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29 pages, 5006 KiB

Open AccessArticle

Influence of Biodiesel from Used Cooking Oil and Sunflower Oil on Engine Efficiency and Emission Profiles

by Ruxandra-Cristina Stanescu, Adrian Soica and Cristian-Ioan Leahu

Energies 2025, 18(3), 583; https://doi.org/10.3390/en18030583 - 26 Jan 2025

Viewed by 305

Abstract

This study evaluates the performance and emissions characteristics of a compression ignition engine fueled with biodiesel blends derived from used cooking oil (UO) and sunflower oil (SF) at concentrations of 5%, 10%, 20%, and 50%. Tests were conducted under different load conditions (20%, [...] Read more.

This study evaluates the performance and emissions characteristics of a compression ignition engine fueled with biodiesel blends derived from used cooking oil (UO) and sunflower oil (SF) at concentrations of 5%, 10%, 20%, and 50%. Tests were conducted under different load conditions (20%, 50%, and 100%) across engine speeds ranging from 1500 to 3600 rpm, focusing on effective power, torque, brake specific fuel consumption (BSFC), and emissions of NOx, CO, HC, particulate matter (PM), smoke, and CO₂. Consistent engine operating conditions were maintained for all fuel blends. The results indicated that increasing the biodiesel concentration led to a decrease in brake power and torque—up to 3.18% reduction for SF50 compared to diesel—due to the lower calorific value of biodiesel. For SF biodiesel, the BSFC increased with higher biodiesel content, while for UO biodiesel the results varied across concentrations. Emissions analysis revealed lower CO and HC at 2500 rpm for all biodiesel blends relative to diesel, while NOx emissions varied depending on fuel type and concentration. In terms of particles, both PM and smoke were measured, and while PM showed different results across blends, smoke was lower for all blends compared to diesel. Our overall analysis shows that biodiesel blends up to 20% can be effectively used in diesel engines without substantial modifications, offering a balance between performance and reduced emissions. Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

15 pages, 2505 KiB

Open AccessArticle

Exhaust Emissions from a Direct Injection Spark-Ignition Engine Fueled with High-Ethanol Gasoline

by Miłosław Kozak, Marek Waligórski, Grzegorz Wcisło, Sławomir Wierzbicki and Kamil Duda

Energies 2025, 18(3), 454; https://doi.org/10.3390/en18030454 - 21 Jan 2025

Viewed by 473

Abstract

Ethyl alcohol is a known additive to automotive gasoline. In commercially available gasolines, its concentration is between 5 and 10%. Since ethyl alcohol can be considered as a renewable fuel, efforts are being made to further increase its content in gasoline. This article [...] Read more.

Ethyl alcohol is a known additive to automotive gasoline. In commercially available gasolines, its concentration is between 5 and 10%. Since ethyl alcohol can be considered as a renewable fuel, efforts are being made to further increase its content in gasoline. This article describes the results of comparison experiments on a Euro 5 direct injection spark-ignition car engine fueled with conventional gasoline and gasoline with 30% v/v ethyl alcohol content (E30). The test results showed that a significant share of ethanol in the fuel did not affect most of the regulated emissions of gaseous components (namely: CO, HC, NO), i.e., a three-way catalyst effectively removed these components, regardless of the fuel composition. Slightly lower CO₂ emissions with the E30 fuel were noticeable. A significant difference, however, in lower particulate number emissions for the fuel with high-ethanol content was seen. At high engine load, the use of the E30 fuel resulted in a tenfold reduction in particulate number emissions. This might be considered as a very valuable effect of ethanol since direct injection spark-ignition engines are typically characterized by higher particulate emissions compared to engines equipped with other types of injection systems. Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

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17 pages, 2736 KiB

Open AccessArticle

Effects of Decanol Blended Diesel Fuel on Engine Efficiency and Pollutant Emissions

by Kwonwoo Jang, Jeonghyeon Yang, Beomsoo Kim and Jaesung Kwon

Energies 2024, 17(24), 6223; https://doi.org/10.3390/en17246223 - 10 Dec 2024

Viewed by 597

Abstract

This study examined the effects of blending decanol, an oxygenated fuel, with diesel on diesel engine performance and emissions. Experiments were conducted on a single-cylinder engine at 1700 rpm and 2700 rpm, using diesel/decanol blends at 10%, 30%, and 50% by volume (D90de10, [...] Read more.

