This study aims to provide a clear relationship of how the storage status and duration of the urea affect the efficiency and performance of the SCR system. Focusing on the marine environment, the research compares NOx emissions using new urea solution versus urea solution stored for 5 years on ships. The results indicate that using new urea solution reduces NOx emissions by an average of 30%. Additionally, the study confirms that the impact of the SCR system on the combustion process is negligible. These findings the importance of regular urea solution replacement to optimize the performance of SCR systems installed to meet environmental regulations. Currently, there are no detailed procedures or regulatory standards for urea management and replacement on ships. Considering the strict NOx emission regulations and harsh storage conditions in ship, the study proposes the establishment of effective urea replacement cycles and management procedures.

To comply with rules on air pollutants released by ships, two-stroke dual-fuel engines with liquefied natural gas (LNG) as the primary fuel have been marketed and offered to the market. However, there are still reports of gas-injection nozzles being damaged after they have been put on the market. Damage to the nozzles might result in secondary accidents in addition to worsening engine combustion conditions from improper injection. This study aims to gather fundamental information regarding the impact of different types of gas-injection nozzles on durability and to pinpoint the prerequisites for an ideal nozzle design. The results of total deformation and equivalent stress were examined for 27 nozzles that each variable was applied to in order to compare and confirm the durability by changing the nozzle shape. The cause of the nozzle temperature change according to the change in nozzle length was found to have the biggest impact on the total deformation, and it was confirmed that the effect was increased at higher temperatures. As the nozzle length increased and decreased by 2 mm, the average temperature of the nozzle increased by 47% and decreased by 53%, but the total deformation increased by 100% and decreased by 70%. It was verified that the equivalent stress was determined by the complicated interplay between the pressure inside the nozzle and turbulent kinetic energy impacted by a change in the nozzle shape. The factor that has the largest influence on the equivalent stress is the adjustment of the nozzle hole pipe angle, and the difference in equivalent stress according to this factor was found to be up to 118% and at least 44%. As a result, it has been proven that shortening the nozzle length, increasing the hole pipe angle, and enlarging the hole diameter are the most effective and expected to be used as basic data for future nozzle development.

In line with the global trend for environmental protection, the shipping industry is also making significant efforts. The International Maritime Organization introduced carbon intensity indicator and energy efficiency existing ship index to reduce greenhouse gases and presented “Initial IMO Strategy on reduction of GHG emissions from ships”. In contrast to previous environmental indices, carbon intensity indicator is calculated based on the operation information of ship. In this study, the annual fuel consumption was calculated based on the operation information of 4,151 ships and CO2, N2O, and CH4 emissions among greenhouse gases were estimated. The results of the study showed that CO2 accounted for 98% of the greenhouse gases emitted from ships, the highest, and N2O and CH4 were found to be insignificant at 1.5% and 0.5%. The major types of ships that emitted greenhouse gases were cargo ships, chemical tankers, oil tankers, and gas carriers. Ships subject to data collection system and carbon intensity indicator regulations include only 69% of the fuel consumed by all ships. This proportion increases to 87% of the total fuel consumption if it is expanded to include ships over 400 GT that are regulated by energy efficiency existing ship index.

This study aims to provide a clear relationship of how the storage status and duration of the urea affect the efficiency and performance of the SCR system. Focusing on the marine environment, the research compares NOx emissions using new urea solution versus urea solution stored for 5 years on ships. The results indicate that using new urea solution reduces NOx emissions by an average of 30%. Additionally, the study confirms that the impact of the SCR system on the combustion process is negligible. These findings the importance of regular urea solution replacement to optimize the performance of SCR systems installed to meet environmental regulations. Currently, there are no detailed procedures or regulatory standards for urea management and replacement on ships. Considering the strict NOx emission regulations and harsh storage conditions in ship, the study proposes the establishment of effective urea replacement cycles and management procedures.

To comply with rules on air pollutants released by ships, two-stroke dual-fuel engines with liquefied natural gas (LNG) as the primary fuel have been marketed and offered to the market. However, there are still reports of gas-injection nozzles being damaged after they have been put on the market. Damage to the nozzles might result in secondary accidents in addition to worsening engine combustion conditions from improper injection. This study aims to gather fundamental information regarding the impact of different types of gas-injection nozzles on durability and to pinpoint the prerequisites for an ideal nozzle design. The results of total deformation and equivalent stress were examined for 27 nozzles that each variable was applied to in order to compare and confirm the durability by changing the nozzle shape. The cause of the nozzle temperature change according to the change in nozzle length was found to have the biggest impact on the total deformation, and it was confirmed that the effect was increased at higher temperatures. As the nozzle length increased and decreased by 2 mm, the average temperature of the nozzle increased by 47% and decreased by 53%, but the total deformation increased by 100% and decreased by 70%. It was verified that the equivalent stress was determined by the complicated interplay between the pressure inside the nozzle and turbulent kinetic energy impacted by a change in the nozzle shape. The factor that has the largest influence on the equivalent stress is the adjustment of the nozzle hole pipe angle, and the difference in equivalent stress according to this factor was found to be up to 118% and at least 44%. As a result, it has been proven that shortening the nozzle length, increasing the hole pipe angle, and enlarging the hole diameter are the most effective and expected to be used as basic data for future nozzle development.

