Computer modelling of the influence of process parameters on the heating and acceleration of particles during plasma spraying

In the first part of the present study, an appropriate inflow turbulent boundary condition is chosen. Then, a comparison is made between two turbulence models for a plasma jet discharged into air atmosphere. The plasma jet gas phase flow is predicted with the standard k−ε model and the RNG model of turbulence. Particles behavior is modeled using stochastic particles trajectories. A validation of the plasma jet model is made by comparison with experimental data.This part of the study shows that the flow features are better predicted with the RNG model. The choice of appropriate boundary conditions seems to be crucial for a better simulation of plasma thermal spraying. Afterwards, computations are performed for projection of Ni particles. It is found that the computed particles velocities and temperatures are also better predicted with the RNG model compared with the k−ε model. The second part of this study is concerned with the effect of the substrate movement on the gas flow field. This is performed in order to simulate a realistic coatings process where a relative movement between the torch and the substrate always exists. Three substrate velocities have been used and it is found that the flow fields are affected only very near the substrate wall.

Section: Plasma Jetmentioning

confidence: 99%

“…Several researchers have used a CFD code to simulate plasma spraying processes. For example, Zhang et al (6) studied the influence of process parameters on the heating and acceleration of particles during plasma spraying. The authors used the STAR-CD CFD code to solve the problem.…”

Section: Introductionmentioning

confidence: 99%

Comparison between Two Turbulence Models and Analysis of the Effect of the Substrate Movement on the Flow Field of a Plasma Jet

El-Hadj

Messaoudene

2005

“…(16,17) However, it is impractical to trace each individual particle and so the particles were grouped into a number of parcels in this work. In each parcel, the particles are considered to have the same size and are injected into the plasma flame at the same position.…”

Section: Methodsmentioning

confidence: 99%

Statistical Analysis of the Motion and Heating of Particles in a Plasma Jet

Zhang

Liu

Bao

et al. 2005

Self Cite

In plasma spraying, the size and initial velocity of indivdual feedstock particles injected into the flame are essentially random variables within the fairly wide ranges of the injection conditions and powder characteristics. As a result, the motion and heating of particles cannot be specified in a deterministic manner and so a simulation based on a single particle cannot provide a realistic prediction of the deposition process. In the present study, these random elements are simulated using a statistical method. The distributions of the motion and heating of a whole population of particles are simulated rather than those of a single particle.

“…Many workers [9][10][11][12] have investigated and showed that for typical plasma jet injection conditions, many operating parameters affecting heat, momentum and mass transfers between the plasma jet and the entrained particles. However, most of these efforts were conducted with the exclusion of substrate in the computational fluid dynamics (CFD) models for the sake of idealization simplicity [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Comparative Study of Plasma Spray Flow Fields and Particle Behavior Near to Flat Inclined Substrates

Kang

2006

Numerical models have been developed using computational fluid dynamics (CFD) analysis program FLUENT V6.02 © to investigate the effect of the substrate on the behavior of the plasma flow fields and in-flight particles. Simulations are performed for cases where flat substrates are either present or absent, for the former, the substrate is oriented perpendicularly or inclined to the torch axis. It is shown that although the presence of perpendicular or inclined substrate significantly influences the plasma flow fields at the vicinity of the substrate, the particle behavior remain relatively unaffected. The insignificant effect of the substrate on particle behavior is qualitatively verified by experimental observation using SprayWatch © imaging diagnostics equipment. Images captured by the equipment confirm that the particles travel through the plasma plume with high momentum and show no sudden change in their trajectories right before impacting the substrate. Both the numerical and experimental findings show that the freestream model is sufficiently detailed for future work of this nature.Keywords Atmospheric plasma spray · CFD modeling · Particle behavior · Inclined substrate Nomenclature ACross section area (m 2 ) BEmpirical constant (= 9.81) C D Drag coefficient C µ Empirical constant (= 0.09) C 1ε Empirical constant (= 1.44) C 2ε Empirical constant (= 1.92) C p Specific heat capacity (J/kg K) D Diffusion coefficient (m 2 /s)