Annex 10: Characterisation of New Fuel Qualities
Many standardised tests to evaluate fuel properties have originally been designed for screening hydrocarbon products. In the case of fuels blended with new components or treated with additives traditional test methods may give misleading results. The objective of the task was to evaluate the correlation between the results obtained by standardised testing and the real-life serviceability of new diesel fuel qualities. The following properties were studied: combustion properties, properties affecting exhaust emissions, low-temperature operability and stability and diesel fuel lubricity.
The diesel fuel matrix comprised conventional diesel fuels, low-emission diesel fuel, conventional diesel fuel blended with rapeseed methyl ester, tall oil methyl ester and ethanol. Some of the fuels were tested with and without ignition improver and cold flow improver additives to find out the response of additive in different base fuels.
The results showed that the traditional cetane number measurement describes well ignition delay of heavy-duty engine at low and medium loads, but is more suitable for hydrocarbon fuels than for alternative fuels. Cetane number does not describe combustion process with advanced light-duty vehicles. Cetane number overestimates the effect of cetane improvers, especially for biodiesels. Esters were found to act as effective lubricity additives according to HFRR tests.
VTT Energy, Engine Technology, Espoo, Finland