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Stringent regulations on fuel economy have driven major innovative changes in the internal combustion engine design. (E.g. CAFE fuel economy standards of 54.5 mpg by 2025 in the U.S) Vehicle manufacturers have implemented engine infrastructure changes such as downsizing, direct injection, higher compression ratios and turbo-charging/super-charging to achieve higher engine efficiencies. Fuel properties therefore, have to align with these engine changes in order to fully exploit the possible benefits. Fuel octane number is a key metric that enables high fuel efficiency in an engine. Greater resistance to auto-ignition (knock) of the fuel/air mixture allows engines to be operated at a higher compression ratio for a given quantity of intake charge without severely retarding the spark timing resulting in a greater torque per mass of fuel burnt. This attribute makes a high octane fuel a favorable hydrocarbon choice for modern high efficiency engines that aim for higher fuel economy.

Manganese oxide deposits which are exclusively in the form of Mn3O4, a benign form of manganese, are introduced in the exhaust stream from use of MMT, an octane-enhancing, emission-reducing fuel additive. The physical and chemical effect of these deposits on catalytic converters has generated some controversy in the literature. In this paper, we will focus on the effects that manganese oxide deposits have on catalytic converters. The physical effect of these deposits on the morphology of the converters was investigated by B.E.T surface area measurements, scanning electron microscopy (SEM), and x-ray fluorescence (XRF). The chemical effect was investigated with tests using both slave-engine dynamometers and a pulse-flame combustor to probe for differences in catalyst performance. Data from an extensive vehicle fleet which was tested according to a program designed in consultation with the EPA and the automobile industry will be presented.

The gas-phase chemical kinetics of diesel fuel ignition, without and with ignition-enhancing additives, have been studied. A kinetics chain mechanism was developed to analytically describe the ignition processes. The mechanism treats a surrogate diesel fuel mixture consisting of representative alkane, aromatic and naphthenic components. Wind tunnel experiments were conducted wherein premixed, prevaporized diesel fuel-air flames were stabilized in a model combustor for times measured in minutes, thereby permitting extensive emissions measurements to be made. Ignition delay times predicted by the analytical model were in good agreement with those deduced experimentally.