Measuring injectors fouling in internal combustion engines through imaging

The use of liquid fuels derived from biomass in internal combustion engines, based on direct fuel injection, involves the formation of a large amount of carbon deposits on the tip of injectors which significantly influence emissions and engine performance. Currently most of the research activities are focused on the physical and chemical evaluation of deposits, using GC/MS (gas chromatography/mass spectrometry) analysis of alcoholic solutions with dissolved samples and FESEM (Field Emission Scanning Electron Microscopy) and EDS (Energy Dispersive X-ray Spectroscopy) analysis to characterize their microstructures. There are few methodologies to quantify the temporal fouling on the injectors in order to define a correlation between fouling, fuel and engine performance. The development of a methodology to compare the different effects of fouling obtained diversifying the fuel input of a direct injection engine is the aim of this work. The methodology is based on photography and post-processing of images to obtain a pixel count linked to a fouling index. The effect of lighting and visual angle is taken into account and a preliminary qualitative evaluation of the performance of the methodology is carried out. This methodology was also carried out to determine the minimum number of photos required to quantify the deposit independently by the orientation.