The use of alternative fuels in ships faces the dual challenge of emission regulations and cost of use. In this paper, the impact of biodiesel blends from cooking waste as a carbon-neutral fuel for inland waterway vessels was investigated. The software AVL FIRE was used to simulate the detailed chemical combustion process of a marine diesel engine running on D100 (pure diesel), B5 (5% biodiesel by volume), B10 (10% biodiesel by volume), and B15 (15% biodiesel by volume). The results showed that B5, B10, and B15 all provided a better air-fuel mixture and significantly reduced soot production. Based on the performance and emission values, B5, B10, and B15 cause relatively small differences in engine performance compared to diesel and are readily applicable in practice. Optimizing exhaust gas recirculation (EGR) and varying injection timing can further optimize biodiesel fuel combustion while reducing NO_x and soot emissions. The results of this study are helpful for the application of waste cooking oil biodiesel fuel and reducing exhaust gas emissions from ships.

With increasing environmental pollution from ship exhaust emissions and increasingly stringent International Maritime Organization carbon regulations, there is a growing demand for cleaner and lower-carbon fuels and near-zero-emission marine engines worldwide. Liquefied natural gas is a low-carbon fuel, and when liquefied natural gas (LNG) is used on ships, dual-fuel methods are often used. The pre-chamber plays a key role in the working process of dual-fuel engines. In this paper, an effective three-dimensional simulation model based on the actual operating conditions and structural characteristics of a marine low-pressure dual-fuel engine is established. In addition, the effects of changing the Precombustion chamber (PCC) volume ratio and the PCC orifice diameter ratio on the mixture composition, engine combustion performance, and pollutant generation were thoroughly investigated. It was found that a small PPC volume ratio resulted in a higher flame jet velocity, a shorter stagnation period, and an acceleration of the combustion process in the main combustion chamber. When the PCC volume was large, the Nitrogen oxygen (NOx) ratio emission was elevated. Moreover, the angle of the PCC orifice affected the flame propagation direction of the pilot fuel. Optimizing the angle of the PCC orifice can improve combustion efficiency and reduce the generation of NOx. Furthermore, reasonable arrangement of the PCC structure can improve the stability of ignition performance and accelerate the flame jet velocity.

Methanol is a promising low-carbon fuel that can effectively reduce environmental pollution from ships compared to traditional fuels. The timing of methanol injection is a major factor affecting the performance of internal combustion engines, and either too late or too early injection can severely impact the combustion efficiency of an engine. This paper focused on a 4135Aca marine diesel engine produced by the Shanghai Diesel Engine Factory in China. Using CONVERGE/3.0 software for numerical simulation, the study analyzed the impact of methanol injection timing on the combustion and emission characteristics of marine diesel engines. It was found that the determination of methanol injection timing should comprehensively consider the effects of the combustion start point, mixture quality, flame front propagation speed, and evaporation heat absorption. Appropriate methanol injection timing can improve the combustion duration, cylinder pressure, and heat release rate, enhancing the power performance of marine diesel engines. This study shows that methanol injection at −30 °CA can effectively control the in-cylinder combustion process, improve combustion efficiency, and significantly reduce the emissions of pollutants such as soot (by 60.5%), HC (by 3.6%), CO (by 95.3%), etc. However, it can lead to an increase in NOx (by 3.7%) generation under high-temperature conditions. This research can provide a certain reference for the engineering application of methanol direct injection engines for ships.

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.

As a clean alternative fuel oil for marine engines, methanol has received increasing attention, but its low cetane number requires diesel ignition, which increases the difficulty of retrofitting existing engine fuel injection systems. Polymethoxy dimethyl ether (PODE_n) is an ether fuel mixture whose chemical structural formula can be expressed as CH₃O(CH₂O)_nCH₃ ($n\ge 2$). PODE₃ is the predominant component in the blend, and its properties are representative of the blend. PODE is a low-carbon fuel with a high cetane number and is easy to compression ignite, and, as such, can be used to ignite methanol in a marine diesel engine. This article explores the combustion mechanism of mixed methanol–PODE fuel using the characteristics of PODE that can be easily mixed with methanol for combustion. Taking methanol and PODE₃ as representative fuels, the detailed combustion mechanism of PODE₃ and the detailed combustion mechanism of methanol are simplified using a DRGEPSA (direct relationship graph with error propagation (DRGEP) and sensitivity analysis (SA)) method. Based on the target engine cylinder combustion environment, a simplified mechanism for mixed methanol–PODE fuel is obtained, and the new mechanism is validated in terms of the ignition delay period and laminar flame speed. The results indicate that the newly constructed simplified mechanism is basically consistent with the ignition delay data and flame propagation speed data measured by a rapid compression machine (RCM), laying the foundation for the application of alternative methanol fuels in marine engines.

In addition to the use of waste heat from the vessel’s exhaust gas to save energy onboard, reduce the carbon emissions of the ship, and combine the characteristics of ship waste heat, mathematical modeling and testing of ship waste heat temperature difference power generation were carried out in this study. Finally, an experimental platform for temperature differential power generation was established to assess the impact of influencing agents on the efficiency of temperature differential power generation. The results show that the effect of different thermally conductive greases on the efficiency of temperature differential power generation tablets is basically the same. In addition, the rate of flow of cooling water, the cooling plate area, and the heat source temperature have more significant effects on the open-circuit voltage and maximum output power. The results show that the maximum power output growth rate increases with increasing cooling water flow, reaching 8.26% at 4 L/min. Likewise, increasing the heat source temperature enhances the maximum output power growth rate by 15.25% at 220 °C. Conversely, the maximum output power of the temperature difference power generation device decreases as the cooling plate area increases, and the maximum output power reduction rate is 15.25% when the cooling plate area is 80 × 200 mm² compared to the case of using a cooling plate area of 80 × 80 mm². Moreover, the maximum output power of the temperature differential power generation device reaches 13.6 W under optimal conditions. Assuming that the temperature difference power generation plate is evenly distributed on the tailpipe of the 6260ZCD marine booster diesel engine, it could save approximately 5.44 kW·h electric power per hour and achieve a reduction in CO₂ emissions of 0.3435 kg per hour.