Shaft-Power-Based Load Reconstruction for Operating-Point Alignment During Sea Trials of a CPP-Equipped Two-Stroke Marine Diesel Engine

This study examines operating-point alignment during full-scale sea trials of a controllable pitch propeller (CPP)-equipped vessel by reconstructing engine load from measured shaft power and relating it to engine performance, fuel-consumption behavior, and combustion indicators. Engine-side performance and fuel-oil consumption records were integrated with shaft measurement data for a MAN 5S35ME-B9.5 low-speed two-stroke marine diesel engine to establish a common propulsion-based operating-point framework. The average shaft power at the 100% speed-trial point was 3471.1 kW, differing from the rated power by only −0.11%, and was adopted as the reference for shaft-load reconstruction. The reconstructed speed-trial operating points were aligned at 24.91%, 49.04%, 80.85%, and 100.00%, while the endurance points corresponded to 76.99% at NCR and 95.29% at MCR. Relative to the corresponding speed-trial references, the endurance points showed about 4.7% lower delivered shaft power, indicating that they should not be interpreted as identical to nominal speed-trial load labels. Fuel flow and combustion-related indicators showed physically consistent variation with increasing reconstructed load. These results demonstrate that measured shaft power provides a practical basis for harmonizing sea-trial datasets and for distinguishing propulsion-side operating conditions more consistently than nominal load labels alone. The proposed framework is particularly applicable to representative operating-point alignment in full-scale sea trials of CPP-equipped low-speed two-stroke marine diesel engines under comparable test conditions.