Search Results (354)

In this study, cottonseed oil biodiesel and waste lard biodiesel were produced through a transesterification process and blended with conventional diesel at different ratios (B10 and B20). The performance and emission characteristics of these fuels were systematically evaluated in a single-cylinder, four-stroke, water-cooled diesel engine operating at speeds of 1000–1800 rpm under a constant 50% load. The physicochemical properties of the fuels were analyzed, and engine parameters including brake-specific fuel consumption (BSFC), brake thermal efficiency (BTE), exhaust gas temperature (EGT), and emissions of carbon monoxide (CO), hydrocarbon (HC), carbon dioxide (CO₂), and nitrogen oxides (NOx) were measured. The results demonstrated that, compared with diesel, biodiesel blends significantly reduced CO, HC, and CO₂ emissions. At 1800 rpm, the LB20 blend showed reductions of 31.03% in CO, 47.06% in HCs, and 19.14% in CO₂ relative to diesel. These reductions are mainly attributed to the higher oxygen content and lower hydrogen-to-carbon ratio of biodiesel, which promote more complete combustion. However, all biodiesel blends exhibited higher NOx emissions than diesel, with the increase being more pronounced at higher blend ratios. At 1800 rpm, the LB20 blend recorded the highest NOx emissions, which were 20.63% higher than those of diesel under the same condition. In terms of performance, biodiesel blends showed higher BSFC and lower BTE compared with diesel, mainly due to their lower calorific value and higher viscosity. The lowest BTE and the highest BSFC were both observed with the LB20 blend, at 22.64% and 358.11 g/kWh, respectively. Full article

The growing dependence on fossil fuels has raised concerns over energy security, resource depletion, and environmental impacts, driving the need for renewable alternatives. Coffee husk, a widely available agro-industrial residue, represents an underutilized feedstock for biodiesel production. In this study, biodiesel was synthesized from coffee husk oil using a two-step transesterification process to address its high free fatty acid content (21%). Physicochemical analysis showed that Coffee Husk Oil Methyl Ester (CHOME) possessed a density of 863 kg m⁻³, viscosity of 4.85 cSt, and calorific value of 33.51 MJ kg⁻¹, compared to diesel with 812 kg m⁻³, 2.3 cSt, and 42.4 MJ kg⁻¹. FTIR analysis confirmed the presence of ester carbonyl and C–O functional groups characteristic of CHOME, influencing its combustion behavior. Engine tests were then conducted using B0, B10, B30, B50, and B100 blends under different loads, both with and without fuel preheating. Results showed that neat CHOME (B100) exhibited 11.8% lower brake thermal efficiency (BTE) than diesel, but preheating at 95 °C improved BTE by 5%, with preheated B10 slightly surpassing diesel by 0.5%. Preheating also reduced brake-specific fuel consumption by up to 7.75%. Emission analysis revealed that B100 achieved reductions of 6.4% CO, 8.3% HC, and 7.0% smoke opacity, while NOx increased only marginally (2.86%). Overall, fuel preheating effectively mitigated viscosity-related drawbacks, enabling coffee husk biodiesel to deliver competitive performance with lower emissions, highlighting its potential as a sustainable waste-to-energy fuel. Full article

Internal combustion engines remain a predominant source of global energy consumption, contributing substantially to both operational costs and greenhouse gas emissions. This work evaluates a nanomaterial-based engine oil additive that reduces friction and wear and increases torque, horsepower, and fuel efficiency. This novel nano oil additive contains functionalized carbon nanotubes and hexagonal boron nitride nanosheets that are dispersed in base oil using a proprietary ultrasonication process. Block-on-ring tests performed by multiple testing facilities demonstrated up to a 17% decrease in coefficient of friction and up to a 78% decrease in wear compared to the base oil after treating with the nano oil additive. Thermal properties enhancement by the nano oil additive was evaluated and increases up to 17 °C in thermal stability were obtained. Additionally, the nano oil additive increased torque and horsepower by an average of 7% in motorcycles and 2.4% in pickup trucks. Most importantly, the nano oil additive demonstrated improvements in fuel economy in both gasoline and diesel engines, with laboratory tests reporting 3–5% increases and practical field tests on a commercial truck fleet reporting an average of a 6% increase. The improved engine efficiency leads to reduced turbo temperature in heavy diesel engines and prolonged engine life expectancy and will significantly improve global environmental sustainability. Full article

