Explore the vast range of titles available.

This review paper examines the applicability of biogas and biomethane as potential maritime fuels and examines issues of these fuels from a supply chain perspective (from production to end use). The objectives are to identify: (1) the latest research, development, and innovation activities; (2) issues and key barriers related to the technology readiness to bring biogas/biomethane to market; and (3) commercialisation issues, including cost parity with natural gas (the main competitor). A survey of the literature was carried out based on research articles and grey literature. The PESTEL and SWOT analyses identified opportunities for these fuels due to the relevant regulations (e.g., Fit for 55; the recent inclusion of the Mediterranean Sea as a SECA and PM control area; MPEC 79), market-based measures, and environmental, social, and governance strategies. The potential of biomass feedstock is estimated to have a substantial value that can satisfy the energy needs of the maritime industry. However, production costs of biomethane are high; estimated to be 2–4 times higher compared to natural gas. The market is moving in the direction of alternative drop-in fuels, including liquefied and compressed biomethane (LBM and CBM) and biogas. In terms of potential market penetration, LBM can be used as a marine drop-in fuel for the existing fleet that already combust LNG and LPG due to similar handling. Currently, these vessels are LNG and LPG tankers. However, in newly built vessels, LBM can be also supplied to container ships, vehicle carriers, and bulk carriers (about 20% of newly built vessels). Provided that compressed natural gas infrastructure exists, CBM can be exploited in vessels with low energy needs and low space requirements and shore-side electrification, because investments in retrofits are lower compared to constructing new infrastructure.

International shipping is responsible for approximately 2.7% of the global greenhouse gas emissions, a share expected to rise by as much as 250% by 2050. In response, the International Maritime Organization (IMO) has set ambitious targets to reduce these emissions to near-zero by 2050, focusing on alternative fuels like LNG. This study examines the energy consumption patterns of dual-fuel engines powered by LNG and develops machine learning models using LightGBM to predict fuel usage for both fuel oil (FO) and gas (GAS) modes. The methodology involved analyzing operational data to identify patterns in fuel usage across different voyage conditions. The FO mode was found to be predominantly used for rapid propulsion during speed changes or directional shifts, while the GAS mode was optimized for stable conditions to maximize fuel efficiency. Additionally, a mixed mode of FO and GAS was occasionally applied on complex routes to balance safety and efficiency. Using these insights, LightGBM models were trained to predict fuel consumption in each mode, achieving high accuracy with R2 scores of 0.94 for the GAS mode and 0.98 for the FO mode. This model enables ship operators to optimize fuel decisions in response to varying voyage conditions, resulting in reduced overall fuel consumption and lower CO2 emissions. By applying the predictive model, operators can adjust fuel usage strategies to match operational demands, potentially achieving notable cost savings and meeting stricter environmental regulations. Furthermore, the accurate estimation of fuel usage supports CO2 emissions management, aligning with the Carbon Intensity Indicator (CII) and providing ship operators with actionable data for fleet management optimization. This research provides essential data to support carbon emission compliance, improves fuel efficiency, and offers practical insights into fuel management strategies. The predictive model serves as a valuable resource for ship operators to optimize fuel use and aligns with the IMO’s environmental targets, aiding the maritime industry’s transition toward carbon neutrality.

To realize zero carbon emission in internal combustion engines and boost the growth of ammonia fuel, we mixed a few hydrogens into ammonia fuel to boost the atomization and combustion performance in the combustion chamber. We study hydrogen and ammonia mixed and injected directly through two injectors, the intake temperature is 551k, to find the best injection advance angle combination to ensure the overall working performance of the ammonia Dual fuel engine. The investigation shows that when the main/auxiliary fuel injection timing is 704°CA, the knock value is less than 2, the combustion in the cylinder is gentle, and the negative work phenomenon of knock combustion is avoided. The engine power is the highest and the best economy. The emissions of soot, CO, HC, and CH 2 O are at a very low level, the CO 2 content before and after combustion increases to zero, and the NO x emission is slightly higher than the original engine. We will improve engine NOx emission through SCR Technology in the future. The investigation results will boost the development of an ammonia and hydrogen compression ignition engine and boost the internal combustion engine to zero carbon combustion mode.

