| A study of flight, impact, and solidification of molten ceramic droplets generated by suspension plasma spraying (SPS) is conducted. A three-dimensional model is developed for predicting behavior of droplets generated by SPS impacting a solid substrate. The model combines Smoothed Particle Hydrodynamics (SPH) integral interpolations with enthalpy formulations to capture the phase change process (solidification/melting). Surface tension is modeled as an internal force between all particles, that will be canceled in the bulk of fluid and generate unbalanced surface tension forces near the free surface. A Finite-Volume solver is also used to predict properties of the droplets at the time of reaching the substrate, i.e. temperature, velocity, and diameter. This solver uses discrete phase models to track flight, evaporation, and atomization of suspension droplets injected into plasma flow. Effects of high temperature gradients and non-continuum on solid particles in plasma flow are taken into account.;Results are presented here in three steps. First, the newly developed numerical models for capturing solidification/melting in SPH are validated among various experimental, analytical, and numerical results from literature. These phase change models mainly fall into two main categories: (1) inclusion of latent heat as a source term in the enthalpy equation, (2) inclusion of latent heat by modifying the effective heat capacity in the enthalpy equation. Results confirm accuracy and robustness of the new methods.;Secondly, results for droplet generation in SPS are presented. Effects of different parameters on droplets flight and impact are investigated. The goal here is to find suitable operating conditions for the plasma torch and injection process that guarantee impact of high quality droplets on the surface. Effects of injector parameters like injection location, flow rate, and angle along with effects of change in physical properties of droplets are studied.;Finally, the newly improved SPH model is used to predict impact of molten ceramic droplets that are collected on the substrate. These cases include predictions for the spread factor and droplet behavior based on their impact velocity and temperature. Results are used to explain different scenarios happening in substrate coating using SPS. |