This study examined the effects of blending decanol, an oxygenated fuel, with diesel on diesel engine performance and emissions. Experiments were conducted on a single-cylinder engine at 1700 rpm and 2700 rpm, using diesel/decanol blends at 10%, 30%, and 50% by volume (D90de10, D70de30, D50de50). Results showed that brake thermal efficiency decreased with higher decanol ratios at low speeds. As a result, brake specific fuel consumption and brake specific energy consumption increased due to decanol’s lower calorific value. Regarding emissions, decanol blending reduced NO_x, CO, HC, and smoke. NO_x emissions were lowered by the cooling effect resulting from decanol’s higher latent heat of vaporization and lower calorific value, especially at low speeds. CO and HC emissions declined as decanol’s oxygen content promoted oxidation, reducing incomplete combustion. Smoke emissions were minimized in fuel-rich zones by preventing unburned carbon particle formation. This study highlights decanol’s potential as an eco-friendly diesel blending option. Future work should optimize blending ratios and injection settings to enhance diesel engine performance. Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

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31 pages, 7485 KiB

Open AccessArticle

Micro Gas Turbines in the Global Energy Landscape: Bridging the Techno-Economic Gap with Comparative and Adaptive Insights from Internal Combustion Engines and Renewable Energy Sources

by A. H. Samitha Weerakoon and Mohsen Assadi

Energies 2024, 17(21), 5457; https://doi.org/10.3390/en17215457 - 31 Oct 2024

Viewed by 1084

Abstract

This paper investigates the potential of Micro Gas Turbines (MGTs) in the global shift towards low-carbon energy systems, particularly focusing on their integration within microgrids and distributed energy generation systems. MGTs, recognized for their fuel flexibility and efficiency, have yet to achieve the [...] Read more.

This paper investigates the potential of Micro Gas Turbines (MGTs) in the global shift towards low-carbon energy systems, particularly focusing on their integration within microgrids and distributed energy generation systems. MGTs, recognized for their fuel flexibility and efficiency, have yet to achieve the commercialization success of rival technologies such as Internal Combustion Engines (ICEs), wind turbines, and solar power (PV) installations. Through a comprehensive review of recent techno-economic assessment (TEA) studies, we highlight the challenges and opportunities for MGTs, emphasizing the critical role of TEA in driving market penetration and technological advancement. Comparative analysis with ICE and RES technologies reveals significant gaps in TEA activities for MGTs, which have hindered their broader adoption. This paper also explores the learning and experience effects associated with TEA, demonstrating how increased research activities have propelled the success of ICE and RES technologies. The analysis reveals a broad range of learning and experience effects, with learning rates (α) varying from 0.1 to 0.25 and experience rates (β) from 0.05 to 0.15, highlighting the significant role these effects play in reducing the levelized cost of energy (LCOE) and improving the net present value (NPV) of MGT systems. Hybrid systems integrating MGTs with renewable energy sources (RESs) and ICE technologies demonstrate the most substantial cost reductions and efficiency improvements, with systems like the hybrid renewable energy CCHP with ICE achieving a learning rate of α = 0.25 and significant LCOE reductions from USD 0.02/kWh to USD 0.017/kWh. These findings emphasize the need for targeted TEA studies and strategic investments to unlock the full potential of MGTs in a decarbonized energy landscape. By leveraging learning and experience effects, stakeholders can predict cost trajectories more accurately and make informed investment decisions, positioning MGTs as a competitive and sustainable energy solution in the global energy transition. Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

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26 pages, 25428 KiB

Open AccessArticle

Virtual Development of a Single-Cylinder Hydrogen Opposed Piston Engine

by Enrico Mattarelli, Stefano Caprioli, Tommaso Savioli, Antonello Volza, Claudiu Marcu Di Gaetano Iftene and Carlo Alberto Rinaldini

Energies 2024, 17(21), 5262; https://doi.org/10.3390/en17215262 - 22 Oct 2024

Viewed by 1077

Abstract

A significant challenge in utilizing hydrogen in conventional internal combustion engines is achieving a balance between NOx emissions and brake power output. A lean premixed charge (Lambda ≈ 2.5) allows for efficient and stable combustion with minimal NOx emissions. However, this comes at [...] Read more.

