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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]

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]

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]

Steam-methane reformers are one of the most effective environmental systems used to obtain hydrogen with the effect of temperature. This study investigated hydrogen production efficiency numerically with exhaust waste heat. Two different scenarios were studied parametrically at five various engine loads. In this study, steam methane reactor temperature change, hydrogen, CO and CO 2 formation amounts were determined according to each exhaust temperature and mass flow rate. As a result of the study, the temperature changes for the scenario 1 and scenario 2 conditions of the steam methane reformer were examined and it was found that the maximum temperature change was 26.7% at the 25% engine load condition. The maximum hydrogen production mass flow rate in proportion to the temperature was approximately 7020 g/h in scenario 2 at 25% engine load condition. Radical CO formation showed that system performance is not realized efficiently enough. The study's significant finding is that increasing the temperature and using catalysts throughout the system increases hydrogen production. • A 2D CFD reforming model is developed to predict H 2 production. • Investigation of H 2 production potential with waste heat of marine diesel engine. • CFD shows that H 2 production increases with rising temperature. • The effect of modified exhaust temperatures on H 2 production was simulated. • The use of catalysts obviously promotes H 2 production. [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]

In this study, the ammonia-diesel stratified injection (ADSI) is explored on a marine low-speed engine., The effect of three injection timings(IT S = −3°CA ATDC, −1°CA ATDC, and 1°CA ATDC) coupling with three diesel energy fractions (DEF S = 1%,5%, and 10%) on combustion and emission characteristics of the engine under full load is investigated. The results show that advancing IT has an obvious effect on increasing peak cylinder pressure while enhancing DEF can increase the heat release rate under ADSI mode, and the ignition delay time is less than original diesel engine. The ADSI has higher indicated thermal efficiency than original diesel engine except for IT of 1°CA ATDC coupling DEF of 1%, and its combustion efficiency can be significantly improved. Furthermore, the NO x increases with advancing IT and increasing DEF while the unburned ammonia is the opposite. The NO x emissions are all lower than original diesel engine under different IT coupling DEF. Advancing IT is an effective measure to reduce unburned ammonia. The greenhouse gas (GHG) can be greatly reduced. A priority strategy of the IT coupling DEF is proposed through comprehensive comparison under the ADSI mode, which can meet the Tier III regulations. This strategy reduces indicated specific fuel consumption and GHG around by 4% and 94% compared with the diesel engine respectively, and the combustion efficiency reaches more than 99%. The unburned ammonia is limited to less than 150 ppm. • A new ammonia-diesel stratified injection (ADSJ) mode was explored in detail. • The effect of multi-parameter coupling was studied on combustion and emissions. • The ADSJ mode was easier ignition than the original diesel engine. • The ADSJ had better combustion characteristics than the original diesel engine. • An optimized parameter control strategy is proposed. [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]

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]

[Display omitted] • The combustion characteristics of ammonia/hydrogen in marine engine were studied; • HPDP-1C mode improves engine performance; • A 30 % hydrogen was proposed based on the overall performance of marine engines; • The NO x emissions should be concerned for ammonia/hydrogen combustion; Studies show that blending ammonia and hydrogen fuels is a feasible approach to achieve zero carbon emissions in internal combustion engines. The prevalent use of high-pressure dual fuel (HPDF) injection primarily originates from its high efficiency and relatively low emission. However, ammonia exhibits poor ignition performance, and adding hydrogen increases cylinder temperatures, leading to the formation of nitrogen oxides. The present study explores various injector arrangements, ignition modes, and ammonia/hydrogen blend ratios to devise effective combustion strategies and mitigate NO x emissions. Comparative analysis reveals that the injector arrangement in close position of ammonia and hydrogen exhibits superior performance in terms of indicated power, thermal efficiency, and heat release rate. Regarding ignition modes, transitioning from ammonia/hydrogen blend compression ignition mode to hydrogen piloted ammonia mode increases the indicated power by 0.7 %, while remarkably raising NO x emissions by 29.4 %. Moreover, increasing hydrogen content enhances indicated power by 3.7 % but elevates nitrogen oxide emissions by a factor of 2.2, while reducing ammonia and hydrogen escape, with a maximum not exceeding 0.058 %. Consequently, a 30 % ammonia/hydrogen blend ratio coupled with HPDF-1C arrangement is recommended for marine engines, prioritizing combustion stability and lower NO x emissions. The findings of the present research offer invaluable insights into advancing the development of ammonia/hydrogen blended fuel engines and provide a guideline for blending fuels in engineering and industrial applications. [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]

