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ABSTRACT
Compared to conventional diesel fuels, biodiesels normally have lower smoke and particulate matter, while higher nitrogen oxides (NOX) emissions. In our study, an attempt was made to reduce the NOX emissions of biodiesels by increasing the cetane numbers (CNs). Three kinds of biodiesels with extremely high CNs (70.1, 76.9, 80.9, respectively) were developed. Their main physical and chemical properties were tested. With a two-cylinder direct injection diesel engine, their emission performances were experimentally investigated. The results indicate that, CN, freezing point, as well as viscosity of biodiesels are linearly increased with the increase of carbon number. The NOX emission for biodiesels with high CNs is lower than that of conventional diesel fuels. High CN promotes smoke formation as well while lower smoke emissions are still obtained for biodiesels when certain oxygen contents are present. That is, the smoke/NOX tradeoff is broken. Besides, as fuel CN is elevated, NOX for biodiesels decreases but smoke and carbon monoxide emissions are increased.
Funding
This project was granted financial support from the China Natural Science Foundation (No. 50976125).
Nomenclature
| CN | = | Cetane Number |
| NOX | = | Nitrogen oxides |
| CO | = | Carbon monoxide |
| HC | = | Unburned hydrocarbon |