Numerical Study on Injector Parameters for Improving Medium-Speed Marine Diesel Engine Performance

Based on high-performance engine technologies, this study investigated the performance enhancement of marine diesel engines through a numerical analysis based on computational fluid dynamics simulations. Three key injector parameters—spray angle, insertion depth, and nozzle hole diameter—were selected for the analysis. A total of 27 simulation cases were generated to examine their combined effect on engine output and efficiency. The simulation model was validated using engine commissioning data, and the error margin was within ±5%, thus confirming the reliability and accuracy of the computational approach. The nozzle hole diameter had the greatest influence on performance, followed by spray angle and insertion depth. Notably, Case 21 (150° spray angle and 0.27 mm diameter) and Case 27 (150° spray angle, 0.27 mm diameter, and 2.7 mm depth) achieved the highest efficiency. In both cases, engine output was maintained while fuel injection was reduced by approximately 10.3% compared with the reference condition (from 0.155 to 0.139 g). Unlike previous studies that were limited to single- or dual-parameter analysis, this study simultaneously varied three injector parameters, yielding a comprehensive set of performance outcomes. The results provide valuable baseline data for the future design and development of high-efficiency marine diesel engines.