32nd AIAA Plasmadynamics and Lasers Conference, 2001
This work analyses the ability of an electrohydrodynamic actuator to modify the characteristics o... more This work analyses the ability of an electrohydrodynamic actuator to modify the characteristics of an airflow around a circular cylinder. We analyze the flow regimes characterized by transition to turbulence of the shear layers and concentrate our analysis in the displaced and near wake regions. We have considered a device consisting of electrodes flush mounted on the surface of the cylinder. The electrodes are excited with d.c. power. This system is operated in a regime that gives rise to a plasma sheet contouring the cylinder which changes the boundary condition of the flow. From flow visualizations and particle image velocimetry data we show that it can induce a strong acceleration of the flow close to the surface, leading to a decrease of the size of the near wake.
... Leonard's experiment [5] used the liquid JP-4, in which was mixed the ionic interfac... more ... Leonard's experiment [5] used the liquid JP-4, in which was mixed the ionic interface activation agent ASA-3. As is well known, the dissociation rate for ... additive concentration x and con-stant B, and if we use A = (Z,'/Zi)n;, we obtain ALCOHOL CONC ENT RAT I 0 N [X ~OOKO~] ...
In this paper, particle velocity fields inside Dielectric Barrier Discharge (DBD) electrostatic p... more In this paper, particle velocity fields inside Dielectric Barrier Discharge (DBD) electrostatic precipitators are investigated experimentally using Particle Image Velocimetry (PIV). The main objective of this study is to analyze the effect of the ionic wind on the particle collection efficiency in such electrostatic precipitators. An ac high voltage is applied to create the DBD inside a wire-to-plane precipitator and a plane-to-plane one. After the establishment of the DBD, the particle flow velocity field in the precipitators changes significantly compared to that observed without DBD. Results obtained with the wire-to-plane configuration show a strong interaction between the primary flow and the secondary flow (ionic wind). Near the wire electrode, the strong electric forces move the particles from the central part of the channel to the plate electrodes. Within the drift region, the velocity magnitude depends essentially on the balance between the electric and the viscous forces. In the case of plane-to-plane DBD, two-dimensional analysis of the flow can be accepted. The timeaveraged flow is only modified in the boundary layer, which becomes thinner. The time-averaged effect of ionic wind on the primary flow in such configuration is probably negligible. Keywords—Electrostatic Precipitation, Dielectric Barrier Discharge, Electrohydrodynamic Flow, Particle Image Velocimetry Corresponding author: Noureddine Zouzou e-mail address: noureddine.zouzou@lea.univ-poitiers.fr Presented at the International Symposium on Electro-hydrodynamics, in March 2009 Dielectric Electrodes
ICDL'96. 12th International Conference on Conduction and Breakdown in Dielectric Liquids
This paper shows the electrical conduction characteristics of commercial diesel oil in solution w... more This paper shows the electrical conduction characteristics of commercial diesel oil in solution with surfactants. Theories usually considered with pure hydrocarbons are able to explain satisfactorily the behaviour of this complex mixture.
Proceedings of Conference on Electrical Insulation and Dielectric Phenomena - CEIDP '96
In this article we develop a linear stability analysis for a dielectric liquid jet with charges o... more In this article we develop a linear stability analysis for a dielectric liquid jet with charges on its surface flowing at high speed in a gaseous atmosphere. We analyse the growth rate and the propagation velocity of a perturbation, the jet break-up and the influence of the charges on them
In this work we analyze the d.c. corona discharge between a wireplate electrode configuration pla... more In this work we analyze the d.c. corona discharge between a wireplate electrode configuration placed on the surface of an insulating cylinder. The influence of different parameters are analysed in order to characterize the discharge and to determine the best configuration to study the possibility of drag reduction of the flow acting in immersed bodies. A generalized glow regime seems the most suitable to undertake studies with this goal.
