The Advanced Low Pilot Ignited Natural Gas Engine: A Low NO_x Alternative to the Diesel Engine

High nitrogen oxides (NO_x) and particulate matter (PM) emissions restrict future use of conventional diesel engines for efficient, low-cost power generation. The advanced low pilot ignited natural gas (ALPING) engine described here has potential to meet stringent NO_x and PM emissions regulations. It uses natural gas as the primary fuel (95 to 98 percent of the fuel energy input here) and a diesel fuel pilot to achieve compression ignition. Experimental measurements are reported from a single cylinder, compression-ignition engine employing highly advanced injection timing (45°–60°BTDC). The ALPING engine is a promising strategy to reduce NO_x emissions, with measured full-load NO_x emissions of less than 0.25 g/kWh and identical fuel economy to baseline straight diesel operation. However, unburned hydrocarbons were significantly higher for ALPING operation. Engine stability, as measured by COV, was 4–6 percent for ALPING operation compared to 0.6–0.9 percent for straight diesel.