Ashraf Yehia

• PhD
• Professor of the Experimental Plasma Physics at Department of Physics - Faculty of Science - Assiut University

An analytical model has been suggested in this paper, and it was validated experimentally to investigate the thermal energy loss in the dielectric barrier discharge plasma. The dielectric barrier discharge plasma has been formed inside a coaxial cylindrical reactor equipped with a simple cooling system. A sinusoidal ac voltage was applied to the re...

This paper is aimed to perform an analytical study to identify the optimum operating conditions for the ozone generation in the dielectric barrier discharges. The dielectric barrier discharges have been formed inside a reactor in the form of two coaxial cylindrical electrodes. The reactor was fed by constant flow rates from the dry air and the oxyg...

In this paper, the electrical characteristics of both the dielectric barrier corona discharge and the usual ac corona discharge have been studied in parallel with the ozone generation under the same operating conditions. Therefore, the corona discharges were formed inside two identical reactors in the form of a coaxial wire-to-cylinder with and wit...

A pulsed microwave-excited atmospheric pressure plasma jet MWAPPJ in helium, has been investigated by optical emission spectroscopy OES. Beside helium spectral lines various excited species such as atomic oxygen OI, hydrogen Hα line, N2⁺ ion and nitrogen molecule species N2 (C³Πu) which are responsible for metal surface activation. The rotational T...

The electrical characteristics of the dielectric barrier discharges have been studied in this paper under different operating conditions. The dielectric barrier discharges were formed inside two reactors composed of electrodes in the shape of two parallel plates. The dielectric layers inside these reactors were pasted on the surface of one electrod...

This paper is aimed to study the characteristics of the positive dc corona discharges in single wire-duct electrostatic precipitators. Therefore, the corona discharges were formed inside dry air fed single wire-duct reactor under positive dc voltage at the normal atmospheric conditions. The corona current-voltage characteristics curves have been m...

An experimental study was made in this paper to investigate the relation between the places of the dielectric barriers, which cover the surfaces of the electrodes in the coaxial cylindrical reactors, and the rate of change of the electric power that is consumed in forming silent discharges. Therefore, silent discharges have been formed inside three...

An analytical study was made in this paper for calculating the ozone generation by negative dc corona discharges. The corona discharges were formed in a coaxial wire-cylinder reactor. The reactor was fed by dry air flowing with constant rates at atmospheric pressure and room temperature, and stressed by a negative dc voltage. The current-voltage ch...

An analytical study was made in this paper to calculate the ozone generation inside an ac corona discharge reactor. The corona discharges were formed in a coaxial wire-cylinder reactor. The reactor was fed by dry air flowing with constant rates at atmospheric pressure and room temperature and stressed by an ac voltage. Concentration of the ozone ge...

Two equations have been derived in this paper for expecting the ozone generation inside dry air fed silent discharge reactors. The derived equations have been built on theories of the silent discharges and their applications, reported in the literature. The two equations have been investigated individually with experimental results for ozone genera...

Corona discharges in gases exist under several distinctive forms. In this paper, a survey study has been made of ac corona discharge modes generated in some different gases fed in a wire-duct reactor with a constant rate of flowing at atmospheric pressure. The properties of different corona modes are analyzed under some condition transitions from T...

An experimental parametric study is made to investigate how the electrical corona discharge characteristics are influenced by the geometrical configuration and dimensions of the reactor and the electrode polarity of the applied voltage. Furthermore, features of the corona discharge plasma formed around the stressed electrode in some different gases...

The physical mechanisms of the electrical discharges formed in coaxial cylindrical reactors have been investigated in this paper under different operating conditions for the reactors. The reactors were fed by natural air flowing with a constant rate at atmospheric conditions and stressed by an ac voltage. The wave form of the ac voltage applied to...

A theoretical equation has been derived in this paper for calculation of ozone generation by positive dc corona discharge in coaxial wire-cylinder reactors. The derived equation has been based on the theories of the positive dc coronas reported in the literature and extended to account the ozone destruction within the corona discharge plasma genera...

The aim of this paper is to suppress the ozone production in dc corona discharges, and is to report the effect of material of the discharge electrode on the ozone production. In this study, corona discharges were generated in a coaxial wire-cylinder reactor stressed by positive or negative dc voltage. A set of high purity wires made of different me...

This paper is aimed to investigating how the electrical power consumed in generating silent discharges is influenced by the width of the annular discharge gap in the reactor. The silent discharges have been generated in conventional tubular reactors forming annular discharge gaps of 1×10-3-, 2×10-3-, and 3×10-3-m width, with one dielectric barrier...

The aim of this work is to study the analytical calculation of ozone generation in an ac corona discharge reactor. The corona discharges were generated in a dry air-fed wire-duct reactor stressed by an ac voltage at atmospheric pressure and room temperature. The current-voltage characteristics of the ac corona discharges relative to ozone generatio...

We have studied the effect of Zn substitution on the temperature dependence of the resistivity and the Curie temperature T p of La1−x Cax Mn1−y Zny O3 system (with x=0, y=0, and x=0.33, 0.00≤y≤0.15) during their pass to the paramagnetic conducting phase. All the specimens show a clear metal-insulator transition passing through the Curie temperature...

This paper is aimed at investigating how the characteristics of corona and silent discharges including ozone generation are influenced by geometry of the discharge reactor. The corona discharges have been generated in coaxial wire-cylinder and wire-duct reactors stressed by dc and ac voltages. The silent discharges have been generated in the same r...

The aim of this paper is to study the effects of the magnitude and direction of air flow rate on the characteristics of the corona discharge generated in a wire-duct reactor. Two air flow directions were attempted: one parallel to, and the other normal to the discharge wire in the reactor. The corona current-voltage characteristics correlative with...

A review is made of the theories proposed for quantitative assessment of ozone generation in dc-energized electrostatic precipitators. The underlying simplifying assumptions adopted by these theories are discussed. Among the most important assumptions is ignoring the ozone destruction which takes place at high ozone generation rates. Therefore, a m...

An experimental study was carried-out to investigate the effect of magnitude and direction of the air flow rate on characteristics of the corona discharge generated in a wire-duct reactor. The study is aimed to understand the mechanism played by magnitude and direction of the air flow rate on efficiency of ESPs that have been widely used in industr...

The DC corona current-voltage characteristics of coaxial cylindrical configurations with straight and helical wires are studied. Oscillograms describing the spatial development of streamers from helical and straight wires are recorded under fast, high-voltage pulses. These streamers proceed from the discharge wire (helical or straight) toward the o...