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To limit the negative impact on the environment, increasingly stringent regulations are being introduced regarding the reduction of pollutant emissions. In automotive applications, reciprocating internal combustion engines (ICE) are under immense pressure due to emissions. Society aims to move away from fossil fuels. However, it is acknowledged that ICE will continue to play a significant role in electricity generation systems and certain transportation sectors. To achieve zero emissions or drastically reduce emissions, alternative carbon-free fuels are being pursued. Hydrogen (H 2) is a natural substitute for fossil fuels, and recently, ammonia (NH 3) has been considered an intriguing fuel. Ammonia is easier to transport and store compared to hydrogen. NH 3 is a good hydrogen carrier with significant potential for use in ICE. However, ammonia combustion in such applications exhibits challenges related to its low burning rate. Here, hydrogen emerges as a high reactivity fuel, used as a combustion enhancer for NH 3. Hydrogen-assisted ammonia combustion shows great promise for future of ICE. This paper presents a summary of research findings on the NH 3 /H 2 combustion process in a spark-ignition ICE. Concepts of dual-fuel NH 3 /H 2 engine operation, the influence of fuel proportions on cylinder pressure profiles, heat release, combustion stages, and engine emissions aspects are discussed. The directions of development of SI piston engines powered by NH 3 /H 2 are given. • Assessment of NH 3 and NH 3 /H 2 combustion strategies in the SI engine • Direct injection of ammonia reduces its content in exhaust gases. • SI engine powered by NH 3 requires high ignition energy. • The challenge is to reduce N 2 O emissions. • Hydrogen expands the spectrum of application of NH 3 as a fuel for the SI engine. [ABSTRACT FROM AUTHOR]

The depleted state of fossil fuels has led to the need to find an alternate solution for the utilization of transportation vehicles. The use of hydrogen, fuel additives, and nanoparticles has been part of the research in the recent past. Additionally, the use of artificial neural network was applied to anticipate the results for the optimization of the work and output, which has also been a study of interest recently. In the current work, different blends of diesel with hydrogen, TGME as a fuel additive, and Al 2 O 3 nanoparticles were utilized to check for the best performance and the least emissions. The best performance was seen with the inclusion of TGME in diesel along with hydrogen, while the use of nanoparticles increased CO formation. An improvement in the BTE was also found with the blends of TGME and nanoparticles in diesel along with hydrogen. The usage of TGME along with H 2 performed the best in terms of BTE (15.8%) and while the least emission of NOx, HC, and CO was found with the combination of diesel and H 2. The artificial neural network was applied afterwards to predict the results using the obtained data from the experimental results. It was found that the values of regression coefficients for BTE and ITE were close to 1 (0.99 for BTE and 0.98 for ITE). In the above cases, the value of the mean square error was also observed to be least. Furthermore, the results for the regression coefficient of emissions were close to 1 for NOx (0.94), HC (0.89), and CO (0.93) with minimum possible mean square errors in all the cases. The results showed that they were in line with the predicted data as well as the available literature for the anticipation of the obtained results. • Hydrogen substitution increased BTE by 10.4%. • Addition of Al 2 O 3 and TGME increased BTE by 2% and 13.7%, respectively. • Good prediction of experimental results were obtained with ANN. • Lowest mean square error was found with CO emission. [ABSTRACT FROM AUTHOR]

Hydrogen fuel offers promising decarbonization pathways for hard-to-electrify transport sectors such as long-haul trucking, international maritime, and aviation. The internal combustion engine (ICE) is and will continue to be important in the transition to net zero emissions (NZE), especially in the transport sector. In this review, the research trend, hotspots, and evolutionary nuances of hydrogen-fuelled ICEs have been investigated. Our analysis reveals that while earlier research primarily focused on the performance and emission characteristics of hydrogen-fuelled ICEs, recent studies are increasingly paying more attention to combustion and emission control strategies. NOx emissions have received a lot of attention, as it is the most important pollutant from hydrogen engines. Several techniques, namely exhaust gas recirculation (EGR), water injection, and lean combustion, have been predominantly adopted and studied for controlling NOx emissions. Another major research area in the field has centered on combustion anomalies such as backfiring and knocking, which are key setbacks to the hydrogen-fuelled ICE. Owing to its ability to produce fewer emissions and greater performance than diesel-only operation, hydrogen in diesel engines as dual fuel has also become a major research hotspot in the field within the last decade. Our analysis also showed that there is a strong interest in this field where researchers are focusing on the use of hydrogen with other alternative fuels such as methane, biogas, biodiesel, ammonia, and methanol for optimal operation of the ICE. Finally, we provide some critical challenges and potential solutions related to the use of hydrogen as an ICE fuel. It is anticipated that the results from the present work will pave the way for the continuous development of hydrogen engine research for the ongoing fight to decarbonize the transport sector. [ABSTRACT FROM AUTHOR]

The global need for petroleum and its dwindling availability throughout the world demand an alternative fuel. Hydrogen-enriched algal biodiesel (ABD) is a potential option against conventional fuels due to its availability and positive effects on performance and emissions. Azolla pinnata algae is a high-yield fuel with reduced adverse impacts on the environment, requiring 2–5 days to double its biomass. This research work involves post-experimentation modeling to assess the performance and emissions of a CRDI diesel engine using a hydrogen-enriched blended fuel of Azolla pinnata ABD. Response surface methodology has been applied to optimize the load, fuel blend, and hydrogen gas substitution for performance and emissions characteristics. The ABD and hydrogen gas are varied between 0 and 40% in the pilot fuel for loads between 0 and 80%. The model indicates that the optimized load, blend, and hydrogen fuel substitution for this research are, respectively, 80%, 40%, and 40%. At the above-mentioned optimized parameters, the optimized values of BTE, CO, CO 2 , HC, and NO x are found to be 30.90%, 19.99 g/kWh, 288.89 g/kWh, 0.21 g/kWh, and 1.57 g/kWh, respectively. Adequacy precision greater than 4 and a percentage error between predicted and experimental values less than 5% indicate the model's ability to predict performance and emissions characteristics eventually. [Display omitted] • The experiment is performed on a CRDI dual-fuel diesel engine. • Diesel and biodiesel (Azolla pinnata) blends enriched with H 2 are used as fuel. • Experimental data has been used for developing mathematical & RSM models. • BTE & emissions are optimized for 80% load, 40% blend, and 40% GFS experimentally. • With a percentage error of less than 5%, RSM validated the experimental results. [ABSTRACT FROM AUTHOR]

The addition of hydrogen in a dual-fuel mode based on natural gas and diesel offers great potential for improving engine efficiency and reducing emissions. Therefore, detailed numerical simulations have been used to explore the effects of soot formation characteristics of natural gas-diesel dual-fuel engines doped by hydrogen at elevated pressure. Numerical simulations are compared with available experimental data, the effects of H 2 addition on soot formation in laminar CH 4 + n-heptane, H 2 + CH 4 + n-heptane, FH 2 + CH 4 + n-heptane diffusion flames at 2, 4, 6 and 8 atm are simulated, FH 2 is added to separate the H 2 chemical effects. The results show that the dilution and thermal effects of H 2 inhibit soot formation, while the chemical effects of H 2 promote soot formation under different pressures. The addition of H 2 increases the concentration of H and OH radicals, which promotes the formation of C 2 H 2 and benzene (A1). By simplifying the reaction path and analyzing the production rate of A1, the mechanism of H 2 addition to promote A1 formation is illustrated. The concentrations of polycyclic aromatic hydrocarbon (PAH) pyrene (A4), benzo(ghi)fluoranthene (BGHIF) and benzo(a)pyrene (BAPYR) are inhibited at higher pressures that result in lower inception and condensation rates. Therefore, the increase of hydrogen abstraction acetylene addition (HACA) rate is the main reason for the increase of soot formation under chemical effects. While the O 2 oxidation rate decreases and the OH oxidation rate increases, that is due to the decrease of O 2 concentration and the increase of OH concentration in the soot formation area under chemical effects. • The dilution, thermal and chemical effects of H 2 addition on soot formation in methane/n-heptane flame were investigated at high pressures. • Key specie A1 formation pathways and related reactions were confirmed when H 2 addition. • The changes of soot formation and oxidation mechanisms with H 2 addition in different pressure were explained. [ABSTRACT FROM AUTHOR]

