Fast-running high-performance diesel engines are usually used for the propulsion of very fast ships. The high power density of these engines is normally achieved by significantly improved exhaust gas turbochargers.

This developement resulted, however, in the sensitivity of the engine and the turbocharger system to deviations in the operation conditions from the nominal. The flue gas counterpressure behind the turbocharger is usually limited by the engine manufacturer, to avoid excessive thermal loading of the engine and increased fuel consumption.

For the shipyards these requirements turn out to be more and more problematic for the construction of the flue gas system. Due to confined space and for cost reductions reasons the pipe diameters are usually designed as small as possible. This requires in turn exact knowledge of the pressure losses within the piping.

In this research project therefore a unitized calculation program was developed to allow determination of the flow resistance in complex flue gas systems. A preliminary library of all established components makes a fast modelling and calculation of the flue gas system possible. Interactions between single components are highlighted. A verification of the simulated results was made through measurements aboard existing flue gas systems in ships.

Another part of the project involved examinatins of the flow procedures at sub-surface flue gas outlets. Using diferent models it was determined whether numerical flow simulation is suitable for calculating the pressure at flue gas outlets just below water level.