Investigation of the droplet characteristics and size distribution during the collaborative atomization process of a twin-fluid nozzle

Abstract

To overcome the environmental problems during manufacturing process, the twin-fluid atomization has been demonstrated as an efficient technique to reduce the lubri-cooling fluid consumption and its pollution emission. However, the coupling between the gas, liquid, and structure of the twin-fluid nozzle directly affect the droplet characteristics and size distribution, which has a significant effect on the processing performance. In the current work, the droplet characteristics during the collaborative atomization process of a twin-fluid nozzle with two kinds of atomizing cores are investigated and compared via a phase Doppler particle analyzer (PDPA), and the droplet diameter and size distribution of a new twin-fluid nozzle (NTN) with different atomizing cores are further investigated. The results reveal that the spray atomization characteristics and droplet size distribution are obviously influenced by the performance of primary and secondary atomization, which mainly depend on the atomizing core structure and the gas to liquid mass flow rate ratio (GLR). Because the gas acceleration performance of the new atomizing core is better than that of the standard atomizing core at the same GLR, compared with the standard twin-fluid nozzle (STN), the droplet diameter decreases by approximately 33.97%, the droplet number concentration and axial velocity increase by approximately 36.39% and 34.51%, respectively, and the spray cone angle of the STN is only approximately 80% of that of the NTN. Meanwhile, the higher GLR of the twin-fluid nozzle provides more energy for the droplets, so the viscous force between the liquids is easier to overcome and the atomization characteristics are improved. Nevertheless, for a smaller GLR, the droplet size distribution is significantly affected by the structural parameters of the NTN atomizing core due to the insufficient atomization power. Moreover, a smaller throat diameter, a smaller exit diameter, and a moderate distance between the liquid channel and the atomizing core exit are beneficial for improving the droplet cumulative distribution.