IMO has pushed out strict regulations to limit marine diesel engine emissions. EGR is a mature measure to reduce NOx emissions which would lead PM emissions risen. In this paper, An EGR system combined with a scrubber was built on a marine diesel engine. Based on the experimental platform, the characteristics of PM emissions were studied when the engine burning two kinds of sulfur diesel oils. The results showed that the particle size concentration curves show multimodal distribution and the average particle sizes increased. Most of the PM emissions were distributed in the nuclear mode interval. Moreover, EGR scrubber had a significant effect on removing PM with an efficiency of over 98% and the weighted value of PM emissions was 22.136 mg / kWh, which met China's first and second-stage emission regulations and US EPA Tier 4 emission regulations. [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]

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]

Water/steam direct injection is an effective method to lower emissions and improve the power of engines by using waste heat recovery (WHR). The parameters of water injection (WI) and steam injection (SI) were analyzed at compression stroke on the effect of brake power and emissions in marine engines, including injected timing, mass, and temperature. The results demonstrated that NOx emissions were substantially reduced by using WI method. However, brake power was also decreased. The SI method not only decreased NOx emissions but also improved brake power. The NOx emissions were ascended with increasing temperature and delaying injected timing of water. Opposing trends were found for SI method. The injected mass has a large effect on power and emissions compared with the influence of temperature and timing. The NOx emissions can be reduced by 72.8% with 2.08% power loss when the 20 g of water was injected into the cylinder at −50 °CA, 15 bar and 400 K. The NOx emissions can be reduced by 38.9% with 24.7% power improvement when the same mass of superheated steam with 500 K of temperature was injected into the cylinder. It can be obvious that SI method can increase power while reducing fuel consumption and emissions. [ABSTRACT FROM AUTHOR]

A study is presented to determine the technical, regulatory, and economic feasibility of a coastal research vessel (named the "Zero-V") powered solely by hydrogen fuel cells. Feasibility is examined in the context of science mission profiles of particular significance in coastal oceanography that require a modern, capable, general-purpose coastal research vessel. These missions translate into the primary Zero-V vessel requirements against which technical feasibility is assessed. Hull form analysis indicated a trimaran design enables a vessel that can meet all of the space and volume requirements as well as for fitment of the machinery, service, and control spaces necessary for operation of the vessel. To meet speed and range (endurance) requirements, the vessel needs to be constructed of aluminum to reduce weight. The beam (56 feet), length (170 feet) and draft (12 feet) of the vessel enable it to dock at all primary ports of call. With 1800 kW of installed proton exchange membrane (PEM) fuel-cell power for primary propulsion, the cruising speed is 10 knots. With 10,900 kg of consumable LH 2 stored in two LH 2 tanks, the range of the vessel is 2400 nautical miles, with an endurance of 15 days. Both the greenhouse gas (GHG) and criteria pollutant (NO x , HC, PM 10) emissions were estimated based on a complete "well-to-waves" (WTW) analysis. Using renewable hydrogen, the annual WTW GHG emissions predicted for the Zero-V are 91.4% less than those from an equivalent vessel running on conventional diesel fuel. Analysis of the WTW criteria pollutant emissions show that hydrogen PEM fuel-cell technology can reduce these emissions below stringent U.S. Environmental Protection Agency (EPA) Tier 4 marine diesel engine emissions limits regardless of whether the hydrogen is made using natural gas or renewable methods. The capital construction cost is estimated to be ~ $79 M, not unreasonable when compared to other modern diesel-fueled research vessels of similar size and capabilities. The operations and maintenance (O&M) costs of the Zero-V were estimated to be 7.7% higher than operating the equivalent diesel-fueled vessel at the assumed fuel prices for LH 2 made from steam reforming of fossil natural gas. The approach to safety for the Zero-V is described in terms of the arrangement of hazardous areas on the vessel. Regulatory review of the vessel design by the United States Coast Guard (USCG) and the Class society DNV GL found no fundamental or "show-stopping" design concerns that would prevent eventual deployment of the Zero-V. Overall, this study found it feasible from technical, regulatory, and economic perspectives to design, build and operate a coastal research vessel powered solely by hydrogen fuel cells. [ABSTRACT FROM AUTHOR]

