Danish contribution to IEA-AMF Annex 53: Fuels for efficiency

The objective of this IEA Annex is to determine the state of the art of fuels for high efficiency combustion engine operation. The rationale behind this is that engines of today are restricted by fuel properties from obtaining the highest possible efficiency. For instance the octane number of commercial gasoline limits the possible compression ratio which in turn limits efficiency. On the diesel side the cetane rating of commercial fuels has similar impact. In both cases high efficiency operation typically leads to increased NOx emission, which is why manufacturers often settle for a lower efficiency to save cost on aftertreatment systems. It has also been demonstrated that the efficiency of an engine can raised by as much as 20% by means of thermochemical pretreatment of the fuel, providing a heat source is avaiable. Specifically prepared blends of biofuels and diesel have also shown remarkable improvements on both efficiency and emissions. Nowadays a range of new motor fuels are becoming available on the market while at the same time efficiency received ever more attention. These include high-octane alcohol and gaseous fuels high cetane renewable diesels and fuel with special energy saving additives such as friction modifiers. All these new Technologies provide opportunities for raising the efficiency of both new and existing combustion engines. The annex was created in order to provide an overview and to deliver unbiased tests of some of the more promisiong high efficiency fuel techniologies. The specific Danish interest in the annex is due to the need for efficiency gains and optimum utilisation of non-fossil fuels.