微/纳米粒子在缩放喷管中的加速特性

The acceleration of micro-and nano-particles in supersonic de-laval-type nozzle

冷喷涂(CGDS)过程中粒子速度是决定粒子粘附性的最重要的因素之一。本文对确定进出口压力和温度边界条件下氮气(N2)在拉阀尔喷管中的流动进行了数值分析研究,并计算了粒径在100nm到50μm之间铜和铂两种金属粒子在喷管中的加速运动过程。结果表明在喷管扩张部分的出口处有圆锥状的微弱震荡(压缩波)产生;材料密度对微米尺度的粒子的加速特性有显著影响,而对纳米尺度粒子的加速行为影响不大;在相同的入口条件下,粒子越小则其在喷管出口处的速度越大。

The particle velocity in cold gas dynamic spray （CGDS） is one of the most important factor that can determine the property of the bonding to the substrate. The acceleration of carrier gas Nitrogen to particles is strongly dependent on the densities of particles and the particle size. In this paper, the accelerating process of micro-scale and nano-scale copper （Cu） and platinum （Pt） particles in De-Laval-Type nozzle is investigated. A numerical simulation is performed for the gas particle two-phase flow with particle diameters ranging from 100 nm to 50μm, which are accelerated by carrier gas Nitrogen in a supersonic De-Laval-type nozzle. The results show that cone-shape weak shocks （compression waves） occur at the exit of divergent section and the particle density has significant effect on the acceleration of micro-scale particles. At the same inlet condition, the velocity of the smaller particles is higher than that of larger particles at the exit of the divergent section of the nozzle. Higher inlet pressure and temperature should be applied to nano-scale particles in order to obtain higher velocity.