Fuel Communications最新文献

We used crowdsourced data in Alaska and the literature to develop a light-duty electric vehicle model to help policymakers, researchers, and consumers understand the trade-offs between internal combustion and electric vehicles. This model forms the engine of a calculator, which was developed in partnership with residents from three partner Alaskan communities. This calculator uses a typical hourly temperature profile for any chosen community in Alaska along with a relationship of energy use vs. temperature while driving or while parked to determine the annual cost and emissions for an electric vehicle. Other user inputs include miles driven per day, electricity rate, and whether the vehicle is parked in a heated space. A database of community power plant emissions per unit of electricity is used to determine emissions based on electricity consumption. This tool was updated according to community input on ease of use, relevance, and usefulness. It could easily be adapted to other regions of the world. The incorporation of climate, social, and economic inputs allow us to holistically capture real world situations and adjust as the physical and social environment changes.

This work focuses on the design of a reactor for producing clean hydrogen from methane pyrolysis in the form of the so-called “turquoise hydrogen”. In addition to its simple geometry, the fundamental concept and the main novelty of the proposed method rely on using part of the methane to produce the required heat needed for the thermal decomposition of methane (TDM). The reactor configuration for hydrogen production is shown to produce significant advantages in terms of greenhouse gas (GHG) emissions. A reactive flow CFD model incorporating also soot formation mechanism has been first developed and validated with experimental results available in the literature and then used to design and characterize the performances of proposed reactor configuration. 3D CFD simulations have been carried out to predict the behavior of the reactor configuration; a sensitivity analysis is used for clearing the aspect related to key environmental parameters, e.g., the global warming impact (GWI). The real potential of the proposed design resides in the low emissions and high efficiency with which hydrogen is produced at the various operating conditions (very flexible reactor), albeit subject to the presence of carbon by-product. This suggests that this type of methane conversion system could be a good substitute for the most common hydrogen production technologies.

Unique fatty acid methyl esters (FAME) containing β‑hydroxy esters were produced using an engineered microorganism by glucose fermentation. This study investigated the properties of the unique FAME mixture both neat and in blends with conventional diesel, as well as properties of β‑hydroxy esters. The unique FAME blend contained relatively shorter-chain FAME (average fatty acid chain carbon number 14.6) with 58 % monounsaturated fatty acids and 9 % saturated and monounsaturated β‑hydroxy acid chains. The unique FAME had significantly lower distillation T90 (321 °C versus 352 °C) and higher cetane number (56.7 versus 52) compared to soy biodiesel. Cloud points were within method repeatability. Unexpectedly (because of the lack of methylene-interrupted double bonds), the unique FAME had low oxidation stability (1.5 h) as determined by Rancimat induction period. Stability could be improved through addition of commonly used antioxidants. We speculate that monounsaturated β‑hydroxy FAME may be the source of this instability. Blends with conventional diesel up to 50 vol% showed similar kinematic viscosity (within method repeatability) as blends of conventional FAME. The unique FAME had no effect on distillation T90 even at the 80 % blend level. A 30 vol% blend into conventional diesel had a Rancimat induction period of only 2 h, very nearly the same as the neat unique FAME sample. The addition of antioxidants produced blends of acceptable stability. Based on an assessment of the properties of individual β‑hydroxy FAME molecules, they have higher boiling point, higher cloud point, lower cetane number, and potentially lower storage stability than analogous FAME not having the β‑hydroxy group. Removing them from the fuel product in the production process may result in a biodiesel product with superior properties to what is on the market today.

Ghana is currently facing challenges in aligning its energy options with future energy demands and reducing its dependency on fossil fuels. This study assessed Ghana's current energy types and their potential to meet future energy needs. A structured questionnaire with a cross-sectional survey and random sampling technique was employed to gather information on energy choices, drivers and challenges from 868 respondents. A multiple linear regression model was used to evaluate the impact of energy drivers on preferences in Ghana. Results showed that 82 % of Ghanaians are ready to transition to cleaner energy sources, with preferences for hydropower/grid electricity (45.70 %) and natural gas/LPG (32.90 %) and biofuels (12.00 %). Economic (16.20%) and population (15.50%) growth are the main drivers of energy transitions, while challenges include high initial costs (11.20%) and limited awareness (4.90%). Strategies such as financial support, education, renewable energy promotion, technological advancement and international collaboration should be promoted to actualise Ghana's transition to future renewable energy usage.

