This study investigates the impact of reducing waiting times for port berth on improving the Carbon Intensity Indicator (CII) ratings of Korean-flagged container ships. As the International Maritime Organization (IMO)’s CII regulation mandates corrective actions for poorly rated ships for Greenhouse Gas (GHG) reduction in international shipping, the analysis focuses on container ships with projected D or E ratings by 2035. Using Automatic Identification System (AIS) data from ships, this study identifies annual waiting times and simulates changes in CII ratings under scenarios of reduced waiting times (30%, 50%, 70%, and 100%). The relationship between ship speed and fuel consumption was established by analyzing the recent literature, and the CII improvement was evaluated based on IMO Data Collection System (DCS) 2022 data. The results show that a 30% reduction in waiting time can lower CO₂ emissions by 12.18% and improve the CII rating by one or two levels for approximately half of the sample ships. However, a 50% reduction or more is required to maintain improved ratings beyond 2030. The findings highlight the significance of just-in-time (JIT) practices in minimizing latency and enhancing regulatory compliance. The policy recommendations advocate for prioritizing port call optimization and recommend the adoption of JIT as a measure to achieve the IMO’s GHG reduction targets.

The increasing adoption of shaft generator (SG) systems in eco-friendly ships has highlighted the importance of evaluating the dynamic stability of marine propulsion shafting under actual operating conditions. However, current classification society rules mainly rely on whirling vibration analysis and critical speed assessment and do not provide a comprehensive framework for evaluating the dynamic behavior of the SG rotor and the rotor-stator dynamic air gap. This study proposes a Dynamic Stability Evaluation Framework for SG-integrated marine propulsion shafting and validates its effectiveness through full-scale sea trial measurements. The proposed framework integrates finite element-based whirling vibration analysis with Overall Vibration, Order Tracking, Shaft Orbit, Rotor Center Migration, and Dynamic Air Gap evaluation. Full-scale measurements were performed under both SG OFF and SG ON conditions over the normal propulsion operating speed range. The results showed that the 10th-order blade passing frequency component, predicted by numerical analysis to have only a minor influence, became the dominant excitation source near 70 rpm under actual operating conditions. Although electromagnetic excitation during SG operation slightly reduced the 10th-order vibration amplitude, it altered the rotor center migration behavior. Furthermore, the minimum Dynamic Air Gap was governed by the combined effects of Rotor Center Migration and Direct Orbit rather than by the maximum orbit radius alone. The proposed framework quantitatively confirmed sufficient rotor-stator clearance under all operating conditions and provides a practical methodology for the design verification and operational reliability assessment of SG-integrated marine propulsion shafting systems.

암모니아는 선박 온실가스 감축을 위한 대체연료 중 하나로서 검토되고 있으며, 화물컨테이너 운송전문위원회는 암모니아 연료를 사용하는 선박의 임시지침 개발을 완료하였다. 그중 암모니아 독성기준이 국내 산업계 및 관계 법령에서 사용하던 값과 차이가 있어 이에 대한 검토가 필요하다. 본 연구는 울산항에서 암모니아 벙커링 시 발생할 수 있는 누출 시나리오를 가정하고 Korea off-site risk assessment 프로그램을 활용하여 위험 지역을 분석하였다. 연구 결과, 암모니아는 30초 내의 짧은 누설에도 항만 인근 시설 및 타 선박에 상당한 영향을 미칠 수 있으며 항만 접안 시 벙커링 금지 및 암모니아 벙커링 전용 구역 지정 등의 제도 도입의 필요성을 확인하였다.

In selective catalytic reduction (SCR) systems, urea-water solution (UWS) is injected upstream of the catalyst, where water evaporation, urea thermolysis, and isocyanic acid (HNCO) hydrolysis release the NH₃ required for NO_x reduction. Data at pressures of tens of bar combined with rapid temperature variation remain scarce. This study numerically evaluates the evaporation, decomposition, and NH₃ formation potential of UWS sprays in an engine-like, non-combusting transient thermal environment. A motoring direct injection diesel engine model, validated against measured in-cylinder pressure, gave a peak mass-averaged temperature of about 851 K. A three-dimensional CFD model coupling a multicomponent droplet evaporation model with gas-phase urea thermolysis and HNCO hydrolysis was applied to four injection quantities of 11.5, 23.2, 28.2, and 33.1 mg/cycle. UWS injection lowered the peak pressure and temperature through the endothermicity of water evaporation and urea decomposition. The model predicted NH₃ conversion, referenced to the urea content of the injected UWS, and decreased monotonically from about 43% to 17% as the injection quantity increased, while the wall film residue rose from 1% to 31% of the injected mass. Because deposit-forming side reactions are not included and high-pressure species formation was not independently validated, these values represent an upper bound of the model-predicted formation potential. The predicted NH₃, therefore, represents a formation potential under non-firing conditions rather than an exhaust-gas concentration, since NH₃ formed in the cylinder would be largely oxidised at firing temperatures.

As CO₂ reduction in diesel engines has become a very important research topic, many studies on fuel diversification are being conducted. In this study, the effect of emulsion fuel and natural gas dual fuel on exhaust gas emission was evaluated. In a 2,000 cc 4-cylinder diesel engine, the exhaust gas emission characteristics according to the injection pressure of diesel fuel and engine output were analyzed for each fuel. Emissions of NOx, CO and THC were higher in natural gas dual fuel compared to diesel and emulsion fuel. Natural gas dual fuel reduced CO₂ emission by up to 40% but emulsion fuel increased CO₂ emission by about 5% compared to diesel fuel. It was confirmed that this was affected by the ratio of dual fuel.