Particulate morphology and toxicity of an alcohol fuelled HCCI engine

Abstract

Homogeneous charge compression ignition (HCCI) engines are attracting attention as next-generation internal combustion engines mainly because of very low NOx and PM emission potential and excellent thermal efficiency. Particulate emissions from HCCI engines have been usually considered negligible however recent studies suggest that PM number emissions from HCCI engines cannot be neglected. This study is therefore conducted on a modified four cylinder diesel engine to investigate this aspect of HCCI technology. One cylinder of the engine is modified to operate in HCCI mode for the experiments and port fuel injection technique is used for preparing homogenous charge in this cylinder. Experiments are conducted at 1200 and 2400 rpm engine speeds using gasoline, ethanol, methanol and butanol fuels. A partial flow dilution tunnel was employed to measure the mass of the particulates emitted on a pre-conditioned filter paper. The collected particulate matter (PM) was subjected to chemical analyses in order to assess the amount of Benzene Soluble Organic Fraction (BSOF) and trace metals (marker of toxicity) using Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES). Field emission scanning electron microscope (FE-SEM) was used for particulate morphology investigations at 1000X and 5000X resolution. Trace amount of particulates were observed on the filter paper for the test fuels. The concentration of different trace metals analyzed also showed decreasing trends with increasing engine loads.