Performance of a pilot-ignited HCCI engine

With increasingly stringent automotive emissions standards, and rising gasoline prices, Homogeneous Charge Compression Ignition (HCCI) engine research has been increasingly prolific. Pilot-ignited engines, a subset of HCCI engines, have been shown to duplicate the high-load performance of diesel engines, without the drawbacks of high particulate and nitrous oxide emissions. This work focused on evaluating the performance of a Volkswagen 1.9 Liter direct injected turbodiesel. Evaluation of the combustion heat released was achieved using a two-zone, zero dimensional model. Heat release rates, cumulative heat release and mass burned fraction were obtained from the in-cylinder pressure data taken.; The engine was tested in both diesel and pilot-injected dual fuel modes, varying load, speed and natural gas percentage. The engine was tested at one-quarter, one-half and full loads and at speeds of 1800 RPM, 2000 RPM, 2500 RPM and 3000 RPM. Power in pilot-ignited mode duplicated the diesel power except at the highest two speed conditions. High load efficiencies were slightly lower in pilot-ignited mode, with the gap widening as speed was increased. However, heat release analysis indicates that the pilot-ignited efficiency could be higher than diesel efficiency if the correct injection timing is used. Low load efficiencies were much lower for pilot-ignited than diesel. Natural gas substitution rates as high as 95 percent were achieved, with all conditions being misfire-limited, except for 1800 RPM, full load, which was knock-limited.