Assessment of exhaust gas concentration uniformity in a marine engine duct based on dual-point sampling and CFD modelling

The paper presents an analysis of the flow of pollutants in the exhaust pipe of a marine diesel engine, based on measurements taken at two measurement points 2.5 meters apart. The concentrations of the basic exhaust components – CO, NOx, HC, and O₂ – were recorded during engine operation at different load levels, ranging from 30 to 686 kW. The aim of the analysis was to determine whether significant changes in the chemical composition of the exhaust gases occur in the section of the exhaust pipe between the two points. The results showed that the differences in the recorded concentrations were negligible, which confirms the homogeneity of the gas composition in the tested section and allows treating this section of the pipe as a conduit with established flow properties. Based on the measurements, a CFD model of exhaust flow was developed, representing the distribution of velocity and pressure in the exhaust pipe of a marine combustion engine. This model will be used to analyze mixing processes, possible local accumulation, and the effect of the geometry and operating conditions of the engine on the distribution of pollutants in the exhaust system.