Utilization of bulk nanobubbles to influence combustion characteristics of liquid fuels

Abstract Raramuri Criollo (RC) cattle offer substantial sustainability advantages in arid regions. Their adaptation to harsh conditions and ability to adjust forage use according to the season make them efficient in pasture management. Furthermore, their lighter weight reduces soil pressure, and their preference for low-palatability grasses contributes to improved soil health and reduced erosion. These characteristics from RC make them more adaptable to such terrains and conditions than European cattle breeds. Regarding water usage, and compared to European cattle breeds, RC can wander further from water sources, which proves advantageous in the context of climate change. Moreover, their role in fire ecology involves reducing the risk of fires by altering the characteristics of forest fuels and managing fine fuels, which is crucial for minimizing fire hazards in grasslands. The potential use of this breed to produce high-quality meat derived from their grazing behaviour offers an alternative to new consumers’ demands concerning healthy and efficient production options. This narrative review discusses the role of RC in soil health, water sources, and meat production. Overall, attributes from RC cattle make these animals a valuable option for mitigating overgrazing and fostering sustainability in arid regions.

Abstract Butyl palmitate is a long-chain fatty acid ester, similar to fatty acid methyl esters that formulate biodiesel. Butyl palmitate was synthesized in the laboratory by esterification of palmitic acid recovered from depolymerized plastic waste from Malviya National Institute of Technology, Jaipur, India. Butanol used for reaction was purchased from market. The synthesized Butyl palmitate was then tested as a fuel in engine. In this experimental investigation, the impact of diesel and BP25 (75% (v/v) diesel blended with 25%(v/v) butyl palmitate) fuel was evaluated on engine performance, emissions, soot morphology, and nano structural properties. For a comparatives analysis, the experiments were carried out at 3.5 kW@1500rpm in a water cooled, single cylinder, four-stroke diesel engine. The study investigated performance (brake thermal efficiency), combustion (in-cylinder pressure), emissions (HC, CO, NOx), and soot characteristics (morphology, nanostructure via TEM, Raman, and FTIR analyses) of the test fuels. This sustainable biofuel and overall experimental investigation contribute to societal goals such as public health and climate action.

Ammonia has great potential as a clean energy alternative and can contribute to reducing carbon emissions from conventional fossil fuels. To investigate the combustion characteristics of ammonia-doped natural gas and to evaluate its feasibility for practical applications, this study experimentally and numerically examined the temperature and pressure variations of ammonia-doped natural gas mixtures under different initial pressures. In addition, the combustion products corresponding to different ammonia doping ratios were simulated and analyzed. The results indicate that, with increasing ammonia doping ratio, both combustion temperature and pressure decrease to varying degrees. Under atmospheric pressure, the combustion temperature generally decreases by approximately 25%, while the peak pressure reduction reaches up to 87.85% in certain cases. Furthermore, under negative pressure conditions, a relatively low ammonia doping ratio enhances the combustion intensity of the mixture, and the peak combustion temperature occurs at lower ammonia concentrations. From an environmental perspective, the variation in combustion products with ammonia doping ratio was further analyzed. The results show that the CO concentration in the combustion products decreases progressively by approximately 71.11% as the ammonia doping ratio increases. In contrast, the NO concentration increases to a maximum value and then remains nearly constant, whereas the NO2 concentration initially increases and subsequently decreases after reaching a peak value of 0.813 ppm. Overall, these findings provide experimental and theoretical support for understanding the combustion characteristics of mixed gaseous fuels and offer a scientific basis for the application and safety assessment of ammonia-doped natural gas.