Purpose: The emission from marine engines has a crucial effect on energy economy and environment pollution. One of the effective emission reduction schemes is to minimize the friction loss of main friction pairs such as cylinder liner-piston ring (CLPR). Micro-groove textures were designed to accomplish this aim. Design/methodology/approach: The authors experimentally investigated the effects of micro-groove textures at different cylinder liner positions. The micro-groove texture was fabricated on samples by chemical etching and cut from the real CLPR pair. Sliding contact tests were conducted by a reciprocation test apparatus. Findings: The average friction coefficient of grooves at 30° inclination were reduced up to 58.22% and produced better tribological behavior at most conditions. The operating condition was the critical factor that determined the optimum texture pattern. The surface morphology indicated that textures could produce smoother surfaces and less scratches as compared with the untextured surface. Originality/value: Inclined grooves and V-grooves were designed and applied to real CLPR pairs. The knowledge obtained in this study will lead to practical basis for tribological design and manufacturing of CLPR pair in marine diesel engines. [ABSTRACT FROM AUTHOR]

Increasing demands on energy efficiency and environmental acceptance are being imposed on marine propulsion plants. The fulfilment of the conditions set by the MARPOL Convention, Annex VI, regarding the emissions from exhaust gases of marine diesel engines is of particular interest. This paper presents the development and validation of a zero-dimensional, single-zone diesel engine numerical model. Presented numerical model is based on the law of conservation of energy and mass and solving the resulting differential equations. The single-zone model will serve as the basis for a model where the cylinder space is divided into two or three zones during combustion. In this way, the multi-zone model will allow the modelling of nitrogen oxide emissions with satisfactory accuracy. Validation of the diesel engine model was carried out for the Wärtsilä 12V50DF 11700 kW motor designed to drive a synchronous alternator. Obtained results and deviations of certain parameters in the operation of the engine with respect to the data obtained from the measurements on the test bed, are more than satisfactory regarding complexity of the numerical model. This confirmed the usability of the model for research purposes to optimize the marine diesel engine. [ABSTRACT FROM AUTHOR]

Highlights • The spray and evaporation characteristics in the large marine diesel engine were investigated. • Three kinds of optical diagnostic technologies were used. • The empirical correlations of spray tip penetrations and SMDs were updated. Abstract The spray and evaporation characteristics of injector used in the large marine diesel engine directly affect the combustion and emission performance of marine engine. But these characteristics are rarely studied. In this work, three kinds of optical diagnostic technologies (backlight high speed imaging technique, UV-LAS and LIF/MIE) were applied to measure the spray liquid and vapor penetrations, spreading angles, SMDs and the distribution of fuel vapor mass of an injector used in the large marine engine under different conditions. The detailed description of the experiment setups and principle of the three optical diagnostic techniques are provided in this work. The experimental results show that the liquid and vapor penetrations decrease with increasing the ambient density. Increasing the ambient temperature can reduce the liquid penetration, but has no obvious effect on the vapor penetration. For spreading angle, the ambient temperature and ambient density are the main influence factors. Increasing the injection pressure is an effective method to reduce SMD, and also the ambient temperature acts as an important role in the fuel evaporation process. What's more, the empirical correlations of spray tip penetrations and SMDs have been updated to fit the spray characteristics of marine diesel engine injector. In general, this work is helpful to understand the spray and evaporation characteristics within diesel-fueled marine engine conditions, and can provide valuable direction for the design of marine engine combustion system. [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]

