Charge air configurations for propulsion diesel engines aboard fast naval combatants

The Royal Netherlands Navy (RNLN) wants to reduce the fossil fuel dependency of its fleet significantly, to decrease logistic efforts and environmental impact (Defensie, 2015). One of the methods to reduce fossil fuel dependency of ships is to reduce their energy requirement. The operational profile of fast naval combatants for the RNLN requires that the ships operate on the diesel engines for 90 percent of the time, often in part load where the turbocharger cannot supply the engine with the right amount of charge air. This results in a limited operating envelope for the diesel engine, and a decreased efficiency in part load. However, in part load, advanced charge air configurations can potentially resolve this. In this study a Mean Value First Principle (MVFP) diesel engine was used to investigate the effects of advanced charge air configurations on the efficiency and acceleration performance of diesel engines in hybrid configurations aboard fast naval combatants. It was concluded that the application of advanced charge air configurations can significantly improve the engine efficiency in part load. For example, in a diesel hybrid propulsion configuration with power take-off this can lead to an efficiency increase of almost 10 percent at 20 percent load in comparison with a single charged engine. Furthermore, hybrid turbocharging enables extending the operating envelope at low engine speed due to a better air excess ratio. With these concepts therefore, both improved efficiency and improved acceleration performance can be achieved