|
1298 |
|
Tuesday, June 03, 2008, Room 08 2:00 PM Plasma Spraying and Plasma Transferred Arc 3 New trends and modified plasma processes for the application of ceramic-based coatings |
|
Liquid precursor plasma spraying: modeling of the droplet breakup
|
|
Armelle Vardelle* / University of Limoges-CNRS, France Cecile Marchand / University Of limoges , France Christophe Chazelas/ University of Limoges, France Gilles Mariaux/ University of Limoges, France |
|
The use of liquid precursors in plasma spraying makes it possible to produce coatings with more refined microstructures than in conventional plasma spraying. Depending on the injection device, the liquid feedstock is injected into the plasma jet in the form of liquid jet or droplets. The instabilities on the liquid-gas interface cause the breakup of liquids into drops that are subjected to further breakup until the droplets reach a stable state or evaporate. The process breakup strongly influences the trajectories and, therefore, treatment of the droplets in the plasma medium. Besides aerodynamic breakup, droplets may be subjected to thermal breakup due to the inner boiling of liquid or, for solution droplet, to the rupture of the solid shell that develops on the droplet by the pressurization of inner liquid. This study deals with the numerical simulation of aerodynamic breakup under plasma spray conditions. It is modeled by using the Enhanced Taylor Analogy Breakup (ETAB) proposed by Tanner* in which the droplet breakup, that occurs when the normalized drop distortion exceeds a critical value, is calculated with the standard Taylor Analogy Breakup model and the product drop size is determined via a drop breakup-cascade from an exponential law, where the exponent depends on the drop breakup regime. Furthermore, the interactions between product droplets and time-fluctuating plasma jet are also investigated. * Tanner F.X., ``Liquid Jet Atomization and Droplet Breakup Modeling of Non-Evaporating Diesel Fuel Sprays,' SAE Paper 970050, 1997 |