Low Engine-Out NOx Emissions with DME Using High Pressure Injection

Dimethyl Ether (DME) is a promising future compression ignition fuel, particularly when derived from renewable, CO₂-neutral feedstocks. While it is generally well-known that DME produces very little soot when burned, few studies have explored its low-temperature combustion behavior, where the potential for ultra-low engine-out emissions of both NO_x and soot may exist. The present work shows the results of a single-cylinder engine operating with DME below the level of the US 2010 Heavy Duty Onroad Standard for NO_x, without NO_x aftertreatment. A high-pressure oil-over-fuel intensified injection system was used to maintain proper air utilization and high combustion efficiency, in combination with intake oxygen control using relatively high levels of EGR for low NO_x. Fuel-related material issues notwithstanding, the engine results point toward a potentially cost-effective and efficient means of utilizing bio-derived fuels.