The combustion of diesel fuel emulsions with immiscible, low-boiling point liquids, such as water and lower alcohols, presents some interesting outlooks.
A study has been carried out in order to determine the effects on the engine performances and exhaust emissions of ethanol and water as internal phases in diesel fuel unstabilized emulsions - directly formed in the injection line.
Using a four cylinders, direct injection, water-cooled, diesel engine fed with ethanol emulsions (at 10, 20, 30 and 40 mass percentages) and water emulsions (at 10 and 20 mass percentages), data were obtained, the engine speed varying, at full load, from 1100 to 2000 rpm.
Comparison with the diesel fuel operation was made by using two different criteria: constant total energy input rate and constant total mass flow into the engine, Further experiments, varying the load and the injection timing, were also carried out.
The results show that ethanol and water could replace up to 40% and 20%, respectively, of diesel fuel, while keeping the normal engine operating stability.
A better thermal efficiency and an increased ignition delay were obtained by burning both kinds of emulsions.
Carbon monoxide emissions, smoke and particulate mass rates were lower in emulsion - feeding conditions.
Oxides of nitrogen emissions depend mainly on the internal phase amount and on the kind of emulsion and the comparison criteria.
Furthermore, the use of ethanol emulsions seems to affect the size distribution of the exhaust particulate. Such aspect, however, requires additional studies.
Finally, for a better interpretation of the obtained results, a simple zero-dimensional thermodynamic model of the engine cycle was developed.