Speaker
Description
Transient plasma ignition (TPI) – where high-energy, short-pulsed, non-equilibrium plasma are used to ignite flammable mixtures – is of interest to engine developers due to the generation of distributed ignition sites that accelerate initial burn rates and reduced electrode erosion that results from the avoidance of breakdown. Transient plasma discharges produce active radicals (O, OH, etc.) and reactive species such as ozone (O3) that could be used to increase fuel/air mixture reactivity leading to improved auto-ignition characteristics. However, there are currently no experimental or modeling TPI data that explains the role of O3 formation mechanisms by low-temperature plasma (LTP) discharges at high pressures, 1 – 8 bar absolute. In the present study, O3 formation characteristics by LTP discharges in desiccated air are investigated within a custom-built optically accessible spark calorimeter for a groundless barrier discharge igniter (GBDI) with a flush mounted and exposed anode tip. Transient plasma is generated using an available high-voltage (~ 35 kV peak), short duration (~12 nanoseconds) pulse generator. Time-resolved in-situ O3 measurement is acquired via UV light absorption method shows the time-evolution of O3 i.e. formation and eventual decomposition of O3 into molecular and atomic oxygen. The effect of pressure, voltage, number of pulses, and types of electrode on O3 generation are studied in detail. The behavior of generated O3 holds the key to understand reaction pathways in TPI. Numerical modeling of LTP discharges is carried out in VizGlow solver in order to better understand the O3 formation and decomposition processes leading to enhanced mixture reactivity. Chemkin-Pro 0D homogeneous reactor simulations are performed to evaluate chemical kinetic pathways responsible for O3 formation. With sufficient knowledge of LTP characteristics from experimental measurements and numerical models, our final goal is to develop a transient LTP igniter for engine applications.