Greenhouse gas emissions are a significant problem contributing to global warming and climate change and it is essential to increase the use of renewable and biomass-derived fuels in internal combustion engines to reduce greenhouse gas formation. Alcohol fuels and hydrogen have become prominent in recent years due to less harmful emission levels as a result of combustion. While there are very few studies in the literature on ternary mixture + hydrogen in terms of energy and exergy, there is a gap on the effect of the valve lift amount. The aim of this study is to investigate the effects of binary alcohol addition and variable intake valve lift (IVL) in hydrogen-diesel dual fuel mode on energy, exergy, sustainability, and greenhouse gas emissions. The experiments are conducted at variable torque conditions, involving three different IVL values (4, 4.46, and 4.9 mm) and four different fuel combinations (diesel, diesel + H 2 , diesel + binary alcohol, and diesel + binary alcohol + H 2). The binary alcohol addition consists of 10% bioethanol and 10% isobutanol volumetrically, while in the dual-fuel mode, hydrogen is injected into the cylinder at a constant flow rate. When the results are examined, the highest energy and exergy values are obtained with the IVL-Diesel + H 2 operation, providing on average 11% and 8% higher exergy efficiency compared to IVL 4-Diesel and IVL 4.46-Diesel studies, respectively. Additionally, the exergy destruction in the IVL-Diesel + H 2 study shows an average decrease of 16% and 12%, respectively, compared to the IVL 4-Diesel and IVL 4.46-Diesel studies. Additionally, significant reductions in emissions are achieved. In the IVL 4.9-EB20+H 2 study, HC, CO, and CO 2 emissions decrease by 28%, 40%, and 28%, respectively, compared to the IVL 4.0 study. When examining the GHG emission impact, it is analysed that operating a single-cylinder engine with EB20+H 2 fuels under 4.9 mm IVL conditions emits, on average, 36% and 32% less GHG impact over a one-year period compared to IVL 4-Diesel and IVL 4.46-Diesel studies, respectively. [Display omitted] • The effect of IVL, binary alcohol, and H 2 on exergetic performance was examined. • The high IVL reduced the exergy destruction and entropy generation. • Increasing IVL in ternary fuel blends increased exergy efficiencies by 5%. • Increasing the IVL improved sustainability index by approximately 6%. • The use of ternany fuel + H 2 under high IVL reduced the GHG impact and cost by 27%. [ABSTRACT FROM AUTHOR]

Diesel generators are widely used to produce electricity and heat in remote communities. However, their use contributes to harmful pollutant and greenhouse gas (GHG) emissions, negatively impacting the environment and public health. Syngas, which is a sustainable fuel, can play an important role in the transition from petroleum to renewable fuels. When used in dual-fuel diesel engines, it can contribute to reducing GHG emissions and the cost of transporting diesel, especially for rural and remote communities. This study investigates the effects of optimizing the diesel direct injection (DI) and exhaust gas recirculation (EGR) strategies on the combustion and emission performance of a syngas-diesel dual-fuel generator at constant load. The experiments were conducted using a 30-kW generator with a four-stroke, four-cylinder, turbocharged, and electronically controlled direct-injection diesel engine. The intake manifold of the engine was modified to allow introducing syngas upstream of the turbocharger. The syngas was simulated using individually controlled flow rates of hydrogen (H 2), carbon monoxide (CO), carbon dioxide (CO 2), and nitrogen (N 2). The syngas flow rate was adjusted to replace 40% of the energy provided by diesel fuel while optimizing the diesel DI parameters such as the pilot injection timing, main injection timing and diesel direct injection rail pressure, as well as the EGR rate. The findings of this study reveal that optimizing diesel injection strategy and appropriately raising the EGR rate have a positive impact on the engine performance and emissions. • Optimizing diesel injection strategies and EGR rate of a syngas-diesel dual-fuel diesel engine. • Hydrogen-rich syngas enhances combustion efficiency and emissions control. • Fine-tuning of pilot injection timing and duration improved the engine efficiency and emissions. • Increasing EGR rate stabilized emissions, with notable reductions in NOx and CO levels. • Adjustment of the main injection timing positively impacted combustion characteristics. • Increasing the injection pressure resulted in notable reductions in CO and PM emissions. [ABSTRACT FROM AUTHOR]

Due to growing environmental concerns and stringent emissions regulations, optimizing the fuel consumption of marine propulsion systems is crucial. This work deals with the potential in an LNG ship propulsion system to reduce fuel consumption through controlled load distribution between engines in Dual-Fuel Diesel Electric (DFDE) plant. Based on cyclical data acquisition measured onboard and using an optimization model, this study evaluates different load distribution strategies between setups according to the optimization model results and automatic (equal) operation to determine their effectiveness in improving fuel efficiency. The analysis includes scenarios with different fuel types, including LNG, MDO and HFO, at different engine loads. The results indicate that load distribution adjustment based on the optimization model results significantly improves fuel efficiency compared to conventional methods of uniform load distribution controlled by power management systems in almost all load intervals. This research contributes to the maritime industry by demonstrating that strategic load management can achieve significant fuel savings and reduce environmental impact, which is in line with global sustainability goals. This work not only provides a framework for the implementation of more efficient energy management systems on LNG vessels, but also sets a benchmark for future innovations in maritime energy optimization as well as in the view of exhaust emission reduction. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

One of the most important issues in the maritime industry is controlling and reducing the amount of emissions caused by marine vessels. In this respect, the International Maritime Organization sets some air pollution-related regulations and encourages maritime companies to utilise current and innovative emission abatement methods on their ships. The application of these approaches to ships not only provides environmental benefits but also creates additional financial costs for the company. In this study, operational data of a container ship has been acquired and examined. Methods such as ammonia, LNG, scrubber, low sulphur fuel use, and selective catalytic reduction have been considered to determine the most appropriate emission reduction approach. Nine different scenarios have been created with the use of stated methods and each scenario is analysed both environmentally and economically and compared to each other. Finally, the most suitable scenario has been determined by calculating the payback period of each investment. Since there is a relatively longer period of redemption, using a dual-fuel engine could be more suitable for long-lasting and newly built ships. For the currently cruising ships, the use of scrubber systems with selective catalytic reduction is an effective solution to reduce the number of emissions. [ABSTRACT FROM AUTHOR]

Strict emission regulations together with reducing fossil fuels resources lead to more attention on new combustion strategies and alternative fuels such as biodiesel which is renewable, environmentally friendly and more cost-effective than other fuels. In this study, CONVERGE CFD software coupling with chemical kinetics mechanism is used to numerically investigation of natural gas (NG)/biodiesel dual fuel engine. The discussed biodiesel consists of 25% methyl decanoate (MD), 25% methyl-9-decanoate (MD9D) and 50% diesel. A comparative study of NG/diesel and NG/biodiesel fueled cases is performed to highlight the combustion characteristics of biodiesel. For all simulated cases, it is supposed that 5% of energy is supplied by high reactive fuel (i.e., Diesel or Biodiesel) and 95% is coming with low reactive fuel (i.e., Natural Gas). Results revealed that in full load condition, using biodiesel/NG led to 86% lower carbon monoxide (CO) and 91% unburned hydrocarbons (UHC). On the other hand, peak pressure and maximum in-cylinder temperature increased 5% and 83 K, respectively which led to 0.6% efficiency improvement. according to the results of different injection timing, when it was advanced from -4 to -20 crank angle degree after top dead center (CAD ATDC) for biodiesel/NG and diesel/NG, the indicated mean effective pressure (IMEP) and gross thermal efficiency (GTE) reached at their peaks 18.3 bar and 48.2% at -12 CAD ATDC, 18.05 bar and 47.7% at -8 CAD ATDC respectively. [ABSTRACT FROM AUTHOR]