A significant challenge in utilizing hydrogen in conventional internal combustion engines is achieving a balance between NOx emissions and brake power output. A lean premixed charge (Lambda ≈ 2.5) allows for efficient and stable combustion with minimal NOx emissions. However, this comes at the cost of reduced power density due to the higher air requirements of the thermodynamic process. While supercharging can mitigate this drawback, it introduces increased complexity, cost, and size. An intriguing alternative is the 2-stroke cycle, particularly in an opposed piston (OP) configuration. This study presents the virtual development of a single-cylinder 2-stroke OP engine with a total displacement of 0.95 L, designed to deliver 25 kW at 3000 rpm. Thanks to its compact size, high thermal efficiency, robustness, modularity, and low manufacturing cost, this engine is intended for use either as an industrial power unit or in combination with electric motors in hybrid vehicles. The overarching goal of this project is to demonstrate that internal combustion engines can offer a practical and cost-effective alternative to hydrogen fuel cells without significant penalties in terms of efficiency and pollutant emissions. The design of this novel engine started from scratch, and both 1D and 3D CFD simulations were employed, with particular focus on optimizing the cylinder’s geometry and developing an efficient low-pressure injection system. The numerical methodology was based on state-of-the-art commercial codes, in line with established engineering practices. The numerical results indicated that the optimized engine configuration slightly surpasses the target performance, achieving 29 kW at 3000 rpm, while maintaining near-zero NOx emissions (<20 ppm) and high brake thermal efficiency (~40%) over a wide power range. Additionally, the cost of this engine is projected to be lower than an equivalent 4-stroke engine, due to fewer components (e.g., no cylinder head, poppet valves, or camshafts) and a lighter construction. Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

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19 pages, 5402 KiB

Open AccessArticle

Analysis of Energy Transfer in the Ignition System for High-Speed Combustion Engines

by Filip Szwajca, Krzysztof Wisłocki and Marcin Różański

Energies 2024, 17(20), 5091; https://doi.org/10.3390/en17205091 - 13 Oct 2024

Viewed by 1004

Abstract

In order to produce reliable and reproducible ignition of lean fuel–air mixtures and highly stratified mixtures, it is necessary to ensure a high concentration of spark discharge energy and to provide a strong energy impulse for the triggering of chain processes of chemical [...] Read more.

In order to produce reliable and reproducible ignition of lean fuel–air mixtures and highly stratified mixtures, it is necessary to ensure a high concentration of spark discharge energy and to provide a strong energy impulse for the triggering of chain processes of chemical decomposition of fuel molecules. For this reason, studies have been undertaken on the flow of electrical energy from the ignition system to the spark plug and on the formation of an electric discharge arc with a high concentration of thermal energy. The experimental results were obtained using an ignition coil energy test stand and a constant volume chamber with high-speed spark discharge recording capability. It was confirmed that increasing the charging time of the ignition coil from 0.5 ms to 5.0 ms increases the energy delivered to the coil from 9.5 mJ to 330 mJ. In the same range, the energy generated by the coil was recorded to range from 4.2 mJ to 70 mJ. The coil’s efficiency was found to decrease with increasing charging time from 45% up to 20.5%. Further energy losses were presented when the spark discharge energy was analyzed. In the paper, the results of investigations concerning electric discharge arc development have been presented, illustrated by a few exemplary photos, and discussed. The mathematical interpretation of the electrical energy flux in the ignition system resulting from the energy of the discharge arc has been conducted and illustrated by some functional independences and relationships. Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

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31 pages, 4715 KiB

Open AccessArticle

Physical and Energy Properties of Fuel Pellets Produced from Sawdust with Potato Pulp Addition

by Sławomir Obidziński, Paweł Cwalina, Małgorzata Kowczyk-Sadowy, Aneta Sienkiewicz, Małgorzata Krasowska, Joanna Szyszlak-Bargłowicz, Grzegorz Zając, Tomasz Słowik, Jacek Mazur and Marek Jankowski

Energies 2024, 17(16), 3960; https://doi.org/10.3390/en17163960 - 9 Aug 2024

Cited by 1 | Viewed by 3030

Abstract

This paper presents the findings of a study of the pelleting process of pine sawdust with the addition of waste in the form of potato pulp (as a natural binder), in the context of producing fuel pellets. The process of pelleting was carried [...] Read more.

This paper presents the findings of a study of the pelleting process of pine sawdust with the addition of waste in the form of potato pulp (as a natural binder), in the context of producing fuel pellets. The process of pelleting was carried out for sawdust and for a mixture of sawdust and potato pulp (10, 15, 20, and 25%). The highest moisture content was obtained in the case of pellets produced from a mixture of straw with a 25% potato pulp content, i.e., 26.54% (with a potato pulp moisture content of 85.08%). Increasing the potato pulp content in a mixture with sawdust from 10 to 25% reduced the power demand of the pelletizer by approx. 20% (from 7.35 to 5.92 kW). The obtained density values for pellets made from a mixture of sawdust and potato pulp (over 1000 kg∙m⁻³) with a potato pulp content of 10% make it possible to conclude that the obtained pellets meet the requirements of the ISO 17225-2:2021-11 standard. Increasing the potato pulp content from 0 to 25% caused a slight decrease in the heat of combustion, i.e., from 20.45 to 20.32 MJ∙kg⁻¹, as well as in the calorific value, from 19.02 to 18.83 MJ∙kg⁻¹ (both for dry sawdust matter and the mixture). The results of the laboratory tests were used to verify the densification process of mixtures of sawdust and potato pulp under industrial conditions at the PANBAH plant, using pelleting mixtures with a 5%, 10%, and 25% content of potato pulp. Industrial research also confirmed that the use of the addition of potato pulp in a mixture with sawdust significantly reduces the power demand of the pelletizer, and it also increases the kinetic strength of the obtained pellets. Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

