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Blending gasoline with oxygenates like ethanol, MTBE or ETBE has a proven potential to increase the thermodynamic efficiency by enhancing knock resistance. The present research focuses on assessing the capability of a 2- and tert-butanol mixture as a possible alternative to state-of-the-art oxygenates. The butanol mixture was blended into a non-oxygenated reference gasoline with a research octane number (RON) of 97. The butanol blending ratios were 15% and 30% by mass. Both the thermodynamic potential and the impact on emissions were investigated. Tests are performed on a highly boosted single-cylinder gasoline engine with high load capability and a direct injecting fuel system using a solenoid-actuated multi-hole injector. The engine is equipped with both intake and exhaust cam phasers. The engine has been chosen for the fuel investigation, as it represents the SI technology with a strongly increasing market share.

Combustion and pollutant formation in a new recently introduced Common-Rail DI Diesel engine concept with roof-shaped combustion chamber and tumble charge motion are numerically investigated using the Representative Interactive Flamelet concept (RIF). A reference case with a cup shaped piston bowl for full load operating conditions is considered in detail. In addition to the reference case, three more cases are investigated with a variation of start of injection (SOI). A surrogate fuel consisting of n-decane (70% liquid volume fraction) and α-methylnaphthalene (30% liquid volume fraction) is used in the simulation. The underlying complete reaction mechanism comprises 506 elementary reactions and 118 chemical species. Special emphasis is put on pollutant formation, in particular on the formation of NOx, where a new technique based on a three-dimensional transport equation within the flamelet framework is applied.

Ultra-lean burn conditions (λ>1.8) is seen as a way for improving efficiency and reducing emissions of spark-ignition engines. In comparison to conventional operation with stoichiometric mixture, this itself raises fundamental issues in terms of combustion physics, among which the significant reduction of the laminar flame speed, increase of the laminar flame thickness as well as an increased sensitivity to local fuel/air equivalence ratio variations are all essential to be accounted for. In particular, the effect of modified laminar flame characteristics on flame stretch during the early flame development in a spark ignited engine is of importance. In the present work the cycle-to-cycle combustion variations of ultra-lean burn operation is modeled, by utilizing capability of Large-Eddy Simulation (LES). Then results are analyzed after a careful validation of the aerodynamics and spray/flow interactions that have initially been predicted.