The research primarily focuses on investigating the impact of hydrogen induction on parameters of a compression ignition (CI) engine utilizing biodiesel blended with decanol, up to knock limit. The utilization of non-edible oil, exemplified by Prosopis Juliflora seed oil (JFO), presents inherent challenges due to its elevated viscosity, limited atomization, and suboptimal combustion attributes. However, the conversion of JFO into Prosopis Juliflora methyl ester (JFME) biodiesel substantially ameliorates its fuel characteristics, although it still exhibits relatively lower performance in comparison to conventional diesel fuel. To enhance the attributes of JFME blends, decanol is mixed with 20 % on volumetric basis (referred to as D20). Furthermore, the introduction of hydrogen into the engine's intake manifold is employed to bolster performance and curtail emissions. Different hydrogen flow rates, spanning from 2.5 to 10 litres per minute (lpm), are assessed in conjunction with the D20 biodiesel blend. The inclusion of hydrogen into D20 blends yields an enhancement in brake thermal efficiency (BTE), coupled with reductions in hydrocarbon (HC), carbon monoxide (CO), and smoke emissions. However, it should be noted that hydrogen's notable flame velocity and higher calorific value engender escalated combustion temperatures and an associated rise in Nitric oxide (NO) emission. The research also encompasses an evaluation of engine vibration during dual-fuel operation, revealing a proportional increase in engine vibration with heightened rates of hydrogen induction. In summation, the utilization of D20 in conjunction with hydrogen at a rate of 10 lpm emerges as a viable approach for operating diesel engines in a dual-fuel mode. [Display omitted] • Use of Prosopis Juliflora methyl ester in compression ignition engine. • Addition of decanol with Prosopis Juliflora methyl ester and study its effect. • Induction of hydrogen to improve the performance and emissions. • Analyze the vibration of compression ignition engine with different test fuels. [ABSTRACT FROM AUTHOR]

Displacing internal combustion engines (ICE) from the passenger car sector does not mean displacing it from all industries and specific applications. Thanks to the analysis of data on compression ignition (CI) engines used in the world, it is possible to prepare ready-made solutions for the most common engines in selected industries or for those whose greenhouse gas emissions will be the largest and most expensive for their owners in the coming years. The basic solution presented in this article gives the possibility of powering the engines with the most ecological currently known alternative engine fuels and using the already existing methane transmission infrastructure around the world. Their greatest advantage is their availability and low carbon content, which allows to minimize carbon dioxide emissions, both by burning hydrogen-enriched fuels and by increasing the efficiency of the engines modified by dual fuel supply system. Properly made external dual-fuel installation allows to improve the thermal efficiency of the CI engine. Work on this issue may help in the development of, for example, high-efficiency flex fuel power generators, which, as the current situation in Ukraine shows, are worthy. Thanks to the diversification of power sources for power generators, the countries is able to increase the reliability and security of energy supplies even in difficult conditions, such as armed conflict or natural disasters. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The present work aims to investigate the cumulative effect of hydrogen enrichment with the fuels of diesel, Neat chlorella vulgaris oil (NCVO), and Chlorella vulgaris methyl ester (CVME) in a mono-cylinder CI engine. The performance, combustion, and emission parameters of diesel, NCVO, and CVME are analyzed and compared to the findings obtained with hydrogen induction in the intake manifold under dual fuel configuration. With the effect of hydrogen infusion, the metrics of performance, combustion and emission parameters are improved. Under maximum load condition, the induction of hydrogen escalates the BTE from 32.74%, 28.01%, and 23.02%–35.39%, 31.40%, and 28.12% with diesel, CVME, and NCVO at maximal hydrogen share energy of 14.38%, 11.50% and 9.61% respectively. Alongside, the enrichment of hydrogen declines the carbon monoxide (CO) from 4.13, 10.38, and 19.24 g/kWh to 3.16, 8.02, and 15.26 g/kWh, unburned hydrocarbons (UHC) from 0.51, 0.71, and 2.02 g/kWh to 0.36, 0.50, and 1.64 g/kWh, smoke opacity from 55%, 75%, and 85%–43%, 67%, and 71% with diesel, CVME, and NCVO respectively. However, the hydrogen's significant flame velocity and immense calorific value confect to an elevated combustion temperature and subsequent rise in heat release rate (HRR) to, cylinder pressure, and emission of nitrogen oxide (NO). Among the tested fuels, diesel posses maximum HRR and cylinder pressure of 80.46 J/0CA and 88.67 bar respectively. Maximum specific NO emission was observed with CVME having 10.80 g/kWh, whereas diesel and NCVO has 9.49 g/kWh and 4.93 g/kWh respectively. • Explored fuel characterization studies of chlorella vulgaris methyl ester. • Poorer combustion and performance with neat chlorella vulgaris oil. • Using chlorella vulgaris methyl ester in compression ignition engine. • Hydrogen induction improves performance and reduces emissions with all tested fuels. [ABSTRACT FROM AUTHOR]

The current research focuses on enhancing oxygenation through titanium dioxide (TiO 2) nanoparticle-doped biofuel-diesel blend and oxy-hydrogen (HHO) gas. Initially, baseline diesel data was collected on conventional diesel engine. A 20% palmyra oil biodiesel (POB) with an 80% diesel blend was formed as POB20 and operated in the next stage. In the successive stages, the diesel engine is retrofitted to work in dual-fuel mode using HHO gas as inducted fuel along with POB20, 50 ppm TiO 2 -doped POB20, and 100 ppm TiO 2 -doped POB20 are used as primary pilot test fuels The minimal hydrocarbon (HC), carbon monoxide (CO), and smoke emissions were noticed with 100 ppm TiO 2 -doped POB20 along with HHO gas about 0.12 g/kWh, 2.25 g/kWh, and 27%, respectively. For the same test fuel operation, brake thermal efficiency (BTE) [by about 5.5%], maximum cylinder pressure (P max) [by about 5.95%], and maximum heat release rate (HRR max) [by about 7.6%] were increased compared with diesel. Due to the promising results of TiO 2 -doped POB20 and HHO gas operation, this research holds promising potential for practical implementations in various fields like agriculture and stationary electric power generation. [Display omitted] • Palmyra oil biodiesel, HHO gas, and TiO 2 nanoparticles are used to run the engine. • Higher ICP and HRR are noticed for TiO 2 -doped biofuel-diesel blend and HHO gas. • TiO 2 -doped biofuel-diesel blend and HHO gas resulted in higher BTE. • Low HC and smoke emissions are noticed with all the oxygenated test fuels. [ABSTRACT FROM AUTHOR]

Ammonia (NH 3), as a carbon-free fuel, has gained widespread attention for its application in marine engines. A three-dimensional model of an ammonia-diesel dual-fuel marine engine was established and the effects of ammonia energy ratio (AER) and diesel injection strategies on the combustion and emission characteristics were analyzed. The results revealed that, for diesel single-injection strategy, as AER increases, the indicated thermal efficiency (ITE) decreases, NH 3 and unburned hydrocarbon (UHC) emissions increase, while both CO 2 and soot emissions decrease. With the increase of AER, the NO x emissions significantly decrease until AER = 0.5, then increase due to the fuel NO x dominant. Due to the large greenhouse gas effect of N 2 O, the greenhouse gas (GHG) emissions firstly increase and then decrease. Advancing the diesel injection timing (DIT) when AER = 0.4, NH 3 and soot emissions decrease, but CO, UHC and NO x emissions increase. Due to the low equivalence ratio and the low reactivity of NH 3 , the average cylinder temperature remains low, resulting in an increase of N 2 O and GHG emissions with DIT advances. However, Advancing DIT at AER = 0.8, NH 3, N 2 O and GHG emissions are closely associated with combustion efficiency. In addition, for the pre-injection strategy, at diesel pre-injection energy ratios of 0.2 and 0.4, as the diesel pre-injection timing (DIT pre) advances, the homogeneity and ignition performance of the mixture improve, the combustion duration shortens, ITE improves, and NH 3 emissions decrease, but NO x , UHC and soot emissions increase. However, excessively advancing DIT pre reduce the ITE with more unburned NH 3 emissions. This may be attributed to the pre-injection diesel entering the crevice area, thereby reducing the pre-injection diesel in the cylinder and weakening its positive effect on the mixture. GHG emissions increase initially with the advancement of DIT pre , then fluctuate once the maximum average cylinder temperature reaches approximately 1630 K. [Display omitted] • Effects of AER and injection strategy on ammonia/diesel engine were investigated. • NO x emissions decrease by 90% at AER of 0.5 compared to original diesel engine. • N 2 O is generated at the edge of the high-temperature areas. • As DIT pre advances, the trend of soot emissions is similar to the UHC emissions. [ABSTRACT FROM AUTHOR]