ABSTRACT Research on two-phase fuels has advanced significantly in rotating detonation engines. However, the combustion process of liquid-phase fuels involving multiple complex stages like evaporation, mixing, and chemical reactions has not been studied in-depth. In order to investigate the macroscopic physical characteristics and performance of two-phase kerosene rotating detonation, this study employs a two-dimensional numerical simulation to compare the combustion processes and characteristics of gas-phase and two-phase fuels under inhomogeneous conditions. The results demonstrate that for gas-phase fuels, the detonation wave intensity exhibits a negative correlation with the injection total temperature and a positive correlation with the injection total pressure. In contrast, for two-phase fuels, the detonation wave intensity reaches a maximum at an optimal injection total temperature within a specific pressure range. Furthermore, an in-depth analysis is conducted on the diameter variation and spatial distribution of droplets within the flow field. Finally, a concept characterizing the intensity of detonation waves was proposed. This concept can represent thrust to a certain extent and provides the operational range of detonation waves under different fuels. This research provides a theoretical basis for the design and optimization of rotating detonation engines, especially for the application of two-phase fuels.

combustion spread behavior and heat transfer characteristics of forest fuels under Point-Source ignition

Evaluation of the combustion characteristics of polymeric solid fuels for solid fuel scramjets

Accurate vertical distribution of fire-induced heat fluxes in the atmosphere is critical for realistic coupled fire–atmosphere simulations. In response to concerns raised by Shamsaei et al. (2023) regarding potential energy conservation issues in the WRF-SFIRE heat distribution scheme, this study first conducts a comprehensive theoretical analysis, demonstrating that the original exponential formulation exhibits negligible error under typical domain configurations. Then, it introduces a novel formulation, called the Versatile Energy-Conservative Distribution scheme, that rigorously guarantees energy conservation while providing enhanced flexibility in specifying vertical distribution profiles. The proposed method accommodates multiple profiles, including exponential, Gaussian, and gamma, and enables the independent treatment of surface and canopy heat fluxes, thereby yielding a more flexible representation of fire heat fluxes. Numerical evaluations on both fine and coarse non-uniform meshes confirm that the new formulation maintains perfect energy balance across various configurations and overcomes the limitations observed in other schemes, such as the truncated Gaussian approach. These advancements not only refute previous claims of significant energy misrepresentation but also offer a robust and flexible framework intended to improve the representation of fire–atmosphere interactions in numerical models.

Paulownia forestry in Japan has traditionally focused on producing high-value solid wood for traditional household goods. In the present study, to explore the potential of a new Paulownia plantation forestry model aimed at meeting Japan’s increasing demand for biofuels, the volume and weight of stems and the fuel characteristics of wood and bark were investigated for 15 four-year-old Paulownia trees planted in Tochigi, Japan. Fuel characteristics were also examined for nine common Japanese species as a reference. For Paulownia species, the bark had higher extractives, ash, and Klason lignin, lower contents of holocellulose and α-cellulose, and higher gross calorific value than wood. Potassium was the predominant inorganic component in both wood and bark in Paulownia species. Although the gross calorific value per unit volume of Paulownia species was the lowest among the tested nine Japanese species, the estimated annual gross calorific value per unit area was almost the same between Paulownia species and Cryptomeria japonica (the most common plantation softwood species in Japan) when the whole stem was used for biofuel production. Thus, Paulownia species might be used for biofuel production under short rotation cycles, even in lower bulk density of wood. On the other hand, wood from higher stem positions exhibited lower moisture content in Paulownia species. Therefore, drying costs might be reduced by using the lower stem portions for solid wood production, improving the overall economic efficiency of biofuel production.

Abstract The plasma fueling system is an indispensable component in current fusion devices and is required to compensate for continuous particle loss. Recently, a low-temperature supersonic molecular beam injection (LT-SMBI) system has been developed and implemented successfully to increase the fueling efficiency on the Experimental Advanced Superconducting Tokamak (EAST). The fueling gas in the reservoir tank is cryogenically cooled to a temperature lower than 120 K before injection to increase the size of the clusters and their formation probability in the beam. A series of LT-SMBI experiments were conducted on EAST, and the fueling characteristics, including the fueling efficiency, delay time, injection depth, and fuel consumption, were compared with those of room-temperature SMBI (RT-SMBI). The experimental results demonstrate that LT-SMBI results in greater plasma density enhancement with an equivalent number of injected particles. The fueling efficiency of both SMBI systems decreases with increasing plasma density. Compared with the RT-SMBI, the LT-SMBI results in about 5–7 cm deeper injection depth, as measured via microwave reflectometry. Furthermore, the fueling gas consumption is decreased by 33% in the feedback control experiments using the LT-SMBI. Although LT-SMBI has a longer delay time because of its low temperature, it is recognized as an efficient method for plasma fueling and other impurity injections, such as edge localized mode mitigation and divertor heat flux reduction, for EAST and future fusion devices.

