Experimental study on a small diesel genset dual fuelled with methane

A dual fuel engine is an internal combustion engine where the primary gaseous fuel source is ignited by a small quantity of diesel known as the ‘pilot’ that is injected towards the end of the compression stroke. The motivation to dual-fuel a CI engine is partly economic due to the lower cost of the primary fuel, and partly environmental as some emissions characteristics are improved. In this study, a direct injection four cylinder CI engine, typically used in engine-generator set or genset applications, was fuelled with methane. The performance and emissions (NOx and smoke) characteristics of various gaseous concentrations were recorded at 1500rpm (synchronous speed) and at no load, ¼, ½, ¾ and full load. In order to investigate the combustion performance under these different conditions, a three zone heat release rate analysis was applied to the data. The resulting mass burned rate, ignition delay and combustion duration are used to explain the emissions and performance characteristics of the engine. The results of the study showed that the combined effect of dual fuelling a DI engine with methane reduces both NOx and smoke emissions. This technology provided a beneficial method to manipulate the classic diesel engine NOx-smoke tradeoff.