Many standardized tests for evaluating fuel properties have originally been designed for screening straight-run hydrocarbon products. In the case of fuels blended with new components or treated with additives, the traditional test methods may give misleading results. The objective of the work was to evaluate the correlation between the results of standardized testing and of the real-life serviceability of new diesel fuel qualities. Combustion properties, properties affecting exhaust emissions, low-temperature performance and diesel fuel lubricity were studied.
The test fuel matrix comprised of typical conventional hydrocarbon diesel fuels, low-emission hydrocarbon fuels, rapeseed and tall oil esters and ethanol-blended diesel fuels. The base fuels were blended with a cetane improver additive and some fuels also with a cold flow improver additive. Combustion and emission tests were carried out with a heavy-duty bus engine and a diesel passenger car. A farm tractor engine was used for cold-start testing.
The traditional cetane number measurement described well ignition delay of the heavy-duty engine at low and medium loads, but was more suitable for hydrocarbon fuels than for alternative diesel fuels. Cetane number measurement overestimated the effect of cetane improver, especially for biodiesels. HFRR tests show that esters are effective lubricity additives. The cold startability of blends containing esters improved with cold flow additives. The ignition properties of ethanol blended diesel fuel improved significantly when ignition improver additive was used.