An experimental study of liquid micro-jets produced with a gas dynamic virtual nozzle under the influence of an electric field

Bor Zupan; Gisel Esperanza Peña-Murillo; Rizwan Zahoor; Jurij Gregorc; Božidar Šarler; Juraj Knoška; Alfonso M Gañán-Calvo; Henry N Chapman; Saša Bajt

doi:10.3389/fmolb.2023.1006733

An experimental study of liquid micro-jets produced with a gas dynamic virtual nozzle under the influence of an electric field

Front Mol Biosci. 2023 Jan 19:10:1006733. doi: 10.3389/fmolb.2023.1006733. eCollection 2023.

Authors

Bor Zupan¹, Gisel Esperanza Peña-Murillo², Rizwan Zahoor¹, Jurij Gregorc¹, Božidar Šarler^{1

3}, Juraj Knoška², Alfonso M Gañán-Calvo^{4

5}, Henry N Chapman^{2

6

7}, Saša Bajt^{2

6}

Affiliations

¹ Laboratory for Fluid Dynamics and Thermodynamics, Faculty of Mechanical Engineering, University of Ljubljana, Ljubljana, Slovenia.
² Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
³ Laboratory for Simulation of Materials and Processes, Institute of Metals and Technology, Ljubljana, Slovenia.
⁴ Departamento de Ingeniería Aeroespacial y Mecánica de Fluidos, Universidad de Sevilla, Sevilla, Spain.
⁵ Laboratory of Engineering for Energy and Environmental Sustainability, Universidad de Sevilla, Sevilla, Spain.
⁶ The Hamburg Centre for Ultrafast Imaging, Hamburg, Germany.
⁷ Department of Physics, Universität Hamburg, Hamburg, Germany.

Abstract

The results of an experimental study of micro-jets produced with a gas dynamic virtual nozzle (GDVN) under the influence of an electric field are provided and discussed for the first time. The experimental study is performed with a 50% volume mixture of water and ethanol, and nitrogen focusing gas. The liquid sample and gas Reynolds numbers range from 0.09-5.4 and 0-190, respectively. The external electrode was positioned 400-500 μm downstream of the nozzle tip and an effect of electric potential between the electrode and the sample liquid from 0-7 kV was investigated. The jetting parametric space is examined as a function of operating gas and liquid flow rates, outlet chamber pressure, and an external electric field. The experimentally observed jet diameter, length and velocity ranged from 1-25 μm, 50-500 μm and 0.5-10 m/s, respectively. The jetting shape snapshots were processed automatically using purposely developed computer vision software. The velocity of the jet was calculated from the measured jet diameter and the sample flow rate. It is found that micro-jets accelerate in the direction of the applied electric field in the downstream direction at a constant acceleration as opposed to the standard GDVNs. New jetting modes were observed, where either the focusing gas or the electric forces dominate, encouraging further theoretical and numerical studies towards optimized system design. The study shows the potential to unlock a new generation of low background sample delivery for serial diffraction measurements of weakly scattering objects.

Keywords: Taylor cone; electric field; experimental study; flow-focusing; gas dynamic virtual nozzle; jetting modes; micro-jet.

Grants and funding

For this research is provided by the Center for Free-Electron Laser Science (CFEL) under the project: Innovative methods for imaging with the use of x-ray free-electron laser (XFEL) and synchrotron sources: simulation of gas-focused micro-jets, and Slovenian Grant Agency (ARRS) within Program Group P2-0162 and Project J2-4477. This work is also partly supported by the Cluster of Excellence “CUI: Advanced Imaging of Matter” of the Deutsche Forschungsgemeinschaft (DFG)—EXC 2056—project ID 390715994, and the Human Frontiers Science Program (RGP0010/2017).