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20 pages, 3460 KiB

Open AccessArticle

Hydroprocessing Microbial Oils for Advanced Road Transportation, Aviation, and Maritime Drop-In Fuels: Industrially Relevant Scale Validation

by Athanasios Dimitriadis, Loukia P. Chrysikou, Ioanna Kosma, Nikos Tourlakidis and Stella Bezergianni

Energies 2024, 17(15), 3854; https://doi.org/10.3390/en17153854 - 5 Aug 2024

Viewed by 1104

Abstract

Triacylglycerides (TAGs) produced via the syngas fermentation of biogenic residues and wastes were evaluated as a potential feedstock for advanced road transportation, aviation, and maritime drop-in fuels via hydroprocessing technology. Due to the limited availability of TAGs, a simulated feedstock (SM TAGs) was [...] Read more.

Triacylglycerides (TAGs) produced via the syngas fermentation of biogenic residues and wastes were evaluated as a potential feedstock for advanced road transportation, aviation, and maritime drop-in fuels via hydroprocessing technology. Due to the limited availability of TAGs, a simulated feedstock (SM TAGs) was utilized by blending various commercial oils, simulating the fatty acid composition of TAGs. At first, the simulated feedstock and the real TAGs were hydrotreated on a TRL 4 (technology readiness level) pilot plant to evaluate the potential of the SM feedstock to simulate the TAGs based on product quality. The hydrotreatment technology was evaluated and optimized on a TRL 4 plant. The research was further extended to a TRL 5 hydrotreatment plant with the optimum operating window for scaling up the technology. The resulting product was fractionated on a batch fractionation unit under vacuum to separate the jet and diesel fractions. The produced fuels were analyzed and evaluated based on the aviation Jet A1, EN590, EN15940, and marine diesel DMA specifications. The results show that the TAG composition was successfully simulated via a blend of vegetable oils. In addition, the hydrotreatment of the real TAGs and simulated feedstock resulted in similar-quality liquid products. The technology was successfully scaled up on a TRL 5 unit, leading to advanced, high-quality aviation and diesel drop-in fuels from TAGs, while the reaction pathways of hydrotreating can be controlled via the operating parameters of pressure, temperature, and H₂/oil ratio. The hydrotreatment process’s optimum conditions were 13.8 MPa pressure, 643 K temperature, 1 h⁻¹ liquid hourly space velocity (LHSV), and 5000 scfb hydrogen-to-oil ratio. Finally, a storage stability study of the hydrotreated liquid product showed that it can be stored for more than 6 months at ambient conditions without any noticeable changes to its properties. Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

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24 pages, 2500 KiB

Open AccessFeature PaperArticle

Simulation of a Continuous Pyrolysis Reactor for a Heat Self-Sufficient Process and Liquid Fuel Production

by Antonio Chavando, Valter Bruno Silva, Luís A. C. Tarelho, João Sousa Cardoso and Daniela Eusebio

Energies 2024, 17(14), 3526; https://doi.org/10.3390/en17143526 - 18 Jul 2024

Cited by 1 | Viewed by 1089

Abstract

This study investigates the potential of utilizing pyrolysis byproducts, including char and non-condensable gases, as an energy source to promote autothermal pyrolysis. A total of six pyrolysis experiments were conducted at three distinct cracking temperatures, namely, 450 °C, 500 °C, and 550 °C. [...] Read more.

This study investigates the potential of utilizing pyrolysis byproducts, including char and non-condensable gases, as an energy source to promote autothermal pyrolysis. A total of six pyrolysis experiments were conducted at three distinct cracking temperatures, namely, 450 °C, 500 °C, and 550 °C. The experiments utilized two types of biomasses, i.e., 100% pine chips and 75% pine chips mixed with 25% refuse-derived fuels (RDF). The findings from the experiments were subsequently incorporated into a process simulation conducted on Aspen Plus for an energy balance and a techno-economic analysis. The results of the experiments revealed that the energy produced by the byproducts utilizing only pine chips is 1.453 kW/kg, which is enough to fulfill the energy demand of the pyrolysis reactor (1.298 kW/kg). However, when 25% of RDF is added, the energy demand of the reactor decreases to 1.220 kW/kg, and the produced energy increases to 1.750 kW/kg. Furthermore, adding RDF increases bio-oil’s lower heating value (LHV). The techno-economic study proposed three scenarios: optimistic, conservative, and tragic. The optimistic has a payback period (PBP) of 7.5 years and a positive net present value (NPV). However, the other two scenarios were unfavorable, resulting in unfeasibility. Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

