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Marine diesel engines are crucial for powering large vessels in the maritime sector and are known for their efficiency across various industries. However, increasing environmental concerns and stringent regulations targeting air pollutants such as nitrogen oxides (NOx) and particulate matter (PM) have heightened the need for advanced emission control technologies. Addressing this challenge, the study focuses on developing a reliable method to predict NOx emission levels in marine engines, reducing reliance on resource-intensive experimental testing. Leveraging machine learning techniques, particularly k-nearest neighbors (kNN)-based algorithms, the research classifies NOx emissions in marine engines operating under the Reactivity-Controlled Compression Ignition (RCCI) strategy. Comparative performance analysis reveals that the FPFS-kNN algorithm achieves the highest accuracy (90.00%) alongside strong precision (84.23%), recall (82.37%), and F1 score (82.47%). These findings underscore the potential of machine learning in emission prediction and highlight directions for future exploration in this domain [ABSTRACT FROM AUTHOR]

Ship traffic substantially contributes to air pollution, thus affecting climate and human health. Recently introduced regulations by the International Maritime Organization (IMO) on the fuel sulfur content (FSC) caused a shift in marine fuel onsumption from heavy fuel oils (HFO) to diesel-like distillate fuels, but also to alternative hybrid fuels and the operation of sulfur scrubbers. Using multi-wavelength thermal-optical carbon analysis (MW-TOCA), our study provides emission factors (EF) of carbonaceous aerosol particles and link the fuel composition to features observed in the soot microstructure, which may be exploited in online monitoring by single-particle mass spectrometry (SPMS). Particulate matter from distillate fuels absorbs stronger light of the visible UV and near-infrared range than HFO. However, Simple Forcing Efficiency (SFE) of absorption weighted by EF of total carbon compensated the effect, leading to a net reduction by >50% when changing form HFO to distillate fuels. [ABSTRACT FROM AUTHOR]

With the tightening of emission regulations for marine engines, it has become increasingly important to explore efficient and clean combustion strategies in diesel–natural gas dual–fuel marine engines. This study, for the first time, compared and analyzed the effects of single and split injection strategies on the combustion process in a marine medium-speed dual-fuel engine with a natural gas substitution rate of 93.3%. Optimal strategies were compared for single injection [Case A: start of injection (SOI)=−15° crank angle (CA) after top dead center (ATDC)] and split injection (Case B: SOI1=−60°CA ATDC, SOI2=−10°CA ATDC). The analysis of Cases A and B revealed that employing a split pilot diesel injection strategy enhances engine thermal efficiency—Case B had a 0.77% increase in efficiency compared with Case A. More importantly, the split injection strategy proved to be more effective in reducing emissions; compared with Case A, Case B had a 36.3% and 49.4% decrease in NOx and CH4 emissions, respectively. A deeper examination of the combustion process in Case B revealed that the reactivity in specific cylinder regions was enhanced, thereby increasing the flame propagation speed in those areas. Moreover, the strategy reduced the proportion of pilot diesel diffusion combustion, leading to lower high temperatures and aiding in the reduction of NOx formation. These findings provide a technological reference for improving energy conversion efficiency and facilitating cleaner combustion in future applications of low-carbon fuels in dual-fuel marine engines. [ABSTRACT FROM AUTHOR]

This document discusses the importance of computational and data-driven modeling in understanding and optimizing combustion in reciprocating engines and gas turbines. The Paris Agreement's goals to reduce greenhouse gas emissions and global warming necessitate the reduction of pollutants emitted by transportation and energy production. While new technologies like electrification and carbon capture are emerging, internal combustion engines and gas turbines remain crucial in the short and medium term. Computational modeling allows for the investigation of various operating conditions, reducing costs and risks. The document includes research articles and a review on the role of micro gas turbines in distributed energy production, covering topics such as reducing emissions in internal combustion engines, exploring alternative fuels, and improving the efficiency of gas turbines. [Extracted from the article]

Due to increasing emissions and global warming, in parallel with the increasing world population and energy needs, IMO has introduced severe rules for ships. Energy efficiency on ships can be achieved using the organic and inorganic Rankine cycle (RC) driven by exhaust heat from marine diesel engines. In this study, toluene, R600, isopentane, and n-hexane as dry fluids; R717 and R718 as wet fluids; and R123, R142b, R600a, R245fa, and R141b as isentropic fluids are selected as the working fluid because they are commonly used refrigerants, with favorable thermal properties, zero ODP, low GWP and are good contenders for this application. The cycle and exergy efficiencies, net power, and irreversibility of marine diesel engine exhaust-driven simple RC and RC with a recuperator are calculated. For dry fluids, the most efficient fluid at low turbine inlet temperatures is n-hexane at 39.75%, while at high turbine inlet temperatures, it is toluene at 41.20%. For isentropic fluids, the most efficient fluid at low turbine inlet temperatures is R123 with 23%, while at high turbine inlet temperatures it is R141b with 23%. As an inorganic fluid, R718 is one of the most suitable working fluids at high turbine inlet temperatures of 300 °C onboard ships with a safety group classification of A1, ODP of 0, and GWP100 of 0, with a cycle efficiency of 33%. This study contributes to significant improvements in fuel efficiency and reductions in greenhouse gas emissions, leading to more sustainable and cost-effective maritime operations. [ABSTRACT FROM AUTHOR]

Decarbonizing maritime transport hinges on transitioning oil-fueled ships (98.4% of the fleet) to renewable and low-carbon fuel types. This shift is crucial for meeting the greenhouse gas (GHG) reduction targets set by the IMO and the EU, with the aim of achieving climate neutrality by 2050. Ammonia, which does not contain carbon atoms that generate CO2, is considered one of the effective solutions for decarbonization in the medium and long term. However, the concurrent increase in nitrogen oxide (NOx) emissions during the ammonia combustion cycle, subject to strict regulation by the MARPOL 73/78 convention, necessitates implementing solutions to reduce them through optimizing the combustion cycle. This publication presents a numerical study on the optimization of diesel and ammonia injection phases in a ship's medium-speed engine, Wartsila 6L46. The study investigates the exhaust gas emissions and combustion cycle parameters through a high-pressure injection strategy. At an identified 7° CAD injection phase distance between diesel and ammonia, along with an optimal dual-fuel start of injection 10° CAD before TDC, a reduction of 47% in greenhouse gas emissions (GHG = CO2 + CH4 + N2O) was achieved compared to the diesel combustion cycle. This result aligns with the GHG reduction target set by both the IMO and the EU for 2030. Additionally, during the investigation of the thermodynamic combustion characteristics of the cycle, a comparative reduction in NOx of 4.6% was realized. This reduction is linked to the DeNOx process, where the decrease in NOx is offset by an increase in N2O. However, the optimized ammonia combustion cycle results in significant emissions of unburnt NH3, reaching 1.5 g/kWh. In summary, optimizing the combustion cycle of dual ammonia and diesel fuel is essential for achieving efficient and reliable engine performance. Balancing combustion efficiency with emission levels of greenhouse gases, unburned NH3, and NOx is crucial. For the Wartsila 6L46 marine diesel engine, the recommended injection phasing is A710/D717, with a 7° CAD between injection phases. [ABSTRACT FROM AUTHOR]

