冷喷涂过程中气固两相流的数值模拟

Numerical Modeling on Cold Gas Dynamic Spray Process

冷喷涂过程中,由于基板的存在,板前有激波出现,从而对喷涂粒子的运动产生影响。文中建立了二维的气固两相流模型,得出在基板存在的情况下,输送气体、粒子密度和粒子直径等对喷涂速度的影响,并通过调整基板与射流管道出口的距离,找出这一距离对整个流场、粒子速度的影响。

Numerical simulations are performed for the gas particle two phase flow in the cold gas dynamic spray process to investigate the acceleration of micro and nano particles with diameters ranging from 100 nm to 50 μm. Nitrogen (N 2) and Helium (He) are chosen as the carrier gas, respectively. The acceleration of carrier gas to particles in the De Laval Type supersonic nozzle is strongly dependent on the characteristics of flow field, as well as the densities and the size of the particles. Two kind of particles Copper (Cu) and Platinum (Pt) are chosen as the spraying materials. The computed results show that the flow structures of the carrier gas are very different for different gas and different spraying distance, which results in consequently different accelerating features. The cone-shape weak shocks (compression waves) occurr at the exit of divergent section, and the bow-shaped strong shock wave is found right before the substrate, which plays a resistance role to the particles and prevents the smaller particles from approaching on the substrate.