Analysis of the influence of the n-hexane content in the mixture with rapeseed oil on the auto-ignition delay angle of the fuel
Increasing emission-reduction requirements and EU renewable-energy targets have created a demand for biofuels that can be operated in diesel engines without modification. Current production routes—FAME and HVO—although markedly improving the physicochemical properties of rapeseed oil, are carried out in capital-intensive industrial plants and depend on continuous feedstock supply. To simplify the production chain, rapeseed oil was diluted with the inert hydrocarbon n-hexane; the resulting decrease in viscosity and flash point facilitated spray formation and ignition initiation. The effect of n-hexane content (v/v) in blends with rapeseed oil on the ignition-delay angle in a direct-injection diesel engine was analysed. Cylinder-pressure traces were used to determine the crank-angle interval between the start of injection and the start of combustion, and the results were compared with data for commercial diesel fuel and neat rapeseed oil. A progressive increase in the n-hexane fraction was found to shorten the ignition-delay angle relative to neat rapeseed oil, bringing it closer to the value observed for diesel fuel. The results confirm the suitability of the investigated blends as an alternative fuel and indicate that they can be used in currently operated diesel engines without costly modifications.
Topic: Fuels and lubricants
Author: Przemysław Sander
Co-authors: Rafał Longwic
