Avello-Iturriagagoitia, A. (Alejo)
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- Experimental study of the influence of operational and geometric variables on the powders produced by close-coupled gas atomisation.(ELSEVIER, 2021-02) Urionabarrenetxea, E. (Ernesto); Martín-García, J.M. (José Manuel); Avello-Iturriagagoitia, A. (Alejo); Rivas-Nieto, A. (Alejandro)The effect of several operational and geometric variables on the particle size distribution of powders produced by close-coupled gas atomisation is analysed from a total of 66 experiments. Powders of three pure metals (copper, tin and iron) and two alloys (bronze Cu-15 wt% Sn and stainless steel SS 316 L) have been produced. Nitrogen, argon and helium were used as atomising gases. It is shown that the gas-to-metal ratio of volume flow rates (GMRV) is more relevant than the ratio of mass flow rates (GMR) in order to analyse the effect of atomisation variables on the particle size. Kishidaka's equation, originally proposed for water atomisation, is modified to predict the median particle size in gas atomisation. The accuracy of the new equation is compared with that of Lubanska, and Rao and Mehrotra. Kishidaka's modified empirical correlation is the most accurate in predicting the median particle size of the powders produced in this work. The morphology of the produced powders is studied by scanning electron microscopy (SEM) and it is observed that the melt superheat can play an important role in the aggregation of fine particles (< 10 mu m), which increases the fraction of large particles (> 100 mu m).
- Simulation and validation of the gas flow in close-coupled gas atomisation process: Influence of the inlet gas pressure and the throat width of the supersonic gas nozzle.(Elsevier, 2022-07) Urionabarrenetxea, E. (Ernesto); Avello-Iturriagagoitia, A. (Alejo); Rivas, A. (Alejandro); Martín, J.M. (José Manuel)The effectiveness of a close-coupled gas atomisation process largely depends on the operational and the geometric variables. In this study, Computational Fluid Dynamics (CFD) techniques are used to model and simulate the gas flow in the melt nozzle area for a convergent-divergent, close-coupled gas atomiser in the absence of the melt stream. Firstly, a reference case, in which the atomisation gas is nitrogen at 50 bar and a supersonic gas nozzle with a throat width of L0 has been modelled, is presented. Then, the influence of both the inlet gas pressure and this design parameter are investigated, comparing the numerical results provided by simulations varying the inlet pressure from 5 to 80 bar and modelling different convergent-divergent gas nozzles with throat widths of 0.29 center dot Lo, 0.5 center dot Lo, 0.77 center dot Lo and 2 center dot Lo respectively. The simulation results show how similarly these two parameters modify gas mass flow rates, gas velocity fields, aspiration pressures in the melt delivery tube or the size of the recirculation zones below the melt nozzle. Therefore, it can be stated that this geometric variable of the gas nozzle may be as relevant as the inlet pressure in the atomisation process. The most important novelty of this study is related to experimental validation of the numerical results using the Particle Image Velocimetry (PIV) technique and through direct measurements of gas mass flow rates, with a clear correlation between simulated and measured data. Moreover, some results obtained with experimental atomisations using copper and nitrogen are also presented. The experimental results show that finer powders are produced by increasing the
- Multiphase model to predict particle size distributions in close-coupled gas atomization(Elsevier, 2022) Urionabarrenetxea, E. (Ernesto); Martín-García, J.M. (José Manuel); Avello-Iturriagagoitia, A. (Alejo); Amatriain, A. (Aitor)A novel two-stage multiphase model is developed for close-coupled gas atomization by combining formulations available in the literature. Primary atomization is simulated using an Eulerian atomization model, and the outputsa reused as input so fa Lagrangian particle tracking approach to predict the particle size distribution resulting from second aryatomization. Theresults given by the primary atomization mode lare validated with published Direct Numerical Simulations (DNS) values and by comparisonwith experimental images of the spray, while the particle size distributions obtained are accurately fitted toa log-normal distribution, and with powder meandiameters showing good agreemen twith experimental data. The variation of powder characteristic diameters 𝑑10,𝑑50,and𝑑 90 as a function of thegas-to-meltmass flow rate ratio follows correct trends, and the value sofpowder mean diameters 𝑑50 are correctly predicted by the model.
- Teoría de Máquinas(2014-01-07) Avello-Iturriagagoitia, A. (Alejo)