Investigation of the effects of biodiesel aging on the degradation of common rail fuel injection systems

- A test method was developed to compare the effects of biodiesel on the fuel injection system.
- It was demonstrated that biodiesels can be discriminated based on time to failure of the injection system.
- The importance of the fuel TAN value on fuel injection system failure timing was revealed.

Subject of this study is the parametric investigation of the effect of biodiesel aging on the formation of deposits inside common rail Fuel Injection Equipment (FIE). The parameters investigated are key fuel properties and their degradation rate, FAME composition as well as FIE component design. Fuel degradation and deposit formation is simulated in a prototype FIE test rig. A market study was initially performed to monitor market diesel fuel quality in Europe. The sensitivity of the FIE to FAME concentration was investigated with market B7 and B20 test fuel. B20 pre-aging and fuel enhancement with anti-oxidant were studied to assess the impact of fuel degradation speed and level relatively to deposit formation. A selection of EU market B7 fuels with different fresh fuel properties and FAME composition, were comparatively evaluated on the rig as regards their impact on injection flow and pump response deterioration together with their tendency to form deposits. Test rig operation with 2 different injector designs was utilized to further investigate deposit sensitivity. Injection flow deterioration and internal deposits were affected by injector design and fuel aging speed and were found to be related to Total Acid Number. A correlation between initial B7 Rancimat IP and FIE failure due to fuel aging was identified. The methodology developed is proposed as reference test for the evaluation of current and future automotive fuels as regards their tendency to form deposits.