Particle emissions from marine activities next to gaseous emissions have attracted increasing attention in recent years, whether in the form of black carbon for its contribution to global warming or as fine particulate matter posing a threat to human health. Coastal areas are particularly affected by this. Hence, there is a great need for shipping to explore alternative fuels that both reduce greenhouse gas emissions, as anticipated through IMO, and also have the potential to reduce particle emissions significantly. This paper presents a comparative study of the particulate emissions of two novel synthetic/biofuels (GTL and HVO), which might, in part, substitute traditionally used distillate liquid fuels (e.g., MDO). HFO particulate emissions, in combination with an EGCS, formed the baseline. The main emphasis was laid on particle concentration (PN) and particulate matter (PM) emissions, combining gravimetric and particle number measurements. Measurements were conducted on a 0.72 MW research engine at different loads (25%, 50%, and 75%). The results show that novel fuels produce slightly fewer emissions than diesel fuel. Results also exhibit a clear trend that particle formation decreases as engine load increases. The EGCS only moderately reduces particle emissions for all complaint fuels, which is related to the formation of very fine particles, especially at high engine loads. [ABSTRACT FROM AUTHOR]

There is a consensus on the need to reduce the emissions of carbon compounds. The increase in global greenhouse gas (GHG) emissions in the maritime industry poses a serious challenge to environmental sustainability, climate change, and the operating costs of ships. This article shows how hybrid versus diesel propulsion technology for ships can help reduce carbon dioxide (CO2) emissions and fuel consumption, and how these changes can be achieved. The need to reduce exhaust emissions and the increasing need for the shipping industry to seek alternative fuels means that existing regulations for marine engines and engine emissions are being updated almost constantly and new regulations are being formulated. The cost implications of the new regulations may lead to an increase in emissions as engines with lower fuel consumption are chosen, i.e., larger marine engines. Alternative approaches are needed to reduce CO2 emissions and fuel consumption, which could ultimately lead to hybrid propulsion for ships. This paper examines the current state of greenhouse gas emissions in shipping by analyzing the CO2 emissions and operating costs of two ships of the same type with similar technical and technological characteristics and different propulsion systems to gain insight into the problem. This paper compares the reductions in CO2 emissions, fuel consumption, and fuel costs for two suction hopper dredgers with standard diesel and hybrid propulsion. The technical characteristics, CO2 emissions, fuel consumption, and price of the two ships were analyzed to determine the advantages and disadvantages of each propulsion system. The novelty of this study is that two suction hopper dredgers from the same company with similar technical–technological characteristics but different propulsion systems were used for the case study and a mathematical procedure for calculating CO2 and other greenhouse gasses was presented in comparison, all to determine to what extent and in what way the hybrid propulsion system of a ship can contribute to reductions in CO2 emissions and fuel costs at the ship and company levels compared to a standard diesel propulsion system. This comparative analysis shows how much lower CO2 emissions, fuel consumption, and fuel cost savings can be expected when using a hybrid propulsion system compared to a standard diesel propulsion system. Finally, a conclusion is drawn on the efficiency and environmental compatibility of the two systems. [ABSTRACT FROM AUTHOR]

In diesel-ignited natural gas marine dual-fuel engines, the pilot diesel injection timing (PDIT) determines the premixing time and ignition moment of the combustible mixture in the cylinder. The PDIT plays a crucial role in the subsequent development of natural gas flame combustion. In this paper, four PDITs (− 8 °CA, − 6 °CA, − 4 °CA, and − 2 °CA) were studied. The results show that the advancement of PDIT increased the engine's power, thermal efficiency, and natural gas flame spread velocity, and increased NO emissions and CH4 emissions of the marine engine. The PDIT affected the ignition delay period and the rapid combustion period to a greater extent than the slow combustion period and the post combustion period. With each 2 °CA advancement of PDIT, the engine's power increased by 69.87 kW, thermal efficiency increased by 0.42%, radial flame spread velocity increased by 2 m/s, axial flame spread velocity increased by 1.7 m/s, NO emissions increased by 6.1%, and CH4 emissions increased by 3.75%. [ABSTRACT FROM AUTHOR]

The capability of operational marine diesel engines to adapt to renewable and low-carbon fuels is considered one of the most influential methods for decarbonizing maritime transport. In the medium and long term, ammonia is positively valued among renewable and low-carbon fuels in the marine transport sector because its chemical elemental composition does not contain carbon atoms which lead to the formation of CO2 emissions during fuel combustion in the cylinder. However, there are number of problematic aspects to using ammonia in diesel engines (DE): in-tensive formation of GHG component N2O; formation of toxic NOx emissions; and unburnt toxic NH3 slip to the exhaust system. The aim of this research was to evaluate the changes in combustion cycle parameters and exhaust gas emissions of a medium-speed Wartsila 6L46 marine diesel engine operating with ammonia, while optimizing ammonia injection intensity within the limits of Pmax, Tmax, and minimal engine structural changes. The high-pressure dual-fuel (HPDF) injection strategy for the D5/A95 dual-fuel ratio (5% diesel and 95% ammonia by energy value) was investigated within the liquid ammonia injection pressure range of 500 to 2000 bar at the identified optimal injection phases (A −10° CAD and D −3° CAD TDC). Increasing ammonia injection pressure from 500 bar (corresponding to diesel injection pressure) in the range of 800–2000 bar determines the single-phase heat release characteristic (HRC). Combustion duration decreases from 90° crank angle degrees (CAD) at D100 to 20–30° CAD, while indicative thermal efficiency (ITE) increases by ~4.6%. The physical cyclic deNOx process of NOx reduction was identified, and its efficiency was evaluated in relation to ammonia injection pressure by relating the dynamics of NOx formation to local combustion temperature field structure. The optimal ammonia injection pressure was found to be 1000 bar, based on combustion cycle parameters (ITE, Pmax, and Tmax) and exhaust gas emissions (NOx, NH3, and GHG). GHG emissions in a CO2 equivalent were reduced by 24% when ammonia injection pressure was increased from 500 bar to 1000 bar. For comparison, GHG emissions were also reduced by 45%, compared to the diesel combustion cycle. [ABSTRACT FROM AUTHOR]

For many years, the Suez Canal (also known as the Suez Route) has been the main route connecting Europe and Asia. However, compared with the Suez Route, the Northeast Passage could save up to 41% of the journey. The ship carbon intensity index (CII) rating system of the International Maritime Organization (IMO) came into effect in 2023. This study took an existing bulk carrier on the Europe–Asia route as an example to calculate the attained CII values at different sailing speeds. It was found that, regardless of external factors, when the ship speed dropped from 14.4 knots (85% maximum continuous rating (MCR)) to 12.6 knots (55% MCR), the corresponding attained CII value decreased from 6.48 g/ton·nm to 5.19 g/ton·nm. Therefore, sailing speed was the key factor influencing the attained CII value, and it was independent of the shipping distance. In addition, when the ship's sailing output power was between 85% MCR and 75% MCR, for every 5% decrease in MCR, its attained CII value would decrease by 0.13 g/ton·nm, and the fuel consumption amount would decrease by 1 ton/day. However, when the ship sailed at an output power of 75% MCR to 55% MCR, for every 5% decrease in MCR, the attained CII value would decrease even more, up to 0.26 g/ton·nm. In addition, the attained CII value would be reduced by up to 100% and fuel consumption amount would be reduced by up to 1.5 ton/day, resulting in a 50% fuel saving effect. Therefore, to obtain a better CII rating, the optimal ship speed should be set between 75% MCR and 55% MCR according to the wave and wind strengths. However, although slow-speed sailing is the most efficient factor, the number of sailing days would also be extended. Through the ratio created by dividing the distance of the Northeast Passage by the Suez Route, whether the Northeast Passage has the benefit of balancing shipping schedules could be judged. The outcome indicated that a ratio lower than 1 would result in a more balanced shipping schedule. Compared with 2019, the number of ships sailing through the Northeast Passage in 2021 increased significantly by 132%, and the average dead weight tonnage of the ships also rose from 18,846 tons to 23,736 tons. This study found that, with the implementation of the carbon reduction policy of the CII rating, ships sailing through the Northeast Passage could continue to develop toward the trend of large-sized vessels and steady increase in ship number. [ABSTRACT FROM AUTHOR]

