Direct Modeling of the Simultaneous Flow of Compressible Atomizing Gas Jets and a Weakly Compressible Liquid Intermetall
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1128-U05-52
Direct Modeling of the Simultaneous Flow of Compressible Atomizing Gas Jets and a Weakly Compressible Liquid Intermetallic Stream during Gas Atomization
Mingming Tong, David J. Browne Engineering and Materials Science Centre, University College Dublin, Belfield, Dublin 4, Ireland ABSTRACT The authors have developed a new atomization model enabling direct numerical simulation of the simultaneous flow of compressible atomizing gas jets and a weakly compressible liquid metal stream. It has been used to simulate the atomization of a Ni-50wt.%Al melt stream by argon gas jets in a closed-coupled atomizer. The 2D simulation results show that the presence of the liquid intermetallic stream significantly influences the field variables, particularly the aspiration pressure. At the gas plenum pressure used, the gas nozzles are choked and hence the gas flow upstream of the tip of the liquid delivery tube is not influenced by the presence of the liquid intermetallic stream, whereas the downstream gas flow is affected. Significant differences between model predictions assuming either incompressible or compressible gas are reported. Besides the atomization of liquid intermetallic stream by argon gas, this unified atomization model is available for use to simulate a variety of different twin-fluid atomization processes. INTRODUCTION Due to the high catalytic activity caused by their high specific area, porous Raney nickel powders [1] have been widely used in industry. Gas atomization is a very efficient route to fine, clean, and spherical catalytic powders directly from the melt. The hydrodynamic interaction between the melt stream and impinging atomizing gas jets is a key issue. Based on the experience of the authors on front-tracking formulation [2-5], they developed an atomization model [6-7] for direct numerical simulation of the forced disintegration of a continuous Ni-Al melt stream by gas jets during the early stages of the process, based on the assumption that the gas is incompressible. In order to improve the accuracy of the model and enable more realistic simulations for the industry, the compressibility of gas needs to be considered. Although the flow of compressible atomizing gas jets has been investigated by many researchers using numerical modelling and simulation [8-15], such numerical models are only capable of handling compressible gas flow in the gas-only case, i.e. ignoring the interaction with the liquid metal. The authors have developed a new compressibility model [16] for 2D studies of gas-only flow in a typical atomizer. This model also has the potential to simulate the simultaneous flow of compressible fluid and weakly compressible fluid. In this paper, based on front-tracking [7] and gas compressibility [16], the authors report on their development of a novel unified atomization model. This model can be used to directly simulate the interaction between the compressible atomizing gas jets and weakly compressible liquid metal stream during their simultaneous flow in the atomization process. The
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