The Research Of Plasma Spraying With Liquid Material Injection By FLUENT

Liquid plasma spraying is a novel thermal spraying technology. It adopts suspensionliquid instead of traditional power as the spraying material which effectively solves transportdifficulties of the micro-nano scale powder and the growing tendency of nano grains. Theplasma morphology during spraying process and its physical and chemical properties directlyaffect coating performances. Using numerical simulation technology to analyze the plasma jetmorphology and the temperature field, velocity field is an economic and efficient method.According to computational fluid dynamics and theories of heat transfer, also adoptedthe finite volume method to control discrete equations, the plasma jet and its distributionfeatures are simulated in this work with the aid of FLUENT software. The key of the researchis to establish a appropriate mathematical model and enforce the velocity and temperaturedistribution at the plasma jet boundary by UDF(User-Defined Function) in FLUENT.Simulation Results indicate that with the increase of the spraying power, the maxvelocity and temperature of the plasma jet also ascend. With the increase of the Ar gas flow,the max velocity ascends while the max temperature descends. Take the value of whichequals the major to minor axis ratio of the same second order central moment ellipse and theresults show values of between simulation results and CCD images are very close. Referto the liquid phase injection, under the same plasma power and Ar gas flow, the max velocityand temperature of the plasma jet remains the same however the liquid injection rate, spatialposition or injection angle changes. With the increase of the injection velocity, the airdisturbed by the plasma jet is normally weakened around the jet tail. Different axial positionsof the liquid injection mainly effect the plasma jet morphology around the jet tail. With theincrease of the injection angle, the injection enhances its disturbance to the plasma jet aroundthe arc gun exit while the disturbance weakens around the jet tail. Take the value of whichequals the lateral distance between jet velocity isoline center and jet axis to describe thedeviation degree of the plasma jet morphology, results show that values of betweensimulated results and CCD images consistently agree.