Karl Alexander Heufer

Hot surface pre-ignition in direct injection spark ignition engines investigations with tailor-made fuels from biomass

Two promising alternative fuel candidates for spark-ignition engines, 2-butanone and 2-methylfuran, have been identified in the context of the Cluster for Excellence ‘Tailor-Made Fuels from Biomass’. To further explore the potential of these fuels for spark-ignition engine application, experimental and numerical investigations into the occurrence of the abnormal combustion phenomenon of hot surface–induced pre-ignition have been conducted, with pure ethanol, RON97 E10, and pure iso-octane as reference fuels. For the experimental investigations, a single-cylinder engine with a compression ratio of 11, equipped with a glow-plug to create a hot spot in the cylinder, was operated at 1500 r/min and 1500 mbar charge pressure. Each fuel was tested with several glow-plug temperatures until a minimum pre-ignition frequency of 2% was observed. The results show that 2-methylfuran reaches its 2% pre-ignition frequency at a glow-plug temperature of 880 °C, which is 16 °C higher than the 2% pre-ignition frequency of ethanol at 864 °C and 10 °C less than RON97 E10 with 890 °C. Iso-octane showed the lowest pre-ignition resistance with a 2% pre-ignition frequency at a glow-plug temperature of 853 °C, and 2-butanone was most resistant against pre-ignition in this study with a 2% pre-ignition frequency at 932 °C. Further numerical investigations, including zero-dimensional ignition delay time calculations and three-dimensional computational fluid dynamics simulations, revealed a clear connection between the surface ignition frequency of these fuels and their reaction kinetics.

Development of a Model for Predicting the Knock Boundary in Consideration of Cooled Exhaust Gas Recirculation at Full Load

Engine knock limits the efficiency of turbocharged SI engines at high loads. The occurrence of this phenomenon can be inhibited by deploying recirculation of cooled exhaust gas (EGR) at full load. However, the development of full load EGR combustion systems cannot be per-formed in the 0D/1D engine simulation, as no meaningful models for the reliable prediction of the knock limit under the influence of EGR exist.