Ultra-fast emission measurements can provide important information about the combustion system of an engine, especially during its development phase. The ability to measure NOx as soon as it exits the cylinder provides an insight to engine designers and combustion engineers about the in-cylinder process with regards to formation of NOx emissions. There are mainly two areas where such information can be used. First, the fast measurements can be used for the tuning of CFD models that are used during the development phase of an engine. Secondly, such a method could be useful in the first phases of engine testing during the development of the combustion system where engine tuning could lead to an overall superior compromise between an engine’s fuel economy and emission behaviour.
The current research work investigated the potential of performing ultra-fast emission measurements in the exhaust port, immediately downstream of the exhaust valve, of a specified engine cylinder of a two-stroke large engine. A methodology was therefore developed and tested, by which emission measurements with fast temporal response can be conducted for individual engine cylinders.
More specifically, an ultra-fast NOx measurement sampling probe was designed and developed to be applied mainly to 2-stroke engines, with the flexibility to also be applicable to 4-stroke engines. The development of the sampling system was done by initially performing NO measurements on the 4-stroke MAN L16/24 research engine, installed at the test bed of the Laboratory of Marine Engineering (LME), at the National Technical University of Athens (NTUA). Once developed, the final fast sampling system was then used for measurements of NO at the exhaust port of the 2-stroke MAN 4T50ME-X engine, at the MAN Diesel & Turbo test-centre in Copenhagen. The employed NO emissions measurement method provided the results on a cycle-by-cycle basis, and also as phase averaged values. The extremely fast response time of the instrument captured important details of the NO concentration in the exhaust gases, as soon as they exit the cylinder.