Ammonia, gaining attention as a carbon-free fuel amid declining fossil fuel reserves, faces challenges like combustion instability and misfiring in its application in internal combustion engines. In this study, polyoxymethylene dimethyl ethers (PODE 3), a clean, renewable, and electrically synthesized fuel with high cetane number and oxygen content, is evaluated as a pilot fuel for ammonia in dual-fuel engines. The study, performed in a dual-fuel optical engine, investigates the use of PODE₃ compared to diesel as direct injection fuels for ammonia combustion, focusing on the impact of PODE 3 injection timing and dwell (the interval between dual-stage injections) on the ignition characteristics of ammonia. The results demonstrate that, compared to diesel, using PODE 3 enhances ammonia combustion in dual-fuel engines. This is evident from increased in-cylinder pressure, higher apparent heat release rate (AHRR), advanced combustion phases, and improved indicated mean effective pressure (IMEP), enhancing overall stability. PODE 3 also effectively minimizes soot generation, evidenced by a 71.5 % reduction in spatially integrated natural luminosity (SINL), accompanied by a 16.9 % increase in peak flame area. Adjusting PODE 3 injection timing is crucial; initial retardation improves combustion performance, marked by higher in-cylinder pressure and AHRR, as well as expanded flame area. However, over-delaying injection timing reduces these gains. The optimal performance is achieved under the SOI-25 condition, balancing combustion and flame development, though some areas remain unburnt. In a dual-stage injection strategy using PODE 3 , where the second injection timing remains fixed at −25 °CA ATDC, the critical adjustment of advancing the first injection timing to −35 °CA ATDC markedly enhances combustion performance compared to a single injection condition. This setting reduces ignition delays, increases peak in-cylinder pressures, and improves stability, which collectively contribute to a significant 20.4 % increase in the peak flame area, particularly between adjacent fuel jets. Expanding upon this, advancing the first injection timing further to −45 °CA ATDC leads to a decrease in peak in-cylinder pressure and AHRR, accompanied by a notable 40.3 % reduction in the peak flame area. This research affirms the advantages of PODE 3 over diesel in ammonia-powered dual-fuel engines, markedly enhancing combustion performance and environmental sustainability, where the injection strategy of PODE 3 emerges as a crucial element. • Research explores PODE 3 as a pilot fuel for NH 3 in dual-fuel engines, focusing on combustion enhancement. • PODE 3 improves ammonia flame propagation, leading to a substantial reduction in soot compared to diesel. • Optimal PODE 3 injection timing (SOI-25) balances combustion and flame development, with some unburnt areas. • Dwell-10 condition in dual PODE 3 injection enhances combustion, increasing peak flame area by 20.4 % and IMEP. [ABSTRACT FROM AUTHOR]

The present study aims to evaluate numerically the thermal parameters of dual fuel diesel engine working on two different hybrid fuels using the simulation code Diesel-RK. The combustion chamber is divided into several independent zone and the governing equation are solved for each zone. Initially the standard diesel fuel is tested in the engine to report the basic data for comparison. Then, the engine is turned to work on dual fuel mode operating on two hybrid fuels contains different blends of aqueous ammonia (NH4OH), Dimethyl ester (DME), and algae biodiesel derived from spirulina algae. The hybrid 1 consists of (20% diesel+50% NH4OH+30% DME) and the hybrid 2 involves (40% diesel+40% NH4OH+20% biodiesel). All blends are calculated on energy replacement. The obtained results showed decrease in the rate of heat release and compared to the fuel of diesel. An apparent increase in the brake specific fuel consumption is noticed due to the difference in the density, viscosity, and heating values for both hybrid fuels relative to diesel. The Bosch smoke number (BSN) is strikingly reduced by 51.2% and 53.2%, when hybrid 1 and hybrid 2 is used respectively. Promising reductions in NOx emissions achieved as follows: 48.12% for hybrid 1 and 37% for hybrid 2. The results highlighted that using hybrid 2 (40% DF+40% NH4OH+20% biodiesel) is preferable more than hybrid 1 (20% DF+50% NH4OH+30% DME) since the presence of biodiesel's properties showed better response than DME. The considered results showed noticeable altitude to fight the trade-off relation NOx-BSN. The validation of the results is checked through studies conducted by different researchers. [ABSTRACT FROM AUTHOR]

This study proposes the slope of the engine speed trend line (SlopeESTL) as a new misfire detection index for a four-cylinder engine, not limited to four-cylinder engines. SlopeESTL is defined as angular acceleration between the first and the last teeth of each cylinder in the cycle. SlopeESTL is flat and near 0 when the cylinder is normally combusted. A misfire leads to an abrupt decrease under the threshold. While it is affected by post oscillation just after misfires, there is enough margin between SlopeESTL of the misfired cylinder and post-oscillated SlopeESTL. The mean misfire detection and detection fault rates of the SlopeESTL were over 97% and under 1% in this study, making it a good misfire detection index. However, most of the first misfired cylinder on dual cylinder misfire can seldom be detected as a misfire at the high engine speed over 5000 rpm in the single cylinder misfire pattern. This is caused by the inertia force of the crankshaft system and is a demerit for the misfire detection index. It is one of the two RPM slopes used to calculate the Gap and ΔGap slopes proposed by the author. SlopeESTL can be used with Gap and ΔGap slopes, because they have their specific characteristics as misfire detection indices and their combination logic should be studied more. Furthermore, SlopeESTL can be affected by the machining tolerance of the teeth in the sensor wheel, torsional vibration, and non-uniformity in the stroke operation of the piston. However, it uses the tooth time measured using the existing crankshaft position sensor; an additional sensor is not required, which makes it economical. [ABSTRACT FROM AUTHOR]

In large-bore two-stroke diesel/nature gas dual-fuel marine engines, a certain quantity of diesel is injected into the cylinder to satisfy the full-power output engine rated power of the gas mixture. However, the ignition and flame propagation process based on the injection strategy of diesel direct injection combined with diesel jet flame on the ignition and combustion of natural gas is unclear, which directly affects the power and the thermal efficiency of engine and emissions. Therefore, this work numerically investigates the flame propagation characteristic under the strategy of the main and pilot diesel modes. The influence of the injection timing and proportion of diesel on combustion and emission performance are further analyzed. The results show that the influence of the injection timing of main diesel (MDIT) on the combustion process and emission performance is more obvious than that of the injection timing of pilot diesel (PDIT). The results indicate that the MDIT increased from −2°CA to −8°CA, the power increased by 316 kW, and the thermal efficiency improved by 1.5%. However, the CO2 emissions increased by 10.5 g/kWh, and the NOx emissions increased by 0.7 g/kWh. Additionally, an early PDIT is not conducive to the rapid organization of combustion, resulting in decreased engine power and thermal efficiency. Furthermore, it was found that the power improved by 50 kW and the thermal efficiency improved by 0.6%, with a decrease in the main diesel ratio (MDR) from 100% to 90%. Meanwhile, the CO2 emissions decreased by 4 g/kWh, although there was no obvious change in NOx emissions with the advance of MDR. [ABSTRACT FROM AUTHOR]

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

This study experimentally investigated the influence of gasoline injection pressure (GIP) on the performance and hydrogen knock limit of a gasoline direct-injection hydrogen–gasoline dual-fuel engine. The GIP was varied from 50 to 140 bar, and hydrogen was introduced at a step size of 2 LPM until knock onset at spark timings of 4° and 12° CA before top dead center (BTDC). The hydrogen knock limit was extended at a higher GIP, with maximum hydrogen flow rates of 10 and 16 LPM at 12° CA and 4° CA BTDC, respectively. Increasing the GIP and retarding the spark timing negatively affected brake thermal efficiency, brake mean effective pressure, and in-cylinder pressure. The CO 2 and NO x emissions decreased, and the CO emissions increased with an increase in the GIP. The cyclic variation increased considerably with GIP. However, hydrogen blending exhibited a completely opposite trend to that of GIP. • Study of the effect of gasoline injection pressure in a hydrogen-gasoline dual fuel engine. • The hydrogen knock limit was influenced by the variation in gasoline injection pressure. • Increasing the gasoline injection pressure showed a negative effect on the performance and combustion characteristics. • Cyclic variation increased at higher gasoline injection pressure and reduced with hydrogen blending. • Increased hydrogen flow rate was observed at higher gasoline injection pressure and retarded spark timing. [ABSTRACT FROM AUTHOR]

