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Author: Foest, Rüdiger × End date: 2023 × Start date: 2023 × End date: 2022 × DDC: 670 ×

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    Energy Flux Characterisation of Atmospheric Pressure Plasma Spray Torches with Passive Thermal Probes
    (Boston, Mass. : Springer, 2022) Reck, Kristian A.; Hansen, Luka; Stummer, Maximilian; Kewitz, Thorben; Testrich, Holger; Hinterer, Andreas; Foest, Rüdiger; Kersten, Holger
    Passive thermal probes were applied on two different plasma spraying devices to gain a detailed understanding of the energy flux towards the substrate under atmospheric pressure. The challenge of very high thermal load was solved by using an advanced time-resolved measuring and evaluation technique. The combination with a controlled movement of the jets allowed to obtain insightful radial profiles. The energy flux to the substrate changes linearly to the electrical input power. When adding diatomic gases (H2/N2) to the gas mixture the energy flux increases significantly, suggesting a more efficient energy transport. For increasing the axial distance, the energy flux shows a quadratic reduction. The obtained radial profiles are exemplarily utilized to show the inhomogeneous effect of powder injection on the energy flux distribution.
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    Self-Consistent Cathode–Plasma Coupling and Role of the Fluid Flow Approach in Torch Modeling
    (Boston, Mass. : Springer, 2021) Baeva, Margarita; Zhu, Tao; Kewitz, Thorben; Testrich, Holger; Foest, Rüdiger
    A two-dimensional and stationary magnetohydrodynamic model of a plasma spray torch operated with argon is developed to predict the plasma properties in a steady operating mode. The model couples a submodel of a refractory cathode and its non-equilibrium boundary layer to a submodel of the plasma in local thermodynamic equilibrium in a self-consistent manner. The Navier–Stokes equations for a laminar and compressible flow are solved in terms of low and high Mach number numerical approaches. The results show that the Mach number can reach values close to one. Simulations are performed for electric currents of 600 A and 800 A, and gas flow rates of 40, 60, and 80 NLPM. The plasma parameters obtained by the two approaches differ, and the differences become more pronounced for higher currents and gas flow rates. The arc voltage, the electric power, and the thermal efficiency from both the low and high Mach number models of the plasma agree well with experimental findings for a current of 600 A and a flow rate of 40 NLPM. For higher currents and gas flow rates, the results of the low and high Mach number models gradually differ and underline the greater appropriateness of the high Mach number model.