Are Internal Diesel Injector Deposits (IDID) Mainly Linked to Biofuel Chemical Composition or/and Engine Operation Condition?

The increased use of alternative fuels has been linked to performance deterioration of injectors and engines as a result of internal diesel injector deposits (IDID). The present paper investigates fuel composition impact on injector tendency to blockage. Three main areas were investigated : (1) deposits linked to paraffins and aromatics content; (2) deposits linked to biodiesel composition using fatty acid methyl esters (FAME) and hydrotreated vegetal oil (HVO); and (3) deposits linked to the presence of additives (Dodecenylsuccinic anhydride DDSA, Dodecenyl Succinimid DDSI and Sodium Naphthenate). A deposit formation method was developed for the injection bench in order to discriminate the impact of fuels on system performance in terms of fuel volume injected, injection duration and stability. Three operation conditions were tested to represent low, intermediate and high load. In addition, the influence of soaking time and injector heating temperature was evaluated. The nature of the deposit was studied based on its morphology and chemical composition determined using Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM/EDX) Spectroscopy. Deposits were observed for all fuels, even the highly paraffinic biofuel like HVO. Two main results are presented: Firstly, the main impact of fuel soaking period and high load operation on the occurrence of IDID, it was observed that deposit formation can be controlled by the time the fuel remains in contact with the hot metallic surface of the injector; Secondly, the complex correlation between deposit nature and characteristics and the injector’s tendency to blockage, for example, there is no straightforward link between deposit thickness and injector blockage, other parameters seem to be more appropriate to predict injector blockage. These are discussed in more detail in this study.