The Potential of Enhanced HCCI / CAI Control Through the Application of Spray Guided Direct Injection 2008-01-0035
In the current study a single cylinder Spark Ignited engine has been operated in Controlled Auto Ignition mode with centrally mounted spray guided direct injection, employing negative valve overlap to achieve the conditions required for auto-ignition. The injector is a type known in the market and utilises air at elevated pressure to assist preparation of the fuel and delivery of the fuel spray into the combustion chamber. Operation of the injector enables a high degree of control for fuel and air delivery, particularly with regard to stratification of fuel, temperature, air and turbulence within the chamber.
Engine test data show that variation in injection parameters at a fixed engine condition yields high authority over the CAI combustion process. A range of combustion phasing is achieved from 355 to 375 degrees ATDC for the timing of 50% Mass Fraction Burned, whilst the range of maximum pressure rise rate is 70 to 450 kPa / degree. The application of these injection strategies to load range extension enables a Net IMEP of 100 to 700 kPa at an engine speed of 2000 rpm whilst observing a maximum pressure rise rate of 300 kPa / degree.
The ability to vary injection parameters on an individual cylinder and per-cycle basis, coupled with the high authority of this injection system over CAI combustion, indicates a clear potential to address the key issues of CAI operation in a dual-mode SI engine.