In this study, the influence of direct steam injection (DSI) on the performance and emissions of marine engines is investigated. Simulation models are developed and tested based on experimental data. Steam is obtained by waste heat recovery in a marine engine. The limitations of DSI parameters are investigated based on the exhaust gas temperature. The steam quantity and temperature decrease with a decrease in load. The results show that steam mass plays an important role in NOx reduction and improving power. For a steam/fuel ratio of 1.27 at 100% load, the brake power improved by 3.09% and NOx emissions decreased by 4.67%. A higher degree of improvement is obtained with an increase in steam mass. The steam temperature and injection timing only slightly influenced the brake power and NOx emissions. When steam-injection timing improved to 12°CA at 100% load with injection duration decreasing from 85°CA to 25°CA, brake power improved from 3,485.7 to 3,529.7 kW. All of this demonstrates that the DSI approach has excellent energy-saving and emission reduction potential for marine engines. The steam-injection strategy should be optimized in the future. [ABSTRACT FROM AUTHOR]

Particulate matter (PM) is a major pollutant in the exhaust of marine diesel engines, which seriously endangers human health and the atmospheric environment, and how to reduce particulate matter emissions from marine engines has become a key research direction in the field of environmental protection and diesel engines. In this study, we analyzed the components and sources of PM from marine engines and conducted tests on the performance of Wärtsilä 20DF Diesel Particulate Filter (DPF) catalysts to verify the capture efficiency, gaseous pollutant removal rate, regeneration effect and the relationship between carbon loading and pressure loss of DPF catalysts in the context of Tier III emission regulations. The results showed that PM emissions of 20DF in diesel mode after adding the DPF system meet the requirements of the regulatory limit, but the pressure drop of the engine increases after adding the DPF system. Therefore, numerical simulation was used to optimize the DPF structure by evaluating the system velocity field, flow field distribution uniformity and system pressure drop to improve the pressure drop. [ABSTRACT FROM AUTHOR]

Most large commercial vessels are propelled by low-speed two-stroke diesel engines due to their fuel economy and reliability. With increasing international concern about emissions and the rise in oil prices, improvements in engine efficiency are urgently needed. In the present work, a zero-dimensional model for a low-speed two-stroke diesel engine is developed that considers the exhaust gas bypass and geometry structures for the gas exchange model. The model was applied to a low-speed two-stroke 7G80 ME-C9 marine diesel engine and validated with engine shop test data, which consisted of the main engine performance parameters and cylinder pressure diagrams at different loads. The simulation results were in good agreement with the experimental data. Thus, the model has the ability to predict engine performance with good accuracy. After model validation, the variations in compression ratio, fuel injection timing, exhaust gas bypass valve opening portion, exhaust valve opening timing, and exhaust valve closing timing effects on engine performance were tested. Finally, the influence level of different parameters on engine performance was summarized, which can be used as a reference to determine the reasons for high fuel consumption in some cases. The developed engine performance model is considerable in digital twins for performance simulation, health management, and optimization. [ABSTRACT FROM AUTHOR]

Nowadays, the ocean shipping carbon emission accounting for 2–3% of global carbon emission. As a zero-carbon fuel with higher volumetric heat density than hydrogen, ammonia has the potential to serve for marine engines, thereby aiding in the decarbonization of ocean shipping. However, as a fuel with weak flammability, ammonia engine still faces the problem of how to organize its combustion. This study investigates the feasibility of utilizing ammonia as the main fuel for marine engines and its combustion characteristics. A centralized jet-flame controlled combustion strategy for two-stroke marine engine are proposed to better organize the ammonia combustion in large combustion chamber. Firstly, the relative injection direction of ammonia and diesel was researched, ammonia and diesel injected in an opposite direction has better performance as the ignition happens downstream of ammonia spray with better fuel-air mixture for ignition and flame transport from downstream to upstream preventing flame hitting liner to avoid extinguishing. Secondly, centralized jet-flame controlled combustion strategy was researched in engine model. There are two phases of this combustion strategy, premixed combustion and diffusion combustion. The ITE and unburn ammonia most related to the premixed ammonia which was influenced by ammonia injection timing. The unburn ammonia most related to diffusion combustion. Ammonia injection direction concentrating in the center and flame transport from downstream to upstream can preventing ammonia flame from hitting liner and better the diffusion combustion efficiency than existing ammonia-diesel injected in same direction mode. A replacement rate of up to 98% for ammonia can be achieved while maintaining an indicated thermal efficiency (ITE) ranging from 43.7% to 50.4%. Unburned ammonia can be optimized from 4.4% to 0.18%. [ABSTRACT FROM AUTHOR]

The reported findings help to understand the treatment technology for studying shipping emissions and air pollution, especially in the context of near-zero emissions. Ship emissions primarily consist of two categories: air pollutants such as SOx, NOx, PM, CO, and NMVOCs, as well as greenhouse gases, including CO SB 2 sb , CH SB 4 sb , and N SB 2 sb O [[5], [7]]. However, engine combustion will produce a lot of harmful emissions such as particulate matter (PM), sulfur oxides (SOx), and nitrogen oxides (NOx), which cause severe pollution to the atmosphere and marine environment [[4]]. [Extracted from the article]

Techniques such as exhaust gas recirculation (EGR) and water-in-fuel emulsions (WFEs) can significantly decrease NOx emissions in diesel engines. As a disadvantage of adopting EGR, the afterburning period lengthens owing to a shortage of oxygen, lowering thermal efficiency. Meanwhile, WFEs can slightly reduce NOx emissions and reduce the afterburning phase without severely compromising thermal efficiency. Therefore, the EGR–WFE combination was modeled utilizing the KIVA-3V code along with GT power and experimental results. The findings indicated that combining EGR with WFEs is an efficient technique to reduce afterburning and enhance thermal efficiency. Under the EGR state, the NO product was evenly lowered. In the WFE, a considerable NO amount was created near the front edge of the combustion flame. Additionally, squish flow from the piston's up–down movement improved fuel–air mixing, and NO production was increased as a result, particularly at high injection pressure. Using WFEs with EGR at a low oxygen concentration significantly reduced NO emissions while increasing thermal efficiency. For instance, using 16% of the oxygen concentration and a 40% water emulsion, a 94% drop in NO and a 4% improvement in the Indicated Mean Effective Pressure were obtained concurrently. This research proposes using the EGR–WFE combination to minimize NO emissions while maintaining thermal efficiency. [ABSTRACT FROM AUTHOR]

