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The diesel/natural gas engine configuration provides a potential alternative solution for PM and NOx emissions reduction from typical diesel engine operations. However, their engine operations suffer from high NMHC/methane emissions and poor engine performance, especially at light loads. By increasing the diesel pilot quantity, the performance and reduction of NMHC/methane emissions can be improved but the emission levels are still very high. Clearly, a typical DOC is not good enough to treat NMHC/methane emissions. Methane has been known as one of most stable species that is difficult to catalytically oxidize in lean burn environment and low exhaust temperatures. An aftertreatment system exclusively designed for treating methane emissions from DDF operations is therefore necessary. The current work is aimed to establish an effective computational tool in order to study the newly proposed catalytic converter system concept on treating methane from DDF operations.

Diesel Dual Fuel (DDF) operation is a promising alternative engine operating mode. Previous research studies have reported a DDF engine operating under low load conditions suffers from high HC emissions, mostly Methane. The current study investigated the use of a multiple direct injection strategy for improvement of low-load DDF operation in a commonrail direct injection single-cylinder diesel engine. Natural gas was supplied at 70% of energy replacement ratio. Results indicated that depending on engine conditions, a double-pulse injection had potential for combustion control and provided an effective way to reduce NOx and methane emissions. Moreover, the double-pulse injection helped improve the combustion stability, reduce the pressure rise rate, and decrease the maximum cylinder pressure, compared to DDF operation with a single pulse injection.

In the skyrocketing fuel price situation, using natural gas by means of a diesel dual fuel (DDF) conversion technique is a promising technology as it is flexible for diesel trucks. However, DDF engines suffer from low engine efficiency and poor emission characteristics at low-to-medium load operations. In this study, two DDF concepts were proposed by using five operating parameters including 1) the number of injection pulses, 2) duration of each injection pulse, 3) injection timing, 4) throttle position, and 5) EGR. The first three parameters were varied in the first concept whereas all parameters were varied in the second one. Results from these two DDF conversion concepts were compared to the simple conversion where the operating parameters for diesel injections were fixed by the standard ECU of the OEM. At light load (2000 rpm, 3.1-bar IMEP), the brake efficiencies in the first and the second concepts were improved from the simple conversion by 21% and 35%, respectively.