Simulation of Effervescent Atomization and Nanoparticle Characteristics in Radio Frequency Suspension Plasma Spray
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JTTEE5 21:226–239 DOI: 10.1007/s11666-011-9714-1 1059-9630/$19.00 ASM International
Simulation of Effervescent Atomization and Nanoparticle Characteristics in Radio Frequency Suspension Plasma Spray Hong-Bing Xiong, Li-Juan Qian, and Jian-Zhong Lin (Submitted November 23, 2010; in revised form November 9, 2011) In this paper, a comprehensive model was developed to investigate the suspension spray for a radio frequency (RF) plasma torch coupled with an effervescent atomizer. Firstly, the RF plasma is simulated by solving the thermo-fluid transport equations with electromagnetic Maxwell equation. Secondly, primary atomization of the suspension is solved by a proposed one-dimensional breakup model and validated with the experimental data. Thirdly, the suspension droplets and discharged nanoparticles are modeled in Lagrangian manner, to calculate each particle tracking, acceleration, heating, melting and evaporation. Saffman lift force, Brownian force and non-continuum effect are considered for nanoparticle momentum transfer, as well as the effects of evaporation on heat transfer. This model predicts the nanoparticle trajectory, velocity, temperature and size in the RF suspension plasma spray. Effects of the torch and atomizer operating conditions on the particle characteristics are investigated. Such operating conditions include gas-to-liquid flow ratio, atomizer orifice diameter, injection pressure, power input level, plasmas gas flow rate, and powder material. The statistical distributions for the multiple particles are also discussed for different cases.
Keywords
atomization, nanoparticle, numerical simulation, RF plasma, suspension plasma spray
1. Introduction Radio frequency suspension plasma spray (RF-SPS) is an innovative and promising technique under development, having potential applications for materials processing such as nano-structure coatings, powder spheroidization, materials reaction and synthesis (Ref 1-3). The RF-SPS technology has advantages of stability, cleanness, largevolume, long residence time, controlled injection and high chemical reactivity for various materials. Feeding of the liquid suspension is crucial for the success of RF-SPS. Its importance originates mainly from two aspects. Firstly, evaporation of the liquid phase has great influence on the nanoparticle trajectory and melting status. Secondly, a narrow droplet size distribution with small mean value is desirable but difficult to obtain. An effective and credible atomization device is necessary for suspension feeding. Atomization of the suspension could be accomplished by different pneumatic atomizers, for example, air blast
Hong-Bing Xiong, Li-Juan Qian and Jian-Zhong Lin, Department of Mechanics, Zhejiang University, Hangzhou 310027, China; and Li-Juan Qian and Jian-Zhong Lin, China Jiliang University, Hangzhou 310018, China. Contact e-mails: [email protected]; [email protected] and [email protected].
226—Volume 21(2) March 2012
atomizer and twin-fluid effervescent atomizer. The former refers to a two-phase flow in
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