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17 pages, 1081 KiB

Open AccessArticle

Compatibility of Methanol-Hydrotreated Vegetable Oil Blends with Chosen Steels and Aluminum

by Huaying Wang-Alho, Katriina Sirviö, Carolin Nuortila, Jonna Kaivosoja, Maciej Mikulski and Seppo Niemi

Energies 2024, 17(14), 3423; https://doi.org/10.3390/en17143423 - 11 Jul 2024

Viewed by 956

Abstract

Methanol and hydrotreated vegetable oil (HVO) are complementary in the context of achieving ultra-low emission levels via low temperature combustion. HVO is a high-quality fuel fully compatible with compression ignition engines. Standalone methanol combustion is relatively straight-forward according to the Otto principle, with [...] Read more.

Methanol and hydrotreated vegetable oil (HVO) are complementary in the context of achieving ultra-low emission levels via low temperature combustion. HVO is a high-quality fuel fully compatible with compression ignition engines. Standalone methanol combustion is relatively straight-forward according to the Otto principle, with a spark ignited or in conventional dual-fuel (“liquid spark”) engines. These two fuels have by far the largest reactivity span amongst commercially available alternatives, allowing to secure controllable partially premixed compression ignition with methanol–HVO emulsification. This study investigates the corrosion of aluminum, carbon steel, stainless steel, and a special alloy of MoC210M/25CrMo4+SH, exposed to different combinations of HVO, HVO without additives (HVOr), methanol, and emulsion stabilizing additives (1-octanol or 1-dodecanol). General corrosive properties are well determined for all these surrogates individually, but their mutual interactions have not been researched in the context of relevant engine components. The experimental research involved immersion of metal samples into the fuels at room temperature for a duration of 60 days. The surfaces of the metals were inspected visually and the dissolution of the metals into fuels was evaluated by analyzing the fuels’ trace metal concentrations before and after the immersion test. Furthermore, this study compared the alterations in the chemical and physical properties of the fuels, such as density, kinematic viscosity, and distillation properties, due to possible corrosion products. Based on these results, methanol as 100% fuel or as blending component slightly increases the corrosion risk. Methanol had slight dissolving effect on aluminum (dissolving Al) and carbon steel (dissolving Zn). HVO, HVOr, and methanol–HVOr–co-solvents were compatible with the metals. No fuels induced visible corrosion on the metals’ surfaces. If corrosion products were formed in the fuel samples, they did not affect fuel parameters. Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

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18 pages, 2358 KiB

Open AccessEditor’s ChoiceArticle

Automotive e-Fuels via Hydrocracking of FT-Wax: e-Gasoline and e-Diesel Production

by Athanasios Dimitriadis, Loukia P. Chrysikou and Stella Bezergianni

Energies 2024, 17(11), 2756; https://doi.org/10.3390/en17112756 - 5 Jun 2024

Viewed by 1299

Abstract

The main goal of this research is the production of e-fuels in gasoline- and diesel-range hydrocarbons via the hydrocracking of wax from Fischer–Tropsch (FT-wax) synthesis. The hydrogen for the hydrocracking process originated from solar energy via water electrolysis, thus, the produced fuels were [...] Read more.

The main goal of this research is the production of e-fuels in gasoline- and diesel-range hydrocarbons via the hydrocracking of wax from Fischer–Tropsch (FT-wax) synthesis. The hydrogen for the hydrocracking process originated from solar energy via water electrolysis, thus, the produced fuels were called e-fuels. The FT-wax was produced via the Fischer–Tropsch synthesis of syngas stream from the chemical looping gasification (CLG) of biogenic residues. For the hydrocracking tests, a continuous-operation TRL3 (Technology Readiness Level) pilot plant was utilized. At first, hydrocracking catalyst screening was performed for the upgrading of the FT-wax. Three hydrocracking catalysts were investigated (Ni-W, Ni-W zeolite-supported, and Ni-W Al₂O₃-supported catalyst) via various operating conditions to identify the optimal operating window for each one. These three catalysts were selected, as they are typical catalysts that are used in the petroleum refinery industry. The optimal catalyst was found to be the NiW catalyst, as it led to high e-fuel yields (38 wt% e-gasoline and 47 wt% e-diesel) with an average hydrogen consumption. The optimum operating window was found at a 603 K reactor temperature, 8.3 MPa system pressure, 1 hr⁻¹ LHSV, and 2500 scfb H₂/oil ratio. In the next phase, the production of 5 L of hydrocracked wax was performed utilizing the optimum NiW catalyst and the optimal operating parameters. The liquid product was further fractionated to separate the fractions of e-gasoline, e-diesel, and e-heavy fuel. The e-gasoline and e-diesel fractions were qualitatively assessed, indicating that they fulfilled almost all EN 228 and EN 590 for petroleum-based gasoline and diesel, respectively. Furthermore, a 12-month storage study showed that the product can be stored for a period of 4 months in ambient conditions. In general, green transportation e-fuels with favorable properties that met most of the fossil fuels specifications were produced successfully from the hydrocracking of FT-wax. Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

