NON-THERMAL PLASMA-ASSISTED COMBUSTION RESEARCH AT LOS ALAMOS

摘要

The application of electric fields to flames has been reported as early as 1814, was applied to furnaces in the 1920's and developed into several applications in the last half of the 20th Century. When the electric field strength is sufficient to cause electrical breakdown of a fuel or fuel/air mixture, plasma effects will dominate. Plasma effects can increase electron and ion temperatures and promote combustion through the formation of 'active' species (such as free radicals) or the dissociation of fuel molecules into smaller, easily-combusted fragments [1]. Plasma-assisted combustion (PAC) is now a timely research topic worldwide [2], pointing to more efficient fossil-fuel usage, conversion of low-grade fuels into higher-grade fuels, and pollution reduction through ultra-lean burn combustion. Our work focuses on non-thermal ('cold') plasmas (NTPs), particularly for enhancing combustion stability, efficiency, and reducing undesirable emissions. This is in contrast to thermal ("hot") plasmas. Here we discuss representative PAC experiments focused on combustion stability, efficiency, and pollution reduction. Our work has been mainly carried out with silent electrical discharges (also called dielectric-barrier discharges -^sDBDs) - where only the fuel is activated. DBDs are convenient sources for producing atmospheric-pressure NTPs. Using DBD devices, we have tested hydrocarbon fuel activation/conversion systems that fragment hydrocarbons into smaller compounds, increase flame speed, stabilize flames, and operate in very lean burn regimes (where the production of pollutants such as NO{sub}x and CO are expected to decrease). Experiments have been carried out with methane, ethane, propane and butane, as well as the gasoline surrogate liquid iso-octane.