This paper aims at improving power generation efficiency of marine diesel engine waste heat recovery systems. It presents a novel technique of integrating the heat rejected in the scavenge air cooling process and the exhaust gas in operating a single and dual pressure steam power generation cycles. Moreover, a thermodynamic analysis of proposed systems was performed to identify the optimum operating parameters for achieving an overall efficiency improvement. The analysis considered the exergy destruction in each component and the energy/exergy efficiencies. A performance analysis was conducted to assess applicability and power output at off design conditions. An evaluation of achieved improvements by suggested designs was presented from both an economical and environmental standpoint. In conclusion, results show that, the recommended cycle increased overall efficiency improvement from 2.8% for the conventional system to 5.1%, with an additional power output of 1210 kW, representing 9.7% of the engine's power. Also, exergy efficiency increased significantly by 6.6% when using the presented system. Furthermore, the waste heat recovery system attained a reduction in fuel consumption of 1538 Ton/year, reducing carbon dioxide emission by 4790 Ton/year. [ABSTRACT FROM AUTHOR]

• Effect of HP-SCR reactor on pulse effect in the exhaust pipe. • NOx reduction rate is 84.7 %, and the maximum fuel consumption penalty of the engine doesn't exceed 1 g/kWh. • Effect of HP-SCR reactor on HC, CO, and CO 2 emission of low-speed marine engine. The high-pressure selective catalytic reduction (HP-SCR) system arranged before the turbine is more suitable for high-power marine low-speed engines to reduce NOx emission. However, the HP-SCR reactor will cause an increase in engine exhaust back pressure, affecting its performance and brake-specific fuel consumption (BSFC). The 10WM marine low-speed two-stroke diesel engine and its HP-SCR system are taken as the research object in this paper. The engine performance and emissions in International Maritime Organization (IMO) Tier II and Tier III modes are tested by bench experiments. The effects of the HP-SCR reactor on engine performance parameters, emission characteristics, and pulse effect in exhaust pipe are obtained. The research showed that when the HP-SCR reactor is used, the BSFC of the engine will slightly increase, but the maximum will not exceed 1 g/kWh. The weighted specific emission of NOx is 2.09 g/kWh, which can meet Tier III emission regulations. In addition, under the Tier II mode, the engine exhaust pipe has a noticeable pulse effect. The exhaust gas temperature before the turbine is about 30 °C higher than that after the cylinder. However, under Tier III mode, the pulse effect in the exhaust pipe disappears completely. In addition to the fact that the HP-SCR reactor weakens the linear velocity of exhaust gas, the main reason is that the urea injection unit reduces exhaust gas temperature by 36 ∼ 47 °C. [ABSTRACT FROM AUTHOR]

The purpose of this research was to achieve the best performance, combustion and emission characteristics of a marine engine fueled with hydrogen (5%, 10% and 15% energy fraction), water (2, 4 and 6 wt%) and rapeseed methyl ester (RME) blend fuel by the multi-objective optimization. Based on the experimental results of the engine at 50%, 75% and 100% loads, the computational fluid dynamics (CFD) model was developed, and an improved chemical kinetic mechanism was developed to simulate the fuel combustion process. The response surface methodology (RSM) was used to optimize the combustion and emission characteristics of the marine diesel engine. The result showed that the hydrogen and water can improve the combustion and emission characteristics of the marine engine. The best solution was to select the desirable value of 0.632, and the engine achieves the best state by fueling R + 15H + 2.5W at 74.69% load. At the point, the optimum values of brake specific fuel consumption (BSFC), brake thermal efficiency (BTE), nitrogen oxide (NO x), hydrocarbon (HC) and carbon monoxide (CO) emissions were 208.31 g/kW·h, 39.22%, 941.21 ppm, 325.86 ppm and 1073.4 ppm, respectively. For this study, adding appropriate hydrogen and water to biodiesel can achieve efficient, low carbon and clean combustion in marine engine. • Effects of hydrogen/biodiesel/water blend fuels on combustion and emission characteristics are compared. • Optimum blend fuel is obtained for diesel engine. • An improved 3D model and chemical kinetics mechanism are developed. • The performance optimization was carried out by the response surface methodology. [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]

