Browse Publications Technical Papers 2011-01-1391
2011-04-12

Glow-plug Ignition of Ethanol Fuels under Diesel Engine Relevant Thermodynamic Conditions 2011-01-1391

The requirement of reducing worldwide CO₂ emissions and engine pollutants are demanding an increased use of bio-fuels. Ethanol with its established production technology can contribute to this goal. However, due to its resistive auto-ignition behavior the use of ethanol-based fuels is limited to the spark-ignited gasoline combustion process. For application to the compression-ignited diesel combustion process advanced ignition systems are required. In general, ethanol offers a significant potential to improve the soot emission behavior of the diesel engine due to its oxygen content and its enhanced evaporation behavior.
In this contribution the ignition behavior of ethanol and mixtures with high ethanol content is investigated in combination with advanced ignition systems with ceramic glow-plugs under diesel engine relevant thermodynamic conditions in a high pressure and temperature vessel. The investigation focuses on optimizing the injection conditions, especially injection pressure and rate. Optical measurements are performed by high speed imaging of the fuel injection and ignition, and evaluated in terms of ignition and flame propagation. The high speed imaging technology furthermore enables to gain information on the statistical behavior of the ignition process and thus provides a direct assessment of the repeatability of the ignition and combustion process.
The results of the ignition investigation aim at improving the understanding of the glow-plug-induced ignition process in order to provide a reliable ignition strategy for the diesel engine operation with fuel with high ethanol content. The results show that the favorable spray targeting relative to the glow-plug depends on the glow-plug design. Furthermore a moderate injection pressure improves the ignition reliability of the ethanol fuels. The latter leads to the hypothesis that reduced injection-induced shear rates improve the ignition behavior by diminishing shear-induced quenching in the ignition zone in the direct vicinity of the hot glow-plug surface.

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