Reduction of Hydrocarbon Emissions from SI-Engines by Use of Carbon Pistons

Paper #:
  • 952538

Published:
  • 1995-10-01
Citation:
Haag, 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.
Pages:
12
Abstract:
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.
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