Browsing by Author "Namihira, T."

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Ozone generation in dry air using pulsed discharges with and without a solid dielectric layer
(IEEE Transactions on Dielectrics and Electrical Insulation, 2001) Samaranayake, W.J.M.; Miyahara, Y.; Namihira, T.; Katsuki, S.; Hackam, R.; Akiyama, H.
Energy efficient generation of ozone is very important because ozone is being used increasingly in a wide range of industrial applications. Ozonizers usually use dielectric barrier discharges and employ alternating current (ac) with consequent heat generation, which necessitates cooling. In the present study, very short duration pulsed voltage is employed resulting in reduced heating of the gas and discharge reactor. A comparison of ozone generation in dry air using a coaxial concentric electrode system with and without a solid dielectric layer is reported. Two types of dielectric layers were employed, ceramic and polyvinylchloride (pvc). The effects of peak pulsed voltage (12.5 to 62 kV), reactor length (0.1 to 1 m), pulse repetition rate (25 to 400 pulses per second, pps), gas flow rate (1.5 to 3.0 1/min) and variation of the pitch length of the spiral wire forming the central electrode (5 to 10 mm) on the concentration and production yield of ozone (g/kWh) are reported. A comparison is made between the performance of discharge reactors with (ceramic reactor Type IIC and pvc reactor Type IIP) and without (reactor Type I) a dielectric layer, using the same electrode gap separation (15 mm) and reactor lengths (0.157 and 1 m). High production yields of ozone in dry air of ~125 52 and 60 g/kWh were obtained when using, respectively ceramic, pvc, and no dielectric layer, for a fixed pulse rate of 100 pps, 15 1/min now rate and for a relatively short length of the reactor of 157 mm
Ozone production using cylindrical reactors with and without solid dielectric layers in dry air
(1999) Samaranayake, W.J.M.; Miyahara, Y.; Namihira, T.; Katsuki, S.; Hackam, R.; Akiyama, H.
An investigation into ozone production in dry air-fed ozonizers under different operating gas discharge conditions at a pressure of 1.01?105 Pa using a spiral wire made to a cylindrical configuration is reported. A magnetic pulse compressor provided voltage and current pulses with a repetition rate of up to 500 pulses per second (pps). A cylindrical configuration with ceramic and polyvinyl chloride (PVC) on the outer electrode and without solid dielectric were used. High production yields were obtained of ozone of about 122, 60 and 57 g/kWh by the ceramic, PVC and without dielectric layers, respectively for 15.7-cm length reactor. The length of the cylindrical reactors was varied from 15.7 cm to 1 m. The flow rate of the gas was varied from 1.5 to 3.0 1/min. The dependence of the concentration and the production yield of ozone on different pulse voltages (17 to 63 kV) and varying pulse repetition rate (25 to 400 pps) with and without solid dielectric layer is reported. This investigation has industrial applications for construction of advanced ozone generators
Ozone production using pulsed dielectric barrier discharge in oxygen
(IEEE Transactions on Dielectrics and Electrical Insulation, 2000) Samaranayake, W.J.M.; Miyahara, Y.; Namihira, T.; Katsuki, S.; Hackam, R.; Akiyama, H.
The production of ozone was investigated using a dielectric barrier discharge in oxygen, and employing short-duration pulsed power. The dependence of the ozone concentration (parts per million, ppm) and ozone production yield (g(O3)/kWh) on the peak pulsed voltage (17.5 to 57.9 kV) and the pulse repetition rate (25 to 400 pulses/s, pps) were investigated. In the present study, the following parameters were kept constant: a pressure of 1.01?105 Pa, a temperature of 26�4�C a gas flow rate of 3.0 1/min and a gaseous gap length of 11 mm. A concentric coaxial cylindrical reactor was used. A spiral copper wire (1 mm in diameter) was wound on a polyvinylchloride (PVC) cylindrical configuration (26 mm in diameter) and placed centrally in a concentric coaxial electrode system with 4 mm thick PVC dielectric layer adjacent to a copper outer electrode of 58 mm in internal diameter. HV and current pulses were provided by a magnetic pulse compressor power source
Pulsed power production of ozone in O2/N2 in a coaxial reactor without dielectric layer
(IEEE Transactions on Dielectrics and Electrical Insulation, 2001) Samaranayake, W.J.M.; Miyahara, Y.; Namihira, T.; Katsuki, S.; Hackam, R.; Akiyama, H.
Very short duration pulsed streamer discharges have been used to produce ozone in a gas mixture of nitrogen and oxygen at atmospheric pressure. The ratio of nitrogen to oxygen in the mixture was varied in the range from 2.5/0.5 to 0.5/2.5, while maintaining a total flow rate of 3 l/min. The production of ozone was found to be higher for a specific mixture ratio of N2/O2 than that in oxygen or in dry air. The production of ozone in O2 was higher than that in dry air. The production yield of ozone (g/kWh) increased with decreasing nitrogen in the O2/N2 mixture. It has been found that the peak of the streamer discharge current decreased with time after application of the pulsed power. This decrease in the current corresponded with the increase in the ozone production and is attributed to the loss of electrons in the discharge current due to their attachment to ozone to form negative ions
Pulsed power production of ozone using nonthermal gas discharges
(IEEE Transactions on Dielectrics and Electrical Insulation, 2001) Samaranayake, W.J.M.; Miyahar, Y.; Namihira, T.; Katsuki, S.; Sakugawa, T.; Hackam, R.; Akiyama, H.
This paper discusses ozone synthesis by employing a short duration (?120 ns) of pulsed power and using positive voltages in dry air and in oxygen, with and without a dielectric barrier. Ozone concentration and ozone production yield (efficiency) are measured at various peak pulsed voltages, pulse repetition rates, varying input energy densities, and different gaseous gap spacings.
Pulsed streamer discharge characteristics of ozone production in dry air
(IEEE Transactions on Dielectrics and Electrical Insulation, 2000) Samaranayake, W.J.M.; Miyahara, Y.; Namihira, T.; Katsuki, S.; Sakugawa, T.; Hackam, R.; Akiyama, H.
Experimental investigation of HV short pulsed streamer discharges in dry air-fed ozonizers under various operating conditions are reported. Ozone concentration, energy input and ozone production yield (efficiency) were measured at various voltages (14 to 37 kV), pulse repetition rates (25 to 400 pulses per second, pps), flow rates (1.5 to 3.0 1/min) and different gap spacings (10 to 20 mm) at a pressure of 1.01?105 Pa in dry air. A spiral copper wire (1 mm in diameter) made to a cylindrical configuration (18 to 38 mm in diameter) in a concentric coaxial electrode system of various dimensions was employed. A magnetic pulse compressor provided the HV and current pulses. Higher voltage and higher repetition rates yielded higher concentrations of ozone at a fixed air flow rate. The present investigation was extended to assess the performance of this pulsed ozone generator using dry air under desired conditions of high concentration and high yield of ozone for industrial applications