Ammonia (NH₃) is a promising carbon-free fuel for internal combustion engines, but its low reactivity and poor ignition properties present significant challenges for stable operation. This study presents the development and experimental validation of a spark-ignited combustion process that enables stable engine operation using 100% liquid NH₃ as a single fuel. A modified single cylinder research engine, equipped with NH₃ port fuel injection and a high-energy capacitive ignition system was used to investigate combustion behavior under various load conditions. The results show that stable, knock-free combustion with pure NH₃ is feasible at every operating point without any ignition aids like diesel fuel or hydrogen (H₂). The full load conditions of a diesel engine can be represented with an indicated efficiency of 50% using this combustion process. The emission measurements show nitrogen oxides (NO_x) and NH₃ emissions in a 1:1 ratio, which is advantageous for a passive SCR system. Increased nitrous oxides (N₂O) formation occurs at low loads and cold combustion chamber temperatures. This work demonstrates the technical viability of carbon-free NH₃ combustion in spark-ignited (SI) engines and represents a promising step towards net-zero combustion. Full article

The ammonia-n-heptane reaction mechanism is essential for simulation of the in-cylinder process for diesel-ignited ammonia engines. To gain insight into the differences in predictive performance among various ammonia-n-heptane reaction mechanisms, four mechanisms were comprehensively evaluated and analyzed based on the modeling of ignition, oxidation, laminar flame propagation and in-cylinder combustion processes. The result shows that only under high ammonia blending ratios and elevated temperatures are discrepancies in predicted ignition delay times observed among the studied reaction mechanisms. Regarding the oxidation process, on the whole, the concerned mechanisms can reasonably predict concentrations of reactants and complete combustion products. However, significant discrepancies exist among the mechanisms in predicting concentrations of intermediate species and other products. For laminar burning velocity, the modeled values from the studied mechanisms are consistent with experimental results under both fuel-lean and -rich conditions. The Wang mechanism exhibits significant deviations from the other three mechanisms in predicting reaction pathways of ammonia and n-heptane. From the perspective of reaction class, the studied mechanisms are similar to each other, to some extent, in the key reactions governing consumption of ammonia and n-heptane. For the engine simulation, the predicted in-cylinder pressure and temperature profiles show minimal variations across different reaction mechanisms. In conclusion, the Fang mechanism can be selected to understand more accurately ignition, oxidation and flame characteristics of ammonia-n-heptane mixtures, while to reduce the engineering computational cost of the engine simulation, the Wang mechanism tends to be a good choice. Full article

With the increased power density of internal combustion engines (ICE) and growing demands for lightweight design, the connecting rod big-end bearings are subjected to significant alternating loads. Consequently, the interference–fit interfaces become susceptible to fretting damage, which can markedly shorten engine service life and impair reliability. In the present study, the effects of the big end manufacturing process, bolt preload, and bearing bush interference fit are considered to develop a coupled lubrication–dynamic model of the connecting rod big-end bearing. This model investigates the fretting damage issue in the bearing bush of a marine diesel engine’s connecting rod big end. The results indicate that the relatively low stiffness of the big end is the primary cause of bearing bush fretting damage. Interference fit markedly affects fretting wear on the bush back, whereas the influence of bolt preload is secondary; nevertheless, a decrease in either parameter enlarges the fretting distance. Based on these findings, an optimized design scheme is proposed. Full article

Universities play a critical role in shaping sustainable mobility strategies, especially in urban contexts where the institutional transport system can influence environmental and social outcomes. This study integrates Environmental and Social Life Cycle Assessment (E-LCA and S-LCA) to evaluate the current university transport system from internal combustion engines, diesel, and compressed natural gas (CNG), focusing on the operation and maintenance phases. Also, it compares seven scenarios, including electric, renewable sources, and biodiesel technologies. Environmental impacts were assessed using the ReCiPe 2016 midpoint method, which considers the following impact categories: Global Warming Potential (GWP); Ozone Formation, Human Health (OfHh); Ozone Formation, Terrestrial Ecosystem (OfTe); Terrestrial Acidification (TA); and Fine Particulate Matter Formation (FPmf). The sensitivity analysis explores scenarios to assess the effects of technological transitions and alternative energy sources on the environmental performance. Social impacts are assessed through a Social Performance Index (SPI) and Aggregated Social Performance Index (ASPI), which aggregates indicators such as safety, travel cost, punctuality, accessibility, and inclusive design. Accessibility emerged as the lowest indicator (ranging from 0.61 to 0.67), highlighting opportunities for improvement. Our findings support decision-making processes for integrating sustainable transport strategies into a University Mobility Plan, emphasizing the importance of combining technical performance with social inclusivity. Full article

