HCCI in a Variable Compression Ratio Engine-Effects of Engine Variables 2004-01-1971
Homogeneous Charge Compression Ignition (HCCI) experiments were performed in a variable compression ratio single cylinder engine. This is the fourth paper resulting from work performed at Southwest Research Institute in this HCCI engine. The experimental variables, in addition to speed and load, included compression ratio, EGR level, intake manifold pressure and temperature, fuel introduction location, and fuel composition. Mixture preparation and start of reaction control were identified as fundamental problems that required non-traditional mixture preparation and control strategies. The effects of the independent variable on the start of reaction have been documented. For fuels that display significant pre-flame reactions, the start of the pre-flame reactions is controlled primarily by the selection of the fuel and the temperature history of the fuel air mixture. The magnitude of the pre-flame reaction, also dependent on the fuel selection, has a dominant effect on the start of the main reaction. Exhaust Gas Recirculation (EGR) affects these relationships in complex interactions with intake manifold temperature and pressure, and overall air fuel ratio.