Abstract
In this study, we evaluated the fundamental physical behavior during droplet formation and flow from a rotary bell spray in the absence of an electrostatic field. The impact of a wide range of operating parameters of the rotary bell sprayer, such as flow rates, rotational speeds, and spatial positioning, on droplet sizes and size distributions using a three-dimensional (3-D) mapping was studied. The results showed that increasing the rotational speed caused the Sauter mean diameter of the droplets to decrease while increasing flow rate increased the droplet sizes. The rotational speed effect, however, was dominant compared to the effect of flow rate. An increase in droplet size radially away from the cup was noted in the vicinity of the cup, nevertheless, as the lateral distances from the cup and rotational speed were increased, the droplet sizes within the flow field became more uniform. This result is of importance for painting industries, which are looking for optimal target distances for uniform painting appearance. Furthermore, the theoretical formulation was validated with experimental data, which provides a wider range of applicability in terms of environment and parameters that could be tested. This work also provides an abundance of measurements, which can serve as a database for the validation of future droplet disintegration simulations.
Highlights
The challenges faced in developing and implementing effective automotive coating processes are evident by research performed to develop new paint formulations [1], new applicator designs [2], and optimum operating parameters for coating apparatus [3,4]
A substantial amount of research has concentrated on simulating the effects of operating parameters on the performance of electrostatic rotary bell sprayers (ERBS) [9,10,11,12,13]
Fluid ofof the rotary bell were varied during the the teststests as the flow rates and rotational speeds of the rotary bell were varied during the tests as the light scattering intensities measured at different vertical and horizontal locations the light scattering intensities werewere measured at different vertical and horizontal locations withinwithin the spray the light scattering intensities were measured at different vertical and horizontal locations within the sprayfield
Summary
The challenges faced in developing and implementing effective automotive coating processes are evident by research performed to develop new paint formulations [1], new applicator designs [2], and optimum operating parameters for coating apparatus [3,4]. Due to the limitations of using only computational techniques, it is preferred that experimental methods in conjunction with computational simulations be used to more fully understand the complex dynamics of spray processes [14,15]. This combined experimental plus computational approach is capable of defining modifications and improvements needed to achieve the highest transfer efficiency, to maintain acceptable costs and environmental impacts, and to meet, consumer expectations of coating quality [16].
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