In line with the global trend for environmental protection, the shipping industry is also making significant efforts. The International Maritime Organization introduced carbon intensity indicator and energy efficiency existing ship index to reduce greenhouse gases and presented “Initial IMO Strategy on reduction of GHG emissions from ships”. In contrast to previous environmental indices, carbon intensity indicator is calculated based on the operation information of ship. In this study, the annual fuel consumption was calculated based on the operation information of 4,151 ships and CO2, N2O, and CH4 emissions among greenhouse gases were estimated. The results of the study showed that CO2 accounted for 98% of the greenhouse gases emitted from ships, the highest, and N2O and CH4 were found to be insignificant at 1.5% and 0.5%. The major types of ships that emitted greenhouse gases were cargo ships, chemical tankers, oil tankers, and gas carriers. Ships subject to data collection system and carbon intensity indicator regulations include only 69% of the fuel consumed by all ships. This proportion increases to 87% of the total fuel consumption if it is expanded to include ships over 400 GT that are regulated by energy efficiency existing ship index.

A numerical study was carried out to investigate the effects of injector spray angle (SA) and injection position (IP) on the combustion and emission characteristics of a two-stroke ME-GI marine engine at full load. Three-dimensional (3D) simulations of the combustion process and emission formations inside the cylinder of the engine operating in the diesel and DF modes were performed using the ANSYS Fluent simulation software to analyze the in-cylinder pressure, temperature, and emission characteristics. The simulation results were compared and showed good agreement with the experimental results reported in the engine’s shop test technical data. The simulation results showed that the IP of 0.02 m with an SA of 40 degrees helps to enhance the engine performance; however, if the main target is reducing engine exhaust gas emissions, an IP of 0.01 m is highly recommended to be used. At this IP, the specific SA of 40, 45, or 50 degrees that should be used will depend on which emissions (NO, soot, CO2, etc.) need to be reduced. This study successfully investigated the effects of injector SA and IP on the combustion and emission characteristics of the researched engine and would be a good reference for engine design and operating engineers.

As regulations on air pollutants emitted by ships are strengthened, the demand for the development of eco-friendly alternative fuels is increasing. Bio-heavy oil (BHO), a by-product of biodiesel manufacturing, is an eco-friendly fuel produced from biodiesel pitch. This study verified the possibility of using BHO as an eco-friendly alternative fuel for ships by analyzing the environmental and economic effects of using BHO in small ships. Compared to bunker A, BHO showed NOx emissions that increased by 5%, but SOx 9%, total hydrocarbons 9%, CO 4%, and CO 2 emissions decreased by 6%, confirming the effect of reducing greenhouse gases and air pollutants. There was also no difference in the engine performance. Furthermore, no discoloration, sludge generation, or fuel separation was observed when the fuel was stored for 90 days. During a total of 120 h of maritime demonstration, there were no engine problems and almost no sediment was produced. It has been proven to be a suitable replacement for ship fuel. The use of the BHO generated social benefits worth $ 2,256,749 per year. Therefore, it is necessary to promote the use of BHO in small ships.

Low-pressure gas-admission marine two-stroke engines have significant potential for reducing emissions in the shipping industry. However, they exhibit poor combustion quality under low-load conditions, leading to lower thermal efficiency and high levels of HC and CO emissions. This study numerically evaluated the impacts of the gas admission location and timing on engine performance and exhaust gas emissions under low load conditions. The study revealed that different gas admission locations form distinct NG-air stratifications. Lower gas admission locations resulted in longer ignition delays and shorter combustion durations. The unburned CH4 and CO emissions were significantly reduced by a maximum of 20.14% and 42.29%, respectively. A trade-off exists between NOx and N2O emissions owing to the different temperature conditions of their formation. The NOx emissions increased continuously as the gas admission location was lowered to a maximum of 3.4218 g/kWh; a value slightly above the Tier III emission standards. Advancing the timing of gas admission further decreased the ignition delay time, NOx, and unburned CH4 emissions. This study revealed that in-cylinder natural gas mixture stratification due to varying gas admission locations and timings can improve the combustion efficiency and exhaust gas emissions of a natural gas-diesel dual-fuel engine under low-load conditions.

ABSTRACTThe International Maritime Organization is making multiple efforts to reduce greenhouse gas and air pollutant emissions. However, it is difficult to achieve this because of the absence of technological developments. Consequently, there is an urgent need to develop alternative fuels. In this study, marine gas oil and biodiesel were blended at ratios of 0%, 5%, 10%, and 20% to assess their applicability to ships (Component analysis, metal corrosion, and storage stability) and potential for emission reduction (engine performance, environmental effects, and engine durability). The composition of the test fuels meet the ISO 8217:2017 standard. Metal corrosion was insignificant for carbon steel, iron, aluminum, and nickel, but not copper. Storage stability showed no sludge generation or fuel separation, although biodiesel experienced some discoloration owing to its high oxygen content. Engine performance showed no significant differences between marine gas oil and biodiesel. Emissions of NOx increased with higher biodiesel blending ratios, whereas SOx, CO, CO2, and Total hydro carbons decreased. Engine durability was good throughout the 160 hours sea trial. This study demonstrated that even at a 20% biodiesel blending ratio exceeding the 7% ratio suggested by ISO 8217:2017, can be safely used as a long-term marine fuel.