The impact of biodiesel and alternative diesel fuel components on filter blocking through accelerated testing on a novel high pressure common rail non-firing rig

Abstract Increases in FAME content in diesel have coincided with advances in high pressure injector system technology. Previously, the unsaturation present in FAME has generally been thought to result in on-vehicle fuel degradation leading to solid formation. However, a growing number of vehicle breakdowns have implicated the increasing temperatures and pressures experienced by the fuel in the new injector system technologies. The majority of studies into diesel degradation are conducted under non-representative laboratory conditions, or extrapolated from the deposits found in filters from vehicles. In this study the cause of this degradation was investigated by using a novel High Pressure Common Rail (HPCR) non-firing rig, simulating realistic, albeit accelerated, conditions. The deposition on the system fuel filter was monitored, for B0, B10 and surrogate diesel components. Degradation was found to occur in the absence of FAME with both B10 and B0 fuels showing a similar rate of deposition. A study of synthetic surrogates demonstrated that, rather than FAME, any trace fuel component, under sufficiently high pressures and temperatures in the HPCR is prone to degradation. This suggests that rather than FAME being the sole factor in the increasing instability of diesel fuels, it is actually the increase in temperatures and pressures that the fuel is subjected to. This also demonstrates that while a large body of work on the oxidative instability of biodiesel in the chemical laboratory is indicative of instability, this does not mimic what is seen under more realistic vehicle conditions and the focus on FAME stability is misleading.