The energies produced by the diesel engines of strong power are largely used in marine propulsion because of their favorable reliability and their significant output. However, the increasingly constraining legislations, aimed at limiting the pollutant emissions from the exhaust gas produced by these engines, tend to call into question their supremacy. The analysis of the pollutant emissions and their reduction in the exhaust gas of the slow turbocharged marine diesel engine using ANSYS 15 constitutes the principal objective of this study. To address problems of global air pollution due to the pollutant emission from fuel oil engine combustion, it is necessary to understand the mechanisms by which pollutants are produced in combustion processes. In the present work, an experimental and numerical study is carried out on a unit of real use aboard a car ferry ship. A numerical model based on a detailed chemical kinetics scheme is used to calculate the emissions of NOx, SOx and Sooth in an internal combustion engine model for the same characteristics of the real unit. The combustion process parameters based on the numerical model might now be optimized in order to decrease the pollutant emissions in order to meet the IMO regulations. [ABSTRACT FROM AUTHOR]

In order to improve the heat utilization of exhaust gas from the small and medium-sized ships without exhaust boilers, a methanol steam reforming (MSR) is proposed in the study. The combustion model of marine engine blended hydrogen-rich reforming gas was developed, and verified in terms of cylinder pressure, BSFC, and NO emissions. The compositions of reforming gas were obtained by the MSR model and employed to investigate the effect of reforming gas at different blending ratios on the combustion and emission characteristics of the marine diesel engine in the AVL-Fire environment. The results obtained show that the performance, emission, and economic characteristics are improved due to the existence of reforming gas. Specifically, the indicated power is decreased by 0.5%–4.26% and the NO mass fraction is reduced by 2.95%–18.25% at different loads, but the CO mass fractions increased by 20.21%–54.73%. Similarly, the NO x weighted emission is reduced by 34.10%, which is close to the NO x emission limit of Tier II, but the CO weighted emission is increased by 30.89%. In addition, the equivalent fuel consumption rate is reduced by 0.45%–3.59% at the maximum blending ratio, and the converted fuel cost is reduced by 6%–10% at medium and high loads. Finally, based on the comprehensive performance analysis, the optimized blending ratio at each load is obtained as follows: Rg7.5 or Rg12.5 for 100% load, Rg10 for 75% load, Rg7.5 for 50% load, and Rg2.5 for 25% load. Thus, the MSR reaction is feasible to improve the energy efficiency and reduce NO x emission of the marine engine. • A blended combustion model of hydrogen-rich reforming gas is established. • The effects of reforming gas blended combustion on economic and emission characteristics of marine diesel engine are obtained. • The optimum blending ratios for reforming gas are obtained for the diesel engine. [ABSTRACT FROM AUTHOR]

• The novel system of ozone-Na 2 SO 3 /(NH 2) 2 CO for marine NO removal was proposed. • The NO x removal efficiency was 97.9% and the nitrate concentration was 21.1 mg/L. • Weak acidic media can efficiently improve NO removal and reduce nitrite residue. • This system can efficiently reduce the (NH 2) 2 CO consumption and nitrite residue. The pollutants from the marine exhaust gas seriously threaten air quality and human health. Wet absorption is one of the most efficient NO x control pathways. The strict emission control regulations require the wet NO x control technology to have high NO x removal efficiency and the nitrate concentration of the absorption solution to be below 60 mg/L. The novel system of ozone-Na 2 SO 3 /(NH 2) 2 CO could not only make the NO x absorption efficiency and the amount of nitrate residue fully meet the regulations but also effectively reduce the (NH 2) 2 CO consumption and the nitrite concentration. The final product of NO was mainly N 2 instead of nitrate. The effects of O 3 concentration, Na 2 SO 3 concentration, (NH 2) 2 CO concentration, O 2 concentration, SO 2 concentration, initial pH value, and temperature were thoroughly investigated. The experimental results showed that the NO x removal efficiency was mostly influenced by the O 3 concentration, Na 2 SO 3 concentration, and the initial pH value. Moreover, the nitrate concentration was mainly controlled by Na 2 SO 3 concentration and initial pH value. While the nitrite concentration was governed by the (NH 2) 2 CO concentration and initial pH value. The increase of O 3 concentration and Na 2 SO 3 concentration promote NO x absorption. Although the decrease of initial pH value resulted in a slight increase of nitrate, it greatly reduced the content of nitrite. Furthermore, the increase of Na 2 SO 3 concentration helped to improve the NO x removal efficiency and inhibited the generation of nitrate. Initial pH value was the critical parameter for the NO absorption process. Ozone-Na 2 SO 3 /(NH 2) 2 CO composite system showed great application potential in the field of marine wet NO x control technology. [ABSTRACT FROM AUTHOR]

