Numerical study of molten and semi-molten ceramic impingement by using coupled Eulerian and Lagrangian method

Abstract

Large temperature gradients are present within ceramic powder particles during plasma spray deposition due to their low thermal conductivity. The particles often impinge at the substrate in a semi-molten form which in turn substantially affects the final characteristics of the coating being formed. This study is dedicated to a novel modeling approach of a coupled Eulerian and Lagrangian (CEL) method for both fully molten and semi-molten droplet impingement processes. The simulation provides an insight to the deformation mechanism of the solid core YSZ and illustrates the freezing-induced break-up and spreading at the splat periphery. A 30 μm fully molten YSZ particle and an 80 μm semi-molten YSZ particle with different core sizes and initial velocity ranging from 100 to 240 m/s were examined. The flattened degree for both cases were obtained and compared with experimental and analytical data

Adhesion of Volcanic Ash Particles under Controlled Conditions and Implications for Their Deposition in Gas Turbines

“…It's clear that detailed study of impact, spreading and adhesion requires modelling of the associated deformation process. Such processes have been analysed [36][37][38][39][40][41] in some depth, but identifying appropriate input data for the mechanical properties of the material presents a major challenge, particularly since deformation occurs at very high strain rates (as well as high temperatures). For particles that are in some kind of semi-solid state, it's not even clear whether treatments should be based on viscous flow or plasticity models, although in both cases the strain rate (and temperature) dependence need to be taken into account.…”

Analysis of semi-molten hollow particle spreading and deformation in plasma spraying

“…where p is the pressure, Γ 0 = α − 1, which is set to 0.29, represents the thermal pressure from a set of vibrating atoms, α is the ratio of specific heats [32], ρ 0 is the reference density, η = 1 − ρ ρ0 is the nominal volumetric compression strain, c 0 is the zero-pressure isentropic sound speed, s, which is chosen as 2.39 as illustrated in [27], is a dimensionless parameter related to the pressure derivative of the isentropic bulk modulus. In this study, the sound speed of the liquid is set as 3000 m s −1 .…”

“…Brittle materials possess ductile behavior under high temperature or high pressure [26]. Considering the plastic deformation of the substrate and the solid core, Zhu et al [27] built a semi-molten YSZ particle impact model by using the coupled Eulerian and Lagrangian (CEL) method to simulate the splash deposit of the liquid and the deformation of the solid core as well as the substrate.…”

Application and benchmark of SPH for modeling the impact in thermal spraying

“…While this approach is quite novel, it relies on a very complex system in which numerical errors can occur at many different places (especially during transfers between discretizations). A coupled Eulerian and Lagrangian approach is also pursued by Zhu et al [25] where it is used in order to simulate spray deposition of semi-molten ceramic droplets.…”