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25 pages, 5904 KiB

Open AccessArticle

Start of Injection Influence on In-Cylinder Fuel Distribution, Engine Performance and Emission Characteristic in a RCCI Marine Engine

by Alireza Kakoee, Maciej Mikulski, Aneesh Vasudev, Martin Axelsson, Jari Hyvönen, Mohammad Mahdi Salahi and Amin Mahmoudzadeh Andwari

Energies 2024, 17(10), 2370; https://doi.org/10.3390/en17102370 - 14 May 2024

Cited by 1 | Viewed by 1462

Abstract

Reactivity-controlled compression ignition (RCCI) is a promising new combustion technology for marine applications. It has offered the potential to achieve low NO_x emissions and high thermal efficiency, which are both important considerations for marine engines. However, the performance of RCCI engines is [...] Read more.

Reactivity-controlled compression ignition (RCCI) is a promising new combustion technology for marine applications. It has offered the potential to achieve low NO_x emissions and high thermal efficiency, which are both important considerations for marine engines. However, the performance of RCCI engines is sensitive to a number of factors, including the start of injection. This study used computational fluid dynamics (CFD) to investigate the effects of start of ignition (SOI) on the performance of a marine RCCI engine. The CFD model was validated against experimental data, and the results showed that the SOI has a significant impact on the combustion process. In particular, the SOI affected the distribution of fuel and air in the combustion chamber, which in turn affected the rate of heat release and the formation of pollutants. Ten different SOIs were implemented on a validated closed-loop CFD model from 96 to 42 CAD bTDC (crank angle degree before top dead center) at six-degree intervals. A chemical kinetic mechanism of 54 species and 269 reactions tuned and used for simulation of in-cylinder combustion. The results show that in early injection, high-reactivity fuel was distributed close to the liner. This distribution was around the center of late injection angles. A homogeneity study was carried out to investigate the local equivalence ratio. It showed a more homogenous mixture in early injection until 66 CAD bTDC, after which point, earlier injection timing had no effect on homogeneity. Maximum indicated mean effective pressure (IMEP) was achieved at SOI 48 CAD bTDC, and minimum amounts of THC (total hydrocarbons) and NO_x were observed with middle injection timing angles around 66 CAD bTDC. Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

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20 pages, 7192 KiB

Open AccessEditor’s ChoiceArticle

Advanced Flame front Detection in Combustion Processes Using Autoencoder Approach

by Federico Ricci and Francesco Mariani

Energies 2024, 17(7), 1759; https://doi.org/10.3390/en17071759 - 6 Apr 2024

Cited by 1 | Viewed by 1552

Abstract

This research explores the detection of flame front evolution in spark-ignition engines using an innovative neural network, the autoencoder. High-speed camera images from an optical access engine were analyzed under different air excess coefficient λ conditions to evaluate the autoencoder’s performance. This study [...] Read more.

This research explores the detection of flame front evolution in spark-ignition engines using an innovative neural network, the autoencoder. High-speed camera images from an optical access engine were analyzed under different air excess coefficient λ conditions to evaluate the autoencoder’s performance. This study compared this new approach (AE) with an established method used by the same research group (BR) across multiple combustion cycles. Results revealed that the AE method outperformed the BR in accurately identifying flame pixels and significantly reducing overestimations outside the flame boundary. AE exhibited higher sensitivity levels, indicating its superior ability to identify pixels and minimize errors compared to the BR method. Additionally, AE’s accuracy in representing combustion evolution was notably improved, offering a more detailed depiction of the process. AE’s strength lies in its independence from specific threshold searches, a requirement in the BR method. By relying on learned representations within its latent space, AE eliminates laborious threshold exploration, ensuring reliability and reducing workload pressures. Comparative analyses consistently confirmed AE’s superior performance in accurately reproducing and delineating combustion evolution compared to BR. This study highlights AE’s potential as a promising technique for precise flame front detection in combustion processes. Its ability to autonomously extract features, minimize errors, and enhance overall accuracy signifies a significant step forward in analyzing flame fronts. AE’s reliability, reduced need for manual intervention, and adaptability across various conditions suggest a promising future for improving combustion analysis techniques in spark-ignition engines with optical access. Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

