Expanding the Low Load Limit of HCCI Combustion Process Using EIVO Strategy in a 4VVAS Gasoline Engine 2012-01-1121
Homogeneous charge compression ignition (HCCI) technology is promising to reduce engine exhaust emissions and fuel consumption in gasoline engine. However, it is still confronted with the problem of its limited operation range. High load is limited by the tradeoff between the quantity of working charge and dilution charge. Low load is limited by the high residual gas fraction and low temperature in the cylinder.
One of the highlights of HCCI combustion research at present is to expand the low load limit of HCCI combustion by developing HCCI idle operation. The main obstacle in developing HCCI idle combustion is too high residual gas fraction and low temperature to misfire in cylinder. This paper relates to a method for achieving the appropriate environment for auto-ignition at idle and the optimal tradeoff between the combustion stability and fuel consumption by employing EIVO valve strategy with an equivalent air-fuel ratio.
HCCI operation range was successfully extended to idle condition. Good combustion stability can be achieved at 800 r/min, 85 kPa NIMEP condition. The EIVO strategy could used to expand the low limit of HCCI combustion with a equivalent air-fuel ratio at different speeds. The fuel consumption could be improved by lean combustion and direct fuel injection strategy.