Electric fields can control charged particles in flames

Researchers at KAUST have conducted a study on the manipulation of charged particles in a burning flame using high voltages. The application of electric fields to control these particles has the potential to reduce soot formation and enhance the stability of flames. The research team, led by Min Suk Cha, believes that this scientific understanding could have implications in various fields such as fire extinction, air and space propulsion, and utilizing flames in space.

Previous knowledge indicated that burning fuels produce electrons and ions. The KAUST team has previously demonstrated that electric fields can induce the flow of these ions, known as an “ionic wind,” which can impact the shape of the flame and the combustion process.

To gain a deeper understanding of this phenomenon, the researchers developed a simulation to illustrate how the electric field influences the ionic wind. The team aimed to create a comprehensive predictive tool, taking into account factors like the strength of the electric field and the distribution of different ion types within the flame.

To validate their predictions, the researchers conducted experiments on a flame inside a cavity exposed to electric fields of up to 2,500 volts. Methane gas entered from one side of the cavity, while oxygen entered from the opposite side, resulting in a central band of flame.

Using a technique called Electric Field Induced Second Harmonic generation (EFISH), the team measured the electric field at various points within the flame using high-power laser pulses. They modified the EFISH technique to incorporate a switch that could rapidly deactivate the voltage, effectively freezing the ions in time and space. This allowed EFISH to capture an accurate snapshot of the ion distribution.

The experimental results generally aligned with the simulation, except for a discrepancy in the local electric field near the fuel outlet. In this region, the experiment revealed an increase in the electric field, whereas the simulation showed minimal change. The heightened electric field was attributed to negatively charged ions from partially burned fuel, which were not accounted for in the simulation. The researchers suggest that future simulations should incorporate measurements of negatively charged ions derived from fuel molecules to improve accuracy.

Cha believes that their scientific investigation in this area is nearing completion, and the team’s next step involves applying their knowledge to practical applications. Potential areas for application include optimizing heat transfer in industrial furnaces, microthrust and propulsion systems, fire extinction techniques, and space utilization.

The research findings have been published in the journal Scientific Reports.

Source: King Abdullah University of Science and Technology

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