Study On Influencing Factors Of Gas-particle Two Phase Flow In Cold Spraying Assisted By Electrostatic Field

It is very important to study gas velocity and particle velocity in the process ofcold spraying, as the spraying quality is directly affected by the gas velocity andparticle velocity. Some scholars have researched the numerical simulation of gas-solidtwo phase flow in the cold spraying, while in their studies, particle diameter arealmost limited to1-50μm, so nano-particle diameter under100nm deposition is notprepared.This thesis presents numerical simulation of nano-scale particle deposition,called electrostatic-force-assisted cold spray. Firstly, two-dimensional axis symmetricgeometry about gas-solid two phase flow is established, numerical simulation of theflow inlet and outlet the nozzle is carried out to study the effects of the differentpressure, different temperature and different spray distance on the gas velocity anddiscuss the effects of the particle material and diameter on particle velocity. Processparameters in cold spray are as follows: the carrier is air, the particles are Cu, Au andC, the particle diameter are0.1μm,5μm,15μm,25μm and35μm, inlet pressure are1.5MPa,2MPa and2.5MPa, inlet temperature are400K,500K and600K, spraydistance are10mm,15mm and25mm. The results show that gas and particle velocityincrease with the increment of pressure and temperature. Different spray distancehave no influence on the gas velocity. Larger particles with low density and smallerparticles with high density are difficult to be accelerated to higher velocity by carriergas, so appropriate coating parameters are selected according to material density andparticle diameter.Secondly, based on the secondary development method of the CFD software,coupling numerical simulation of electric field in supersonic gas-solid two phase flowand the velocity of the same charges with different particle diameter are analyzed, thevelocity of the same particle diameter with different charges and the velocity of thesame particle diameters of different material with the same charges are explored. Thevoltage is70kV, the particles are Cu, Fe and Pt, the particle diameter are30nm,60nm,100nm and400nm, the charges are2000e,6000e and10000e, and the otherparameters are fixed in the simulation. The results show that the smaller charged nano-particle diameter, the higher particle impact velocity. The higher particle chargedensities, higher particle impact velocity, and the bigger the electrostatic forces act onparticles. The different particle density and materials almost has no influence on thevelocity in the same Particle diameter.The study provides theoretical instruction for the preparation of nanometer-sizedcoating.