Method and apparatus for controlling fuel reforming under low-load operating conditions using exhaust recompression in a homogeneous charge compression ignition engine
A direct injection spark ignition multi-cylinder internal combustion engine operative in a controlled auto-ignition combustion mode includes a direct fuel injection system, a spark ignition system and a controllable engine valve system. The air/fuel ratio in the exhaust gas feedstream and an intake mass air flow are measured and an actual air/fuel ratio is calculated based upon the intake mass air flow and engine fueling. Magnitude of a negative valve overlap period between an exhaust valve closing and an intake valve opening is adjusted based upon the measured mass air flow. Timing of pre-injection fueling is adjusted during the negative valve overlap period based upon the measured air/fuel ratio.
GM Global Technology Operations, Inc.
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Tang-Wei Jun-Mo Chen-Fang
Kuo Kang Chang