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Reduction of Hydrocarbon Emissions from SI-Engines by Use of Carbon Pistons
ISSN: 0148-7191, e-ISSN: 2688-3627
Published October 01, 1995 by SAE International in United States
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The use of pistons made of fine grain carbon was investigated in a spark-ignition engine within a European Community funded research project (TPRO-CT92-0008). Pistons were designed and manufactured and then tested in a single cylinder engine. Due to the carbon material's lower coefficient of thermal expansion the top land clearance between piston and cylinder can be reduced by a factor of three in comparison to standard aluminium designs.
Under steady-state part-load operating conditions the emission of unburned hydrocarbons can be reduced by more than 15% compared to aluminium pistons, without significant penalties in NOx-emissions. Simultaneously, a small improvement in fuel economy of about 2% is observed. At full-load blow-by leakage flow is reduced by more than 50%. The piston crown temperature is about 30°C higher with the carbon piston than with the standard aluminium piston, due to the lower thermal conductivity of the carbon material. Under cold-start and warm-up conditions the reduction in hydrocarbon emissions can be as high as 28%, depending on the piston design. For maximum benefit the carbon piston crown has to be coated, in order to close the pistons porosity.
CitationHaag, J., Heuer, J., Krämer, M., Pischinger, S. et al., "Reduction of Hydrocarbon Emissions from SI-Engines by Use of Carbon Pistons," SAE Technical Paper 952538, 1995, https://doi.org/10.4271/952538.
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