• Match and comprehensive optimization for HP-EGR and DC-EGR are carried out. • Effects of HP-EGR on fuel economy and emissions are studied. • Effects of DC-EGR on the inhomogeneity of different cylinders are studied. • Detailed comparisons between HP-EGR and DC-EGR are conducted. • DC-EGR can achieve a higher EGR rate and lower NO x at low and medium loads. With the increasingly stringent emission legislation for marine diesel engines, a higher exhaust gas recirculation (EGR) rate is used to reduce NO x. However, a high EGR rate deteriorates brake specific fuel consumption (BSFC). Therefore, a suitable EGR pattern is critical to balancing NO x and BSFC. In this study, high-pressure EGR (HP-EGR) and donor-cylinder EGR (DC-EGR) were separately established by GT-Power, and NO x and BSFC comprehensive optimization was conducted by adaptive particle swarm optimization. The effect of the EGR-coupled high-pressure turbine on NO x and BSFC for HP-EGR and the effect of the EGR-coupled throttle valve on the inhomogeneity of different cylinders for DC-EGR were studied. Comparisons of two EGR patterns show that the achievable maximum EGR rate for HP-EGR is more sensitive to engine loads than DC-EGR. DC-EGR can achieve a higher EGR rate and lower NO x at low and medium loads. Under the same NO x , the required EGR rate, λ , boost pressure and exhaust pressure of DC-EGR are lower. However, the BSFC of DC-EGR is slightly higher at a 25% load. As the turbine flow characteristic of HP-EGR is insufficiently adjusted with loads, DC-EGR is more inclined to achieve comprehensive optimization of NO x and BSFC under full loads. [ABSTRACT FROM AUTHOR]

• Marine engine performance and emissions are investigated for direct water injection. • Varied amounts, temperature and injection timing of water are considered. • With direct water injection, the indicted power and NO x emissions decreases. • The potential of direct water injection and exhaust gas recirculation were compared. In this study, the effect of direct water injection (DWI) was investigated on the performance of marine diesel engine based on the three-dimensional simulation model. The water injection quantity, temperature and timing were researched on the in-cylinder pressure and temperature, indicated power and NO x emissions. Then, the DWI strategies were compared with the exhaust gas recirculation (EGR). The results showed that the in-cylinder pressure, temperature, indicated power and NO x emissions decrease with increasing of water quantity. Reductions in NO x emissions up to 55.6% were obtained after applying DWI to the engine at the compression stroke. The water injection temperature has a little effect on the combustion and emissions of marine engine. The indicated power decreased when the water injection timing in the compression stroke. However, the indicated power increased when the water injection timing in the late combustion phase. The water injection timing in the compression stroke has more potential in reduction NO x emissions. The NO x emissions with water injection in the compression stroke decreased by 40% compared to the value with water injection in the later combustion phase. The ability of DWI and EGR were researched on the solve the trade-off between power and NO x emissions. The results showed that the DWI strategy can reduce NO x emissions at the higher indicated power compared with the results of EGR. [ABSTRACT FROM AUTHOR]

