The Effect of Piston Topland Geometry on Emissions of Unburned Hydrocarbons from a Homogeneous Charge Compression Ignition (HCCI) Engine 2001-01-1893
The effect of crevice volumes on the emissions of unburned hydrocarbons from a Homogeneous Charge Compression Ignition (HCCI) engine has been experimentally investigated. By varying the size and the geometry of the largest crevice, the piston topland, it was possible to ascertain whether or not crevices are the largest source of HC. Additionally, information on quenching distances for ultra lean mixtures was obtained. The tests were performed on a single cylinder engine fuelled with iso-octane.
The results showed that most of the unburned hydrocarbons descend from the crevices. Increasing the topland width to some degree lead to an increase in HC. A further increase in topland width (>1.3 mm) resulted in a reduction of HC when using mixtures richer than λ ≈ 2.8, indicating that some of the mixture trapped in the topland participates in the combustion. In conditions when combustion occurred in the topland, the HC was rather insensitive to the height of the topland. By opening up the topland, the HC emissions were in some cases reduced by over 50 %.
Citation: Christensen, M., Johansson, B., and Hultqvist, A., "The Effect of Piston Topland Geometry on Emissions of Unburned Hydrocarbons from a Homogeneous Charge Compression Ignition (HCCI) Engine," SAE Technical Paper 2001-01-1893, 2001, https://doi.org/10.4271/2001-01-1893. Download Citation
Magnus Christensen, Bengt Johansson, Anders Hultqvist
Division of Combustion Engines, Lund Institute of Technology, Scania CV
International Spring Fuels & Lubricants Meeting