Elektrische Bögen und thermisches Plasma

Finkelnburg, Wolfgang; Maecker, H.

doi:10.1007/978-3-642-45847-7_4

Cited by 161 publications

(98 citation statements)

References 151 publications

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“…It has been known for a long time that the column of electric arcs can be well represented as a plasma in local thermodynamic equilibrium; Finkenburg and Maecker [7]. The basic equations defining the temperature are conceptually simple, namely the equations for conservation of mass, energy, momentum and current.…”

Section: Arc Columnmentioning

confidence: 99%

A simplified unified theory of arcs and their electrodes

Lowke

Morrow

Haidar

1997

J. Phys. D: Appl. Phys.

234

210

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Abstract. For arcs at atmospheric pressure which have cathodes that are thermionic emitters, it is possible to calculate the major properties of the arc and the electrodes as a function of current, by accounting for electrode shape and the heat transfer processes occurring at the surface of the electrodes. Such processes occur due to eleclron and ion emission and absorption and also from radiation emission and absorption. Electrical resistance of the plasma near the electrodes is calculated either by laking account of ambipolar diffusion or simply using the local plasma value, with mesh sizes sufficiently large to account for ambipolar diffusion. Derived temperature profiles are in fair agreement with experiment. Results of electrode temperatures and arc melting effects, including such phenomena as the transition from globular to spray modes in arc welding, are also in good agreement with experiment. Prediction of properties for non-thermionic cathodes still constitute a major problem. Approximate calculations indicate that electrons at the surface of the non-thermionic cathodes may be produced by photo ionisation of neutral atoms rather than by field emission.

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Section: Arc Columnmentioning

confidence: 99%

A simplified unified theory of arcs and their electrodes

Lowke

Morrow

Haidar

1997

J. Phys. D: Appl. Phys.

234

210

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“…A large number of studies (Jones and Fang 1980;Finkelnburg and Maecker 1956) on these aspects have been undertaken in the past. These studies highlight the phenomenal features and constraints associated with an electric arc.…”

Section: The Electric Arc Phenomenonmentioning

confidence: 99%

Technological Challenges in Thermal Plasma Production

Ramakrishnan¹

1995

Aust. J. Phys.

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Thermal plasmas, generated by electric arc discharges, are used in a variety of industrial applications. The electric arc is a constricted electrical discharge with a high temperature in the range 6000-25,000 K. These characteristics are useful in plasma cutting, spraying, welding and specific areas of material processing. The thermal plasma technology is an enabling process technology and its status in the market depends upon its advantages over competing technologies. A few technological challenges to enhance the status of plasma technology are to improve the utilisation of the unique characteristics of the electric arc and to provide enhanced control of the process. In particular, new solutions are required for increasing the plasma-material interaction, controlling the electrode roots and controlling the thermal power generated by the arcing process. IntroductionA thermal plasma is often considered as a plasma in which local thermodynamic equilibrium (LTE). conditions prevail. Under LTE conditions, the heavy particles in the plasma have approximately the same temperature as the electrons and hence the plasma has a high temperature. This allows the plasma to be used in a number of industrial processes requiring process heat at a high temperature (Pfender 1988). Typical applications of thermal plasmas in industry include joining of metals, plasma cutting, plasma spraying, arc wire spraying, plasma surfacing and material processing.Thermal plasma technology is essentially a process technology that enables the development of an industrial process to manufacture a product that meets market demands. The success of an application of plasma technology in industry will depend upon the technical suitability and advantages the process offers and the cost of the final product.Thermal plasma technology is based on the physical phenomenon of electrical discharges. The basic properties and generic features of the phenomenon create a unique position for the industrial applicability of the process. On the other hand, the limitations and the constraints imposed by the phenomenon on the application process have a strong bearing on the total cost and hence on the acceptance of the process by industry. In this paper, the advantages of plasma technology, its phenomenal constraints and future challenges for technology developments are highlighted.

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“…Pertinent Iiterature references on the electrode regions up to 1955 are given by Finkeinburg and Maecker. 34 A more comprehensive review listing 645 references has been published by Ecker 5 summarizing relevant work on this subject up to 1959. Ecker stressesin his treatment the basic physics involved in the electrode regions with emphasis on low intensity arcs, whereas Guile 36 in a later review which includes 238 references emphasizes those aspects which are of interest for engineers involved in arc applications, particularly in the application of high intensity arcs.…”

Section: Electrode Beat Transfer (A) General Considerationsmentioning

confidence: 99%

Heat Transfer from Thermal Plasmas to Neighboring Walls or Electrodes

Pfender¹

1976

Pure and Applied Chemistry

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Abstrac:t-A successful exploitation of thermal plasmas in the field of high temperature chemistry and material processing requires a fundamental understanding of the interaction between a plasma and matter in the condensed phase. In this paper some of the basic aspects involved in the heat exchange between a thermal plasma and solids or liquids are reviewed, with emphasis on recent experimental results obtained at the U niversity of Minnesota. These results refer to plasma heat transfer situations with and without electric current flow to or from the surface under consideration. For both Situations methods have been developed which allow fairly accurate measurements of local heat fluxes over a wide range of plasma parameters. An effective utilization and exploitation of the plasma state requires a thorough understanding of the heat transfer process from a plasma to a solid or a liquid. This process is much more complicated than in the case of an ordinary gas. The existence of free electrons and positive ions in a plasma and the steep gradients of the plasma parameters, particularly in the vicinity of walls or electrodes, give rise to a number of effects which are still poorly understood. The interaction with relatively strong radiation field~ which are typical for thermal plasmas, complicates the situation further.Research in the field of plasma heat transfer received a strong impetus by plasma applications related to space fiight and reentry simulation. Relevant Iiterature references are summarized in Ref. l.There seems to be renewed interest in this field, precipitated by the energy crisis. Both the availability of nuclear fuels and the abundant supplies of coal suggest that an Electric Energy Economy may be at least part of the solution to the long term energy problems. A shift to electricity as the major energy base will have a profound impact on high temperature chemistry and high temperature material processing for which plasma processes may find increasing applications. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]

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Elektrische Bögen und thermisches Plasma

Cited by 161 publications

References 151 publications

A simplified unified theory of arcs and their electrodes

A simplified unified theory of arcs and their electrodes

Technological Challenges in Thermal Plasma Production

Heat Transfer from Thermal Plasmas to Neighboring Walls or Electrodes

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