Crank-angle resolved NOx measurements from a specific engine cylinder of a large marine two-stroke engine

The ability to measure NOx in the exhaust gases immediately as they exit the cylinder requires special instrumentation, located at the vicinity of the exhaust valve and capable of measuring with extremely fast response times. The information obtained from such a measurement is important to engine designers and combustion engineers with regards to the causes of formation of NOx emissions. This information can be used for the calibration of Computational Fluid Dynamics (CFD) models for engine development purposes, and also, during the development of the combustion system of an engine where engine tuning could lead to an overall compromise between engine’s performance and emission behaviour. The current research work involved the execution of crank-angle resolved NOx emission measurements in the exhaust port of an individual cylinder of a large twostroke marine engine, using a custom designed sampling system. The measurement campaign was performed on the MAN 4T50ME-X test engine, at the MAN Diesel & Turbo test centre in Copenhagen. The extremely fast response time of the sampling system and the analyser provided important details about the NOx profile, as soon as it exits the cylinder of a large marine engine. The observations were further evaluated using CFD analysis of the flow conditions inside the exhaust port.