Influence of the Nozzle Inner Geometry on the Particle History During Cold Spray Process
Influence of the Nozzle Inner Geometry on the Particle History During Cold Spray Process
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DOI：
10.1007/s11666-022-01407-y
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发表时间：
2022-05-11
影响因子：
3.1
通讯作者：
Cavaille, J. -y.
中科院分区：
文献类型：
--
作者：
Bernard, C. A.;Takana, H.;Cavaille, J. -y.
冷喷涂工艺需要较高的颗粒温度和较低的颗粒速度才能成功沉积聚合物颗粒。为了提高颗粒温度，一种解决方案是使用较长的喷嘴来增加颗粒在喷管内的停留时间，并限制超音速流动的膨胀。然而，要做到这一点，由于制造限制，必须串联几个喷嘴(直到达到所需的长度)，或者必须在喷嘴的内部形状中引入不规则性。在这项研究中，我们的目的是用计算流体力学(CFD)分析一个240 mm长的喷管中心截面积减少20%的效果。在两段之间的交叉口，发生了几个现象：(I)流动堵塞，(Ii)颗粒在交叉口反弹，导致它们逆流而上。对于直径大于30微米的颗粒，由于惯性和萨夫曼升力的影响较大，20%~25%的颗粒在喷嘴内反弹。对于这些粒子，记录到了较高的温度和较低的速度。
High particle temperature and low particle velocity are required to successfully deposit polymer particles by cold spray process. To increase the particle temperature, a solution is to use a relatively long nozzle to increase the particle resident time inside the nozzle and limit the expansion of the supersonic flow. However, to do this, due to manufacturing limitations, several nozzles must be attached in series (until the desired length is reached), or alternatively, irregularities must be introduced into the inner shape of the nozzle. In this study, we aim to analyze the effect of 20% nozzle reduction of cross-section area at the center of a 240-mm-long nozzle using computational fluid dynamics (CFD). At the intersection between the two sections, several phenomena take place: (i) the flow chokes and (ii) particles rebound at the intersection leading them to go upstream. For particles with a diameter larger than 30 mu m, 20 to 25% of the particles rebound inside the nozzle due to the larger influence of the inertia and the Saffman lift force. For these particles, larger temperature and lower velocity is recorded.