In order to accurately assess China's port air pollution caused by the shipping industry, two main methods can be used to calculate the emissions of ships, including the method based on ship fuel consumption and the method based on ship activities. Both methods require accurate diesel engine emission factors, or specific emissions. In this paper, the emission characteristics of NOX, CO, CO2 and THC from 197 domestic marine diesel engines were tested under bench test conditions by a standard emission measurement system. The diesel engines were divided into six Classes, A~F, according to their power distribution, and the fuel-based emission factors and energy-based emission factors of marine main engine and auxiliary engine meeting IMO NOX Tier II standards were given. The results showed that the main engine fuel-based emission factors of NOX, CO, CO2 and THC from Class A to Class F were 33.25~76.58, 2.70~4.33, 3123.92~3166.47 and 1.10~2.64 kg/t-fuel, respectively; and the energy-based emission factors were 6.57~11.75, 0.56~0.81, 530.28~659.71 and 0.18~0.61 g/kW h, respectively. The auxiliary engine fuel-based emission factors of NOX, CO, CO2 and THC from Class A to Class D were 27.17~39.81, 2.66~5.12, 3113.01~3141.34 and 1.16~2.87 kg/t-fuel respectively; and their energy-based emission factors were 6.06~8.33, 0.47~0.77, 656.86~684.91 and 0.21~0.61 g/kW h, respectively. The emission factors for different types of diesel engines were closely related to the diesel engine load, and the relation between them could be expressed by quadratic polynomial or power function. The results of this paper provide valuable data for the estimation of waterway transportation exhaust emissions and comprehensive understanding of the emission characteristics of marine diesel engines. [ABSTRACT FROM AUTHOR]

The energy crisis combined with increasingly severe environment pollution have highlighted the significance of the energy conservation and emission reduction in shipping industry. To improve the energy utilization rate and reduce pollution, a dual-pressure organic Rankine cycle system is proposed to reuse the heat of exhaust gas in marine engines. Many researches focused on the thermodynamics and thermos-economics of the waste heat recovery system, and optimized it from these two goals to recover more energy and decrease cost. However, the impact of the system itself on the environment, which was significant to assess the greenness, was often neglected in these studies. The system with high energy recovery rate may also cause serious environment pollution in the manufacturing or operation process, hence the environmental factor should be taken into account in the optimization. To solve the problems, an evaluation method combined thermodynamics, economics and environment is proposed. The parametric study of the dual-pressure organic Rankine cycle system with six common used working fluids is assessed by this method. Finally, taking the indicators of evaluation method as objective function, the multi-objective optimization method is conducted to figure out the optimum operation conditions for the system. Results show cyclopentane is the optimal working fluid considering thermodynamic, economic and environmental properties. Under the conditions of the evaporation pressure in high-pressure circuit 2.79 MPa, the evaporation pressure in low-pressure circuit 1.97 MPa, the condensation temperature 35 °C, the superheating temperature 1.2 °C, the system obtains a good performance with exergy efficiency 60.24%, electricity production cost 0.167 $/kWh and the environmental impact of net power output 11831.9 mPts/GJ. [Display omitted] • Dual-pressure organic Rankine cycle is assessed from thermodynamics, economics and environment. • An efficient approach to select optimal working fluid for the system is provided. • Multi-objective particle swarm optimization is used to optimize the system. • Cyclopentane is the optimal working fluid for the heat source at 200–300 °C. [ABSTRACT FROM AUTHOR]

A novel method based on a Na 2 S 2 O 8 /urea composite system was used to both synchronously absorb SO 2 and NO from marine diesel engine emissions and reduce the nitrate residues in cleaning wastewater. In the Na 2 S 2 O 8 /urea solution, a temperature of over 60 °C and a Na 2 S 2 O 8 concentration of >0.05 mol/L were found to fully absorb SO 2 by overcoming the SO 2 release and effectively absorb NO. Urea successfully reduced the residual nitrate concentration and improves NO absorption at a concentration below 2 mol/L. The NO and SO 2 removal efficiencies reached 97.8 ± 1.5% and 100%, respectively, at 70 °C in 0.1 mol/L Na 2 S 2 O 8 and 1.5 mol/L urea solutions. The residual nitrate concentration was 8.12 ± 0.25 mg/L, far below the regulatory limit of 60 mg/L. Acidic conditions (pH ≤ 5.5) could be conducive to absorbing NO and reducing the residual nitrate concentration. Based on the experimental results, this novel method is highly promising for reducing ship emissions. • Marine NO and SO 2 removal efficiencies reached 100% in Na 2 S 2 O 8 solution. • Urea enhanced NO absorption and inhibited the formation of nitrate residue. • NO and SO 2 removal efficiencies of 97.8 ± 1.5% and 100%, respectively, were found. • Different redox processes coexisted in reducing ship emissions in Na 2 S 2 O 8 /urea. • Acidic conditions (pH ≤ 5.5) were favorable for NO absorption and nitrate inhibition. [ABSTRACT FROM AUTHOR]