Ship emissions are one of the main sources of air pollution in port cities. The prosperous maritime trade has brought great harm to the air quality of port cities while promoting the development of the world economy. During the berthing process, ship auxiliary machines emit a large amount of air pollutants, which have a great impact on air quality and public health. Alternative marine fuels are being studied and used frequently to reduce ship emissions. This research was carried out to investigate the gaseous and particles emission characteristics of a marine diesel engine during the application of experimental biodiesel fuels. To study the influence of mixed fuels on engine performance, measurements were made at different engine loads and speeds. Different diesel fuels were tested using various ratios between biodiesel and BD0 (ultra-low sulfur diesel) of 0%, 10%, 30%, 50%, 70%, 90%, and 100%. The results indicated the use of biodiesel has little influence on the combustion performance but has a certain impact on exhaust emissions. The octane number and laminar flame speed of biodiesel are higher than those of BD0, so the combustion time of the test diesel engine is shortened under the mixed mode of biodiesel. In addition, a high ratio of biodiesel leads to a decrease of the instantaneous peak heat release rate, causing the crank angle to advance. As the biodiesel blending ratio increased, most of the gaseous pollutants decreased, especially for CO, but it led to an increase of particle numbers. The particle size distribution exhibits a unimodal distribution under various conditions, with the peak value appearing at 30–75 nm. The use of biodiesel has no effect on this phenomenon. The peak positions strongly depend on fuel types and engine conditions. The particulate matter (PM) emitted from the test engine included large amounts of organic carbon (OC), which accounted for between 30% and 40% of PM. Whereas the elemental carbon (EC) accounted for between 10% and 20%, the water-soluble ions components accounted for 6–15%. Elemental components, which accounted for 3–8% of PM emissions, mainly consisted of Si, Fe, Sn, Ba, Al, Zn, V, and Ni. Generally, biodiesel could be a reliable alternative fuel to reduce ship auxiliary engine emissions at berth and improve port air quality. [ABSTRACT FROM AUTHOR]

NO has been described as one of the most harmful gases produced under high-temperature conditions from combustion chambers of marine diesel engines. Researchers have stressed the adverse effects of marine diesel engine emissions on human health and other biological systems. The International Convention on the Prevention of Pollution from Ships (MARPOL Annex VI) established NOx global emission limits. It provided a platform to encourage technological innovations toward reduction in NO emissions. Several specialized methods have been in application for NOx emission reductions, but their operational processes and technical efficiencies remain poorly understood. Therefore, a comprehensive review has been conducted on various NO emission reduction methods, classified into primary and secondary methods. The formation process of NOx was assessed in detail, and the multiple methods in application toward NO emission reduction were evaluated based on their technological efficiencies. It was established that scavenge humidification and SNCR-selective noncatalytic reduction is the most efficient NOx emission reduction method, given their emission reduction potentials at 80% and 95%, respectively. [ABSTRACT FROM AUTHOR]

In recent years, the International Maritime Organization (IMO), Europe, and the United States and other countries have set up different emission control areas (ECA) for ship exhaust pollutants to enforce more stringent pollutant emission regulations. In order to meet the current IMO Tier III emission regulations, an after-treatment device must be installed in the exhaust system of the ship power plant to reduce the ship NOx emissions. At present, selective catalytic reduction technology (SCR) is one of the main technical routes to resolve excess NOx emissions of marine diesel engines, and is the only NOx emission reduction technology recognized by the IMO that can be used for various ship engines. Compared with the conventional low-pressure SCR system, the high-pressure SCR system can be applied to low-speed marine diesel engines that burn inferior fuels, but its working conditions are relatively harsh, and it can be susceptible to operational problems such as sulfuric acid corrosion, salt blockage, and switching delay during the actual ship tests and ship applications. Therefore, it is necessary to improve the design method and matching strategy of the high-pressure SCR system to achieve a more efficient and reliable operation. This article summarizes the technical characteristics and application problems of marine diesel engine SCR systems in detail, tracks the development trend of the catalytic reaction mechanism, engine tuning, and control strategy under high sulfur exhaust gas conditions. Results showed that low temperature is an important reason for the formation of ammonium nitrate, ammonium sulfate, and other deposits. Additionally, the formed deposits will directly affect the working performance of the SCR systems. The development of SCR technology for marine low-speed engines should be the compromise solution under the requirements of high sulfur fuel, high thermal efficiency, and low pollution emissions. Under the dual restrictions of high sulfur fuel and low exhaust temperature, the low-speed diesel engine SCR systems will inevitably sacrifice part of the engine economy to obtain higher denitrification efficiency and operational reliability. [ABSTRACT FROM AUTHOR]

Although the exhaust gas recirculation (EGR) technology has been proven effective to decrease the marine engine's nitrogen oxides (NOx) emissions, it is associated with a considerable fuel consumption increase and challenges to the engine–turbocharger matching. This study aims to parametrically optimise the EGR and turbocharging system settings of a large marine two-stroke engine with the objective of obtaining the highest engine efficiency whilst ensuring compliance with the prevailing NOx emissions limits. Two typical configurations of the investigated engine (baseline and alternative) are modelled in the GT-SUITE software. Parametric simulations are performed with EGR rates up to 40% along with cylinder bypass rates up to 50%, and the simulation results are analysed to quantify the impact of the engine operation with EGR on the performance and NOx emissions parameters. For the baseline engine configuration, the EGR rate increase considerably deteriorates the brake specific fuel consumption (BSFC), which is attenuated by opening the cylinder bypass valve. The optimal combinations of the EGR and cylinder bypass rates for each operating point are identified for both configurations. Following the comparative assessment between the two engine configurations, recommendations for the engine operating modes are proposed, leading to BSFC improvement in the region of 0.7 to 2.9 g/kWh. This study provides insights for the operational settings optimisation of two-stroke engines equipped with EGR systems, contributing towards the reduction of the associated environmental carbon footprint. [ABSTRACT FROM AUTHOR]

Black carbon (BC) mass concentration from internal combustion engines can be quantified using a variety of different BC measurement techniques. We compare the relative response of several commercial instruments with different measurement principles to different types of marine exhaust emissions. Exhaust samples were generated using a high-speed 4-stroke marine diesel engine at various engine operating conditions from low to high engine loads. Three different fuel types—diesel, distillate marine oil grade A (DMA) and intermediate fuel oil (IFO)—were used to generate soot particles with a wide range of physical, chemical and optical properties. Based on the standard deviation of the results at all engine conditions evaluated in the present study, the overall spread between the instruments was 24% for diesel, 30% for DMA and 37% for IFO samples. For samples with extremely high organic content (at 10% engine power), the agreement was poor and the standard deviation of the mass concentrations estimated from different instruments was 50% for diesel with OC/EC ≈ 45 and 72% for DMA with OC/EC ≈280. For IFO particles, more scattered mass concentrations were reported by different instruments at all engine loads, possibly due to very complex chemical composition and different optical properties in comparison with well-characterized soot particles. We explain the differences in reported values by combining information on exhaust composition with the measurement principles used in each instrument. [ABSTRACT FROM AUTHOR]

The article briefly describes the problem of air pollution caused by sea-going ships and the resulting restrictions on the emission of toxic and harmful chemical compounds in the exhaust of marine engines, introduced by the International Maritime Organization (IMO) under the International Convention for the Prevention of Sea Pollution from Ships (MARPOL 73/78). Such emissions provide a significant metrological problem, not only for the owners of operating sea-going ships, but also for shipyards, maritime administration offices and environmental protection inspectors. For this reason, the article's author is developing research issues related to the diagnosing the exhaust emissions of marine engines under operating conditions, i.e. with limited control (measurement) susceptibility. This is particularly important in the period of intensive implementation of a new category of marine fuel, so-called modified fuels with low sulphur content. As part of the problem, a computational model of the parameters characterising the exhaust emissions of a marine engine in operation is presented in this article. This model is based on the measurement of the engine's control parameters, using a standard (stationary) measurement system and a portable diagnostic system, configured for the purpose of this research. Presented here are representative measurements and calculation results (both obtained by the author and provided by the manufacturer) from the chemical exhaust gas emissivity of one of the ship engines operated. These confirm the adequacy of the calculation model developed and the diagnostic effectiveness of the measuring equipment applied. The methodology developed for experimental testing may also be implemented for the operation of other types of marine engines, provided that the basic chemical composition of the fuel supply and the engine load characteristics and hourly fuel consumption are known. Moreover, there is the possibility of indicating the cylinders and measuring the chemical composition of exhaust gases in the high-temperature part of the exhaust duct. [ABSTRACT FROM AUTHOR]