The authors have developed titanium oxide-based functionally graded materials (FGMs) offering spe... more The authors have developed titanium oxide-based functionally graded materials (FGMs) offering special properties of high relative permittivity and photocatalysing capability. In the experiment reported, four such FGMs, sintered at furnace temperatures of 673, 873, 1073 and 1273 °K, were examined for their electrical behaviour, particularly relative permittivity and dielectric loss tangent. The measurement frequencies used were 0.25 ∼ 50 MHz. The paper concludes with a discussion of whether these materials can be used as photocatalyses for the sake of improving the environment. This would open up new applications for FGMs in the area of field relaxation and photocatalysis.
1999 Annual Report Conference on Electrical Insulation and Dielectric Phenomena (Cat. No.99CH36319)
In high power transformers, pressboard and oil are required for electrical insulation. On the oth... more In high power transformers, pressboard and oil are required for electrical insulation. On the other hand, the oil is also used as a coolant of the system. The flow electrification process occurring at oil-pressboard interface seems to be initiating on electrical discharge incidents. Our recent investigations of electrification generated by an oil flow through different pressboards showed an influence of the pressboard degradation by artificial electrical discharges. Consequently the goal of this experimental study is to measure and to compare the convected space charge density value obtained with a brand new pressboard sample and with a pressboard coming from a damaged power transformer. The influence of an additive (BTA benzotriazol 1-2-3) in oil is also analyzed. The results show that the pressboard sample obtained from the damaged power transformer induces a high increase of flow electrification due to a modification of the exchange process at the pressboard-oil interface. On the other hand, an addition of BTA permits to reduce significantly flow electrification.
1998 Annual Report Conference on Electrical Insulation and Dielectric Phenomena (Cat. No.98CH36257)
The aim of this work is a better understanding of the flow electrification process occurring in h... more The aim of this work is a better understanding of the flow electrification process occurring in high power transformers. In order to characterize the effect of the pressboard degradation and the additive benzotriazol, the experiments consist in measuring the streaming currents generated by an oil flow through a pressboard sample. Two main results have been obtained: the addition of several
32nd AIAA Plasmadynamics and Lasers Conference, 2001
This work analyses the ability of an electrohydrodynamic actuator to modify the characteristics o... more This work analyses the ability of an electrohydrodynamic actuator to modify the characteristics of an airflow around a circular cylinder. We analyze the flow regimes characterized by transition to turbulence of the shear layers and concentrate our analysis in the displaced and near wake regions. We have considered a device consisting of electrodes flush mounted on the surface of the cylinder. The electrodes are excited with d.c. power. This system is operated in a regime that gives rise to a plasma sheet contouring the cylinder which changes the boundary condition of the flow. From flow visualizations and particle image velocimetry data we show that it can induce a strong acceleration of the flow close to the surface, leading to a decrease of the size of the near wake.
... Leonard's experiment [5] used the liquid JP-4, in which was mixed the ionic interfac... more ... Leonard's experiment [5] used the liquid JP-4, in which was mixed the ionic interface activation agent ASA-3. As is well known, the dissociation rate for ... additive concentration x and con-stant B, and if we use A = (Z,'/Zi)n;, we obtain ALCOHOL CONC ENT RAT I 0 N [X ~OOKO~] ...
