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Journal Article

Dedicated GTL Vehicle: A Calibration Optimization Study

GTL (Gas-To-Liquid) fuel is well known to improve tailpipe emissions when fuelling a conventional diesel vehicle, that is, one optimized to conventional fuel. This investigation assesses the additional potential for GTL fuel in a GTL-dedicated vehicle. This potential for GTL fuel was quantified in an EU 4 6-cylinder serial production engine. In the first stage, a comparison of engine performance was made of GTL fuel against conventional diesel, using identical engine calibrations. Next, adaptations enabled the full potential of GTL fuel within a dedicated calibration to be assessed. For this stage, two optimization goals were investigated: - Minimization of NOx emissions and - Minimization of fuel consumption. For each optimization the boundary condition was that emissions should be within the EU5 level. An additional constraint on the latter strategy required noise levels to remain within the baseline reference.
Journal Article

Emission and Ignition Effects of Alternative Fuels at Conventional and Premixed Diesel Combustion

The growing availability of different biofuels and synthetic fuels is leading to increased diversity of automotive fuels. Understanding how fuel properties affect combustion and how engine calibration strategies can compensate for variations in fuel composition is crucial for ensuring proper engine operation in this world of increased fuel diversity. This study looks at the ability to compensate for wide changes in cetane quality. Four different fuels with variations in cetane number, volatility and composition have been tested in a single cylinder engine and compared to diesel fuel. The selected operating conditions represent the entire engine map of a passenger car diesel engine. In part load the effects were investigated for conventional and premixed Diesel combustion. The results show that part load operation is especially relevant for the detection and compensation of varying fuel properties and that, depending on engine load, different control strategies have to be applied.
Technical Paper

Fuel Octane Effects in the Partially Premixed Combustion Regime in Compression Ignition Engines

Previous work has showed that it may be advantageous to use fuels of lower cetane numbers compared to today's diesel fuels in compression ignition engines. The benefits come from the longer ignition delays that these fuels have. There is more time available for the fuel and air to mix before combustion starts which is favourable for achieving low emissions of NOx and smoke though premixing usually leads to higher emissions of CO and unburned hydrocarbons. In the present work, operation of a single-cylinder light-duty compression ignition engine on four different fuels of different octane numbers, in the gasoline boiling range, is compared to running on a diesel fuel. The gasoline fuels have research octane numbers (RON) of 91, 84, 78, and 72. These are compared at a low load/low speed condition (4 bar IMEP / 1200 rpm) in SOI sweeps as well as at a higher load and speeds (10 bar IMEP / 2000 and 3000 rpm) in EGR sweeps.