Cogongrass (Imperata cylindrica) can be processed into a positive electrode as a battery component to generate electricity by utilizing its carbon element. This study used various activators, KOH and H₃PO_4, and characterized using XRD, FTIR, and SEM-EDX and electrical tests with electric conductivity analysis. The analysis results using XRD diffraction showed that when using both KOH and H₃PO₄ activators, Cogongrass carbon has graphite (C) and silicon (Si) crystals but at different peaks. The carbon has the same functional groups for both activators: OH-bending, C=C-bending, C-O-bending, and C=C-bending. Cogongrass carbon with KOH activator has a pore size of 235-980 nm with a percentage of carbon atoms of 71.29%, while with H₃PO₄ activator has a pore size of 110-960 nm with a higher percentage of carbon atoms of 75.04%. The elements contained in carbon are the same for both activators, namely carbon, oxygen, silicon, indium, potassium, calcium, iron, chlorine, phosphorus, magnesium, and sodium. EC analysis showed that carbon from Cogongrasss showed electric conductivity reaching 140 µs/cm at 60 minutes pyrolysis time.

Experimental test campaigns have begun to demonstrate the potential of methanol as an alternative fuel for heavy-duty spark-ignited engines. However, there is no consensus yet on the scope of this solution in terms of maximum power and engine size. A zero-dimensional combustion model is therefore being developed outside the scope of this work. Its main objective will be to predict key performance parameters such as power and efficiency as function of engine size. Due to the high loads typically encountered in heavy-duty engines, knock will be the main constraint to maximize the engine's potential. This work therefore aims to find an accurate knock model that can be implemented in the modelling framework. The Livengood–Wu knock integral model is being considered as a good candidate, as it is computationally inexpensive and thus allows for a large number of engine configurations to be modelled within a reasonable time. Due to a lack of autoignition delay times of methanol at conditions relevant to heavy-duty engines, a large database was created using chemical kinetics calculations. A neural network model was trained with the tabulated data for fast data retrieval. To validate whether the knock integral approach is robust enough to be applied to a wide range of engine sizes, a calibration constant was added to match the knock predictions to experimental data. Its value was calculated for three different engines, a light and heavy-duty SI engine and a large-bore dual-fuel engine. They highlight a remarkable difference in calibration constant across the different engines investigated.

This study presents a numerical investigation into the effects of physical models on the prediction accuracy of the wall temperature distribution in an industrial radiant tube burner. Utilizing a reacting flow solver based on OpenFOAM, we explored the effects of various physical models, including those for chemistry, combustion, heat transfer, and radiation properties. The choice of combustion model significantly influences prediction accuracy, playing a more dominant role than the chemistry mechanism. Moreover, the simulations captured a distinctive triple flame structure inside the burner, representing the coexistence of rich premixed, non-premixed, and lean premixed flame structures. Conditional scatter plots displayed the development of both premixed and non-premixed flame structures, converging on the fuel-lean side. Notably, accurate prediction of wall temperature distribution depends on the incorporation of a precise heat transfer model, coupled with a detailed radiation property model. Regarding the distribution of tube surface temperature in the main radiation zone (a distance from the burner nozzle greater than 1 m), the most accurate prediction exhibits a maximum deviation of less than 56 K and an average deviation of 24 K compared to experimental results. The simulation closely matched experimental data for exhaust concentration of NO within an error margin of 20 ppm. However, discrepancy was observed in the CO concentration, which was attributed to the simplified representations of fuel chemistry and composition, as well as the difficulties in accurately capturing the unsteady flame dynamics near the wall.

