EPTT 2020

12th Spring School on Transition and Turbulence

EXPERIMENTAL INVESTIGATION OF INITIAL DISTURBANCES FORMATION, INSTABILITIES GROWTH, MULTIPHASE TURBULENCE AND BREAKUP MECHANISM INSIDE A MIXING CHAMBER OF AN AIR-ASSIST ATOMIZER

Submission Author: Vinícius Basso de Godoy , SC
Co-Authors: Vinícius Basso de Godoy, Diogo Alexandre Santos, Bárbara Braatz Vetter, Leonardo Machado da Rosa, Marcela Silva, Jonathan Utzig, Henry França Meier
Presenter: Vinícius Basso de Godoy

doi://10.26678/ABCM.EPTT2020.EPT20-0067

 

Abstract

The purpose of this paper is to perform a preliminary study in the formation of initial disturbances, the growth of instabilities, multiphase turbulence and the primary breakup mechanism that arises inside an air-assist atomizer. To achieve such goal, a mixing chamber device was used on the experiments. This device is composed in such a way that allows for visual techniques to be employed. The experiments were performed using water at 365 kg/h and air as atomizing fluid at 40 kg/h. These operational conditions resulted in a Reynolds number of 10431, a Weber number of 308, an Ohnesorge number of 0.0017, an aerodynamic Weber number of 83364, and a Mach number approximately equal to 3, indicating that the air flow is supersonic. Flow visualization were executed with a high-speed camera at resolutions between 96x64 and 640x1024 pixels, image acquisition rate between 5000 and 58099 frames per second, and exposure time of 8 μs. The pseudo-two-dimensional device allowed for the flow visualization and proved to be effective. With this study, it was possible to observe the initial instabilities and turbulences inside the mixing chamber. The images outside the chamber provided an estimation of spray angle, droplet diameters and ligaments lengths.

Keywords

Atomization, primary breakup, visual techniques, air-assist atomizer, multiphase turbulence

 

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