/ICDL.1990.202925","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202925","url":null,"abstract":"The kinetics of a laser breakdown in liquids taking into account stimulated scattering has been studied theoretically and experimentally. It has been shown that optical breakdown directions coincide with those of stimulated Brillouin scattering and stimulated Raman scattering. It is concluded that the description of the kinetics of extended optical breakdown should be based on the assumption that extended laser breakdown in pure media is a 'catastrophe' in the process of development of absolute and convective instability, which initially corresponds to the processes of cascade stimulated scattering generation.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126796068","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202966
A. Zaky, I. Megahed, M. El-Awa
The effect of forced flow velocity on the breakdown voltage/gap length characteristics of transformer oil was studied using a needle point and a mesh plane electrode system. The velocity of the axial (co-field) oil flow varied from 0 to 280 cm/s. Tests were carried out on degassed oil, O/sub 2/-saturated oil, and SF/sub 6/-saturated oil for negative and positive point polarities. For degassed oil there was a large increase in the breakdown voltage with increasing oil velocity for both polarities of the point and over the whole range of gaps examined. For O/sub 2/- and SF/sub 6/-saturated oils a similar increase in breakdown voltage was observed only with the point negative. With the point positive, velocities above 90 cm/s had no effect.<>
{"title":"Effect of liquid flow velocity on the breakdown voltage of mineral oil under highly nonuniform fields","authors":"A. Zaky, I. Megahed, M. El-Awa","doi":"10.1109/ICDL.1990.202966","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202966","url":null,"abstract":"The effect of forced flow velocity on the breakdown voltage/gap length characteristics of transformer oil was studied using a needle point and a mesh plane electrode system. The velocity of the axial (co-field) oil flow varied from 0 to 280 cm/s. Tests were carried out on degassed oil, O/sub 2/-saturated oil, and SF/sub 6/-saturated oil for negative and positive point polarities. For degassed oil there was a large increase in the breakdown voltage with increasing oil velocity for both polarities of the point and over the whole range of gaps examined. For O/sub 2/- and SF/sub 6/-saturated oils a similar increase in breakdown voltage was observed only with the point negative. With the point positive, velocities above 90 cm/s had no effect.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"36 12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125726392","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202858
A. Belevtsev
The author considers novel analytical methods in the theory of electron transport in electric fields in liquid rare gases. They are developed both for stationary and nonstationary conditions and are based on the exact analytical solutions of the kinetic Boltzman equation for electrons in dense matter consisting of spatially correlated heavy scatterers, taking into account elastic and inelastic collisions of electrons with the liquid particles. Electric fields under consideration may be time-independent or variable.<>
{"title":"Theoretical study of electron transport in nonpolar liquids","authors":"A. Belevtsev","doi":"10.1109/ICDL.1990.202858","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202858","url":null,"abstract":"The author considers novel analytical methods in the theory of electron transport in electric fields in liquid rare gases. They are developed both for stationary and nonstationary conditions and are based on the exact analytical solutions of the kinetic Boltzman equation for electrons in dense matter consisting of spatially correlated heavy scatterers, taking into account elastic and inelastic collisions of electrons with the liquid particles. Electric fields under consideration may be time-independent or variable.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"187 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129781835","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202949
V.F. Klimkin
A six-frame high-speed laser schlieren system which has variable intervals from frame to frame has been developed. A ruby laser with a pulse duration of 5 ns is used as the light source. By means of this system, one can obtain a sequence of six schlieren pictures of an electrical discharge with one shot of the main laser. A time delay between two diagnostic pulses is 5-50 ns and can easily be changed. The applicability of the system is demonstrated for rapidly changing prebreakdown processes in liquid dielectrics in the nanosecond region.<>
{"title":"Multiframe high-speed laser schlieren system for observations of prebreakdown phenomena in liquids in nanosecond region","authors":"V.F. Klimkin","doi":"10.1109/ICDL.1990.202949","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202949","url":null,"abstract":"A six-frame high-speed laser schlieren system which has variable intervals from frame to frame has been developed. A ruby laser with a pulse duration of 5 ns is used as the light source. By means of this system, one can obtain a sequence of six schlieren pictures of an electrical discharge with one shot of the main laser. A time delay between two diagnostic pulses is 5-50 ns and can easily be changed. The applicability of the system is demonstrated for rapidly changing prebreakdown processes in liquid dielectrics in the nanosecond region.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129740438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202851
P. Watson
Optical studies of prebreakdown events in insulating liquids make it possible to identify several stages in the breakdown of negative point-plane gaps, starting with the creation of a rapidly expanding vapor cavity adjacent to the point electrode. As it expands the surface of this cavity becomes unstable and the growth of an electrohydrodynamic instability is observed; the runaway growth of this instability leads to streamers that bridge the gap and cause the actual breakdown. By combining simple electrostatic and hydrodynamic concepts one can derive equations for cavity growth, instability growth rate, and streamer velocity that are in reasonable agreement with experiment.<>
{"title":"The role of electrostatic and hydrodynamic forces in the electrical breakdown of liquid dielectrics","authors":"P. Watson","doi":"10.1109/ICDL.1990.202851","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202851","url":null,"abstract":"Optical studies of prebreakdown events in insulating liquids make it possible to identify several stages in the breakdown of negative point-plane gaps, starting with the creation of a rapidly expanding vapor cavity adjacent to the point electrode. As it expands the surface of this cavity becomes unstable and the growth of an electrohydrodynamic instability is observed; the runaway growth of this instability leads to streamers that bridge the gap and cause the actual breakdown. By combining simple electrostatic and hydrodynamic concepts one can derive equations for cavity growth, instability growth rate, and streamer velocity that are in reasonable agreement with experiment.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"34 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131589154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202916