Performance and emission characteristics of methanol and methanol-blended gasoline fuels in a high compression ratio SI engine

Overview of combustion and emission characteristics of sustainable aviation fuels and standard JET A-1 fuel

Spray dynamic collapse characteristics and mechanism induced by alcohol addition

Evaluating performance, emission and stability characteristics of alcohol fuels in reactivity-controlled compression ignition combustion

The objective of this study is to investigate the effects of Mn2O3 nanoparticle additives on the performance and emission characteristics of biodiesel fuels produced from vegetable- and waste-based oils. Biodiesel fuels were synthesized via the transesterification process, after which Mn2O3 nanoparticles were blended in different concentrations (50, 75, and 100 ppm). The prepared fuels were tested in a single-cylinder diesel engine operating under constant speed and variable load conditions. Engine performance parameters such as specific fuel consumption (SFC) and thermal efficiency, along with emission indicators including CO, HC, NOx, smoke opacity, and exhaust gas temperature, were systematically analyzed. Additionally, the experimental findings were modeled and validated using the machine learning-based linear regression method. The addition of Mn2O3 nanoparticles significantly improved combustion and emission performance. Among all samples, the COB10+ 100 ppm Mn2O3 fuel exhibited the best overall performance, achieving a 37.50% reduction in CO, 38.8% reduction in HC, and 33.84% reduction in smoke (soot) emissions compared to conventional diesel. This fuel also demonstrated an increase in thermal efficiency comparable to that of diesel. The improvement in thermal efficiency was attributed to enhanced the in-cylinder temperature, reduced ignition delay, and shorter combustion duration. Furthermore, the use of waste-derived vegetable oils contributed to lower production costs and a reduction in environmental impact. The linear regression model yielded an optimum prediction accuracy with a mean squared error of 5.86 × 10−6 for CO emission data. These findings indicate that Mn2O3 nanoparticles can effectively enhance the performance and sustainability of biodiesel fuels while maintaining economic and ecological advantages.

The use of biofuels is one way of reducing the increasingly visible harmful impact of diesel engines on the environment. At the same time, it is also a way of gradually reducing dependence on depleting oil reserves. New sources of biodiesel production are currently being sought. New types of plant-based fuels are constantly being introduced to the market. Due to their different chemical composition compared to diesel fuel, these fuels may have significantly lower oxidation resistance. Oxidation stability is one of the basic performance characteristics of fuels used in diesel engines. This article presents the results of oxidation stability tests carried out using the RapidOxy device from Anton Paar, which uses a small-scale accelerated oxidation method in accordance with PN EN 16091:2023-1. The tests were carried out on diesel fuel and biofuels of various origins. Fuels such as diesel fuel without ester additives B 0 , diesel fuel with 7% FAME additive designated as B7, rapeseed fatty acid methyl esters (RME) and methyl esters from animal waste (AME). The tests were carried out at various measurement temperatures ranging from 110 to 140oC.

In this study, energy analysis, engine performance, and noise emission tests of Euro diesel and safflower methyl ester fuels were conducted on a diesel engine. The experiments were conducted independently for each fuel type across engine speeds ranging from 1000 to 2400 rpm, and the physicochemical properties of the fuels were characterized and evaluated through engine testing. Noise emission values were recorded from four different points around the engine at a distance of one meter and were compared with those of reference diesel fuel. According to the test results, the most suitable fuel type was determined based on engine performance. noise emission and energy analysis. In this study, modeling was performed using artificial neural networks (ANNs) based on experimentally obtained data, and the noise emission characteristics of B100 and D100 fuels were analyzed. Both raw and normalized datasets were evaluated to assess the predictive accuracy of the models. It was concluded that the predictive success was closely associated with the choice of training algorithms and transfer functions utilized. The findings highlight that selecting suitable models and algorithms tailored to the structure of the dataset plays a critical role in enhancing prediction accuracy.