Electric passenger vehicles are set to dominate the European car market, driven by EU climate policies and the 2035 ban on internal combustion engine production. This study assesses the sustainability of this transition, focusing on global warming potential and Critical Raw Material (CRM) extraction throughout its life cycle. The intensive use of CRMs raises environmental, economic, social, and geopolitical concerns. These materials are scarce and are concentrated in a few politically sensitive regions, leaving the EU highly dependent on external suppliers. The extraction, transport, and refining of CRMs and battery production are high-emission processes that contribute to climate change and pose risks to ecosystems and human health. A Life Cycle Assessment (LCA) was conducted, using OpenLCA software and the Ecoinvent 3.10 database, comparing a Peugeot 308 in its diesel and electric versions. This study adopts a cradle-to-grave approach, analyzing three phases: production, utilization, and end-of-life treatment. Key indicators included Global Warming Potential (GWP100) and Abiotic Resource Depletion Potential (ADP) to assess CO₂ emissions and mineral resource consumption. Technological advancements could mitigate mineral depletion concerns. Li-ion battery recycling is still underdeveloped, but has high recovery potential, with the sector expected to expand significantly. Moreover, repurposing used Li-ion batteries for stationary energy storage in renewable energy systems can extend their lifespan by over a decade, decreasing the demand for new batteries. Such innovations underscore the potential for a more sustainable electric vehicle industry. Full article

In the era of depletion of fossil fuels, there is an intensive search for renewable fuels for the internal combustion engine, which is the most efficient thermal machine in the power range of several kW to several MW. Hence, this article discusses the results of research on the combustion of renewable fuels such as hydrotreated vegetable oil (HVO) and the rapeseed methyl ester (RME) with the addition of hydrogen, injected in its gaseous form into the intake manifold. The thermodynamic analysis presented in the article discusses progress in the combustion process of these fuels depending on the hydrogen content. The parameters for diesel fuel combustion are given as a reference point. Based on the obtained results, one can conclude that adding hydrogen increases the maximum combustion pressure in the cylinder and significantly accelerates the combustion process in the premixed combustion phase, thus reducing the share of the diffusion combustion phase. This significantly affects exhaust toxic emissions. In connection with this, a shortening of the flame kernels development phase was observed, calculated as the time expressed by the crank angle, to release heat of 10%, and a slight extension of the main combustion phase, managed as the period of the heat released from 10 to 90% was observed as well. Full article

The ammonia energy ratio (AER) is a critical parameter influencing the performance of ammonia/diesel dual-fuel engines. In this study, a numerical simulation was conducted based on a high-pressure dual-fuel (HPDF) direct injection ammonia/diesel engine to investigate the impact of the AER on combustion and emissions under two distinct combustion modes. By adjusting the ammonia start of injection timing (ASOI), the combustion mode was transitioned from diffusion combustion (HPDF1) to partially premixed combustion (HPDF2). The results show that under the HPDF1 mode, a three-stage heat release pattern is observed, and the evolution curves of NO and NO₂ exhibit fluctuations similar to the heat release process. As the AER increases, the second heat release stage is suppressed, the high-temperature region narrows, the ignition delay is extended, and the CA10–CA50 interval shortens, leading to a higher maximum pressure rise rate (MPRR) at a high AER. Conversely, in the HPDF2 mode, the combustion process is characterized by a two-stage heat release. With an increasing AER, the high-temperature region expands, the ignition delay and CA10–CA50 interval are prolonged, while the CA50–CA90 interval shortens, and the MPRR becomes the lowest at a high AER. For both combustion modes, total greenhouse gas (GHG) emissions decrease with an increasing AER. However, in the HPDF2 mode with an AER = 95%, N₂O accounts for up to 78% of the total GHG emissions. Additionally, a trade-off relationship exists between NOx emissions and indicated thermal efficiency (ITE). When the ASOI is set to −8°CA ATDC, the engine operates in a transitional combustion mode between HPDF1 and HPDF2. At this point, setting the AER to 95% effectively mitigates the trade-off, achieving an ITE of 53.56% with NOx emissions as low as 578 ppm. Full article

