Degradation Of Diesel In A Modern Fie System

Trends in the automotive industry in recent years to reduce emissions and fuel consumption have led to diesel vehicles utilising injection systems capable of increasingly higher pressures, with typical peak rail pressures above 2000 bar now common. At the same time fuel composition has been changing around the world to meet legislation, most notably with the increased use of biodiesel. Since the introduction of biofuel regulations, FAME has been implicated in fuel degradation and filter blocking, which can cause fuel starvation and vehicle breakdown. However, more recently there has been growing concern that the increasing pressures and concomitant temperatures the fuel is exposed to in modern vehicles can itself be the cause diesel degradation, even with the absence of bio components.

A rig which simulates the pressures and temperatures that a fuel is subjected to in a modern vehicle was used to investigate the issue of fuel filter blocking. It was found that at a rail pressure of 2000 bar both B0 EN590 and B10 (SME) diesel caused filter blocking to the same degree. This implies filter blocking caused by on board fuel degradation has the potential to occur broadly in a wide range of different fuel compositions independent of bio content. Further testing on the B10 fuel with a rail pressure of 2000 bar resulted in a pressure difference across the fuel filter of 0.5 bar within 200 hours, whilst the corresponding experiment at 1000 bar showed no filter pressure increase. This work concludes that the increases in rail pressure of modern diesel engines have a significant effect on the propensity of vehicle diesel filters to block. An initial study indicates that addition of specifically targeted additives into diesel would delay this filter blocking.