2016 年 11 巻 4 号 p. JFST0024
In this work, three-dimensional, time-dependent magnetohydrodynamic (MHD) simulations of a direct-current (dc) plasma spray with an externally applied magnetic field are performed, and also the trajectories and heating histories of in-flight particles in a plasma spray jet are analyzed by Lagrangian method with one-way coupling between particle and plasma jet. The working gas is pure argon (Ar) and the material of in-flight particles is zirconium dioxide (ZrO2). The representative values of operating current and magnetic flux density of externally applied magnetic field in this work are 350 A and 0.8 T, respectively. Numerical results obtained in the MHD simulation demonstrate that the use of externally applied magnetic field yields the rotation of the arc root on the anode. This rotation generates a plasma jet with a swirling component. Furthermore, it is shown from the numerical results that applying the magnetic field increases the operating voltage and thus boosts an amount of input power compared to the one without applying it. The analytical results of in-flight particles suggest that the impact positions of in-flight particles on the substrate in the case with the externally applied magnetic field change temporally due to the swirling component of the plasma jet, even when the injected position of particles is fixed. However, the utilization of externally applied magnetic field enhances heat transfer to particles, which leads to impacting of particles on substrate with well-molten state because of higher enthalpy plasma jet.