The characteristics of black carbon and nitrogen oxide reduction versus the water content of emulsion fuel were studied by numerical methods, and a method of reducing fuel consumption was achieved by adjusting the turbocharger compression ratio. The results of the combustion period characteristics, versus the three types of emulsion fuel and the turbocharger compression ratios, shows that the combustion period is shortened in the order of CR00 > CR01 > CR02 > CR03, according to the compression ratio of the turbocharger. As the fuel water content increases, the combustion period is shortened in the order of EMDO16 < EMDO13 < EMDO10. The nitrogen oxide and black carbon reduction was because the combustion period increased, with increasing compression ratio, while the combustion period was shortened, with increasing moisture content of emulsion fuel. This also caused is an increase in the combustion pressure and a shortening of the combustion period, due to the expansion of the volume, in turn due to the micro-explosion of water. This may be due to the shortening of the post combustion period and the reduction of black carbon emissions. In addition, combustion was accelerated in the order—CR00 > CR01> CR02> CR03. By optimizing the water content of the emulsion fuel and turbocharger compression ratio, while considering the exhaust emission and combustion state, reduction of the fuel consumption rate and output improvement are shown. [ABSTRACT FROM AUTHOR]

Natural gas marine engines are widely used in the commercial shipping. It is a hot research topic for carbon reduction, energy saving, and emission reduction in shipping. The over-expansion cycle with natural gas high-pressure direct-injection (HPDI) is a promising approach for reducing fuel consumption and emissions in marine engine. Two types of over-expansion cycles in a large-bore (500 mm) low-speed dual-fuel engine were investigated and compared. The variable compression (VC) cycle decreases the effective compression ratio by adjusting the exhaust valve closing (EVC) timing, and the variable expansion (VE) cycle raises the effective expansion ratio by varying the exhaust valve opening (EVO) timing and scavenging ports opening (SPO) timing. A specific sleeve mechanism was designed to precisely control the opening and closing of scavenging ports. The results reveal that the VC cycle exhibits an operable limit with a delay of 40 °CA in EVC, while the VE cycle has a limit with a delay of 60 °CA in EVO. The scavenging effect obtains improvement in the VC cycle, whereas it deteriorates in the VE cycle. Both the two cycles lead to reduced peak pressure and extended combustion duration. Compared to the baseline, the VC cycle and VE cycle can reduce nitrogen oxides (NO x) emissions by a maximum of 51.9% and 70.7%, respectively. However, the VE cycle can even reduce the equivalent indicated specific fuel consumption (EISFC) by 1.14 g/kWh when the EVO is delayed by 5 °CA. Importantly, the VE cycle exhibits a more favorable cost-effectiveness and potential for NO x emission reduction compared to the VC cycle, and it also demonstrates the capability to optimize NO x and EISFC simultaneously. This provides a method to produce cleaner marine engines with less fuel consumption in the future. [ABSTRACT FROM AUTHOR]

Black carbon (BC) emissions intensify global warming and are linked to adverse health effects. The International Maritime Organization (IMO) considers the impact of BC emissions from international shipping. A prerequisite for the anticipated limits to BC emissions from marine engines is a reliable measurement method. The three candidate methods (photoacoustic spectroscopy (PAS), laser-induced incandescence (LII), and filter smoke number (FSN)) selected by the IMO were evaluated with extensive ship exhaust matrices obtained by different fuels, engines, and emission control devices. A few instruments targeted for atmospheric measurements were included as well. The BC concentrations were close to each other with the smoke meters (AVL 415S and 415SE), PAS (AVL MSS), LII (Artium-300), MAAP 5012, aethalometers (Magee AE-33 and AE-42), and EC (TOA). In most cases, the standard deviation between instruments was in the range of 5–15% at BC concentrations below 30 mg Sm−3. Some differences in the BC concentrations measured with these instruments were potentially related to the ratio of light-absorbing compounds to sulphates or to particle sizes and morphologies. In addition, calibrations, sampling, and correction of thermophoretic loss of BC explained differences in the BC results. However, overall differences in the BC results obtained with three candidate methods selected by the IMO were low despite challenging exhaust compositions from marine diesel engines. Findings will inform decision making on BC emission control from marine engines.

Highlights • A novel system for removing NO in marine diesel engine exhaust gases was studied. • The NO removal efficiency was 100% in 0.15 mol/L or 0.2 mol/L Na 2 S 2 O 8 solution at 80 °C. • Urea which can remove nitrate promoted the NO removal. • The Na 2 S 2 O 8 /urea system not only highly removes the NO but also reduces the nitrate in wastewater. Abstract NO is the main precursor of photochemical smog. Since the SCR system of marine diesel engines has many disadvantages, this paper proposes an effective wet method to remove NO from the exhaust gases of marine diesel engines. Experiments were performed in a bubble column reactor to study the absorption of NO using sodium persulfate (Na 2 S 2 O 8)/urea ((NH 2) 2 CO) solutions from a simulated gas stream. The effects of various operating parameters on NO removal were investigated, including reaction temperature, urea concentration, Na 2 S 2 O 8 concentration and the initial pH value of Na 2 S 2 O 8 /urea solutions. The experimental results showed that the NO removal efficiency increased with increasing reaction temperature (25–80 °C) and increasing Na 2 S 2 O 8 concentration (0.01–0.2 mol/L). When the concentration of urea was higher than 0.5 mol/L at 60 °C, 1 mol/L at 70 °C or 2 mol/L at 80 °C, the NO removal efficiency increased with the increase of urea concentration (0.1–4 mol/L). The highest NO removal efficiency was 99.7%, occurring at 80 °C when the concentrations of Na 2 S 2 O 8 and urea were 0.1 mol/L and 4 mol/L, respectively, and the concentration of nitrate was 14.93 mg/L. The optimal urea conditions were well below the legal limit of 60 mg/L. The NO removal efficiency increased with the increase of initial pH value within the herein investigated range of 7–9. All the experimental data showed that the novel system not only achieved effective NO removal efficiency, but also reduced the nitrate in wastewater, which could thus be applied to denitrification of marine engine exhaust gases. [ABSTRACT FROM AUTHOR]

International shipping has been reported to account for 13% of global NO x emissions and 2.1% of global green house gas emissions. Recent restrictions of NO x emissions from marine vessels have led to the development of exhaust gas recirculation (EGR) for large two-stroke diesel engines. Meanwhile, the same engines have been downsized and derated to optimize fuel efficiency. The smaller engines reduce the possible vessel acceleration, and to counteract this, the engine controller must be improved to fully utilize the physical potential of the engine. A fuel index limiter based on air/fuel ratio was recently developed (Turbo, 2016), but as it does not account for EGR, accelerations lead to excessive exhaust smoke formation which could damage the engine when recirculated. This paper presents two methods for extending a fuel index limiter function to EGR engines. The methods are validated through simulations with a mean-value engine model and on a vessel operating at sea. Validation tests compare combinations of the two index limiter methods, using either traditional PI control for the EGR loop or the recently developed fast adaptive feedforward EGR control (Nielsen et al., 2017a). The experiments show that the extended limiters reduce exhaust smoke formation during acceleration to a minimum, and that the suggested limiter, combined with adaptive feedforward EGR control, is able to maintain full engine acceleration capability. Sea tests with engine speed steps from 35 to 50 RPM, made peak exhaust opacity increase by only 5% points when using the proposed limiter, whereas it increased 70% points without the limiter. [ABSTRACT FROM AUTHOR]