In this study, we investigate the dual-fuel operation of compression ignition engines using biodiesel at varying concentrations in combination with biogas, with and without hydrogen enrichment. A response surface methodology, based on a central composite experimental design was employed to optimize energy efficiency and minimize pollutant emissions. The partial substitution of diesel with gaseous fuel substantially reduces the specific fuel consumption, achieving a maximum decrease of 21% compared with conventional diesel operation. Enriching biogas with hydrogen, accounting for 13.3% of the total flow rate, increases the thermal efficiency by 0.8%, compensating for the low calorific value and reduced volumetric efficiency of biogas. Variations in biodiesel concentration exhibits a nonlinear effect, yielding an additional average efficiency gain of 0.4%. Regarding emissions, the addition of hydrogen to biogas contributes to an average reduction of 5% in carbon monoxide emissions compared to the standard dual-fuel operation. However, dual-fuel operation leads to higher unburned hydrocarbon emissions relative to neat diesel; hydrogen enrichment mitigates this drawback by reducing hydrocarbon emissions by 4.1%. Although NOx emissions increase by an average of 26.6% with hydrogen addition, dual-fuel strategies achieve NOx reductions of 11.5% (hydrogen-enriched mode) and 33.3% (pure biogas mode) relative to diesel-only operation. Furthermore, the application of response surface methodology is robust and reliable, with experimental validation showing errors of 0.55–8.66% and an overall uncertainty of 4.84%.

This study aims at developing an integrated model that combines detailed engine thermodynamic modelling and the control system functional modelling paving the way towards the development of high-fidelity digital twins. To sufficiently represent the combustion process, a multi-Wiebe function approach was employed, whereas a database for storing the combustion model parameters was developed. The developed model was employed for the systematic investigation of a marine four-stroke dual fuel engine response during demanding transient operation with mode switching and load changes. The derived results were analysed to identify the critical engine components and their effect on the engine operational limitations. The results demonstrate that the developed model can sufficiently represent the engine and its subsystems/components behaviour and effectively capture the engine control system’s functionality. The appropriate turbocharger matching along with the sufficient design of the exhaust gas waste gate valve and fuel control systems are crucial for ensuring the smooth engine operation of dual fuel engines.

In this article, the modeling and optimization of a dual-fuel diesel engine with the combination of South Pars Refinery gas have been discussed at the idle load. First, using the computational fluid dynamics (CFD) method, the modeling has been validated with experimental data, and the results of the present numerical solution are in acceptable agreement with the experimental data. In order to optimization, the considered objective functions include minimum NO x emission, maximum power generation, and minimum fuel consumption. Optimization variables include start of injection (SOI) time, the mass fraction of mean natural gas (Y NG ), and inlet air pressure (P i ). The number of tests required by the response surface method for the intervals 5 < SOI < 25 before top dead center (BTDC) crank angle (CA), mass fraction 0.02 < Y NG  < 0.04, and 0.75 < P i  < 1.75 (bar) are considered with 20 numerical solutions using the CFD method. The objective functions are set with confidence 95% that has been calculated. In the following, using the non-dominated sorting genetic algorithm method, the objective functions are optimized and the Pareto front is displayed. In addition, by using TOPSIS, the optimal point has been obtained at SOI = 10 BTDC (CA), Y NG  = 0.02, and P i  = 1.6 (bar). Also, in optimal conditions for three revolutions of 850, 1000, and 1250 rpm, the thermal, fluid, and performance parameters of the engine have been compared.

The predicted scarcity, increasing cost of petroleum fuels, and environmental degradation are encouraging researchers to search for alternative fuels throughout the world. Hence, it is intended to utilize acetylene-based DF in the compression ignition (CI) engine with minor modifications. An engine of 5 Hp, four stroke, single-cylinder, water-cooled operated in dual-fuel (DF) mode (acetylene gas-diesel), aiming to reduce the emissions, was deployed to investigate its characteristics. In DF mode, gaseous fuel is injected through intake air manifold with 2, 4, and 6 lpm constantly. According to the research findings, the gas rate of 6 lpm provides the best results, having a superior BTE of 30.7%. Various compression ratios (16:1, 18:1, and 20:1) were used to determine the optimal compression ratio (CR) under a volume flow rate of 6 lpm with diesel. Fuel injector pressure (200, 220, and 240 bar) with injector intervals (19°, 23°, and 27°bTDC) were changed consecutive sequence while adjusting CR, and the best outcomes for improved CI fuel efficiency were determined. From the investigational analysis, the peak in-cylinder pressure and net HRR (heat release rate) are assessed for being better by the increment in CR in DF mode of operation with an acetylene gas of 6 lpm at all operating settings. At a 240 bar injection pressure, the BTE is recorded highest (35.1%), and smoke was decreased. An IT of 23obTDC, the CO and HC were found as to be minimum as 28 ppm and 0.04 ppm.

