Combustion and emission characteristics of a direct-injection gasoline engine using the MMT fuel additive gasoline

• MMT influences engine combustion, gaseous emissions and particulate matter emissions.
• Peak in-cylinder pressure and heat release rate increase slightly with the increase of MMT content in test fuels.
• It reduces HC emission but increases NOx and CO emissions.
• Particulate number and mass concentrations increase significantly with the increasing in MMT.

In recent years, Methyl-cyclopentadienyl Manganese Tricarbonyl (MMT) has been widely used as a gasoline additive to improve the octane rating and antiknock of the fuel. Meanwhile, particulate emissions from the gasoline direct injection (GDI) engine have become a subject of concern. This study is aimed to investigate the impact of fuel (ultralow sulfur gasoline with the additive MMT) on the combustion characteristic, gaseous emissions (HC, CO and NOx) and particulate matter (PM) emissions in a GDI research engine, under the operating conditions of stoichiometric air/fuel ratio, 2000 rpm engine speed and 30–150 N m engine torque. The experimental results show that, in the GDI engine, the cylinder pressure increases slightly with the increase of MMT content in the test fuels. The use of MMT increases the peak heat release rate and ignition delay slightly but the combustion duration does not change significantly. Depending on the fuel used, the HC emissions decrease significantly, while the CO and NOx emissions increase with the increase of MMT content in the test fuels. There was a measurable effect on PM emissions by the introduction of the MMT additive gasoline fuels. The total particulate mass and number concentrations significantly increase with the increase of the MMT content in the test fuels. At low and medium loads, there is little change in geometrical mean diameter of the particles, while it would become larger when the tested engine operated on the high engine condition.