The problematics of installation of sulphur oxides (SOx) scrubber becomes much relevant for today due to the new Annex VI of MARPOL 73/78 requirements, which sets 0.1% SOx limits by 2015 in Emission Control Area (ECA) and globally to 0.5% in 2020. The research in this field becomes more significant for ship-owners. SOx scrubber is most promising alternative because of lower operating costs and suitability to existing ships. Despite the fact that exhausts gas scrubbing is a common and proven technology on land, the conditions on ships differ significantly and still there are not enough practical knowledge of installation of mentioned equipment. In addition, speaking about existing ships there are some limitation factors of SOx scrubber installation on-board, which will be discussed in the paper. Taking into account the size and mass of the SOx scrubber, it can be assumed that the recalculation of ship stability will be required for most ships. Therefore, the most important task for equipment designers is selection of scrubber system location with the minimum impact on ship stability and identification of necessary changes (deadweight, additional space, etc.) in accordance with ship safety requirements. For this reason, the research was carried-out in order to create the algorithm of ship stability assessment and selection of optimal scrubber location on-board. [ABSTRACT FROM AUTHOR]

The performance of marine engines has been consecutively improved over the years, and current marine engines are more efficient year by year. 10.3390/jmse8020109 8 Witkowski K. Research of the Effectiveness of Selected Methods of Reducing Toxic Exhaust Emissions of Marine Diesel Engines. According to this, the Special Issue, "Marine Engines Performance and Engines", published as a book [[1]], was prepared to collect works relating to marine engine performance and emissions in general. [Extracted from the article]

We investigate the representation of emissions from the largest (Class 3) commercial marine vessels (c3 Marine) within the Community Multiscale Air Quality (CMAQ) model. In present emissions inventories developed by the United States Environmental Protection Agency (EPA), c3 Marine emissions are divided into off-shore and near-shore files. Off-shore c3 Marine emissions are vertically distributed within the atmospheric column, reflecting stack-height and plume rise. Near-shore c3 Marine emissions, located close to the US shoreline, are erroneously assumed to occur only at the surface. We adjust the near-shore c3 Marine emissions inventory by vertically distributing these emissions to be consistent with the off-shore c3 Marine inventory. Additionally, we remove near-shore c3 Marine emissions that overlap with off-shore c3 Marine emissions within the EPA files. The CMAQ model generally overestimates surface ozone (O 3 ) compared to Air Quality System (AQS) site observations, with the largest discrepancies occurring near coastal waterways. We compare modeled O 3 from two CMAQ simulations for June, July, and August (JJA) 2011 to surface O 3 observations from AQS sites to examine the efficacy of the c3 Marine emissions improvements. Model results at AQS sites show average maximum 8-hr surface O 3 decreases up to ∼6.5 ppb along the Chesapeake Bay, and increases ∼3–4 ppb around Long Island Sound, when the adjusted c3 Marine emissions are used. Along with the c3 Marine emissions adjustments, we reduce on-road mobile NO X emissions by 50%, motivated by work from Anderson et al. 2014, and reduce the lifetime of the alkyl nitrate species group from ∼10 days to ∼1 day based on work by Canty et al. 2015, to develop the “c3 Science” model scenario. Simulations with these adjustments further improve model representation of the atmosphere. We calculate the ratio of column formaldehyde (HCHO) and tropospheric column nitrogen dioxide (NO 2 ) using observations from the Ozone Monitoring Instrument and CMAQ model output to investigate the photochemical O 3 production regime (VOC or NO X -limited) of the observed and modeled atmosphere. Compared to the baseline, the c3 Science model scenario more closely simulates the HCHO/NO 2 ratio calculated from OMI data. Model simulations for JJA 2018 using the c3 Science scenario show a reduction of surface O 3 by as much as ∼13 ppb for areas around the Chesapeake Bay and ∼2–3 ppb at locations in NY and CT downwind of New York City. These reductions are larger in 2018 than in 2011 due to a change in the photochemical O 3 production regime in the Long Island Sound region and the projected decline of other (non-c3 Marine) sources of O 3 precursors, highlighting the importance of proper representation of c3 Marine emissions in future modeling scenarios. [ABSTRACT FROM AUTHOR]

The experiments were performed in a lab-scale countercurrent spraying reactor to study the NOx removal from simulated gas stream by cyclic scrubbing using NaClO solution. The effects of NaClO concentration, initial solution pH, coexisting gases (5% CO2 and 13% O2), NOx concentration, SO2 concentration, and absorbent temperature on NOx removal efficiency were investigated in regard to marine exhaust gas. When NaClO concentration was higher than 0.05 M and initial solution pH was below 8, NOx removal efficiency was relatively stable and it was higher than 60%. The coexisting CO2 (5%) had little effect on NOx removal efficiency, but the outlet CO2 concentration decreased slowly with the initial pH increasing from 6 to 8. A complete removal of SO2 and NO could be achieved simultaneously at 293 K, initial pH of 6, and NaClO concentration of 0.05 M, while the outlet NO2 concentration increased slightly with the increase of inlet SO2 concentration. NOx removal efficiency increased slightly with the increase of absorbent temperature. The relevant reaction mechanisms for the oxidation and absorption of NO with NaClO were also discussed. The results indicated that it was of great potential for NOx removal from marine exhaust gas by wet scrubbing using NaClO solution. [ABSTRACT FROM AUTHOR]

The article discusses the results of actions performed by marine engine manufacturers towards the reduction of emission of harmful substances in the exhaust gas from these engines. The discussion is limited to main engines produced by MAN B&W. A model is proposed to describe the process of emission of harmful substances from Diesel engines based on the semi-Markov process, discrete in states and continuous in the operating time. The states of this process are: engine ability state (s1) and engine inability state (s2). A method to calculate probabilities P1 and P2 of the appearance of states s1 and s2 is proposed. State s1 is interpreted as corresponding to the inequality ekek(dop), where ek represents the mass of harmful substances emitted by the engine during its operation and ek(dop) is the maximum mass of emission of these substances permitted by relevant regulations. [ABSTRACT FROM AUTHOR]

In this study, a marine engine has been evaluated for waste heat recovery (WHR) using thermoelectric generators (TEG). The feasibility of MgSnGe, CuSe, and CuSe as potential thermoelectric (TE) material were investigated. A straight fin heat exchanger is used to enhance the heat transfer between the hot exhaust gas and TE modules. To facility the analysis, a system level thermal resistance model is built and validated with experiments. After the model is validated, a small marine engine with rated power of 1.7-3 MW is taken as baseline model and it is found that around 2-4 KW electrical power can be extracted from exhaust gas by the TEG at varying design and operating parameters. The back pressure effect induced by the heat exchanger is also considered in this study. Finally, a parameter study is conducted regarding the impact of the TE module height on the output power. It is shown that the height of the TE leg could play a significant role in the module geometry design, and that the optimal height varies between 1 mm and 2 mm under different heat exchangers and exhaust gas flow rates. [ABSTRACT FROM AUTHOR]

