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Experimental investigation of electric arc behavior during cutting of stainless steel
Kavka, Tetyana ; Mašláni, Alan ; Konrád, Miloš ; Tossens, S.
The present work is devoted to experimental investigation of electric arc behaviour during cutting of stainless steel. The goal of this work is to define influence of arc voltage fluctuations and anode attachment behaviour on the cutting performance. In most cases the anode attachment was verz luminous and was observed far from the main arc column close to the plate top. The cut material exhibited stronger surface roughness at the anode attachment location. The measured voltage traces showed a so-called restrike mode of oscillations of different frequencies and amplitudes.
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Vliv připojeni oblouku k anodě na proud termického plazmatu
Chumak, Oleksiy ; Kavka, Tetyana ; Hrabovský, Milan
The paper examines an effect of an argon amount on the thermal plasma jet generated from water/argon mixture in a dc arc plasma torch. In spite of an increase of plasma velocity with an addition of argon a decrease of plasma jet length is observed for bigger argon amount in the plasma. The investigation was based on an analysis of a jet structure based on imaging of the plasma jet by a CCD camera. Statistical processing of plasma jet photographs provided information about a jet shape and its fluctuations space distribution. It was found that an argon amount increase caused significant intensification of the plasma jet fluctuations.
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Výzkum vlivu množství argony na stabilitu proudu Ar-H-O plazmatu
Chumak, Oleksiy ; Kavka, Tetyana ; Hrabovský, Milan
The paper examines an effect of an argon amount on the thermal plasma jet generated from water/argon mixture in a dc arc plasma torch. In spite of an increase of plasma velocity with an addition of argon a decrease of plasma jet length is observed for bigger argon amount in the plasma. The investigation was based on an analysis of a jet structure based on imaging of the plasma jet by a CCD camera. Statistical processing of plasma jet photographs provided information about a jet shape and its fluctuations space distribution. It was found that an argon amount increase caused significant intensification of the plasma jet fluctuations.
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Zplyňování dřeva v plazmatu a produkce plynu s nízkým obsahem dehtů
Hlína, Michal ; Hrabovský, Milan ; Kopecký, Vladimír ; Konrád, Miloš ; Kavka, Tetyana ; Skoblja, S.
Tar content in gas produced by the gasification of biomass always plays an important role because high tar content disables some potentialities of the further treatment of the produced gas. There is a strong effort to produce gas with low tar content from this point of view. High concentrations of hydrogen and carbon monoxide also advance possibilities of the usage of the produced gas. Experiments were carried out in a reactor for plasma gasification equipped with hybrid gas-water stabilized DC torch. They confirmed that the reactor is absolutely suitable for this purpose mainly due to extremely low flow of plasma composed of argon, hydrogen and oxygen and its high inner temperature. The measurements of the tar content, using wood as a treated material, were based on SPE method and the determination of benzene and toluene in a gas phase revealed really low concentrations of tar, mostly below 10 mg/Nm3.
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Procesy v Gerdienovem oblouku generovaném hybridním plynově-vodním plazmatronem
Kavka, Tetyana ; Chumak, Oleksiy ; Sember, Viktor ; Hrabovský, Milan
In the present work the basic principles of the Gerdien arc are described. The arc was generated in the plasma torch with hybrid stabilisation of the arc by water and argon. The paper discusses physical processes determining the arc behaviour and governing plasma generation. As the main mechanism of the plasma generation in the water stabilized part is evaporation from the inner surface of the water vortex, heating and ionisation of vapour, the plasma gas flow rate and composition depends on the working parameters of the torch. The amount of the evaporated water cannot be directly measured and was estimated from the mass and power balances of the torch. The flow rate and composition of the generated plasma for different arc currents and argon flow rates have been studied. Increase of the arc current resulted in higher amount of evaporated water, while modification of the argon flow rate did not influence the evaporation rate.
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Ofukování termického proudu plazmatu generovaného plazmatronem
Kavka, Tetyana ; Hrabovský, Milan ; Chumak, Oleksiy ; Kopecký, Vladimír
The ambient air is entrained intensively into atmospheric pressure thermal plasma jets. A system for shielding plasma jet has been used to improve jet characteristics and reduce oxygen content. Different gases have been applied as a shroud gas – argon, acetylene, methane, mixtures of acetylene-nitrogen and hydrogen-nitrogen. All shroud gases used in experiments affected plasma jet making the profiles of the jet characteristics flattened with higher temperatures and velocities and reduced amount of oxygen.
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Difuzní proud v hraniční oblasti oblouku měřený elektrickými sondami
Chumak, Oleksiy ; Hrabovský, Milan ; Kavka, Tetyana ; Kopecký, Vladimír
Electric probes were used for investigation of an intermediate layer between the arc and anode surface in regions outside the main current channel. Distributions of a diffuse current and the potential were measured. Resistance and heating of the intermediate layer by diffuse current were evaluated. It was found that not only the value of diffuse current strongly depends on distance from the arc but also the shape of the distribution and the position of the maximum of the current change with the distance. These trends can be explained by expanding of the plasma jet. Evaluated equivalent intermediate layer resistance shows widening of the conductive region in a stream wise direction. Variation of resistivity of the intermediate layer is much higher than variation of the potential drop on the layer. That means that distributed current as well as Joule heating of the layer are generally controlled by distributed resistance.
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Studium difuzního proudu na hranici oblouku pomocí elektrických sond
Chumak, Oleksiy ; Hrabovský, Milan ; Kavka, Tetyana ; Kopecký, Vladimír
Electric probes were used for investigation of an intermediate layer between the arc and anode surface in regions outside the main current channel. Distributions of a diffuse current and the potential were measured. Resistance and heating of the intermediate layer by diffuse current were evaluated.It was found that not only the value of diffuse current strongly depends on distance from the arc but also the shape of the distribution and the position of the maximum of the current change with the distance. These trends can be explained by expanding of the plasma jet. Evaluated equivalent intermediate layer resistance shows widening of the conductive region in a stream wise direction. Variation of resistivity of the intermediate layer is much higher than variation of the potential drop on the layer. That means that distributed current as well as Joule heating of the layer are generally controlled by distributed resistance.
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