Future diesel engines will require new hardware to reduce emissions to the levels required by upcoming legislation. Advances in the fuel injection equipment (FIE) of the engine are a key enabler towards meeting such legislation. These modern systems produce temperatures and pressures at the injector tips that are considerably higher than those experienced today. This environment can initiate or increase the rate of deposit formation at and around the injector tip compared with current systems.
Investigations have been carried out to further the understanding of this phenomenon using experimental nozzles simulating a similar deposit build-up as expected in EU 5 engines.
The investigation used a protocol that has recently been released to the industry, commercial 10 ppm S fuel and a commercial diesel fuel detergent. Testing was carried out with both clean and zinc contaminated fuel. Zinc contamination with a fuel soluble salt was used to simulate severe market conditions. The testing executed allowed assessment of the amount of injector deposit formed and the formation rate during the test. Further analysis of the raw data from the test enabled the linking of deposit formation to power loss and increased smoke generation. Moreover, the results obtained have then been used to refine the optimum test conditions.
Commercial detergents, at a variety of treat rates, have been assessed to understand their impact with future FIE. The deposits are proving to be more challenging than those previously seen with older FIE technology. Detergents that have historically been effective in resolving injector deposits are proving less effective in this test.
Another area of investigation focussed on the comparison of current and future FIE using the same fuel and test conditions. The results are clearly demonstrative of the increased severity of future FIE. Additionally, two different low sulphur fuels have been shown to generate different levels of deposits in fuels free of any diesel detergent.
The precision data that have been developed using this protocol show low variability with treated and untreated fuels.