Dispersion and vaporization of a dilute spray of electrified droplets injected in a coflowing hot gas – Application to the vaporization chamber of a minicombustor

• An Eulerian/Lagrangian model is used to simulate the dispersion and vaporization of a dilute spray of small, electrically charged droplets in a hot coflowing gas.
• Vaporization of the spray in a cylindrical chamber is analyzed. The conditions leading to full vaporization without droplet deposition at the walls of the chamber are investigated.
• The effects of the inlet droplet size, inlet gas temperature and overall equivalence ratio on the operation of the chamber are determined.
• The effects of satellite droplets and of a high voltage applied between the bases of the chamber are also investigated.

A numerical model of a dilute spray of electrically charged liquid droplets vaporizing in a hot gas is formulated based on a Eulerian description of the gas and Lagrangian tracking of the droplets. The model is used to simulate the dispersion and vaporization of a spray in a cylindrical chamber where the droplets are axially injected with a coflow of hot gas. The effects of the initial size of the droplets and of the gas-to-liquid mass flux and inlet temperature ratios are analyzed, and the conditions under which the droplets fully vaporize in the chamber without impacting on its walls are determined. The ranges of operation where these requirements are met widen when the flow rate of liquid is split into a number of sources and injected through different orifices, which also improves the uniformity of the temperature and vapor mass fraction distributions at the outlet of the chamber. The effects of satellite droplets and of an applied electric field that pushes the charged droplets in the direction in which they are injected are considered.