Sam-Goo, Lee
The Journal of Mechanical Science and Technology, vol. 22, no. 12, pp.2509-2515, 2008

Abstract : The experimental objective was to compare disintegration characteristics from the internal mixing pneumatic nozzles under the different operating conditions in terms of swirl angles. For this investigation, supplied air pressures and nozzle configuration ratios were fixed. This experimental comparison is of fundamental importance to the understanding and modeling of turbulent atomization because the axisymmetric swirling flows involve relatively complex interactions. For the measurement, four internal swirl mixing nozzles with axisymmetric holes at swirl angles of 15o, 30o, 45o, and 60o to the central axis were employed, which is responsible for the enhancement of mixing in pneumatic jets. To illustrate the swirl phenomena quantitatively, the distributions of mean velocities, turbulence intensities, and SMD (Sauter mean diameter, or D32) variations with different configuration ratio were comparatively analyzed. It indicated that the atomization characteristics are performed well in the case of 30o of swirl angle, and that turbulence intensities are gradually degenerated with the increase of radial distances, showing a slight increment of SMD at downstream region. In particular, measurements showed that nozzle configuration is one of the significant geometrical parameters affecting the spray trajectories.

Keyword : Pneumatic jets; SMD (Sauter Mean Diameter); Turbulence intensity; Penetration; Conservation of momentum; Turbulence suppression; Growth rate