Application of artificial neural networks to model macroscopic spray characteristics of alcohol fuels

The Northern Hemisphere plays an important role in shaping global hydrological, ecological, weather and climate processes. The Arctic tundra biome is experiencing the fastest rate of warming, leading to extensive changes of vegetation, permafrost thaw and increased wildfires. Despite their relevance for global biogeochemical and biogeophysical processes, Siberian tundra ecosystems are still extremely poorly studied, limiting the effective assessment of vegetation productivity and predicting possible fire effects. The purpose of our study was to estimate fuel structure and loads in different tundra ecosystems in the Krasnoyarsk krai, Central Siberia. The lowest fuel loads were found in dry lichen-dominated areas and on the surface of the frost-heaved hummocks. Wet herbaceous and moss tundra ecosystems were characterized by higher stores of dead organic matter due to high moisture and slower decomposition rates. In the southern tundra (near the city of Norilsk), shrub biomass accounted for most of the organic matter reserves (up to 77%), while in the northern tundra (near the settlement of Dikson) its contribution decreased to 7-15%. To better evaluate vegetation productivity and fire risks, further efforts should be made to integrate field studies and remote sensing data across the different tundra ecosystems.

The refining processes of oil refineries, waste lubricantsreplacedby maintenance plants of gasoline and diesel vehicles, and mechanicallubricants of various types of ships produce oily sludge with differentcomplex components, including varying amounts of water, hydrocarbons,metal rust, solid residues, inorganic compounds, and other components.The high heavy content of the sludge results in its high kinematicviscosity, and it exists in a liquid state close to a solid stateat ambient temperature. Although the composition of oily sludge iscomplex and difficult to separate, its heating value can still reach9000 cal/g, which is about 80% of the heating value of gasoline ordiesel. Therefore, it has a great recycling value. This study thereforeintends to develop oily sludge refining technology and establish aneconomical treatment process by nonthermal equilibrium plasma. Thepretreatment technology of solvent extraction combined with filterfiltration was used to extract and separate the oily part of the sludgecontaining hydrocarbons from the oil sludge. Two types of nonthermalplasma, such as DC streamer discharge and dielectric plasma discharge,were considered for the refining processes. Under operating conditions,the oily sludge is cracked and intensified to produce liquid and gaseousfuel products. The gaseous products are condensed and collected intofuel oil by a vacuum rotary concentrator. The composition and fuelproperties of the fuel refined under different operating conditionsof nonthermal plasma, including dielectric particle size of Al2O3 and action time, were tested. The research resultsshowed that the pretreatment procedure can effectively improve theproperties of originally discarded sludge at the beginning of theoil treatment process. In the second part of the experiment, aftercomparing different types of plasma reactors, the direct treatmenttype of dielectric-barrier discharge (DBD) plasma was found to besuperior because the plasma can directly contact the treated sludgeand extended the plasma treatment range. When quartz glass beads wereadded to the sludge, a large number of raised areas were formed onthe surface of the sludge, making it easier to form a tip dischargefor plasma generation and increasing the plasma treatment area. Whenthe weight ratio of dielectric to sludge, the operating time, andthe particle size were 2/1, 8 min, and 100 μm, respectively,there is the highest heating value and the lowest residual carboncontent. In addition, the smaller the dielectric particle size, thesmaller the carbonaceous size of the refined oil after the plasmatreatment. As the plasma treatment time increased, the surface ofthe oily sludge was carbonized, resulting in a reduction in the plasmaoperating range. This research converts waste sludge into a fuel ofprecious energy, thus providing an important contribution to the developmentand application of energy.