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Theoretical modes of electric arc
Vondrák, Michal ; Šenk, Josef (referee) ; Lázničková, Ilona (advisor)
This thesis deals with theoretical models of the electric arc. Plasma arc and plasma torch are explained. Basic approaches of electric arc modeling are described. The indirect method for the determination of the mean temperature and velocity at the exit of plazma jet plasmatron are discussed. Finally the simplified model with axially-cooled electric arc is described.
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Theoretical modes of electric arc
Vondrák, Michal ; Šenk, Josef (referee) ; Lázničková, Ilona (advisor)
This thesis deals with theoretical models of the electric arc. Plasma arc and plasma torch are explained. Basic approaches of electric arc modeling are described. The indirect method for the determination of the mean temperature and velocity at the exit of plazma jet plasmatron are discussed. Finally the simplified model with axially-cooled electric arc is described.
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Properties of Novel Hybrid Water-Gas DC Arc Plasma Torch
Chráska, Tomáš ; Hrabovský, Milan ; Glanc, Aleš ; Mušálek, Radek ; Medřický, Jan
A new type of plasma torch with combined stabilization of electric arc by water vortex and gas flow is presented. This hybrid water/gas stabilization offers the possibility of adjusting plasma jet parameters within a wide range from high-enthalpy low-density plasmas typical for liquid stabilized torches to lower enthalpy higher density plasmas generated in gas stabilized torches. Moreover, gas flow in the cathode part protects a cathode tip and thus a consumable graphite cathode used in water-only stabilized plasma torches could be replaced by a fixed tungsten cathode. Examples of hybrid WSP torch utilization for high temperature application are given.
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Observation of HF Cathode and ARC Root Inside Cutting Plasma Torch
Šonský, Jiří ; Gruber, Jan
Electric arc and a cathode of a cutting plasma torch was observed through fused silica window in a specially modified nozzle. Sample rate of used high-speed camera was up to 120 kHz, sufficient for detecting high-frequency fluctuations in arc plasma intensity, produced mainly by current ripple. Fluctuations were examined up to 60 kHz by Fast Fourier Transformation (FFT). Increased cathode material loss at start-up and shut-down phase of the plasma torch was observed. At start up phase, large number of small particles are ejected from the cathode. After electric current shuts down, large droplets of molten material are usually detected.
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Prostorové rozložení oscilací v modulovaném proudu plazmatu
Gruber, Jan ; Šonský, Jiří
Electric current in a vertically oriented DC plasma torch was modulated with frequencies varying in the range 15 Hz ? 7.5 kHz. Resulting plasma jet optical radiation was recorded by the high-speed CCD camera. The length of the record and the time resolution were sufficient for the application of the FFT yielding a detailed view of the oscillation phenomena in the plasma flow. Significant oscillations were identified and their distributions in the jet plane examined. In this work we show influence of current modulation on the dominant frequencies of oscillations and their spatial distributions.
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Comparism of Diagnostic Methods Employing Matrix of Photodiodes and Linear Camera
Šonský, Jiří
Both devices are composed of array of PIN photodiodes, amplifiers, multiplexer and analog-digital converter. Diferent layout of these devices lead in to diferent overall performance. Linear camera outperformed the photodiode matrix in horizontal resolution and total data rare, PIN photodiodes have higer sensivity, double line frequency and many times longer acquision time.
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