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The relationship between ignition, lift-off length and soot formation was investigated for a collection of fuels in an optically-accessible modified 2-stroke engine under a set of typical quasi-steady state Diesel DI conditions. Five fuels including biodiesel blends and Fischer-Tropsch fuels have been selected for their potential to substitute conventional diesel with no major modifications on the engine hardware, and were previously characterized under ambient pressure following ASTM standards. Fuels were injected into a large volume through a single-hole nozzle at three levels of injection pressure, by sweeping ambient temperatures at constant density, and ambient densities at constant temperature. The 8 ms single-shot injections were long enough to reach the stabilization of a free diffusion flame. The OH-chemiluminescence was imaged and lift-off length was measured via image post-processing.

The main objective of the study described in this paper is to explore the potential of different post-injection patterns, with a plain common rail system, for reduction of soot emissions in HD diesel engines. Test have been carried out in a single-cylinder engine at several critical engine operation points from the European Steady state test Cycle (ESC). At these operation points, EGR was introduced to reduce NOx emissions to a given value, and then different post-injection patterns were produced. A parametric study was performed, considering the time between injections and the post-injected fuel mass as the main variables. In every case the total injected fuel mass was kept constant. Aside from the experimental data obtained in the engine tests, a diagnosis model was applied to calculate heat release laws and other parameters depicting the combustion process.

Modern DI Diesel engines are widely used in automotive applications. Improvements in performance and emissions have been produced in the last ten years on these engines, so that they are now very competitive in comparison with petrol engines. However, cold startability is one of the main challenges of Diesel engines, since great differences with petrol engines still can be noticed. Today, in small engines glow plugs are universally used as an aid system for cold start. In large engines, where the cold start is less critical, intake air heating technology is employed. In this paper the application of this technology to small engines is evaluated in terms of its viability for cold starting and HC/CO emissions and combustion noise reduction during the warm-up phase of the engine.

Regulatory standards on diesel engines emissions will decidedly become more restrictive in coming years. This has led to the development and implementation of alternative fuels. The objective of this paper is to evaluate the potential of Sasol Fischer-Tropsch (FT) diesel fuel to improve the reduction of emissions in a direct injection diesel engine with a high pressure common-rail injection system (HDI engine from PSA Peugeot-Citroën). In principle, FT diesel fuel shows significant advantages in reducing emissions over a standard diesel fuel due to its low aromaticity, high cetane rating and high H/C rating. Initial tests with two 406 HDI Euro 2 vehicles with standard calibration showed very favourable trends on exhaust emissions in comparaison with reference fuel (CEC RF73-A-93 type). Sasol FT diesel fuel gave significant improvement on specific fuel consumption, and decreased the HC, CO, CO2 and particulate emissions without degrading NOx emissions.