In this study, the differences in the combustion process of ammonia-premixed ignition with conventional diesel and kerosene as pilot fuels were investigated based on flame chemiluminescence, and further study on the effects of ammonia ratio (AMR) and direct injection timing (DIT) on the ammonia-kerosene dual-fuel combustion (AKDC) process was carried out. The results show that the kerosene with stronger volatility is more conducive to promoting rapid and stable combustion of ammonia. A composite flame structure is observed in dual-fuel modes. With the increase of AMR, the capacity to ignite ammonia is lessened, the flame area and luminosity are stabilized and then reduced, and the flame hue is transformed from blue-green to yellow. Higher combustion rates are observed when the DIT lies between −9° and −12° CA ATDC, resulting in higher flame area and luminosity. The overly advanced or delayed DIT leads to the deterioration of ammonia combustion. • An optical study of the AKDC and ADDC mode was conducted. • A composite flame structure is observed in AKDC and ADDC modes. • Kerosene is more conducive to the ignition of ammonia than diesel. • As AKDC phases are roughly the same, the combustion state of pilot fuel dominates. • Adjusting the phase of AKDC towards TDC via DIT helps the rapid combustion of it. [ABSTRACT FROM AUTHOR]

Dual Fuel (DF) combustion concept has demonstrated to be a valid solution to ensure the utilization of diesel engines in heavy duty and naval applications. The substitution of part of diesel fuel with a cleaner gaseous one can reduce among others: carbon dioxides (CO 2), nitrogen oxides (NO x) and surely particulate matter (PM). Nevertheless, the difficulties encountered by the reduced pilot liquid jet to reach out the furthest areas of the combustion chamber, especially at partial load, lead to unburned emissions of the premixed charge. They can be a serious issue to overcome when the premixed fuel is represented by a carbonaceous fuel like natural gas (NG). For this reason, hydrogen, that is carbon-free, represents the new progression to clean mobility. This work aims at deepening the in-cylinder phenomena through a synergetic methodology that involves experimental optical diagnostics and 3D numerical investigations. The experimental activity is carried out on a single cylinder research engine (SCRE) equipped with an optical apparatus allowing the visualization of the combustion process, later processed via high speed visible (VIS) and infrared (IR) imaging. Several filters applied on the IR camera permit to detect specific species such as CO 2. Subsequently, these outcomes are used to validate numerical models, and in turn, the numerical results help to validate the species detected qualitatively via optical diagnostics and to identify which ones majorly affect the physical and chemical processes. Numerical simulations are performed with ANSYS Forte ® code on a geometry which accurately reproduces the shape of the combustion chamber. Combustion models include a turbulent-kinetic interaction model with a mechanism of 124 species and 660 reactions to deal with the autoignition phase and diesel surrogate oxidation, while to account for the flame propagation through the premixed charge the G-equation is considered. The reference test cases are characterized by two different engine speeds, 1500 and 2000 rpm, and a low load level, corresponding to 2 bar of brake mean effective pressure (BMEP) on light-duty vehicle. The hydrogen energy shares are between 83.2 and 81.8%. Results demonstrate that IR images and OH radical are key for the detection of ignition process of both diesel and hydrogen. The flame propagation in the air/H 2 charge can be observed with the help of CFD elaborations. Finally, emission levels are adequately predicted by the chosen oxidation models. • IR and VIS imaging are used to visualize the in-cylinder process in a diesel SCRE operating in DF mode supplied with H 2. • CFD is used to identify the species that better represent the oxidation process of both fuels. • IR imaging together with OH allows to identify the ignition phases of both diesel and H 2. • CFD flame front visualizations are necessary to overcome the limits of IR imaging for the representation of premixed flame. • The chosen kinetics well predict pollutant emissions. [ABSTRACT FROM AUTHOR]

Diesel engines are commonly used due to its higher reliability and better fuel conversion efficiency. However, it produces exhaust emissions like carbon dioxide (CO 2) and particulate matter (PM). Hydrogen gas is regarded as a clean fuel as it is free from carbon. The addition of hydrogen fuel enhances the burning rates and extends the flammability limits of fossil fuels, and therefore has the potential of reduced exhaust emission in diesel engines operating on dual fuel mode. This paper has investigated the effect of hydrogen addition to the performance and emissions of a single-cylinder diesel engine, working in dual fuel mode with additive di-tert butyl peroxide (DTBP). About 25% hydrogen was introduced into the cylinder on a mass basis via the engine intake manifold with the addition of additive di-tert butyl peroxide up to 5% in diesel fuel. In this experimental study, mean gas temperature, indicated mean effective pressure (IMEP), brake mean effective pressure (BMEP), polytropic index, and exhaust emissions were studied at medium (53%) and high (69%) load conditions. The indicated mean effective and brake mean effective pressure was 9.79 bar with a 3% addition of additive and 4.15 bar with the 5% addition of additive as compared with 8.71 bar and 4.11 bar diesel fuel operation. 16% hydrogen addition with 1% di-tert butyl peroxide, IMEP, and BMEP are 10.92 bar, and 4.14 bar respectively. • Additive with hydrogen fuel work as alternative fuel in diesel engine. • Effect of temperature and pressure with additive (1%–5%) and diesel fuel. • At 53% load, the reduction in polytropic index with additive from 3% to 5%. • At 69% load, enhanced in polytropic index from 1% to 5% additive. • Indicated mean effective pressure and brake mean effective pressure enhanced. [ABSTRACT FROM AUTHOR]

Because of their great capability and consistent quality, Diesel engines are commonly employed in Industrial regions, Transportation sectors, and Agricultural fields. The main disadvantage of this engine is the excessive amount of smoke and nitrogen oxide emissions. As a result, Mosambi Peel Pyro oil (MPO) was blended in varying quantities with straight diesel. Methanol enrichment was used to test D90MPO10 (10% MPO +90% Diesel), D90MPO10M21 (10% MPO +90% Diesel +21% Methanol), and D90MPO10M22 (10% MPO +90% Diesel +22% Methanol)Oil parameters.The ultimate, proximate, and FTIR analyses, as well as viscosity, density, flash point, and fire point, are estimated. D90MPO10, D90MPO10M21, and D90MPO10M22 are diesel engine fuels, and D90MPO10M22's combustion and emission performance are investigated. It was shown that using D90MPO10 as pilot fuel and methanol as an induction fuel in diesel engines resulted in lower smoke levels (3.5%) and increased thermal efficiency (2.5%) with no significant Performance Degradation. [ABSTRACT FROM AUTHOR]

Ammonia (NH 3), as a zero carbon, easy to synthesize, and easily obtainable fuel, is one of the choices for future internal combustion engine fuels. However, the slow laminar flames speed and high ignition temperature of NH 3 seriously hinder the development of NH 3 engines. Efficiently igniting NH3 and ensuring its stable combustion is currently a challenging research topic. Utilizing diesel to optimize the NH3 combustion process is one effective solution. However, the increase of unburned ammonia (UNH 3) and unstable combustion, under high load conditions have always been technical challenges that constrain the development of ammonia-diesel dual-fuel (ADDF) engines. Previous studies have found that pre-chambers (PC) have a significant effect on improving ammonia combustion characteristics. Therefore, based on the PC system, this study proposes two combustion modes: Reactivity Assisted Jet Ignition (RAJI) and Reactivity Turbulent Jet Disturbance (RTJD), which greatly optimize the combustion characteristics of ADDF engines under high load conditions. The research results indicate that the RAJI mode effectively improves the thermal environment inside the cylinder. Setting the start of diesel injection of pre-chamber (SODI-PC) at −14 °CA after top dead center (ATDC) can increase the cylinder temperature by 25.05% before the start of diesel injection of main chamber (SODI-MC). The improvement of thermal environment reduces the average generation of N 2 O to 13.56% of the traditional mode. However, if SODI-PC is postponed to −8 °CA ATDC, the effect of creating a thermal environment is no longer significant. Research on the RTJD mode has found that adopting the RTJD mode can significantly optimize emissions. Compared with traditional modes, N 2 O, UNH 3 , and Soot decreased by 28.81%, 27.79%, and 35.08%, respectively. Additionally, SODI-PC is delayed until after 4 °CA ATDC, CO and UHC will be further reduced to 50.00% and 12.24% of the traditional mode, respectively. In addition, the RTJD mode overcomes the deficiency of the slow laminar flame speed of NH 3 , shortening the combustion duration by 23.46%, and effectively improving the gross indicated thermal efficiency (ITEg) by an average increase of 1.08%, with the highest increase reaching 47.57%. This paper provides ideas for optimizing the structure and strategy of ADDF engines, as well as theoretical support and empirical reference for achieving clean and efficient combustion of engines. [Display omitted] • Two combustion modes: RAJI and RTJD are proposed. • The RAJI mode can reduces the average generation of N 2 O to 13.56% of the traditional mode. • In RAJI mode the N 2 O and UNH 3 , was decreased by 28.81% and 27.79%, respectively. • The RTJD mode shortens the combustion duration by 23.46%. [ABSTRACT FROM AUTHOR]

