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Measuring of Mean Plasma Electrical Conductivity in Anode Area of Plasma Torches with an External Anode
Ondáč, Peter ; Mašláni, Alan ; Hrabovský, Milan
We developed a non-intrusive direct procedure of measuring an average electrical conductivity of a plasma volume in hot anode areas of those plasma torches. For our measurements, we used a high-speed camera, a high-voltage probe, and a hybrid water–argon plasma torch. The measurements were made for various values of ambient pressure, arc electric current, and argon flow rate. The measured plasma conductivity is in agreement with a model, camera observations and indirectly also with spectroscopy measurements. The procedure provides missing experimental data on the average plasma electrical conductivity and estimates average plasma temperature in the anode areas. The procedure can be theoretically used in every plasma torch where the anode arc attachment movement can be observed during a restrike process\n
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Enthalpy Probe Diagnostics of Steam/Argon Plasma Jet
Hlína, Michal ; Hrabovský, Milan
DC plasma torch with argon/water stabilization features extreme properties of the exiting plasma jet. The plasma mass flow rate is very low while the temperature reaches very high values. Plasma properties were measured by enthalpy probe connected to a mass spectrometer. The measurements of enthalpy, temperature, density and dynamic pressure were carried out for three different arc currents and at atmospheric pressure. The dependences of plasma characteristics on arc current were shown.
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Arc–Anode Attachment Area in DC Arc Plasma Torch at Low Pressure
Ondáč, Peter ; Mašláni, Alan ; Hrabovský, Milan
Studying the processes in the anode attachment area of a DC arc plasma torch helps to extend the lifetime of the anode, stabilize the plasma flow for plasma spraying and better understand the movement of the anode attachment. In this work, such processes were studied at low pressure, by a non-disturbing method, using a high-speed camera and a high voltage probe. We also found pressure ranges, in which the following transitions were observed: the constricted/diffuse anode attachment, and subsonic/supersonic plasma jet\n
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Photocatalytic Decomposition of Wastewater from the Production of Explosives
Brom, Petr ; Brožek, Vlastimil ; Březina, Václav ; Hlína, Michal ; Mastný, L. ; Novák, M.
Water stabilized plasma generator WSP® H-500, operating on the principle of Gerdien arc was used for the photocatalytic decomposition of furazan- and picraminate-based explosives. The generator emits intensive radiation in the range of 300-660 nm, which allows not only to activate photocatalysts based on TiO2, but also other semiconductor oxides with a narrower band gap, such as tungsten oxide. The photocatalytic decomposition of sewage and slurries containing the potassium salt of 4-hydroxy-4,6-dihydro-5,7- dinitrobenzofurazane-3-oxide (KDNBF) or sodium picraminate (NaC6H4N3O5) was performed using the anatase paste and newly developed photocatalyst produced by the company Precheza a.s. The photocatalytic reactor was built using a quartz tube coil with an internal volume of 650 ml, with a nominal size of the irradiated area of 7.5 dm2 (value reduced by the area of the gaps between coil turns) to enable the flow the processing solution or suspension of up to 10 l / min. The centre of the coil is exposed to the plasma jet with the intensity\nof 80 kW; of which 15 kW is transformed into the light radiation. 11% of the radiation output was used for the presented experiments. The time of exposition was 45 mins and 20 l of solution were treated. In the case of KDNBF, 90% of the compound was decomposed. Moreover, 100% of sodium picraminate were decomposed after 15 minutes into low-molecular inorganic compounds. Advantage of the assembly is the ability to treat highly dangerous chemical compounds in a closed cycle and test selective catalyst
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Investigation of Anode Attachment Area in Water/Argon Stabilized Plasma Arc
Ondáč, Peter ; Mašláni, Alan ; Hrabovský, Milan
Arc-anode attachment in a DC plasma arc stabilized by water vortex and argon, influences power distribution in the plasma, lifetime of the anode and also flow structure of the plasma jet. A movement of the attachment and the surrounding plasma has been directly observed by using a high-speed camera (max. 1,080,000 fps). The observations were compared with cathode–anode voltage measurements (sample rate 80 MHz). More than one attachment was observed in one frame with exposure time 0.25 μs or 0.29 μs. We have directly measured average velocities of the attachments and hydrodynamic waves above them, as well as the characteristic dwell times and dwell frequencies of the attachments
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