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When appropriately sourced, bioethanol and biodiesel fuels provide an opportunity for nations to increase their energy independence or to reduce greenhouse gas emissions by supplying energy-dense fuels which are miscible with fossilderived gasoline and diesel. These fuels can be used in low concentrations in vehicles with no modifications; in the case of ethanol, only minor changes in the fuel system materials together with a low-cost alcohol sensor are necessary for compatibility with a high concentration. Ethanol provides the beneficial property of having a high research octane number which can be exploited at the high-load operating conditions in modern pressure-charged spark ignition engines. However, the availability of sustainable feedstocks constrains the supply of biofuels, and this limits the level at which they are able to displace fossil fuels. The miscibility of methanol with both ethanol and gasoline enables the penetration of alcohols in the fuel pool to be increased. The present work describes the properties of specific mixtures of gasoline, ethanol and methanol which are blended to be iso-stoichiometric and iso-energetic replacements for mixtures of gasoline and ethanol. A simple analytical approach to the formulation of these ternary blends is described on the basis of the volumetric energy density of the pre-blended components, and a number of further physicochemical properties are characterised, including their stoichiometries, vapour pressures, distillation characteristics and propensities to phase separate. Data on the octane numbers of the blends are reported. The properties of quaternary iso-stoichiometric blends of water, gasoline, ethanol and methanol (the so-called hydrous ternary blends) are also examined.

As the control of real driving emissions continues to increase in importance, the importance of understanding emission formation mechanisms during engine transients similarly increases. Knowledge of the NO2/NOx ratio emitted from a diesel engine is necessary, particularly for ensuring optimum performance of NOx aftertreatment systems. In this work, cycle-to-cycle NO and NOx emissions have been measured using a Cambustion CLD500, and the cyclic NO2/NOx ratio calculated as a high-speed light-duty diesel engine undergoes transient steps in load, while all other engine parameters are held constant across a wide range of operating conditions with and without exhaust gas recirculation. The results show that changes in NO and NOx, and hence NO2/NOx ratio, are instantaneous upon a step change in engine load. NO2/NOx ratios have been observed in line with previously reported results, although at the lightest engine loads and at high levels of exhaust gas recirculation, higher levels of NO2 than have been previously reported in the literature are observed.