A computational framework for simulating and analyzing primary atomization in electrically charged Diesel-type jets

Abstract

A robust computational framework for simulating primary atomization in electrically charged liquid hydrocarbon jets is developed, tested and demonstrated in this work. First-principles-based numerical methods developed specifically for high-fidelity direct numerical simulations of electrohydrodynamic (EHD) flows are implemented within a conservative flow solver using an unsplit, geometric volume-of-fluid transport scheme that includes EHD effects. The numerical framework globally conserves mass, momentum, and the electric charge density even at the gas–liquid interface where discontinuities exist. A novel approach using a separate mesh is used to obtain accurate boundary conditions of electric potential on the computational domain. Simulations employ a recently developed physics extraction tool that tracks every breakup and coalescence event occurring during an atomizing spray. Data characterizing the atomization processes are stored in a Neo4j graphical database providing an easily accessible format to query and study the atomization process. The framework is demonstrated in five simulations focused on a region of interest relevant to primary atomization and varying fluid and EHD parameters, confirming the robustness of the methodology and its tools. Statistics for droplet size, breakup and coalescence events, onset of primary atomization, and spray cone angle are reported for all simulations revealing earlier and enhanced liquid breakup and greater spray dispersion with increasing electric charge. Some comparison with experimental work reveals the role of electric stress in de-stabilizing the jets and breakup consistent with the Plateau–Rayleigh mechanism.