J. Chang, F. Tran
The electrohydrodynamically enhanced natural convection of dielectric liquids in a horizontally cylindrical annulus was numerically investigated under DC and pulsed applied electric field conditions over the range of Rayleigh number from 10/sup 4/ to 2*10/sup 4/, the Prandtl number from 5 to 7, and the electric Rayleigh number from 0 to 2*10/sup 3/ for the inner-to-outer radius ratio of 2. Simulation results show that the applied, radial, DC electric field always enhances the heat transfer by natural convection process. The velocity and heat transfer enhancement are from a factor of 2 to 20 and from 10% to 30%, respectively, for EI varying from 5*10/sup 2/ to 2*10/sup 3/.<>
{"title":"Numerical simulation of electrohydrodynamically enhanced natural convection heat transfer of dielectric liquid in a horizontal annulus","authors":"J. Chang, F. Tran","doi":"10.1109/ICDL.1990.202916","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202916","url":null,"abstract":"The electrohydrodynamically enhanced natural convection of dielectric liquids in a horizontally cylindrical annulus was numerically investigated under DC and pulsed applied electric field conditions over the range of Rayleigh number from 10/sup 4/ to 2*10/sup 4/, the Prandtl number from 5 to 7, and the electric Rayleigh number from 0 to 2*10/sup 3/ for the inner-to-outer radius ratio of 2. Simulation results show that the applied, radial, DC electric field always enhances the heat transfer by natural convection process. The velocity and heat transfer enhancement are from a factor of 2 to 20 and from 10% to 30%, respectively, for EI varying from 5*10/sup 2/ to 2*10/sup 3/.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134147950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202927
N. Bonfaci, A. Denat
In a previous study of electrical conduction phenomena in cyclohexane with point-plane electrode geometry, specific conduction regimes were observed as a function of point radius and voltage polarity. In the present work, an analysis is made of the characteristics of light emission (size of the luminous zone, spectral analysis, etc.) of these conduction regimes in nonpolar liquids of different electron mobility, K/sub e/, as a function of hydrostatic pressure, point radius, etc. A similar investigation was carried out on the gaseous hydrocarbons (methane, propane, etc.) as a function of the density. Experimental results, which show a relationship between K/sub e/ and the characteristics of conduction regimes, indicate that hot electron mechanisms have a considerable effect on conduction phenomena in purified nonpolar liquids.<>
{"title":"Spectral analysis of the light emitted by prebreakdown phenomena in liquid and gaseous nonpolar fluids","authors":"N. Bonfaci, A. Denat","doi":"10.1109/ICDL.1990.202927","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202927","url":null,"abstract":"In a previous study of electrical conduction phenomena in cyclohexane with point-plane electrode geometry, specific conduction regimes were observed as a function of point radius and voltage polarity. In the present work, an analysis is made of the characteristics of light emission (size of the luminous zone, spectral analysis, etc.) of these conduction regimes in nonpolar liquids of different electron mobility, K/sub e/, as a function of hydrostatic pressure, point radius, etc. A similar investigation was carried out on the gaseous hydrocarbons (methane, propane, etc.) as a function of the density. Experimental results, which show a relationship between K/sub e/ and the characteristics of conduction regimes, indicate that hot electron mechanisms have a considerable effect on conduction phenomena in purified nonpolar liquids.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"414 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133470935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-09-10DOI: 10.1109/ICDL.1990.202920
K. Arii, M. Fujii, I. Kitani
A point electrode of a 0.1-mm-diam. tungsten wire was enclosed by a of about approximately 1-mm diam. gas bubble. After a voltage pulse application the bubble was deformed and then pushed to the plane electrode in the tested liquid. At the negative point, the bubble surface was rather smooth, although its shape was far from a sphere. Regular current and photocurrent pulses were observed when the bubble was attached to the point cathode. After the departure of the bubble from the point, the period of the pulses became long and random. When the bubble came close to the plane, light was emitted between the bubble and plane just before breakdown. At the positive point, a treelike surface was observed at the plane side of the bubble. Current and photocurrent pulses were not regular. When the tip of the treelike bubble went down to a point some distance from the plane, breakdown occurred. He, O/sub 2/, and SF6 affected the breakdown voltage of the bubble liquid composite for both polarities. Shortening the width of applied voltage pulse increased the breakdown voltage.<>
{"title":"Breakdown of gas liquid composite in divergent fields","authors":"K. Arii, M. Fujii, I. Kitani","doi":"10.1109/ICDL.1990.202920","DOIUrl":"https://doi.org/10.1109/ICDL.1990.202920","url":null,"abstract":"A point electrode of a 0.1-mm-diam. tungsten wire was enclosed by a of about approximately 1-mm diam. gas bubble. After a voltage pulse application the bubble was deformed and then pushed to the plane electrode in the tested liquid. At the negative point, the bubble surface was rather smooth, although its shape was far from a sphere. Regular current and photocurrent pulses were observed when the bubble was attached to the point cathode. After the departure of the bubble from the point, the period of the pulses became long and random. When the bubble came close to the plane, light was emitted between the bubble and plane just before breakdown. At the positive point, a treelike surface was observed at the plane side of the bubble. Current and photocurrent pulses were not regular. When the tip of the treelike bubble went down to a point some distance from the plane, breakdown occurred. He, O/sub 2/, and SF6 affected the breakdown voltage of the bubble liquid composite for both polarities. Shortening the width of applied voltage pulse increased the breakdown voltage.<<ETX>>","PeriodicalId":193137,"journal":{"name":"10th International Conference on Conduction and Breakdown in Dielectric Liquids","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123719847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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