Hydrodynamic effects induced by nanosecond sparks
Résumé
[1] Olsen H. et al, 1952, "Microchronometric Schlieren Study of Gaseous Expansion from an Electric", Spark Journal of Applied Physics 23 1157 [2] Kono M et al, 1989, "Mechanism of flame kernel formation produced by short duration sparks", 22 nd Symp. On Combustion 22 1643-1649 [3] Rusterholtz D et al, 2013, "Ultrafast heating and oxygen dissociation in atmospheric pressure air by nanosecond repetitively pulsed discharges", J. Phys.D: Appl. Phys 46 464010 [4] Castela M et al, 2016, "Direct Numerical Simulations of plasma-assisted ignition in quiescent and turbulent flow conditions", PhD thesis References Conclusions • Ns sparks show fast spatial redistribution of the deposited energy (≈5 mm/100 ms in a single pulse) • One of the mechanisms of the spatial energy redistribution is the recirculation of hot gas • Experiments in a pin-to-plane configuration demonstrate the influence of electrode geometry on HD effects • Characteristic size of the active medium is proportional to the number of pulses (energy) in the burst due to synergy between the pulses • Electrode distance is a key factor for tailoring radical species redistribution (rather than total energy or energy density) Hydrodynamic effects induced by ns sparks are monitored by (i) PLIF, (ii) Schlieren and (iii) electrical energy measurement. Asymmetric electrodes OH PLIF in pin-to-plane geometry (P=1 bar, single pulse of 10 ns, U=30 kV) Repetitive nanosecond sparks have numerous applications in combustion : • Ignition/stabilisation of lean/diluted flames • Control of thermo-acoustic instabilities • Reduction of pollutant emission (soot, NO x) We believe that the hydrodynamic effects induced by ns sparks [1,2] coupled with the production of active species [3] can bring a significant improvement for the applications mentioned above. Motivation
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