Experimental platforms for plasma-assisted combustion and plasma reforming with non-thermal plasma have been developed. We studied how flame speed is affected by pulsed high-voltage stimulation below breakdown and how sustainable discharge plasma controls large swirl-stabilized flames. The next step used highly non-thermal plasmas, generated by ns-pulsed high voltage and current-limited high voltage, to study detailed stimulation effects on flames and gas mixtures.
In parallel, we developed laser-based spectroscopic methods to image atomic and molecular radicals, study electron properties, and perform high-speed imaging across multiple timescales to capture immediate plasma effects. These tools, along with others under development, have been applied to investigate plasma properties and plasma stimulation with high spatial and temporal resolution. We now aim to map the initial steps of high-voltage stimulation effects on various flames and gas mixtures.
Ultra-short laser pulses for imaging atom- and radical species dynamics will be further employed and results will be shared between research groups, industry partners, and at scientific conferences and in journal publications. We also collaborate with chemical kinetics modellers to integrate our findings into plasma chemical kinetics research, with the ultimate goal of understanding plasma reaction dynamics in gas mixtures and combustion processes.
Overview: The outcomes are divided into two parts:
(A) Development of state-of-the-art diagnostics:
1. 3D reconstruction of plasma discharges and radicals in turbulent, stochastic conditions.
2. High-repetition rate laser imaging of plasma-based radical dynamics.
3. Collision phenomena captured via fluorescence- and coherence lifetime imaging, including strategies for improving streak cameras.
4. Mirror-less lasing achieved in oxygen-rich volumes, promising for high-temperature plasma studies.
5. Two-photon wide-field imaging of atoms with high signal-to-noise ratios using light-amplitude control and lock-in analysis, mitigating plasma emission.
These developments enable detailed plasma studies across a broad range of timescales.
(B) Plasma phenomena and applications:
1. Plasma-assisted combustion was achieved using gliding arc and nanosecond plasma stimulation, with a focus on fundamental studies of ammonia and methane combustion under different electrode configurations. A comprehensive data bank on plasma-assisted ammonia combustion was built, covering plasma formation, rapid gas heating, shock wave generation, and radical dynamics. Plasma-assisted methane combustion was similarly investigated, revealing differences based on pulsing and electrode configurations. Modelling remains critical for fully understanding plasma-combustion interactions.
2. Plasma reforming dynamics of O2/N2 and CH₄ gas mixtures were studied using gliding arc and nanosecond plasmas. Novel findings revealed an unexpected slow buildup of oxygen atoms during nanosecond plasma formation. Hydroxyl radical distributions were characterized, suggesting strong gas heating (~4000 K) in the gliding arc. CH₃ and CH radical dynamics during CH₄ reforming displayed faster evolution compared to oxygen atoms. Data is being shared with collaborators developing plasma reforming models for CH₄ with/without CO2 and low O2 concentrations.
