Optical techniques applied to internal combustion engines for soot detection - a review

By 2025, new Euro 7 regulation will be likely focused on the reduction of particulate matter. Besides the tightening of particle number emission limit, the most challenging modification will regard the count of sub-23 nm particulate as the count will include particles down to 10 nm. Despite the effort in the development of Diesel and Gasoline Particulate Filters (GPF), further advances in combustion process are necessary in order to reduce the particulate formation. This paper aims at providing an insight view on the optical diagnostics for the characterization of local detection of soot and its precursors in internal combustion engines. First, a brief description of the different measurement techniques will be provided. Then, a detail on the measurement method and in-cylinder application examples will be provided for the optical techniques which are more appropriate for ICEs application.