Characterization of Internal Diesel Injector Deposits (IDID´s) from heavy-duty vehicles

Sustainable fuels can help to decrease the carbon dioxide emissions compared to standard fossil fuels in the road transportation. Most common sustainable fuels used today in heavy-duty application are biodiesel and hydrogenated vegetable oil (HVO). Biodiesel and HVO are known as drop-in fuels since they are fuels that can be blended with standard diesel. However, due to changes in the chemical properties when the fuels are mixed, solubility problems as precipitants may be found. The insolubilities are also called soft particles. The formation of soft particles leads to driveability problems in the engine and deposits in the fuel system i. e. fuel filters and injectors. Further, the soft particles formed in the injectors are identified as Internal Diesel Injector Deposits (IDID). This study is a part of a project where the goal is to study the process causing the formation of the IDID´s in heavy-duty vehicles. In future studies, the aim is to reproduce in a laboratory environment a test fuel containing soft particles in order to investigate the mechanism behind the IDID´s using a custom-built injector rig. In this paper, the collection and characterization of typical IDID´s that are found in the injectors from heavy duty vehicles are studied. The injector deposits were gathered from two different European markets. IDID´s from injectors using biodiesel fuel from one market and HVO from other market were included. An innovative technique to sampling in GC-MS using Pyrolysis is used to study IDID´S. The advantage of this technique is that a very small amount of sample is needed, and it provides a useful tool to better understand the composition of the deposit on a detailed level. FTIR and SEM-EDX methods were also included. The results showed that the composition of the IDID´s differed significantly. Metal soaps, inorganic salts and nitrogen compounds from the injector deposits were found using biodiesel. The source of these components is believed to be degradation and contamination of the biodiesel. Moreover, the deposits from the HVO market were mainly composed of fuel additives.