Shipping represents a significant source of diesel emissions, which affects global climate, air quality and human health. As a solution to this problem, biodiesel could be used as marine fuel, which could help in reducing the negative impact of shipping on environment and achieve lower carbon intensity in the sector. In Southern Europe, some oily wastes, such as wastes from olive oil production and used frying oils could be utilized for production of the second-generation biodiesel. The present research investigates the influence of the secondgeneration biodiesel on the characteristics of gaseous emissions of NOx, SO2, and CO from marine diesel engines. The marine diesel engine that was used, installed aboard a ship, was a reversible low-speed two-stroke engine, without any after-treatment devices installed or engine control technology for reducing pollutant emission. Tests were carried out on three regimes of engine speeds, 150 rpm, 180 rpm and 210 rpm under heavy propeller condition, while the ship was berthed in the harbor. The engine was fueled by diesel fuel and blends containing 7% and 20% v/v of three types of second-generation biodiesel made of olive husk oil, waste frying sunflower oil, and waste frying palm oil. A base-catalyzed transesterification was implemented for biodiesel production. According to the results, there are trends of NOx, SO2, and CO emission reduction when using blended fuels. Biodiesel made of olive husk oil showed better gaseous emission performances than biodiesel made from waste frying oils. [ABSTRACT FROM AUTHOR]

Major shipping companies utilize fuel oil additives to reduce fuel costs and to comply with emission regulations. Although the use of fuel additives for marine heavy fuel oil has increased dramatically, their effects on performance have not been verified. This study investigated the effects of fuel additives, not only at the scale of the engine test bed but also through chemical laboratory tests. Fuel separability tests were conducted to evaluate fuel oil stability. The results indicated that there was improved stability with certain dosages of fuel additives. Fuel combustion and ignition characteristics were evaluated via a Fuel Combustion Analysis (FCA) test, which showed that combustion parameters, including the pressure trace and rate of heat release (ROHR), were significantly affected by the use of fuel additives. The ROHR results showed modified performance indicators, particularly in regard to the position of the ROHR, ignition delay, end of main combustion, and end of combustion. The testing only aimed to determine the tendency at low engine loads, because engines typically operate at low loads within emission controlled areas. The engine test results showed that some additives were associated with reduced fuel consumption, but that some resulted in higher specific fuel oil consumption levels than those for fuel oils without additives. Nitrogen oxide (NOx) and particulate matter (PM) emission characteristics were also investigated, and data revealed that fuel additives affected the emission components. [ABSTRACT FROM AUTHOR]

Strong restrictions on emissions from marine power plants will probably be adopted in the near future. One of the measures which can be considered to reduce exhaust gases emissions is the use of alternative fuels. Synthesis gases are considered competitive renewable gaseous fuels which can be used in marine gas turbines for both propulsion and electric power generation on ships. The paper analyses combustion and emission characteristics of syngas fuel in marine gas turbines. Syngas fuel is burned in a gas turbine can combustor. The gas turbine can combustor with swirl is designed to burn the fuel efficiently and reduce the emissions. The analysis is performed numerically using the computational fluid dynamics code ANSYS FLUENT. Different operating conditions are considered within the numerical runs. The obtained numerical results are compared with experimental data and satisfactory agreement is obtained. The effect of syngas fuel composition and the swirl number values on temperature contours, and exhaust gas species concentrations are presented in this paper. The results show an increase of peak flame temperature for the syngas compared to natural gas fuel combustion at the same operating conditions while the NO emission becomes lower. In addition, lower CO2 emissions and increased CO emissions at the combustor exit are obtained for the syngas, compared to the natural gas fuel. [ABSTRACT FROM AUTHOR]

Emission reduction from marine engines can be supported by implementing multiple injection strategies. In the present study, the effect of fuel post-injection on the performance and exhaust emissions of a large two-stroke marine diesel engine is investigated by using computational fluid dynamics (CFD). An optimization procedure is formulated by coupling a KIVA-3-based CFD code with an optimization tool based on evolutionary algorithms (EAs). A fuel-injection profile consisting of two pulses (main and post-injection) is considered and parameterized in terms of four design variables. The specific fuel oil consumption (SFOC) and the final concentration of nitric oxides (NOX) and soot constitute the objective functions. Using a parametric study, two multiobjective optimization problems are formulated, an unconstrained and a constrained one; in the latter, the work output per engine cycle and the maximum in-cylinder pressure are the problem constraints. For both problems, significant reductions in pollutant emissions are attained, in comparison with a reference case characterized by continuous injection; for the constrained problem, the reductions reach 23 and 32% for NOX and soot, respectively. [ABSTRACT FROM AUTHOR]

The world is considering various solutions to reduce exhaust emissions, the use of alternative fuels and the development of more efficient marine engines. IMO the company gave guidance for future borders of individual exhaust components, taking into account a variety of applications and conditions for the operation of marine engines. Engine manufacturers have been forced to develop new technologies, to meet the existing IMO rules and regulations that are yet to come, for the emission of harmful exhaust emissions.This paper describes the experimental procedure that support the modeling of the operating parameters of marine internal combustion engines in order to diagnose the condition, optimization of engine and reduce exhaust emissions. Special attention was given to verify the adequacy of the investigation, its accuracy and relevance. It outlines experiments that support the selection procedure tests during sea trials and later in the exploitation of the ship. [ABSTRACT FROM AUTHOR]

The emissions of marine diesel engines have gained both global and regional attentions because of their impact on human health and climate change. To reduce ship emissions, the International Maritime Organization capped the fuel sulfur content of marine fuels. Consequently, either low-sulfur fuels or additional exhaust gas cleaning devices for the reduction in sulfur dioxide (SO 2) emissions became mandatory. Although a wet scrubber reduces the amount of SO 2 significantly, there is still a need to consider the reduction in particle emissions directly. We present data on the particle removal efficiency of a scrubber regarding particle number and mass concentration with different marine fuel types, marine gas oil, and two heavy fuel oils (HFOs). An open-loop sulfur scrubber was installed in the exhaust line of a marine diesel test engine. Fine particulate matter was comprehensively characterized in terms of its physical and chemical properties. The wet scrubber led up to a 40% reduction in particle number, whereas a reduction in particle mass emissions was not generally determined. We observed a shift in the size distribution by the scrubber to larger particle diameters when the engine was operated on conventional HFOs. The reduction in particle number concentrations and shift in particle size were caused by the coagulation of soot particles and formation/growing of sulfur-containing particles. Combining the scrubber with a wet electrostatic precipitator as an additional abatement system showed a reduction in particle number and mass emission factors by >98%. Therefore, the application of a wet scrubber for the after-treatment of marine fuel oil combustion will reduce SO 2 emissions, but it does not substantially affect the number and mass concentration of respirable particulate matters. To reduce particle emission, the scrubber should be combined with additional abatement systems. [Display omitted] • High-sulfur fuel content led to high particle emissions. • A wet scrubber efficiently reduced SO 2 emission. • Only minor reduction of particle emissions was accomplished by a wet scrubber. • Coagulation and adding of sulfide/sulfate caused forming of larger particles. • Reduction of particle emissions was obtained by adding an electrostatic precipitator. [ABSTRACT FROM AUTHOR]

