Droplet transport in simplex and air-assisted sprays

W. H. Lai, K. H. Yang, C. H. Hong, M. R. Wang

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9 Citations (Scopus)


This article reports an experimental study of drop transport phenomena in sprays. Three-dimensional characteristics of a research simplex atomizer (RSA) with and without atomizing air are measured to provide the benchmark database. Methanol flow rate and pressure are controlled at 1.26 g/s and 357 kPa, respectively. The atomizing air is supplied at a pressure of 3.57 kPa with an air-to-liquid mass ratio of 0.64. The performance of the spray with and without atomizing air is measured by a two-component phase Doppler particle analyzer (PDPA). Results show that the spray cone angle and Sauter mean diameter (SMD) decrease in the air-assist case. On the other hand, both axial and azimuthal velocity increase, while the radial velocity remains the same even under atomizing air condition. It is also found that SMD increases along the axial and radial directions for both cases. Analysis of the histogram data shows that the transport of part of the smaller drops from the outer region to the central region is the key process responsible for the SMD increase downstream. The drop transport phenomenon is further supported by the drop number density increase and higher velocity fluctuation at the spray central region in the downstream region. Comparison of the velocity profiles for both cases also shows that the transition length from a wake to a jet profile is shorter in the air-assist case. Furthermore, the axial, radial, and azimuthal velocity fluctuations of the dispersed phase (u′, v′, w′) increase in both the central region and the spray sheet in the air-assist case. However, it is found that this increase is due to the interaction between the droplet and the gas phases in the spray sheet but not due the velocity gradient mechanism as has been widely adapted in the shear layer flow problem.

Original languageEnglish
Pages (from-to)27-49
Number of pages23
JournalAtomization and Sprays
Issue number1
Publication statusPublished - 1996

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)


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