Flow Reactor Studies of Low Temperature Plasma-Assisted Kinetics of Methanol

Recently, low-temperature plasmas (LTP) igniters have gained considerable attention as a promising replacement for conventional spark plugs. For next-generation engine applications, integrating LTP could facilitate the enhancement of combustion at near ignition limit conditions to enable higher-efficiencies with lower emissions to potentially improve the sustainability of future mobility with affordable, and scalable renewable fuels. However, there is a lack of understanding of how plasma chemistry effects can enhance the basic combustion phenomena for oxygenated fuels. In the present work, a LTP flow reactor facility is used to examine the kinetics of methanol plasma-assisted pyrolysis and oxidation. In comparison to the thermal reactions, considerable enhancement in fuel decomposition was observed for both plasma-assisted pyrolysis and oxidation for T < 900 K. For plasma-assisted pyrolysis, fuel decomposition exhibited a linear rate of decomposition with respect to temperature, due to collisional quenching reactions with electronically excited states of nitrogen and electron-impact reactions. In the presence of oxygen, further efficient decomposition of fuel and oxygen is observed with the plasma in comparison to the thermal reactions. Oxidation of methanol in the presence of a plasma exhibited demonstrated a lowering of the hot-ignition temperature of methanol, but also significant coupling to NOx formation kinetics for T < 1200 K. The results demonstrate new insight into the kinetics governing plasma-assisted combustion for renewable fuel applications.