The aim of the research project funded by the BMWi was to identify particularly critical precursor substances of fuel-related deposit formation inside common-rail injectors and, if necessary, to check at which concentration adverse effects on fuel performance have to be feared.
Polar aromatic oxygen, sulphur and nitrogen compounds in diesel fuels are potential precursors for the formation of deposits in injection components. Within the scope of the project, a method for the analysis of polar trace components in diesel fuels has therefore been further developed and tested. A total of 41 different diesel fuels according to DIN EN 590 were examined with this method, including 17 fuels without biodiesel and 24 diesel fuel-biodiesel blends with a FAME content < 7%(V/V). It was shown that biodiesel in this concentration range did not interfere with chromatographic separation, fractionation and enrichment of the target components. The polar species identified by GC-MS in the polar fuel fraction were assigned to 7 different structural groups. The relative total content of polar components in the polar fuel fraction as well as defined deposit precursors were correlated with layer thickness results from the DDFT (Diesel Deposit Formation Test).