Methanol is favored for its excellent physicochemical properties, becoming an ideal alternative fuel for engines. Adopting a dual-fuel injection mode of methanol port injection and gasoline direct injection (MPI + GDI) allows for more flexible injection strategies, enhancing the engine’s power, efficiency, and emission performance. However, observing the processes of fuel injection, atomization, mixing, flow, and combustion in real engine cylinders is challenging, and controlling the fuel–air distribution and turbulence before engine ignition is difficult. Therefore, after validating the simulation model through optical engine bench experiments, this study investigated the performance and emission characteristics of MPI + GDI engines under various injection strategies. The results indicate that delaying the GDI injection timing decreases the uniformity of the fuel–air mixture and reduces cylinder pressure, corresponding to a retarded crank angle. Increasing GDI injection pressure enhances the fuel–air mixing, especially when the injection timing is later. Employing secondary injection and increasing the proportion of the second injection lead to poorer fuel–air uniformity in the cylinder, a decrease in peak pressure value, reduced nitrogen oxides (NOx) emissions, and a gradual increase in carbon monoxide (CO) and total hydrocarbons (THC).

Dual-fuel (DF) engines enable efficient utilization of a low reactivity fuel (LRF), usually port-injected, and a high reactivity fuel (HRF) provided directly into the cylinder. Ethanol and Camelina sativa oil can be ecologically effective but not fully recognized alternatives for energy production using modern CI engines equipped with a common rail system and adopted for dual fueling. The high efficiency of the process depends on the organization of the combustion. The article describes the premixed dual-fuel combustion (PDFC) realized by dividing the Camelina sativa dose and adjusting its injection timing to the energetic share of ethanol in the DF mixture. The injection strategy of HRF is crucial to confine knock, which limits DF engine operation, but the influence of EGR is also important. The research AVL engine’s dual-fueling tests focused on combustion process modification by the proposed injection strategy and cooled EGR at different substitution rates. For all examined points of the engine run, the volumetric heat release rate diagrams, cylinder pressure, and temperature illustrate changes that resulted from the tested fueling options. Additionally, engine thermal efficiency and emissions are presented. Because of potential application, the tests were confined to one engine speed (n = 1500 rpm). The research confirmed the possibility of efficiently applying raw Camelina sativa oil as an HRF for DF engines and ethanol (LRF) under high-load conditions.

In general, a leaner mixture condition improves combustion efficiency in compression ignition (CI) combustion using diesel. However, in the case of leaner air–fuel mixture conditions, it disturbs flame propagation in spark ignition combustion using gasoline, i.e., low reactivity fuel, causing a decrease in combustion efficiency. Since dual-fuel combustion in a CI engine typically involves the use of high- and low-reactivity fuels together, the differing reactivity conditions in the cylinder become as important as the local equivalence ratio in the cylinder. Thus, there is a need to verify the effect of a leaner mixture condition on combustion efficiency in dual-fuel CI combustion. For this reason, this study experimentally evaluates the effects of varying equivalence ratios on the combustion efficiency of gasoline/diesel dual-fueled CI combustion in a 0.4-L single-cylinder engine under low-speed (1500 rpm) and low-load (total LHV 570 J/str) conditions. To vary the equivalence ratios, intake pressures and exhaust gas recirculation (EGR) rates were, respectively, changed under the part-load condition. The results emphasize that as the equivalence ratio becomes leaner by increasing the intake pressure, combustion efficiency worsens due to the low reactivity properties and certain flame propagation modes of gasoline combustion. On the contrary, increasing the EGR rate did not significantly influence combustion efficiency, but it effectively helped reduce nitrogen oxide (NOx) emissions. Based on these results, it is concluded that optimizing dual-fuel CI combustion to suppress NOx emissions is better achieved using EGR, rather than creating a leaner mixture condition.