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In plasma cutting systems, a highly constricted arc plasma is used to locally melt the material to be cut. The workpiece serves as the anode, and a narrow nozzle leads to the arc constriction between the cathode and the anode. The quality of the cut is dependent on the characteristics of the constricted arc near the anode surface, i.e. the temperature and velocity distributions downstream of the nozzle. To determine temperature distributions in the arc, spectroscopic measurements were made on a commercial oxygen plasma cutting system operating with a water-cooled rotating anode. The cutting system was operated with a current of 200 A with oxygen as plasma gas and air as shroud gas.Line intensity measurements were made of both atomic and ionic species of oxygen and nitrogen. Temperatures were derived using several methods, including absolute line intensity, Boltnnann plot and norm temperature (off-axis-peaking) method. Good agreement was observed between the derived temperature values for the different methods using the ion line emission, the centerline values being around 25000 K. Atom line emission data were distorted because of fluctuations in the radial intensity profile. These fluctuations had a frequency in the kHz range, and resulted in a change of the radial location of the maximum emission of the atomic line. Radial temperature profiles were obtained for several axial locations between the nozzle and the anode. Nitrogen emission was used to study the mixing between the oxygen plasma gas and the surrounding air shroud, and it was found that nitrogen reaches the arc center several nozzle diameters downstream of the nozzle exit. The changes in the arc temperature and nitrogen emission distribution, as well as the intensity fluctuations and arc symmetry, were investigated for different torch design parameters. This study shows that care must be taken to choose the appropriate spectroscopic method for temperature determination in a highly constricted arc with superimposed flow, but that for this arc any method based on ion line emission can give consistent values which may serve as design information for torch optimization.The arcanode attachment and anode heat fluxes play an important role for anode erosion characteristics and anode lifetime. A better knowledge of these phenomena is required to optimize the anode performance. In this study we have addressed the question of the interaction of the arc with an anode when there is a cold gas flow parallel to the anode surface forming a cold boundary layer and leading to a constant motion of the anode attachment with a corresponding fluctuation in plasma power. This situation is encountered in many applications of non-transferred plasma torches such as plasma spraying where the fluctuation in plasma jet power can have a detrimental influence on the quality of the produced coating.The motion of the anode attachment and the heat flux to the anode have been determined for a configuration where the arc axis is perpendicular to the anode surface with the plasma gas flo...

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An atmospheric-pressure helium plasma jet was used for the surface treatment of the electrodes in single-chamber solid oxide fuel cells (SC-SOFCs). The jet-type plasma source used in this study is suitable for the continuous and fine-area processing of materials, such as patterned electrodes. The basic plasma property was investigated by optical emission spectroscopy. Improvement in the performance of SC-SOFC was observed for the plasma-treated cell. From the scanning electron microscopy (SEM) observation, it was found that the surface morphology of the cell was largely changed. The increase in the area of the three-phase boundary among the electrode, electrolyte, and gas phase promoted electrochemical reactions. Under single-chamber operation condition at 850 °C, an open circuit voltage of 650 mV and a maximum power density of approximately 75 mW/cm2 were achieved for a coplanar-type cell.