A New Optical Access for Medium Speed Large Bore Marine Engines under Full-Load Operating Conditions

The following work presents a new concept for optical accessibility of a single-cylinder medium-speed large-bore marine engine from the concept development to the implementation and feasibility investigation in a test bench observing the flame chemiluminescence of dual-fuel (DF) combustion. The design’s feasibility is verified using conjugated heat transfer (CHT) and finite element method (FEM) simulation during the whole design process presented herein. Assumptions made for the simulation, e.g., of the mount between the optical component and the steel engine parts, are evaluated in pretesting setups presented and described as follows. The optical access is made to withstand steady-state full-load operating conditions and is proofed so. The optical access is designed for an engine with a bore of 350 mm and a stroke of 440 mm. With the presented approach, optical investigations like particle image velocimetry (PIV), laser-induced fluorescence, and flame chemiluminescence in the whole combustion chamber in a vertical field of view are possible. The observation of the whole combustion chamber is realized via a quartz glass window implemented as a cylindrical lens facing the combustion. With the presented approach, the effectiveness of medium-speed large-bore engines could be increased by investigating the influential factors for the limitations of the combustion process like abnormal combustion as knocking and preignition caused by, e.g., engine oil droplets, a bad charge distribution, or hot surfaces in the combustion chamber.