Carbon emissions are causing a series of environmental problems, seriously threatening the survival and health of human beings, of which the shipping industry accounts for a significant part. Ammonia is a promising carbon-free alternative fuel for carbon emission reduction of marine engines, while the specific application method remains to be discussed. This study explores a potential novel ammonia-diesel stratified injection technology for the application of low-carbon ammonia fuel on marine engines to meet future low-carbon emission regulations. The results illustrate that this strategy can achieve similar engine power as conventional diesel engines and greatly reduce the CO 2 and NO x emissions. The energy ratio of ammonia fuel can be as high as 99%, due to the precise delivery of ammonia to the pilot fuel combustion zone, and the NO x emissions can meet Tier III emission standards at 100% load without any after-treatment because of the heat absorption of ammonia vaporization. Meanwhile, the addition of matching pilot fuel injectors can be avoided to save retrofit and material costs. In addition, the effect of various injection strategies, such as pilot diesel energy proportion, multiple stratified injection and injection pressure, on power and emissions were investigated. The result demonstrated that increasing the injection pressure and pilot diesel proportion can both improve the IMEP but also increase the NO x emissions. While multiple stratified injection has little effect on power and emissions. On the whole, the strategy with high injection pressure and less pilot fuel is the optimal solution to achieve high IMEP, low NO x and carbon emissions. [Display omitted] ● Ammonia and diesel stratified injection can facilitate the application of ammonia. ● This strategy can greatly reduce CO 2 and NO x emissions while increasing IMEP. ● The energy replacement ratio of ammonia can be as high as 99%. ● This strategy can reduce engine modification and save costs. [ABSTRACT FROM AUTHOR]

Marine engine exhaust emissions are increasingly harmful to the natural environment and human health and must be controlled. A self-synthesized amide (BAD, C 12 H 25 NO) in the laboratory shows a strong absorption capacity of nitric acid and nitrous acid, which may solve the problem that only using chlorine-based oxidant as an absorbent cannot completely absorb or retain NO 2 produced by NO oxidation in previous studies. Based on Multiwfn and VMD (Visual Molecular Dynamics) program calculation, the formation mechanism of hydrogen bonds between BAD with nitric acid and nitrous acid was revealed by electrostatic potential (ESP) analysis and further confirmed by FT-IR (Fourier transform infrared spectroscopy) spectra research. Subsequently, simultaneous removal of SO 2 and NO X from simulated flue gas was carried out by using NaClO/BAD as a two-phase composite absorbent, and the maximum removal efficiencies of SO 2 and NO X were 98.9% and 86.6%, respectively. The recycling experiments and the engineering experiments showing that NaClO/BAD can solve the problem of absorption of NO 2 , and it can be a promising composite absorbent in wet desulfurization and denitrification of marine engine exhaust gas in practical applications. [Display omitted] • The two-phase wet oxidation absorption system provide a new idea for exhaust gas denitrification. • The NaClO/BAD composite absorbent can solve the problem of large amount of NO 2 escape by using chlorine-based oxidants. • The reaction mechanism of NaClO/BAD composite absorbent for simultaneous removal of SO 2 and NO X is proposed. • Engineering test was carried out in a local large shipyard in Rongcheng, Shandong. [ABSTRACT FROM AUTHOR]

The problem of marine litter is one of the most important ecological problems in many countries. Lack of ecological consciousness and disregard for environmental regulations for marine pollution, results in increasing and sometimes even dangerous amounts of floating litter that either pollutes coastal areas or end up degrading into ever smaller particles and poi-soning marine fauna. To solve this problem one of innovative marine litter collection nets – a light weight, easy to assemble was created. However marine litter collection would create additional trawling work which results in additional air pollutant emissions. It is there for necessary to evaluate the air pollutant emissions that occur during trawling of nets and aim to provide tools for ecological optimization of trawling work so that the least amounts of air pollution would be created while gathering the greatest amount marine litter. The special raft was designed and constructed for such nets test. The test was performed in Curonian lagoon. Marine litter collection requires additional energy consumption, because of increase of thug's engines power to overcome increase of nets resistance, that also leads to additional fuel consumptions and higher exhaust gas emissions. The article is based on experimental research of a light weight marine litter collection nets resistance measurement. Evaluation of additional energy consumption and increased exhaust gas emissions during trawling. [ABSTRACT FROM AUTHOR]

The current restrictions on emissions from marine engines, particularly sulphur oxides (SOx), nitrogen oxides (NOx) and carbon dioxide (CO2), are compelling the shipping industry to a change of tendency. In the recent years, many primary and secondary reduction techniques have been proposed and employed in marine engines. Nevertheless, the increasingly restrictive legislation makes it very difficult to continue developing efficient reduction procedures at competitive prices. According to this, the paper presents the possibility to employ alternative fuels. A numerical model was developed to analyze the combustion process and emissions using oil fuel, natural gas and hydrogen. A commercial marine engine was studied, the Wärtsilä 6L 46. It was found, that hydrogen is the cleanest fuel regarding CO2, hydrocarbons (HC) and carbon monoxide (CO). Nevertheless, it is very expensive for marine applications. Natural gas is cheaper and cleaner than fuel oil regarding CO2 and CO emissions. Still, natural gas emits more NOx and HC than oil fuel. SOx depends basically on the sulphur content of each particular fuel. [ABSTRACT FROM AUTHOR]

A marine engine pollution abatement system was constructed and tested on a 1.5 MW auxiliary marine engine. The integrated system, designed to abate all of the currently legislated emissions from marine engines, consisted of a monolithic Pt/Al 2 O 3 oxidation catalyst and a seawater scrubber, both of suitable dimensions for the engine size. The test results obtained showed the general validity of the approach adopted, as significant abatement of emissions was achieved. However, under the conditions used, the system showed some limitations with regard to the sulphur content of the fuel. On the basis of the results obtained, the system can be used with fuel sulphur content of up to 0.4%, while problems were encountered when a fuel with a sulphur content of 2.0% was used. Whereas the catalytic section operated satisfactorily, fine tuning of the scrubber operating conditions is necessary to improve abatement of NO x and increase the range of fuel sulphur which can be used with the system. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction (SCR) technology is currently the most effective deNO x technology and has broad application prospects. Moreover, there is a large NO x content in marine engine exhaust. However, the marine engine SCR catalyst will be affected by heavy metals, SO 2 , H 2 O (g) , hydrocarbons (HC) and particulate matter (PM) in the exhaust, which will hinder the removal of NO x via SCR. Furthermore, due to the high loading operation of the marine engine and the regeneration of the diesel particulate filter (DPF), the exhaust temperature of the engine may exceed 600 °C, which leads to sintering of the SCR catalysts. Therefore, the development of new catalysts with good tolerances to the above emissions and process parameters is of great significance for further reducing NO x from marine engines. In this work, we first elaborate on the mechanism of the SCR catalyst poisoning caused by marine engine emissions, as well as the working mechanism of SCR catalysts affected by the engine exhaust temperature. Second, we also summarize the current technologies for improving the properties of SCR catalysts with the aim of enhancing the resistance and stability under complex working conditions. Finally, the challenges and perspectives associated with the performance optimization and technology popularization of marine SCR systems are discussed and proposed further. Consequently, this review may provide a valuable reference and inspiration for the development of catalysts and improvement in the denitration ability of SCR systems matched with marine engines. [Display omitted] • The activity of marine SCR catalyst is affected by multi-pollutants. • Different deactivated mechanisms of catalyst were summarized specifically. • The methods to enhance the resistance and stability of catalyst were exemplified. • Modification of catalyst is crucial to improve the marine SCR performance. [ABSTRACT FROM AUTHOR]