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Review

Jump to: Research

34 pages, 1560 KiB

Open AccessReview

Overview of the e-Fuels Market, Projects, and the State of the Art of Production Facilities

by Olaf Dybiński, Łukasz Szabłowski, Aliaksandr Martsinchyk, Arkadiusz Szczęśniak, Jarosław Milewski, Andrzej Grzebielec and Pavel Shuhayeu

Energies 2025, 18(3), 552; https://doi.org/10.3390/en18030552 - 24 Jan 2025

Viewed by 385

Abstract

E-fuels, or synthetic fuels produced from green hydrogen and captured CO₂, are a promising solution for achieving climate neutrality by replacing fossil fuels in transportation and industry. They help reduce greenhouse gas emissions and efficiently utilize renewable energy surpluses. This study [...] Read more.

E-fuels, or synthetic fuels produced from green hydrogen and captured CO₂, are a promising solution for achieving climate neutrality by replacing fossil fuels in transportation and industry. They help reduce greenhouse gas emissions and efficiently utilize renewable energy surpluses. This study aims to assess the current state and future potential of e-fuel production technologies, focusing on their scalability and market integration. A comprehensive literature review and market trend analysis, including modeling based on historical data and growth forecasts, were used to estimate market penetration. Results indicate that e-fuels could reach a 10% market share within the next 5 years, potentially reaching 30% in 20 years, particularly in aviation, maritime transport, and the steel industry. Ongoing projects expected to be completed this decade may cover about 20% of the global liquid fuel demand for transportation. However, challenges such as high costs, scalability, and recent project terminations due to funding shortages highlight the need for substantial investment, regulatory support, and innovation. Global collaboration and policy alignment are essential for the successful development and integration of e-fuels as a critical pathway to decarbonization. Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

30 pages, 5273 KiB

Open AccessFeature PaperReview

Alcohols as Biofuel for a Diesel Engine with Blend Mode—A Review

by Arkadiusz Jamrozik and Wojciech Tutak

Energies 2024, 17(17), 4516; https://doi.org/10.3390/en17174516 - 9 Sep 2024

Cited by 4 | Viewed by 1093

Abstract

In the era of decarbonization driven by environmental concerns and stimulated by legislative measures such as Fit for 55, the industry and transportation sectors are increasingly replacing petroleum-based fuels with those derived from renewable sources. For many years, the share of these fuels [...] Read more.

In the era of decarbonization driven by environmental concerns and stimulated by legislative measures such as Fit for 55, the industry and transportation sectors are increasingly replacing petroleum-based fuels with those derived from renewable sources. For many years, the share of these fuels in blends used to power compression ignition engines has been growing. The primary advantage of this fuel technology is the reduction of GHG emissions while maintaining comparable engine performance. However, these fuel blends also have drawbacks, including limited ability to form stable mixtures or the requirement for chemical stabilizers. The stability of these mixtures varies depending on the type of alcohol used, which limits the applicability of such fuels. This study focuses on evaluating the impact of eight types of alcohol fuels, including short-chain (methanol, ethanol, propanol) and long-chain alcohols (butanol, pentanol, hexanol, heptanol, and octanol), on the most critical operational parameters of an industrial engine and exhaust emissions. The engines being compared operated at a constant speed and under a constant load, either maximum or close to maximum. The study also evaluated the effect of alcohol content in the mixture on combustion process parameters such as peak cylinder pressure and heat release, which are the basis for parameterizing the engine’s combustion process. Determining ignition delay and combustion duration is fundamental for optimizing the engine’s thermal cycle. As the research results show, both the type of alcohol and its concentration in the mixture influence these parameters. Another parameter important from a usability perspective is engine stability, which was also considered. Engine performance evaluation also includes assessing emissions, particularly the impact of alcohol content on NO_x and soot emissions. Based on the analysis, it can be concluded that adding alcohol fuel to diesel in a CI engine increases ignition delay (up to 57%), p_max (by approximately 15–20%), HRR_max (by approximately 80%), and PPR_max (by approximately 70%). Most studies indicate a reduction in combustion duration with increasing alcohol content (by up to 50%). For simple alcohols, an increase in thermal efficiency (by approximately 15%) was observed, whereas for complex alcohols, a decrease (by approximately 10%) was noted. The addition of alcohol to diesel slightly worsens the stability of the CI engine. Most studies pointed to the positive impact of adding alcohol fuel to diesel on NOx emissions from the compression ignition engine, with the most significant reductions reaching approximately 50%. Increasing the alcohol fuel content in the diesel blend significantly reduced soot emissions from the CI engine (by up to approximately 90%). Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

