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Combustion and emission characteristics of multiple fuel injections on a dual fuel engine

In DFE, it is known that emission and thermal efficiency improve by dividing the diesel injection into two at low load. However, the effect by dividing the diesel injection more than two, has not been investigated. Therefore, in this study, the effect of multiple diesel fuel injections on the combustion and exhaust emission characteristics of DFE using natural gas (city gas 13A) was investigated at low load in experiments. The experiments were conducted using a single-cylinder engine with a common rail injection system, varying the number of fuel injection and injection timing. The injection timing was set so that the interval of the injection becomes the parameter. The total injection quantity in one cycle was fixed and equally divided in multiple injections. By adapting double injection, the thermal efficiency did not improve against single injection. Total hydrocarbon (THC) emissions improved in some injection conditions, however increased in other injection conditions. NOx emission increased in narrow injection interval, but improved in wide injection interval. Furthermore, by adapting triple injection, THC emissions and the thermal efficiency improved against single and double injection. Also, NOx emission increased in narrow injection interval, but in wide injection interval NOx emissions did not increase against single injection.