| 摘要 |
A method and apparatus for injecting a gaseous fuel into a combustion chamber of an internal combustion engine (ICE) cylinder employs a combination of operating modes. First, one of a low load and a high load mode of operation is selected during the operation of the ICE. Low load and high load modes are distinguished by the combustion characteristics of an amount of fumigated fuel added to the combustion chamber. Fumigated fuel that supports combustion will cause high load to be selected. Fumigated fuel that does not support combustion will cause low load to be selected. A directly injected amount of fuel is provided under low load. Under high load, a directly injected quantity of fuel is added when the piston is near top dead center to allow the engine to meet load requirement above that provided by the fumigated fuel. Under low load, two additional operating regions can be selected, namely, a low speed low load operating mode and a high speed low load operating mode distinguished by a pre-defined engine speed. Under low load low speed mode, fumigated fuel is barred from the combustion chamber. Under high speed low load, the amount of fumigated fuel is determined at a lower end by a pre-defined leakage flow rate. Combustion of either of the directly injected and the fumigated fuel can be initiated by a pilot fuel, which is generally injected directly into the combustion chamber when the piston is near top dead center prior to a power stroke. However, a quantity of pilot fuel can be introduced earlier in the compression stroke or in the intake stroke under high load conditions.
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