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32 pages, 6774 KiB

Open AccessEditor’s ChoiceReview

A Comprehensive Review on the Hydrogen–Natural Gas–Diesel Tri-Fuel Engine Exhaust Emissions

by Hassan Sadah Muhssen, Máté Zöldy and Ákos Bereczky

Energies 2024, 17(15), 3862; https://doi.org/10.3390/en17153862 - 5 Aug 2024

Cited by 4 | Viewed by 1187

Abstract

Natural gas (NG) is favored for transportation due to its availability and lower CO₂ emissions than fossil fuels, despite drawbacks like poor lean combustion ability and slow burning. According to a few recent studies, using hydrogen (H₂) alongside NG and [...] Read more.

Natural gas (NG) is favored for transportation due to its availability and lower CO₂ emissions than fossil fuels, despite drawbacks like poor lean combustion ability and slow burning. According to a few recent studies, using hydrogen (H₂) alongside NG and diesel in Tri-fuel mode addresses these drawbacks while enhancing efficiency and reducing emissions, making it a promising option for diesel engines. Due to the importance and novelty of this, the continuation of ongoing research, and insufficient literature studies on HNG–diesel engine emissions that are considered helpful to researchers, this research has been conducted. This review summarizes the recent research on the HNG–diesel Tri-fuel engines utilizing hydrogen-enriched natural gas (HNG). The research methodology involved summarizing the effect of engine design, operating conditions, fuel mixing ratios and supplying techniques on the CO, CO₂, NO_x and HC emissions separately. Previous studies show that using natural gas with diesel increases CO and HC emissions while decreasing NO_x and CO₂ compared to pure diesel. However, using hydrogen with diesel reduces CO, CO₂, and HC emissions but increases NO_x. On the other hand, HNG–diesel fuel mode effectively mitigates the disadvantages of using these fuels separately, resulting in decreased emissions of CO, CO₂, HC, and NO_x. The inclusion of hydrogen improves combustion efficiency, reduces ignition delay, and enhances heat release and in-cylinder pressure. Additionally, operational parameters such as engine power, speed, load, air–fuel ratio, compression ratio, and injection parameters directly affect emissions in HNG–diesel Tri-fuel engines. Overall, the Tri-fuel approach offers promising emissions benefits compared to using natural gas or hydrogen separately as dual-fuels. Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

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35 pages, 2809 KiB

Open AccessReview

Advancements and Challenges of Ammonia as a Sustainable Fuel for the Maritime Industry

by Antonio Chavando, Valter Silva, João Cardoso and Daniela Eusebio

Energies 2024, 17(13), 3183; https://doi.org/10.3390/en17133183 - 28 Jun 2024

Cited by 2 | Viewed by 3418

Abstract

The maritime industry needs sustainable, low-emission fuels to reduce the environmental impact. Ammonia is one of the most promising alternative fuels because it can be produced from renewable energy, such as wind and solar. Furthermore, ammonia combustion does not emit carbon. This review [...] Read more.

The maritime industry needs sustainable, low-emission fuels to reduce the environmental impact. Ammonia is one of the most promising alternative fuels because it can be produced from renewable energy, such as wind and solar. Furthermore, ammonia combustion does not emit carbon. This review article covers the advantages and disadvantages of using ammonia as a sustainable marine fuel. We start by discussing the regulations and environmental concerns of the shipping sector, which is responsible for around 2% to 3% of global energy-related CO₂ emissions. These emissions may increase as the maritime industry grows at a compound annual growth rate of 4.33%. Next, we analyze the use of ammonia as a fuel in detail, which presents several challenges. These challenges include the high price of ammonia compared to other fossil fuels, the low reactivity and high toxicity of ammonia, NOx, and N₂O emissions resulting from incomplete combustion, an inefficient process, and NH₃ slipping. However, we emphasize how to overcome these challenges. We discuss techniques to reduce NOx and N₂O emissions, co-combustion to improve reactivity, waste heat recovery strategies, the regulatory framework, and safety conditions. Finally, we address the market trends and challenges of using ammonia as a sustainable marine fuel. Full article

(This article belongs to the Special Issue Renewable Fuels for Internal Combustion Engines: 2nd Edition)

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