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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]

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]

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]

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]

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]

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]

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]

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]

• 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]