DC Positive Streamer Corona Research Articles

Subnanosecond spectral diagnostics of streamer discharges: I. Basic experimental results

We have carried out cross-correlated high-resolved electrodynamical and spectro-optical measurements of different characterizations in a high-stable regime of the dc positive streamer corona in short gap in atmospheric density laboratory air. Special attention was paid to the measurement of absolute intensities of the second positive (SPS) and first negative (FNS) systems of molecular nitrogen as well as for further improvement in the spatiotemporal resolution along with high synchronization and stability. In the cathode region, the FNS and SPS emission temporal waveforms during primary streamer development have been recorded with the cross-correlated synchronization not worse than 0.1 ns and spatiotemporal resolution around 0.01–0.1 mm along the axis and 0.2–0.4 ns in the multiphoton mode of the PMT-based detector and in the single pulse acquisition mode of the measuring system. The shortest rise-times of the corresponding voltage waveforms were found to be around 0.3–0.4 ns for the SPS (0,0)-band and 0.2–0.3 ns for the FNS (0,0)-band, the full widths at the half-altitude ranging around 1.4–1.5 ns and 0.5–0.6 ns, respectively. Again, the absolute values and the ratio of the synchronized temporal waveforms of the SPS to the FNS (0,0)-bands have been recorded across the entire gap in the accumulation and averaging acquisition mode of the measuring system with somewhat worse temporal resolution but with adequate stability and stochasticity. Various supporting characteristics such as the synchronous anode and cathode electric current waveforms, the streamer velocity and the gas temperature within the streamer channel region have been measured and presented as well. All the data in the aggregate allow reconstruction of the 2D structure of the streamer head generally and of the electric field and the electron number density partially.

LIF imaging of OH radicals in DC positive streamer coronas

In this study, the LIF detection of the hydroxyl (OH) radicals was performed in a nozzle-to-plane electrode system having an electrode gap of 30 mm during the steady-state positive streamer corona discharge at atmospheric pressure. For monitoring the ground-state OH radicals, OH transition [ A 2 Σ +( v′ = 1) ← X 2Π( v″ = 0)] at 282 nm was used. The time relationship between the regular streamer coronas, laser pulse, OH fluorescence and laser-induced streamer was measured. The time dependence of OH radicals between the successive streamers was measured for the evaluation of OH dynamics when the discharge was in a steady-state condition. The two-dimensional OH distribution in the DC streamer corona discharge was observed. The obtained results showed that the ground-state OH radicals were generated mainly in the filamentary part of the streamers. It was found that LIF detectable amount of ground-state OH radicals stayed in the region where streamers propagate during the steady-state DC positive streamer corona in open air.

Two-dimensional distribution of ground-state NO density by LIF technique in DC needle-to-plate positive streamer coronas during NO removal processing

Two-dimensional distribution of the ground-state NO molecules density was investigated using a laser-induced fluorescence (LIF) technique in a DC positive streamer corona reactor (needle-to-plate electrode geometry) during NO removal from a flue gas simulator (NO/air). NO density in the corona discharge reactor was monitored under the steady-state DC corona discharge condition. It was found that NO molecules density decreased due to the corona discharge processing not only in the discharging region but also in the upstream vicinity of the discharge.

Comparison of Copper and Stainless Steel Used for Low Voltage Electrode in Wire-to-Plane Electrode Configuration for NO x Treatment

Copper and stainless steel have been investigated as low voltage electrodes in wire-to-plane electrode configuration under conditions of DC positive streamer corona discharge. Copper has been chosen due to its well-known catalytic activity while, on the other hand, stainless steel was selected as an opposite extreme to copper–due to its high passivity. The initial gas contained 400 ppm NO/N2, 10% O2, and water vapors or 40% aqueous solution citric acid. Removal rates of NOx have been calculated as a function of the applied voltage. Results have shown that the highest removal rate, 56% for NO, have been obtained while employing Cu plate and citric acid. We suppose that Cu participates in the process of treatment, while stainless remains inactive. Therefore, while using a stainless steel plate, removal rates have reached lower values than while employing a copper plate.

DeNO x Characteristics of Tungsten and Copper Wire Electrodes in Wire-to-Plane Configuration under Conditions of DC Positive Streamer Corona

Removal rates of NOx have been examined for two materials, W and Cu, used as a high-voltage electrode in a wire-to-plane configuration, under conditions of a DC positive streamer or positive corona discharge. Input gas composition and series resistance were varied, and the highest removal rate was obtained for water including gas with a W electrode and low resistance value. Discharge characteristics with both the wires are described.

ワイヤ対平板電極を用いた正ストリーマコロナ放電によるNO<sub>x</sub>処理

ワイヤ対平板電極を用いた正ストリーマコロナ放電によるNO<sub>x</sub>処理

5315. Enhancement of DC positive streamer corona in a point-plane gap in air due to addition of a small amount of an electronegative gas: Y Gosho,J Phys D: Appl Phys,14 (11), 1981, 2035–2046

5315. Enhancement of DC positive streamer corona in a point-plane gap in air due to addition of a small amount of an electronegative gas: Y Gosho,J Phys D: Appl Phys,14 (11), 1981, 2035–2046

Enhancement of DC positive streamer corona in a point-plane gap in air due to addition of a small amount of an electronegative gas

When the potential across a positive-point-plane gap in air is increased, discharges proceed in order as follows: intermittent streamer corona, glow corona and spark. The streamer is markedly enhanced by adding a small amount of an electronegative gas e.g. Cl2, NO2 NO etc. This is because the streamer can be initiated at a higher potential than is corona onset potential due to extinction of the glow corona. This effect becomes more marked with increased concentration of the additive. For a gap system mounted in an enclosed chamber (air), the streamer formation is enhanced by successive discharges and a pronounced fall of the sparking potential is expected to occur. This is due to NO2 formation resulting from successive discharges.