A numerical investigation of electric field effects on spray jet flames with charged fuel droplets

The use of electrostatic fields to control the location of charged fuel droplets in a spray jet flame is investigated as a means of developing fuel-flexible combustion systems to accelerate the transition to carbon-neutral transportation. The focus of this work is on the effects of an external electric field parallel to the jet direction on the spray penetration and fuel vapour distribution, and the subsequent effects on flame shape and location. This study is conducted using large-eddy simulations under the assumption that there is negligible production of charged species during combustion. Non-reacting simulations at atmospheric conditions show that with practical electrostatic fields and droplet charges, it is possible to significantly change the spray penetration. Electric forces in the opposite direction to the spray jet lead to a reduction in the spray penetration, an effect that increases with stronger electrostatic fields. This leads to an increase in drag between the droplets and the air flow, resulting in a smaller penetration of the air jet. The reduced droplet penetration confines the fuel vapour to a region closer to the jet inlet and leads to a more compact flame in the corresponding reacting cases. Similar trends are observed in simulations performed at a higher pressure and temperature. This study suggests that electrostatic fields can be used with charged fuel droplets to provide an element of control over spray jet flames, which may allow for the development of novel hybrid thermal–electric combustion systems.