In recent years there have been significant changes in the composition and quality of fuels. In addition to those already present, new biofuels and alternative components are entering the market. At the same time, especially with efficient diesel engines, there is a trend towards long ranges and the associated long dwell times of the fuel in the tank. In addition, high return temperatures of modern common rail injection systems promote fuel ageing in the tank. It is known that aged fuels have an increased tendency to form deposits in the injectors. Modern, highly agile injection components with extremely small gap dimensions or flow cross-sections are becoming increasingly sensitive to internal deposits.
As part of the ENIAK II project, deposit formation mechanisms were investigated and the formation of deposits was simulated on a non-motor test rig. The observed deposit formation was specifically induced by in-situ degradation of the fuel in the test rig. Adapted and partly further developed evaluation routines were used to perform functional tests of injectors in order to assess the impairment of the injection process. Extensive analytical and spectroscopic investigations of the components covered with deposits showed good reproducibility and allowed conclusions to be drawn about possible formation mechanisms as well as cause-effect correlations in the formation of internal deposits.