The work aims to determine the kinetic parameters of reactions for production of light olefins via catalytic cracking reactions of C₄–C₆ n-alkanes based on the energy characteristics of the transition state using quantum chemical calculations. Cracking reactions of C₄–C₆ n-alkanes proceed via protolytic mechanism on the Brønsted acid sites of zeolite-containing catalysts. For kinetic studies in this work, the thermochemical parameters of the intermediate stages, including hydrocarbon adsorption and transition state were determined, then the activation energies and rate constants were determined over the temperature range of catalytic cracking process from 773 to 903 K (500–630 °C).

The results showed that DFT method in combination with B3LYP and ωB97X-D functionals, and 3–21 G basis demonstrated quite high accuracy in determining thermochemical parameters, including enthalpy, entropy and Gibbs free energy at both energetic levels of adsorption and transition state. Then, modeling continued by calculations of activation energies and rate constants of reactions. Obtained kinetic parameters made it possible to determine the reactivity of hydrocarbons with different chain length. It was obtained that the rate constants of butane cracking reactions with the formation of ethylene are 54–90 times higher than the formation of propylene. The rate constants of pentane cracking reactions with the formation of butylene are on average 5 times higher than the formation of propylene. The rate constants for hexane cracking reactions with the formation of butylene are 2.9–3.7 times higher compared to the formation of propylene.

In the pursuit of decarbonization, the reduction of greenhouse gas emissions from power generation through gas turbine (GT) engines plays a crucial role in the whole industrial sector. As industries strive to transition towards cleaner energy sources, the design and optimization of novel GT burners require a deep comprehension of the complex interaction between fluid dynamics and combustion processes embedded within the system. Computational Fluid Dynamics (CFD) plays a pivotal role in these processes by providing valuable insights into the complex flow patterns, flame topology, and stability limits within the combustor. Concurrently, the burner design phase necessitates a considerable number of simulations to ascertain flame stability limits under various burner designs and operating conditions. Therefore, it is imperative to control computational costs while ensuring a high level of accuracy. The present work is focused on a comprehensive comparative analysis of two widely employed turbulent combustion closure models: the Flamelet Generated Manifold (FGM) and the Artificially Thickened Flame (ATF). Both models utilize extended versions with specific modifications aimed at effectively addressing their respective limitations. The investigation is performed through a Large Eddy Simulation (LES) based CFD analysis within the context of a lean premixed burner designed by Baker Hughes and operated with methane at atmospheric pressure. The primary benchmark for numerical validation will be provided by detailed chemiluminescence images from a test campaign conducted by the University of Florence, thereby yielding valuable insights into flame topology and positioning. Furthermore, potential disparities in the flow field and fuel concentration at the burner exit between the two models will be revealed.

Chemical activation was employed to convert algal biochar obtained from hydrothermal carbonization of lipid-extracted algae (LEA) to activated carbon. Potassium hydroxide, previously utilized on cellulosic biomass but not on algal biomass, was employed as activating agent and the impact of the activation conditions, namely temperature, activation time, and amount of activating agent, were investigated. The yield of activated carbon from biochar ranged from 28 % to 52% and decreased as the temperature was raised from 400 to 600 °C, the residence time from 30 to 60 min, and the KOH/biochar mass ratio from 0.25 to 1.0. In contrast, surface area increased by 2.1-fold when the activation temperature was raised to 600 °C and by 1.5-fold when the KOH: biochar ratio was raised to 1.0. Maximum BET surface area of 847 m²/g was achieved at 600 °C after 30 min at a mass ratio of 1:1. The integrated hydrothermal carbonization and activation process of LEA was simulated in Aspen Plus® and the technoeconomic feasibility was assessed based on our experimental data at 1,000 and 10,000 acres of cultivation area. For the latter, net present value analysis determined a minimum selling price of $2,200/ton for algal activated carbon with a financial breakeven achieved in 3.5 years. This is cost-competitive with the current price of commercial fossil-derived activated carbon, which is $1,543-$2,645/ton. Sensitivity analysis showed that the minimum selling price is significantly affected by algal biomass yield during cultivation and is more sensitive to the operating expenses than to the capital investment.