Liquid flow on a rotating disk prior to centrifugal atomization and spray deposition

Abstract

Video observations of the flow patterns that develop on a rotating disk during centrifugal atomization and spray deposition, and subsequent metallographic studies conducted on solid skulls removed from the disk after processing, have indicated a circular discontinuity or hydraulic jump, which is manifested by a rapid increase in the thickness of the liquid metal and by a corresponding decrease in the radial velocity. A mathematical model has been developed that is capable of predicting both the occurrence and location of the jump, and the associated changes in the thickness profile and in the radial and tangential velocities of the liquid metal. Good correlations have been observed between model predictions and the flow patterns observed on the skull after atomization, and the effects of changes in material and operational parameters such as kinematic viscosity, volume flow rate, metallostatic head, and disk rotation speed have been quantified. Liquid metal flow is controlled primarily by the volume flow rate and by the metallostatic head prior to the hydraulic jump and by the centrifugal forces after the jump. The implications of these observations in terms of the atomization process are discussed.

Ligament and Droplet Generation by Oil Film on a Rotating Disk

“…Some analyses on the liquid flow on a rotating disk were carried out by a numerical simulation. The description of the numerical approach is not included here and the interested reader is referred to the literatures, for example, [26,27]. Here, we resort to the same approach.…”

CFD Modelling of the Effects of Operating Parameters on the Spreading of Liquids on a Spinning Disc

“…(2), for each phase. (2) where, apart from the conventional symbols (see NOMENCLATURE), F a is an additional momentum source accounting for surface tension at the free surface that is approximated by using the Continuum Surface Force method of Brackbill et al [13]; and C αβ is the interphase drag force calculated using a free surface approach described by Eq. (3) [11]: 3where and C D = 0.44.…”

“…Emslie et al [1] utilised a method of characteristic curves to demonstrate that a film with an initial irregular fluid distribution develops towards a uniform distribution under centrifugal effect. Zhao et al [2] conducted experimental work to visualise the flow of liquid metal on a spinning disc and observed that for their operating conditions a hydraulic jump formed at a radial distance, depending on the liquid kinematic viscosity, the volume flow rate, the hydrostatic head of feeding stream, and the disc spinning speed, resulting in a sudden increase in film thickness. An analytical model was developed by Zhao et al [2] that described the flow of a liquid film on the spinning disc and predicted the occurrence and location of the hydraulic jump.…”

“…Zhao et al [2] conducted experimental work to visualise the flow of liquid metal on a spinning disc and observed that for their operating conditions a hydraulic jump formed at a radial distance, depending on the liquid kinematic viscosity, the volume flow rate, the hydrostatic head of feeding stream, and the disc spinning speed, resulting in a sudden increase in film thickness. An analytical model was developed by Zhao et al [2] that described the flow of a liquid film on the spinning disc and predicted the occurrence and location of the hydraulic jump. Employing lubrication theory Myers and Charpin [3] investigated the effect of Coriolis force on liquid film formation on a spinning disc and found that, when the flow is axisymmetric, the Coriolis force has no effect on the height of the liquid film.…”

Production of fine calcium powders by centrifugal atomization with rotating quench bath

“…Considering the complexity of melt flow on an atomization disk and the speed of the disk edge, the atomization mode on the disk edge is difficult to identify as a specific mode without clear high speed image [5]. Therefore, mathematical models based on the flow behavior of liquid melt must be experimentally verified before they can be relied upon to predict particle shape and particle size distribution [5,9]. Ideally, centrifugally atomized powders have an approximately spherical shape.…”