An experimental study to assess the potential of homogeneous charge compression ignition diesel combustion with various fuels for light-duty engines

Abstract

Single-cylinder engine tests were carried out to assess the potential of homogeneous charge compression ignition (HCCI) diesel combustion compared to the conventional heterogeneous operation mode. For the experiments a single-cylinder engine with a cylinder volume of 0.421 litre was used. Besides the comparison of conventional operation and HCCI operation of the same engine special emphasis was put on the utilization of synthetic fuels such as gas-to-liquid (GtL) or biomass-to-liquid (BtL) fuels. Therefore, in addition to a standard winter diesel, a fuel with mid-sized n-alkanes and mixtures of n-alkanes and aromatic hydrocarbons was used to investigate the influence of different ignitabilities and boiling curves on the combustion. A great advantage of synthetic fuels is the possibility to design them according to the combustion process requirements. In addition, these GtL or BtL fuels will lead to a higher independence from fossil fuels. To assess the potential of HCCI combustion compared to conventional diesel combustion the engine must have the capability to run in both modes. While using the different fuels several engine operation parameters like injection timing and splitting were varied in order to obtain information about their effect on combustion as well as on engine out-emissions. Furthermore, full-load curves for the different fuels were identified to find out where HCCI operation can be applied in an engine map.