In this work, a numerical model was developed to analyze the performance and emissions of a marine diesel engine, the Wärtsilä 6L 46. This model was validated using experimental measurements and was employed to analyze several pre-injection parameters such as pre-injection rate, duration, and starting instant. The modification of these parameters may lead to opposite effects on consumption and/or emissions of nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons (HC). According to this, the main goal of the present work is to employ a multiple-criteria decision-making (MCDM) approach to characterize the most appropriate injection pattern. Since determining the criteria weights significantly influences the overall result of a MCDM problem, a subjective weighting method was compared with four objective weighting methods: entropy, CRITIC (CRiteria Importance Through Intercriteria Correlation), variance, and standard deviation. The results showed the importance of subjectivism over objectivism in MCDM analyses. The CRITIC, variance, and standard deviation methods assigned more importance to NOx emissions and provided similar results. Nevertheless, the entropy method assigned more importance to consumption and provided a different injection pattern. [ABSTRACT FROM AUTHOR]

Du, J.; Zhao, H., and Xue, Y.F., 2020. Flow field simulation and experimental analysis of flue guide plate of marine desulfurization tower. In: Bai, X. and Zhou, H. (eds.), Advances in Water Resources, Environmental Protection, and Sustainable Development. Journal of Coastal Research, Special Issue No. 115, pp. 396-400. (Coconut Creek, Florida), ISSN 0749-0208. In this paper, the exhaust gas of marine diesel engine under rated condition is taken as the research object, the newer version of fluent18.0 software is used as the platform, the self-defined function and SO2 absorption model are compiled by using C++software and double membrane theory, and the compiled self-defined function is imported through UDF interface. The uneven distribution of flue gas and the phenomenon of sticking to the wall in the side feed desulfurization tower lead to the reduction of desulfurization efficiency. The number and position of the guide plates in the flue of the marine desulfurization tower need not be simulated and optimized. Through the analysis and comparison of the velocity flow field and SO2 mass fraction cloud chart, the desulfurization efficiency of zero to three guide plates is 94.31%, 95%, 96.84% and 97.63% respectively. Then, compared with the experimental data, and the difference of simulation results is small, which has great practical value and theoretical significance for optimizing desulfurization tower and improving sodium alkali desulfurization system. [ABSTRACT FROM AUTHOR]

• A state of the art of marine Diesel engine emission technologies is proposed. • The synergy between between emission technologies and heat recovery is presented. • Organic Rankine Cycles are among the most studied systems to recover engines' heat. Reducing emissions from internal combustion engines is becoming one of the most important tasks for engine manufactures and transport regulatory organizations. In particular, the marine transportation sector is one of the most polluting, due to the intense maritime activity and the use of low-quality fuels, burned in Heavy Duty Diesel Engines, for ship propulsion and auxiliary power generation. In order to reduce the global shipping environmental impact, the IMO (International Maritime Organization) is restricting NO x and SO x ships' emissions through the introduction of the IMO Tier III legislation, which requires to consider a wide spectrum of emissions reduction technologies and strategies, which are going to have an impact on the engine performance and fuel consumption. In this work, the main solutions being currently developed or adopted for low and medium speed Diesel engines have been reviewed from a qualitative, and sometimes quantitative, point of view, but, in comparison to previous literature, focusing more on their potential with respect to possible waste heat recovery systems utilization, such as, in particular, steam Rankine cycles and Organic Rankine Cycles (ORC). Indeed, even though many of the considered emissions mitigation technologies lead to a certain amount of penalty in fuel economy, the use of waste heat recovery systems to recover wasted engines energy could become interesting in order to develop more efficient but, at the same time, cleaner engines. [ABSTRACT FROM AUTHOR]