Due to growing interest in utilizing natural gas as an alternative fuel in internal combustion engines, a study on the use of natural gas for dual-fuel combustion strategies in a heavy-duty engine was performed to examine the diesel pilot ignition (DPI) and reactivity controlled compression ignition (RCCI) combustion strategies. In Part 1 of this work, the transition between the DPI and RCCI combustion regimes was studied via the direct control of the SOI timing. At the relatively rich condition of ϕ = 0.72, the performance of both combustion strategies was comparable. In Part 2 of this work, the effect of the equivalence ratio on each combustion regime was examined. It was observed that at richer conditions the performance of each combustion regime was similar. However as the conditions became leaner, the performance improved for RCCI combustion and was degraded for DPI combustion. In Part 3 of this work, the effect of fueling rate was explored at a relatively lean operating condition (ϕ = 0.52). It was seen that the fueling rate has little effect on the combustion performance as the engine load was increased. The strong influence of the equivalence ratio on the combustion performance of the RCCI and DPI combustion strategies indicates the both combustion regimes are recommended to engine applications with air handling systems which generate relatively rich in-cylinder conditions; for engine applications with air handling systems which allow for relatively lean in-cylinder conditions, the RCCI combustion regime is recommended.

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