Numerical and experimental investigation of the influence of bio-Diesel blends on the mixture formation, combustion and emission behavior of a modern HSDI Diesel engine

The aim of this work has been to investigate the influence of bio-diesel (FAME - fatty acid methyl ester) and reasonable blends of FAME and diesel, on the behavior of the mixture formation, the combustion process and the emission levels of a modern diesel engine. Therefore experimental investigations have been carried out on a single cylinder engine which is a modification of a four cylinder production HSDI (high speed direct injection) diesel engine. Cylinder pressure and tail-pipe emissions have been measured. Additionally the injector has been mounted on a flowmetering device to gather information about the pure flow through the injection system depending on the fuel type. In parallel with the experimental investigations CFD (computational fluid dynamics) calculations have been carried out in order to closely check local effects inside the injector and the combustion chamber. The applied chemical and physical models have been extended with the relevant property data for FAME and blends of FAME and diesel. The different methods lead to a quite uniform picture about the effects of bio-diesel, which means, that generally the hardware of modern diesel engines is capable of dealing with the investigated amounts of bio-fuel without any modification. The fuel efficiency usually decreases but emissions can be improved with raising amount of FAME.