超音速火焰喷涂焰流特性和粒子沉积行为

摘要

为了研究氧气-空气混合助燃超音速火焰喷涂过程中预混气体当量比对焰流特性的影响，基于FLUENT软件建立了焰流的计算流体力学(CFD)模型．运用有限元软件LS-DYNA来研究不同粒径Ni60粒子的撞击行为，并与粒子截面的 SEM 形貌进行了对比．结果表明：合理的丙烷和全部氧气的当量比应小于1.2；在燃气过量时，焰流中过多的N2会引起熄燃；与基体结合较好的粒子尺寸为20～40,µm；粒径小于20,µm的粒子速度高，回弹力大，与基体结合力差；粒径大于50,µm的粒子速度低，熔化不充分，粒子与基体结合面缺陷较多．%To clarify the relationship between flame flow state and equivalence ratio of the premixed gas in high ve-locity oxygen/air fuel(HVO/AF)process,a computational fluid dynamic(CFD)model based on FLUENT software was established. Subsequently,the impact behavior of Ni60 particles with different diameters was simulated by em-ploying finite element software LS-DYNA,the results of which were compared with the cross sectional SEM mor-phologies of the particles. The results indicate that the reasonable propane-oxygen equivalence ratio should beless than 1.2. The excessive nitrogen would extinguish the flame,when the flame is in the fuel-rich condition. The diame-ter of the particle showing fairly good adhesion with the substrate ranges from 20 µm to 40 µm. Particles with a diame-ter under 20 µm have high velocity and rebound force,which weakens the adhesion between particles and substrate. By contrast,the velocity and melting of the particles with a diameter above 50 µm are both very low,creatinglots of defects at the interfaces between particles and substrate.