Experimental Study On Performance And Emissions Characteristics Of CI Engine Operated With Methanol/DME Dual-Fuel

Global energy crisis and environmental issues makes the development of clean alternative fuels arousing increasing attention from people. As clean and oxygen-containing fuels, both dimethyl ether and methanol have been considered to be the most promising alternative fuels due to the broad resources of its feed stocks and excellent performance of emissions. Compared with conventional combustion mode, Homogeneous charge compression ignition (HCCI) combustion enables lower emissions and higher thermal efficiency, however the operating range in the DME HCCI engine is limited to low load because of knocking, and the methanol can not compression ignition in diesel engine. We can solve these two problems by the combination of DME injected into intake pipe and methanol injected directly into cylinder.The test bed of combination combustion engine is modified and established on a ZS195 prototype diesel engine. By adjusting the amount of DME/methanol supply and the advance angle, the experimental study on engine's performance of combustion and exhaust emissions were carried out, with EGR to expand the operating range. With the use of Gas Chromatography (GC) and Fourier Transform Infrared Spectrometry (FTIR), some unregulated emissions such as methanol, formaldehyde, formic acid, methyl formate from the DME/methanol combination combustion engine are specially analyzed.The result shows that the operating region of DME/methanol engine can be extended effectively with combination combustion mode, and can be extended further with EGR. With the increase of methanol proportion, formic acid, methyl formate, HC and NO_x emissions are reduced, while methanol emissions are increased. And with the increase of eeffective power, formic acid, methyl formate, HC and CO emissions are reduced, while NO_x emissions are increased, the methanol emissions are increased first and then declined, the formaldehyde emissions are declined a little first and then climbed up. As pump timing decreases to 14°BTDC, indicated thermal efficiency increased, the operating region of the engine is extended further, the methanol, HC and CO emissions are increased, while the formaldehyde, NO_x emissions declined. Methyl formate emissions are related to methanol proportion, as increased in the larger proportion while reduced in smaller proportion.