A New Methodology to Study the Mechanisms of Combustion-Chamber Deposit Formation and the Effects of Engine Parameters on the Quantity and Morphology of Combustion-Chamber Deposits

In this work, a methodology is developed to study engine deposit formation mechanisms. It relies on analyzing the deposit with electron microscopy for morphology and infrared absorption spectroscopy for identifying typical chemical functions. Two lab-scale experiments are used to calibrate these measurement techniques by creating deposits through the two main phases: liquid film and soot deposition. To test this methodology, an optical engine is used to create a library of deposits. Two main deposit morphologies are found: a homogeneous underlayer as well as soot-like agglomerates. The underlayer is attributed to a fuel-film mechanism whereas the latter is attributed to particles formed through the combustion process. The influence of engine parameters, such as injection phasing and cooling temperature, on the quantity and morphology of the deposits is studied. Various substrate materials, such as quartz, sapphire, aluminum, and steel were used on the piston surface to investigate the materials influence on the morphology, the composition, and the quantity of the deposits.