Heavy fuel oil (HFO) is a widely used fuel in compression ignition engines, primarily in Brazilian thermoelectric plants, mainly due to its availability, low cost, and low operational expenses. However, heavy fuel oil is not compatible with most diesel engines and combustion systems in use and must be treated to maintain combustion process efficiency. The high viscosity of heavy fuel oil must be reduced before being introduced into the engine. To achieve this, appropriate heating devices are added to the fuel lines, with steam being the primary working fluid in these devices. Steam-generating boilers that burn fossil fuels, including HFO itself, are the most viable option from an economic standpoint and in terms of utilizing locally available fuels for this function. However, the need to mitigate the effects of environmental pollution has encouraged the adoption of other types of boilers, such as electric ones. In this work, a case study of a combustion steam generator installed in a Brazilian thermoelectric plant is developed. This study involves the thermodynamic and combustion modeling of the steam generator through the balancing of the respective thermodynamic and combustion equations. The models and the proposed chemical formula of HFO were validated, and through simulations using real data collected during the boiler’s operation throughout 2024, it was also possible to estimate the carbon dioxide emissions produced. Additionally, a hypothetical scenario was simulated in which the combustion boiler currently installed in the plant is replaced by two electric boilers. A simple economic analysis demonstrated that such a replacement would result in a total steam production cost of only 25% of the amount spent on the current combustion boiler, in addition to reducing $C{O}_2$ emissions to the atmosphere by 62.55 tons. Full article

This article presents the test results of a turbocharged Common Rail Direct Injection (CRDI) diesel engine operating on diesel fuel and methyl ester biodiesel with nanoparticle additives. The use of nanomaterials has been shown to improve the combustion process. In this study, various nanoparticles, including zinc oxide and carbon plates, were investigated as additives to enhance the combustion performance of selected fuels. The fuel of choice was conventional diesel, and a methyl ester of rapeseed oil called biodiesel. A turbocharged Common Rail Direct Injection (CRDI) diesel engine, model FIAT 192A1000, was used for the experiments. The following engine parameters were measured and recorded: torque (Ms, Nm), fuel consumption (Bd, kg/h), carbon monoxide (CO, ppm), and nitrogen oxides (NO_x, ppm). The results show that nanoparticles can improve the combustion performance of the fuels studied in the engine. However, the effect of nanoparticles on engine parameters varied. In summary, the influence of nanoparticles is noticeable: the ID is shorter with diesel fuel with carbon nanotubes at 50 ppm and 100 ppm concentration, the NO_x is reduced with zinc oxide and D, and CO is diminished in all load modes when using RME with carbon nanotubes. Full article

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

This study examined how adding ethanol to diesel fuel affects combustion characteristics, cylinder pressure and NO_x emissions in an AVL engine. The research focused on key engine parameters, including autoignition delay, in-cylinder pressure rise rates, the peaks of the mean in-cylinder temperature and NO_x emissions. Three fuel types were tested: pure diesel (DF) and blends with 10 and 20% ethanol by volume (DF10 and DF20). The results obtained indicate that increasing the ethanol content in diesel fuel significantly affects the combustion process of the fuel mixture, particularly in its early stage, reducing the benefits of the pilot fuel injection. Moreover, it was observed that the combustion of the DF20 mixture leads to a substantially higher pressure increase in the cylinder, exceeding the values recorded for pure diesel fuel by approximately 25%. Furthermore, the study revealed that ethanol addition increases the peaks of the mean in-cylinder temperature, with a recorded difference of up to 60 °C between pure diesel fuel and DF20. Since NO_x formation is highly temperature-dependent, this temperature rise is likely to result in higher NO_x concentration. Additionally, a slight effect of ethanol on increasing the ignition delay angle was observed. This remained minor, and did not exceed approximately 1 CA. These findings highlight the complex relationship between ethanol content in diesel fuel, combustion dynamics, and emissions. They emphasize the need for optimizing the injection process for ethanol–diesel blends to balance the benefits of ethanol addition with potential challenges related to combustion efficiency, engine load and NO_x concentration. Full article

Dual-fuel combustion technology allows for lower emissions of particulate matter (PM) and nitrogen oxide (NOx). However, under low load conditions, this mode of combustion has large amounts of emissions of carbon monoxide (CO) and unburned hydrocarbons (HCs) and low thermal efficiency. Several solutions have been presented to solve the issues associated with this operating mode. Optimizing the injection strategy is a potential method to enhance engine performance and reduce emissions, given that the injection parameters have significant effects on the combustion process. The present investigation optimized a methane/diesel dual-fuel engine’s emissions and performance using response surface methodology (RSM). Three parameters were investigated as input variables: dwell time (DT), diesel pre-injection timing (IT), and engine load (EL). RSM was used to optimize brake thermal efficiency (BTE), NOx emissions, and HC emissions, aiming to identify the best combination of these input factors. The RSM analysis revealed that the optimal combination of input parameters for achieving maximum BTE and minimum NOx and HC emissions is an 87% engine load, an 8° crank angle (CA) dwell time, and a 11° bTDC pre-injection timing. The RSM model demonstrated high accuracy with a prediction error less than 4%. Full article