PARTIALLY STRATIFIED COMBUSTION OF NATURAL GAS FOR SPARK IGNITION ENGINES

In this work, the advantages of partially stratified direct injection natural gas versus premixed port-fueled injection natural gas spark ignited engines has been studied. The volumetric efficiency, ratio of specific heats and turbulent kinetic energy was found to be higher with direct injection versus port-fueled injection thus improving thermal efficiency. A background study of optical chamber experimental data was performed to develop an understanding on the effect of pressure ratio on direct injection of methane under both fully-expanded (sub-sonic) and under-expanded (super-sonic) conditions. Under-expanded jets had a noticeable advantage in terms of turbulent kinetic energy, which led to enhanced air entrainment and mixing. An experimental study using a 200bar four hole 1mm diameter injector was performed repeatedly for upstream versus downstream pressure ratios, within the range 1.3 \u3c pressure rati