Reproducing Internal Injector Deposits found in Heavy-Duty Vehicles with a Novel Injector Rig

In recent years, deposit formation in the fuel systems for heavy-duty engines, using drop-in fuels, have become increasingly common. Drop-in fuels are particularly appealing because as they are compatible with existing engines, allowing for higher proportions of alternative fuels to be blended with conventional fuels. However, the precipitation of insoluble substances from drop-in fuels can result in fuel filter clogging and the formation of internal injector deposits, leading to higher fuel consumption and issues with engine drivability. The precise reasons behind the formation of these deposits in the fuel system remain unclear, with factors such as operating conditions, fuel quality, and fuel contamination all suggested as potential contributors. In order to reproduce and study the formation of internal injector deposits, for heavy-duty engines under controlled conditions, facilitating a more precise comparison to field trials, a novel injector test rig has been developed. This newly constructed, non-firing rig includes the main components of heavy-duty vehicle engines and uses an electric motor to simulate the pressure and revolutions per minute found in the common rail of an engine. A tailored run cycle has been developed to enable the continuous monitoring of injector performance during the deposit formation process, as well as to meticulously mimic the actual operations of a real engine. The deposits formed on injectors during the rig tests were analyzed using scanning electron microscopy with energy dispersive X-ray (SEM-EDX), Fourier-transform infrared spectroscopy (FTIR), and pyrolysis connected to gas chromatography-mass spectroscopy (Pyr GC-MS). This work presents the outcomes of analyzing injector deposits using the test rig, comparing these findings with deposits gathered from field operations. The deposits obtained from the injector test rig were found to be similar in terms of deposit location, composition, and microstructure, with both sets containing metal carboxylates and derivatives of engine oil additives. This similarity demonstrates that the test rig effectively reproduces the formation of injector deposits observed in real-world conditions.