This project aims to model the atomization of pure liquids and suspensions for a wide range of viscosities, which are characterized by detailed experiments. The final model shall be valid for a range of air-blast atomizers, mass flows and system pressures, to establish a Virtual Spray Test Rig.

The atomization of pure liquids and suspensions with different viscosities is of great importance in many process engineering applications. This research work aims to explore and extend the capabilities of volume-of-fluid methods in the context of large eddy simulation (VOF-LES) for the numerical prediction of the atomization process. While VOF-LES methods can reliably predict the primary breakup, they are known to be sensitive to mesh quality and grid size, which limits their capability of predicting secondary breakup phenomena and downstream droplet size distributions. Therefore, this project explores dynamic mesh refinement techniques and coupling methods for VOF-LES with Euler-Lagrange models to allow for enhanced predictions of the atomization process within a Virtual Spray Test Rig (VSTR). This research is embedded in the Helmholtz funded research program MTET: Materials and Technologies for the Energy Transition and is conducted in close collaboration with the Liquid fuels / Atomization research group of the Gasification Technology section at the Institute for Technical Chemistry (ITC). ITC provides state-of-the-art experimental data that guides the development and validation of the VSTR at EBI.

Comparison of experimental and simulation results [1,2]: Primary jet break-up of a highly viscous glycerol/water mixture (η_liq = 100 mPa^.s) at elevated pressure (p = 6 bar). A coaxial air-blast atomizer is used, where the liquid jet is atomized outside the nozzle orifice by a high velocity gas stream. The atomizer is operated at a Gas-to-Liquid-Ratio of GLR = 0.6 with a gas velocity of v_gas = 60 m^.s^-1 . Left: High-speed camera video recorded at the Institute for Technical Chemistry. Right: Visualization of the liquid volume fraction integrated along a line of sight from VOF-LES predictions at Engler-Bunte-Institute.

[1] S. Wachter, T. Jakobs, T. Kolb, Towards system pressure scaling of gas assisted coaxial burner nozzles – An empirical model, Applications in Energy and Combustion Science 5 (2021).
(https://doi.org/10.1016/j.jaecs.2020.100019)

[2] F. Zhang, T. Zirwes, T. Müller, S. Wachter, T. Jakobs, P. Habisreuther, N. Zarzalis, D. Trimis, T. Kolb, Effect of elevated pressure on air-assisted primary atomization of coaxial liquid jets: Basic research for entrained flow gasification, Renewable and Sustainable Energy Reviews 134 (2020).
(https://doi.org/10.1016/j.rser.2020.110411)