The key is the modification of the fuel by the addition of water. This is dispersed in the form of tiny, nanometer-fine structures in the fuel and water is shielded by a layer of surfactant molecules (interfacial film) from the oil component. By this effect the nanodisperse mixture is thermo-dynamically stable (in contrast to an ordinary emulsion which separates into an oil phase and a water phase after a certain time).
In the diesel motor combustion soot as well as nitrous oxide emissions are reduced simultaneously. The so-called "diesel dilemma", a counter-acting effect of reductions in soot and nitrous oxide emissions, can thus be avoided. Besides, the application of water turns out in the combustion to be consumption-neutral, i.e. there are no additional CO2 emissions adverse to climate. This is an essential advantage in comparison to the widespread soot filter technology. The water addition to the fuel already begins with avoiding raw emissions and thus makes a costly and efficiency-lowering exhaust gas aftercare effectively superfluous.
Such nanodisperse, thermo-dynamically stable mixtures are called "microemulsions" for historical reasons. This naming leads to misunderstanding repeatedly. On the one hand, the size scale of the water domains in a microemulsion lies in the nano- and not in the micrometer range. They are clearly smaller. On the other hand, this kind of mixture guarantees a molecularly disperse mixture of water and fuel in the gas phase influencing the combustion process unequalled positively. For the production of such water diesel microemulsions (hydroFUEL), only a minimum of energy is needed, the components must be merely stirred. The water fraction can be chosen at will. Flexibility and stability of these mixtures permits their use as a fuel ready in the tank or an "on-board" production immediately before the combustion process in the vehicle.
The scientists at the chair of Prof. Dr. Reinhard Strey have been working on the realisation of this idea in the Department of Chemistry at the University of Cologne already since 2003. Since then, the research field could be transferred to a variety of different fuels. Beside diesel, microemulsions with petrol and with biofuels of the first (rapeseed oil and biodiesel) and the second generation (Fischer-Tropsch fuels) were formulated. At present, research is directed towards administering water-containing fuels with arbitrary water content to the diesel engine. The aim is to reduce the necessary exhaust gas aftercare to a minimum in order to fulfill the exhaust gas norms becoming more and more strictly.
Source: Universität Köln