The study investigates, numerically, the potential use of introducing aqueous H 2 O 2 as an ignition promoter in a statistically homogeneous NH 3 /H 2 fuelled, medium speed (1250 rpm), 4-stroke, 1.3 litre cylinder displacement, mildly boosted CI engine with a compression ratio of 17.6:1. The H 2 is considered to be produced on-board from ammonia cracking. An extensive campaign is undertaken using the commercial stochastic reactor model, SRM Engine Suite, which allowed the modelling of temporal, temperature and spatial stratification in the cylinder. The engine performance, combustion phasing, maximum pressure rise rate and emissions (NOx, N 2 O and unreacted NH 3) are investigated in view of: (i) the share of molecular hydrogen in the initial NH 3 /H 2 mixture from 10 to 40 percent; (ii) the mass of aqueous H 2 O 2 introduced from 0.1 to 16 mg; (iii) the start of injection (−10 to ＋6 CAD aTDC) and duration of injection (1, 4 and 8 CAD); (iv) the amount of exhaust gas recirculation (up to 30 percent by mass); (v) the share of energy from the H 2 O 2 in the aqueous solution mixture at less than 0.5 percent of that in the main fuel; (vi) engine load corresponding to a variation in the equivalence ratio from 0.32 to 1.2 by changing the mass of the NH 3 /H 2 mixture in the combustion chamber. A wide range of loads (evaluated against the engine's rated power when operated with diesel and at its rated boost levels) can be achieved (44%–93%) with the energy share of H 2 O 2 being as little as equivalent to 2.7% vol% that of the main fuel, ammonia, which is introduced into the cylinder. This implies that the required storage volume of the H 2 O 2 is low, at a few percent that of the main ammonia tank. NOx emissions peak between ϕ = 0.6−0.65 and rapidly decrease as the equivalence ratio increases or decreases reaching values marginally above the Tier III standard at high loads (> 90%) while ammonia slip and N 2 O emissions are generally extremely low (10−12 mg for NH 3 and < 0.01 mg/kWh for N 2 O). • Aqueous H 2 O 2 pilot ignites NH 3 /H 2 mixture (80/20/vol) with BDC state of 1.3 bar, 390K. • We report engine operation with 1 – 4 mg of aqueous H 2 O 2 pilot at 10% vol%. • A wide range of engine loads can be achieved (44%–93%), without any optimisation. • The maximum pressure rise rate, N 2 O and NH 3 slip are within acceptable limits. • NOx peak at global ϕ ≈ 0.6 and reach marginally above Tier III standard under high load. [ABSTRACT FROM AUTHOR]

The study was conducted to uncover the emission, combustion, and performance features of the blend of Water Hyacinth biodiesel and Mesua Ferrea seed oil biodiesel with Hydrogen addition on a diesel engine in dual fuel. Pilot fuel is a blend of 50% Water Hyacinth biodiesel and 50% Mesua Ferrea seed oil biodiesel. A single-cylinder compression ignition engine was modified to operate on dual fuel mode with hydrogen. Variations of engine operating parameters such as injection timing, and engine load were performed. The study was conducted with three pilot fuel injection timings (23, 26, and 29°bTDC) and variable engine loadings (20%–100% with an increment of 20%) at an injection pressure of 200 bar and compression ratio of 18. The results indicated that the maximum brake thermal efficiency of 28.11% and a replacement of liquid fuel by 85% was obtained for the WHMF blend powered dual fuel diesel engine at pilot fuel injection timings of 26°bTDC at 100% load. HC, CO, and smoke emissions are reduced with hydrogen due to faster combustion. On the other hand, there was a slight increase in NOx emissions noticed with hydrogen enrichment. [Display omitted] • Pilot fuel is a blend of 50% Water Hyacinth Biodiesel and 50% Mesua Ferrea Biodiesel. • Hydrogen is used with pilot fuel under dual fuel mode to improve combustion. • Hydrogen enrichment improves the brake thermal efficiency of the pilot fuel. • Emissions of CO and HC were reduced with hydrogen addition in the pilot fuel. • Liquid fuel replacement of 85% is achieved at an IT of 26⁰bTDC of the pilot fuel. [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]

Due to stringent emission regulations, vehicle manufacturers must control diesel engine emissions. To address these regulations, this study introduces a novel approach for generating methane-enriched biogas through ultrasonic pretreatment and using it in dual fuel-mode diesel engines with a Hiptage biodiesel blend and biohydrogen. The study employs an RSM-based central composite design (CCD) approach to develop the L 54 orthogonal array for five factors and five levels of parameters. Additionally, seven different machine learning algorithms (DTR, RFR, ETR, GBR, LR, CBR, and XGBR) are used to develop a prognostic model based on the acquired experimental data. These models are used to estimate key performance indicators such as brake thermal efficiency (BTE), brake-specific fuel consumption (BSFC), carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxides (NO x). Based on the evaluation of performance indicators, including R2 values (0.9021–0.97344), RMSE (0.00203–26.5539), MAE (0.00114–23.5944), and MAPE (0.0215–0.04438), the GBR model establishes the most accurate predictions. Furthermore, the RSM-based desirability approach is used to evaluate the trade-off between performance and emissions, thereby identifying the optimal engine operating condition. This condition includes an engine load of 83%, a compression ratio of 18:1, a fuel injection pressure (FIP) of 243 bar, a fuel injection timing (FIT) of 26° crank angle advance, and a biogas flow rate of 1.2 kg/h. Experimental investigation validates the RSM analysis findings, revealing an error margin of 7%. Overall, the introduction of methane-enriched biogas into a dual-fuel diesel engine improves combustion, resulting in increased engine performance and reduced emissions. [Display omitted] • Examine the effect of ultrasound on methane yield in the co-digestion of waste. • Study the behavior of a dual-fuel diesel engine with biodiesel, biogas, and biohydrogen. • Apply ML-RSM for prediction and optimization of engine characteristics. • The GB Regressor model demonstrated the most accurate predictions for key performance. • Experimental validation shows a maximum error of 7%. [ABSTRACT FROM AUTHOR]

Pilot-ignition Otto marine engines are known for greatly reduced emissions of air pollutants (sulphur oxides, nitrogen oxide, particulates) compared to marine diesel engines. However, lubricating oil emissions still are about one order of magnitude higher than in land-based systems. To identify reduction potentials, a better understanding of oil emission mechanisms has to be gained. For this purpose, mass spectrometric oil emission measurements and fluorescence lubricating film thickness measurements were performed on a medium-speed marine engine. With the fluorescence measuring system, the varying lubricating oil film on the cylinder wall can be visualised and analysed in sub-crank-angle resolution. By applying the developed calibration method to the measurement data, the oil film thickness can be determined in µm. It is shown that the oil film left by the piston rings on the liner as it moves down is almost halved after ignition compared to during intake stroke. The authors have further been able to detect and time operating point dependent ring rotation and investigations show a connection between ring rotation and cylinder liner temperature distribution. Aligning ring gaps allow blow-by to happen. This and other high intensity events such as engine knock, load shedding or the transition from diesel-mode to gas-mode, heavily disturb the oil layer and cause peaking oil emissions. [ABSTRACT FROM AUTHOR]

The combustion process of a dual‐fuel engine was calculated by characteristic timescale model (CTM), eddy breakup model (EBM), and coherent flamelet model (CFM) to verify the accuracy of the combustion models. The results show that the peak pressure calculated by EBM is 2.78 % higher than the experimental value, and the peak pressure calculated by CFM is closest to the experimental value. The EBM is the most accurate for CO2 emissions. The deviation of CO emissions from the experimental values calculated by CTM is the smallest (< 1 %). The NOx emission calculated by CTM is good agreement with the experimental value at low speed, and EBM is in best agreement with the experimental value at high speed. The hydrocarbon emission calculated by CFM is the most accurate, with a deviation of less than 0.6 %. [ABSTRACT FROM AUTHOR]

