The goal of future multi-mode (SI/CI) engines is to operate at higher dilution limits and in-cylinder pressures than currently possible, resulting in higher efficiency and lower emissions. However, implementing SACI across the entire load-speed map with extended dilution limits has proven a technological challenge. These operating conditions require spark plugs to deposit large amounts of energy in order to achieve ignition reliably. At such high rates of energy deposition, spark plugs experience increased electrode erosion and thermal losses, which shorten the spark-plug lifetime and lower ignition efficiency. Consequently, in order to safeguard the efficiency gains of future multi-mode engine concepts, new ignition systems are required. Recently, ignition technology based on low-temperature plasmas (LTP) has gained considerable attention as a promising replacement for conventional spark plugs. For multi-mode applications, LTP igniters have been shown to extend the dilution limits of combustion, reduce ignition delay, and suppress end-gas knocking.<br/>For future engines to adopt LTPs in their design, accurate and comprehensive numerical models of LTP ignition must be included into existing engine design software tools. However, there is a lack of validated kinetic mechanisms and an understanding of how plasma chemistry effects can enhance the basic combustion phenomena to promote efficient ignition. In this study, a plasma coupled flow reactor facility is used to examine the kinetics of iso-octane plasma-assisted pyrolysis and oxidation. Experiments were performed in nearly isothermal conditions, by heavily diluting reactive mixtures in nitrogen and several interesting results were observed. For example, oxidation of iso-octane in the presence of a plasma exhibited a transition in the rate of reactivity depending on temperature. For T &gt; 550 K, efficient radical production from plasma reactions enhanced the neutral chemistry to provide a chain-propagating reaction. At T &lt; 550 K, fuel reactivity experienced an acceleration in the rate of reactivity. The results demonstrate new insight into the kinetics governing PAC and provide a new experimental database to facilitate the development and validation of a PAC-specific kinetic mechanisms.

Non-equilibrium plasma assisted kinetics studies of iso-octane

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.