Effect of addition of Oxygenated fuels on combustion and emission performance of diesel engine
Oxygenates blended into diesel fuel can serve at least two purposes. Components based on renewable feedstock make it possible to introduce a renewable component into diesel fuel. Secondly, oxygenates blended into diesel fuel might help to reduce emissions. Particulate matter (PM) and oxides of nitrogen (NOx emissions) are the two important harmful emissions in diesel engine. Fuel modification, modification of combustion chamber design and exhaust after treatments are the important mean to reduce such emissions. Among different alternative fuels, oxygenated fuel is a kind of alternative fuel. Diethylene glycol dimethyl ether (DGM), dimethoxy methane (DMM), dimethyl ether (DME), methyl tertiary butyl ether (MTBE), dibutyl ether (DBE), dimethyl carbonate (DMC), methanol, ethanol and diethyl ether (DEE and DME-a Cetane Improver) have played their role to reduce diesel emissions. These fuels can either be used as a blend with conventional diesel fuel or as a neat fuel. The presence of oxygen in the fuel molecular structure plays an important role to reduce PM and other harmful emissions from diesel engine. It has been found that the exhaust emissions including PM, total unbrunt hydrocarbon (THC), carbon monoxide (CO), smoke and engine noise were reduced with oxygenated fuels. NOx emissions were reduced in some cases and were increased depending on the engine operating conditions. The reductions of the emissions were entirely depended on the oxygen content of the fuel. It has been reported that the combustion with oxygenated fuels were much faster than that of conventional diesel fuel. This was mainly due to the oxygen content in the fuel molecular structure and the low volatility of the oxygenated fuels. The presence of DEE and DME increases the volatility and decrease the boiling point in comparison to diesel fuel. The blended fuel retains the desirable properties of diesel fuel but includes the cleaner burning capability of DEE/DME.