Biofire – Biogenic Fuel Ignition Research

Abstract

The increasing use of biofuels is a major challenge for combustion engine manufacturers in terms of performance and CO2 efficiency. The cetane number, as it is one of the most important fuel numbers for Diesel fuels, is derived from the ignition delay which represents the period between the beginning of fuel injection and the start of combustion. This ignition delay is evaluated by using a single cylinder test engine and measuring the time difference between the signal of the needle stroke sensor which is mounted directly at the injection valve and the maximum pressure increase in cylinder.This conventional test method for fossil fuels, however, determines ignition behavior of biofuels only insufficiently. The pressure increase of biofuels at start of combustion is less steep due to their lower reaction kinetics and spray quality and therefore results in inaccuracies concerning the determination of cetane numbers.The method suggested by the bioFIRe project starts with a pressure pattern analysis in order to receive parameters that provide important conversion points in the combustion process. Thus, the ignition delay of fuels - as currently understood - is reflected correctly. This can be achieved by the calculation of statistically, thermodynamic and reaction kinetic parameters for the combustion and the pressure pattern. This allows to determine the cetane number for biogenic as well as for fossil diesel fuels.The final aim for a successful introduction of the new determination method for cetane numbers is to proof its reproducibility and accurateness. Besides, this method has to be licensed by the Standards Committee.