To meet climate targets, a global shift away from fossil fuels is essential. For sectors where electrification is impractical, it is crucial to find sustainable energy carriers. Renewable methanol is widely considered a promising fuel for powering heavy-duty applications like shipping, freight transport, agriculture, and industrial machines due to its various sustainable production methods. While current technological efforts focus mainly on dual-fuel engines in shipping, future progress hinges on single-fuel solutions using renewable methanol to achieve net-zero goals in the heavy-duty sector. This review examines the research status of technologies enabling methanol as the sole fuel for heavy-duty applications. Three main categories emerged from the literature: spark-ignition, compression-ignition, and pre-chamber systems. Each concept's operational principles and characteristics regarding efficiency, stability, and emissions were analyzed. Spark-ignition concepts are a proven and cost-effective solution with high maturity. However, they face limitations due to knock issues, restricting power output with larger bore sizes. Compression-ignition concepts inherently do not suffer from end-gas autoignition, but encounter challenges related to ignitability due to the low cetane number of methanol. Nonetheless, various methods for achieving autoignition of methanol exist. To obtain stable combustion at all load points, a combination of techniques will be required. Pre-chamber technology, despite its lower maturity, holds promise for extending the knock limit and enhancing efficiency by acting as a distributed ignition source. Furthermore, mixing-controlled pre-chamber concepts show potential for eliminating knock and the associated size and power limitations. The review concludes by comparing each technology and identifying research gaps for future work. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical analysis of the selected properties of HCNG fuel calculations and a literature review of the other fuels that allow the storage of ecologically produced hydrogen. Hydrogen has the most significant CO2 reduction potential of all known fuels. However, its transmission in pure form is still problematic, and its use as a component of fuels modified by it has now become an issue of interest for researchers. Many types of hydrogen-enriched fuels have been invented. However, this article will describe the reasons why HCNG may be the hydrogen-enriched fuel of the future and why internal combustion (IC) piston engines working on two types of fuel could be the future method of using it. CO2 emissions are currently a serious problem in protecting the Earth's natural climate. However, secondarily, power grid stabilization with a large share of electricity production from renewable energy sources must be stabilized with very flexible sources—as flexible as multi-fuel IC engines. Their use is becoming an essential element of the electricity power systems of Western countries, and there is a chance to use fuels with zero or close to zero CO2 emissions, like e-fuels and HCNG. Dual-fuel engines have become an effective way of using these types of fuels efficiently; therefore, in this article, the parameters of hydrogen-enriched fuel selected in terms of relevance to the use of IC engines are considered. Inaccuracies found in the literature analysis are discussed, and the essential properties of HCNG and its advantages over other hydrogen-rich fuels are summarized in terms of its use in dual-fuel (DF) IC engines. [ABSTRACT FROM AUTHOR]

Reactivity-controlled compression ignition (RCCI) combustion is considered one of the most promising low-temperature combustion (LTC) concepts aimed at reducing greenhouse gases for the transportation and power generation sectors. RCCI combustion mode is achieved by combining different fuel types with low and high temperatures. The aim of this study is to investigate combustion characteristics and reduce nitrogen oxide (NOx) and carbon dioxide (CO2) emissions. In this experimental study, the effects of the RCCI strategy using methanol/diesel fuel on combustion characteristics (ignition delay, combustion duration), engine performance (brake-specific fuel consumption and brake-specific energy consumption), and emissions were examined in a four-cylinder, turbocharged, dual-fuel engine. The experiments were conducted at a constant speed of 1750 rpm at partial loads (40 Nm, 60 Nm, 80 Nm, and 100 Nm). The test results obtained with diesel fuel were compared with the test results obtained with methanol at different mass flow rates. When the results were examined, the minimum ignition delay (ID) occurred at 40 Nm torque, 5.63 crank angle (CA) with M12 fuel, while the maximum ID occurred with M26 fuel at 80 Nm torque, showing an increasing trend as engine load (EL) increased. The highest combustion time (CD) was achieved with M26 fuel at 100 Nm torque, whereas the lowest was achieved with the same fuel (M26) at 40 Nm. While the minimum brake-specific fuel consumption (bsfc) was 45.9 g/kWh for conventional diesel fuel at 40 Nm, the highest bsfc was 104.88 g/kWh for 100 Nm with M26 fuel. Generally, bsfc tends to increase with increasing load. Brake-specific energy consumption (bsec) had the lowest value of 1950.58 kJ/kWh with conventional diesel fuel at 40 Nm and the highest value of 4034.69 kJ/kWh with M26 fuel at 100 Nm. As the methanol content increased, significant improvements were observed in (NOx) and (CO2) emissions, while hydrocarbon (HC) and oxygen (O2) emissions increased as well. Smoke emissions decreased at low loads but tended to increase at high loads. [ABSTRACT FROM AUTHOR]

Zero-carbon shipping is the prime goal of the seaborne trade industry at this moment. The utilization of ammonia and liquid hydrogen propulsion in a carbon-free propulsion system is a promising option to achieve net-zero emission in the maritime supply chain. Meanwhile, optimal ship voyage planning is a candidate to reduce carbon emissions immediately without new buildings and retrofits of the alternative fuel-based propulsion system. Due to the voyage options, the precise prediction of fuel consumption and carbon emission via voyage operation profile optimization is a prerequisite for carbon emission reduction. This paper proposes a novel fuel consumption and carbon emission quantity prediction method which is based on the onboard measurement data of a smart ship. The prediction performance of the proposed method was investigated and compared to machine learning and LSTM-model-based fuel consumption and gas emission prediction methods. The results had an accuracy of 81.5% in diesel mode and 91.2% in gas mode. The SHAP (Shapley additive explanations) model, an XAI (Explainable Artificial Intelligence), and a CO2 consumption model were employed to identify the major factors used in the predictions. The accuracy of the fuel consumption calculated using flow meter data, as opposed to power load data, improved by approximately 21.0%. The operational and flow meter data collected by smart ships significantly contribute to predicting the fuel consumption and carbon emissions of vessels. [ABSTRACT FROM AUTHOR]

The utilization of waste biomass-derived producer gas in dual-fuel engines has attracted a lot of interest as a sustainable energy option that encourages waste reduction as well as cleaner energy production. This research proposed a glass-box modeling strategy that combined the robust Huber and Tweedie regression approaches with SHAP (SHapley Additive exPlanations) analysis to estimate the performance and emissions of the test engine. The research demonstrated robustness over heteroscedasticity by using Huber and Tweedie regression methods, which are critical factors in real-world engine functioning. The Huber method consistently outscored both the LR and Tweedie-based prediction models in a comparison of prediction techniques for various parameters. Huber obtained remarkably high R2 values as 0.941 to 0.984, in addition to quite low root mean squared error. SHAP analysis helped in revealing the degree and direction of individual features' effect on the model. The engine load was observed to be having the most profound effect on the final model output. This study contributed to the development of waste biomass utilization in dual-fuel engines by providing a reliable prognostic tool for developing and running such systems in sustainable practices. [Display omitted] • Using waste biomass-derived producer gas for diesel engines improves sustainability. • ML with SHapley Additive exPlanations (SHAP) enhances prediction interpretability. • LR and Tweedie-based models reach high R-squared values and low RMSE. • SHAP pinpoints engine load as the key factor influencing the output power. [ABSTRACT FROM AUTHOR]

In the first phase of this investigation, the ability of hydrogen induction into the jatropha biodiesel-ethanol (biohol) mixture on the efficiency, emissions and exergy characteristics of a dual fuel engine is highlighted. The biohol mixture exhibits a lower brake thermal and exergetic efficiencies with higher carbon emissions than the diesel at all brake power. Hydrogen supply enhances the performance and exergy parameters with noteworthy enhancement in unburned hydrocarbon (up to 31.03 %), carbon monoxide (up to 60.68 %), and particulate matter (up to 26.67 %) of the biohol piloted dual fuel engine. In the second phase, an artificial neural network model is constructed with the purpose of forecasting the exergy, energy and emission parameters of the engine under biohol-hydrogen strategies. The topology (2-9-8) is found to be the optimal model with mean square error of (0.00012–0.00053), mean absolute error of (2.12%–4.54 %), and regression coefficient of (0.9965–0.99959). [Display omitted] • Biohol represents lower energy and exergy with higher carbon emissions. • Hydrogen supply improves carbon emissions of the Biohol piloted CI engine. • Biohol-hydrogen enhances brake thermal and exergetic efficiencies of the CI engine. • The topology (2-9-8) is found to be optimal than other varying hidden neurons. • The optimal topology forecasts the biohol-hydrogen powered engine by 99.21 %. [ABSTRACT FROM AUTHOR]