In this paper, particle velocity fields inside Dielectric Barrier Discharge (DBD) electrostatic p... more In this paper, particle velocity fields inside Dielectric Barrier Discharge (DBD) electrostatic precipitators are investigated experimentally using Particle Image Velocimetry (PIV). The main objective of this study is to analyze the effect of the ionic wind on the particle collection efficiency in such electrostatic precipitators. An ac high voltage is applied to create the DBD inside a wire-to-plane precipitator and a plane-to-plane one. After the establishment of the DBD, the particle flow velocity field in the precipitators changes significantly compared to that observed without DBD. Results obtained with the wire-to-plane configuration show a strong interaction between the primary flow and the secondary flow (ionic wind). Near the wire electrode, the strong electric forces move the particles from the central part of the channel to the plate electrodes. Within the drift region, the velocity magnitude depends essentially on the balance between the electric and the viscous forces. In the case of plane-to-plane DBD, two-dimensional analysis of the flow can be accepted. The timeaveraged flow is only modified in the boundary layer, which becomes thinner. The time-averaged effect of ionic wind on the primary flow in such configuration is probably negligible. Keywords—Electrostatic Precipitation, Dielectric Barrier Discharge, Electrohydrodynamic Flow, Particle Image Velocimetry Corresponding author: Noureddine Zouzou e-mail address: noureddine.zouzou@lea.univ-poitiers.fr Presented at the International Symposium on Electro-hydrodynamics, in March 2009 Dielectric Electrodes
ICDL'96. 12th International Conference on Conduction and Breakdown in Dielectric Liquids
This paper shows the electrical conduction characteristics of commercial diesel oil in solution w... more This paper shows the electrical conduction characteristics of commercial diesel oil in solution with surfactants. Theories usually considered with pure hydrocarbons are able to explain satisfactorily the behaviour of this complex mixture.
Proceedings of Conference on Electrical Insulation and Dielectric Phenomena - CEIDP '96
In this article we develop a linear stability analysis for a dielectric liquid jet with charges o... more In this article we develop a linear stability analysis for a dielectric liquid jet with charges on its surface flowing at high speed in a gaseous atmosphere. We analyse the growth rate and the propagation velocity of a perturbation, the jet break-up and the influence of the charges on them
In this work we analyze the d.c. corona discharge between a wireplate electrode configuration pla... more In this work we analyze the d.c. corona discharge between a wireplate electrode configuration placed on the surface of an insulating cylinder. The influence of different parameters are analysed in order to characterize the discharge and to determine the best configuration to study the possibility of drag reduction of the flow acting in immersed bodies. A generalized glow regime seems the most suitable to undertake studies with this goal.
The authors have developed titanium oxide-based functionally graded materials (FGMs) offering spe... more The authors have developed titanium oxide-based functionally graded materials (FGMs) offering special properties of high relative permittivity and photocatalysing capability. In the experiment reported, four such FGMs, sintered at furnace temperatures of 673, 873, 1073 and 1273 °K, were examined for their electrical behaviour, particularly relative permittivity and dielectric loss tangent. The measurement frequencies used were 0.25 ∼ 50 MHz. The paper concludes with a discussion of whether these materials can be used as photocatalyses for the sake of improving the environment. This would open up new applications for FGMs in the area of field relaxation and photocatalysis.
1999 Annual Report Conference on Electrical Insulation and Dielectric Phenomena (Cat. No.99CH36319)
In high power transformers, pressboard and oil are required for electrical insulation. On the oth... more In high power transformers, pressboard and oil are required for electrical insulation. On the other hand, the oil is also used as a coolant of the system. The flow electrification process occurring at oil-pressboard interface seems to be initiating on electrical discharge incidents. Our recent investigations of electrification generated by an oil flow through different pressboards showed an influence of the pressboard degradation by artificial electrical discharges. Consequently the goal of this experimental study is to measure and to compare the convected space charge density value obtained with a brand new pressboard sample and with a pressboard coming from a damaged power transformer. The influence of an additive (BTA benzotriazol 1-2-3) in oil is also analyzed. The results show that the pressboard sample obtained from the damaged power transformer induces a high increase of flow electrification due to a modification of the exchange process at the pressboard-oil interface. On the other hand, an addition of BTA permits to reduce significantly flow electrification.
1998 Annual Report Conference on Electrical Insulation and Dielectric Phenomena (Cat. No.98CH36257)
The aim of this work is a better understanding of the flow electrification process occurring in h... more The aim of this work is a better understanding of the flow electrification process occurring in high power transformers. In order to characterize the effect of the pressboard degradation and the additive benzotriazol, the experiments consist in measuring the streaming currents generated by an oil flow through a pressboard sample. Two main results have been obtained: the addition of several
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