Natural gas/Diesel RCCI engines suffer from a lack of combustion efficiency and a high level of unburned hydrocarbon and carbon monoxide emissions, especially at low load ranges. Therefore, this study seeks to enhance RCCI engine combustion efficiency and also reduce engine emissions, especially greenhouse gases, through the complete replacement of natural gas by hydrogen as a low-reactivity fuel. To achieve this objective, a single-cylinder heavy-duty diesel engine tested as an NG/Diesel RCCI engine was nominated to operate as an H2/Diesel RCCI engine. For better control of H2/Diesel RCCI engine performance, the exhaust gas recirculation method and nitrogen addition were simultaneously used to dilute the engine intake mixture. The simulation results show that complete natural gas replacement by hydrogen in the single-cylinder NG/Diesel RCCI engine under investigation leads to a reduction in natural gas consumption up to 27,000 cubic meters per year. However, the RCCI engine operating cost would be increased more than 4.0 times by replacing the hydrogen fuel. The use of hydrogen as the sole low-reactivity fuel guarantees a 2 % increase in the RCCI engine's output power and an efficiency of more than 50 %. By reducing the fossil fuel energy share to 22 % in the RCCI engine at low load, reductions in carbon dioxide levels more than 4.0 times, unburned Methane up to 33,000 times, carbon monoxide up to 500 times, and Formaldehyde emission levels up to 2600 times can be achieved only in the absence of natural gas consumption. However, it is possible to control the thermal NOx level to less than 0.2 g/kWh in the range of EURO VI. Of course, considering the concern about the high risk of hydrogen explosions, the results confirm that the amount of unburned hydrogen emitted by the engine is less than 0.3 % of the amount of hydrogen entering the engine cylinder as a fuel. [Display omitted] • Save the natural gas consumption up to 27,000 cubic meters per year. • Achieving the gross indicated efficiency more than 50 %. • Improving the engine output power to 2 %. • Reduction in the amount of CO2 more than 4.0 times. [ABSTRACT FROM AUTHOR]

The microneedle (MN) delivery system presents an attractive administration route for patients with Alzheimer's disease (AD). However, the passive drug delivery mode and low drug loading of MNs often result in unsatisfactory therapeutic efficiency. To address these dilemmas, we developed dual engine-drive bionic MNs for robust AD treatment. Specifically, free rivastigmine (RVT) and RVT particles were co-loaded within the MNs to construct the valve and chambers of the guava, respectively, which can serve as an active engine to promote drug permeation by generating capillary force. K 2 CO 3 and citric acid were introduced as a pneumatic engine into the MNs to promote the permeation of free RVT into deeper skin layers for early intervention in AD. Further, the RVT particles served as a drug depot to provide continuous drug release for prolonged AD treatment. Compared with free RVT-loaded MNs, the dual engine-driven bionic MNs showed an increase in drug loading, cumulative transdermal permeability, and normalized bioavailability of approximately 40%, 22%, and 49%, respectively. Pharmacodynamic studies further confirmed that the dual engine-driven bionic MNs were most effective in restoring memory and recognition functions in mice with short-term memory dysfunction. Therefore, the dual engine-driven bionic MNs hold great promise for highly efficient AD treatment. [Display omitted] • Bionic MNs driven with dual pneumatic and capillary forces significantly enhanced the drug loading and bioavailability of rivastigmine. • Bionic MNs with biphasic drug release behavior provided early intervention and prolonged treatment of Alzheimer's disease. • Bionic MNs effectively restored the memory and recognition functions of mice. [ABSTRACT FROM AUTHOR]

The research aims to investigate the features of a dual-fuel mode diesel engine that runs on hydrogen gas and sapota seed biodiesel (SSB) blend. Using gaseous hydrogen in diesel engines is a practical solution for enhancing energy efficiency and reducing emissions. The use of sapota fruit waste seeds as a new and innovative source to produce biodiesel has been recognized. It is essential to mention that sapota seeds are only used for sowing purposes other than those considered wasteful. A comprehensive review of earlier research indicates that this study, which uses an SSB blend in addition to hydrogen in dual-fuel operation, is essential. The primary objective of this research is to analyze the impact of hydrogen in SSB dual-fuel mode in single-cylinder diesel engines. Hydrogen was introduced into the intake manifold via a port fuel injector at flow rates of 3 and 6 liters per minute (LPM), with SSB as the fuel. The hydrogen energy share for 3 LPM and 6 LPM at maximum brake power (BP) conditions is 16.17% and 31.07%, respectively. The results revealed that hydrogen induction 3 LPM and 6 LPM increased cylinder pressure by 17.26% and 21.03%, heat release rate (HRR) by 43.91% and 56.13%, brake thermal efficiency (BTE) by 6.29% and 14.62%, and decreased brake specific energy consumption (BSEC) by 21.73% and 39.13% than diesel at maximum BP. Moreover, hydrogen 3 LPM and 6 LPM reduced carbon dioxide (CO 2), carbon monoxide (CO), hydrocarbon (HC), and smoke emissions by 18.61% and 28.26%, 49.68% and 77.20%, 63.01% and 83.28% and 23.24% and 34.63% than diesel at maximum BP. Oxides of nitrogen (NOx) emissions were increased by 2.84% in biodiesel when compared to diesel; however, when hydrogen was added, NOx emissions increased by 9.40% and 16.15% compared to diesel at maximum BP. This study found that adding hydrogen to SSB increased BTE and decreased emissions with slightly increased NOx emissions. This research concluded that biodiesel and hydrogen induction can substitute diesel fuel in diesel engines. [Display omitted] [ABSTRACT FROM AUTHOR]

In response to increasingly stringent emissions regulations and the depletion of conventional fuel sources, integrating carbon-free fuels into the transport sector has become imperative. While hydrogen (H2) presents significant technical challenges, ammonia (NH3) could present a better alternative offering ease of transport, storage, and distribution, with both ecological and economic advantages. However, ammonia substitution leads to high emissions of unburned NH3, particularly at high loads. Combustion chamber retrofitting has proven to be an effective approach to remedy this problem. In order to overcome the problems associated with the difficult combustion of ammonia in engines, this study aims to investigate the effect of the piston bowl shape of an ammonia/diesel dual fuel engine on the combustion process. The primary objective is to determine the optimal configuration that offers superior engine performance under high load conditions and with high ammonia rates. In this study, a multi-objective optimization approach is used to control the creation of geometries and the swirl rate under the CONVERGETM 3.1 code. To maximize indicated thermal efficiency and demonstrate the influence of hydrogen enrichment on ammonia combustion in ammonia/diesel dual fuel engines, a synergistic approach incorporating hydrogen enrichment of the primary fuel was implemented. Notably, the optimum configuration, featuring an 85% energy contribution from ammonia, outperforms others in terms of combustion efficiency and pollutant reduction. It achieves over 43% reduction in unburned NH3 emissions and a substantial 31% improvement in indicated thermal efficiency. [ABSTRACT FROM AUTHOR]

In the presented research, the authors dealt with the specific properties of the combustion process of dimethyl ether (DME) in a combustion car (Volkswagen Golf IV) engine AJM 1.9 TDI PDE made by Volkswagen factory. Dimethyl ether is an alternative fuel produced most often from natural gas, which can be used in compression ignition engines as a single fuel or co-burned with diesel oil. This work describes the impacts of using exhaust gas recirculation (EGR) system and various diesel to DME substitution ratios from 0% to approximately 25% (on an energy basis), on the combustion process in a dual-fuel diesel engine. The engine has been modified so that DME fuel is introduced into the intake manifold just before the intake valves. The diesel fuel supply system, operation algorithms of the engine electronic control unit and other engine elements were left unchanged as it was built by the manufacturer. [ABSTRACT FROM AUTHOR]