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Understanding the ignition and dynamic processes for the combustion of hydrate is crucial for efficient energy utilization. Through reactive force field molecular dynamics simulations, we studied the high-temperature decomposition and combustion processes of methane hydrates in a pure oxygen environment. We found that at an ignition temperature of 2800 K, hydrates decomposed from the interface to the interior, but the layer-by-layer manner was no longer strictly satisfied. At the beginning of combustion, water molecules reacted first to generate OH•, followed by methane oxidation. The combustion pathway of methane is C H 4 → CH 3 • → C H 3 O • → C H 2 O → H C • O → HCO O • → CO (C O 2 ). During the combustion process, a liquid water layer was formed between melted methane and oxygen, which hindered the reaction's progress. When there is no heat resistance, oxygen will transform into radicals such as OH• and O•, which have faster diffusion rates, allowing oxygen to conveniently cross the mass transfer barrier of the liquid water layer and participate in the combustion process. Increasing the amount of OH• may cause a surge in the reaction. On the other hand, when significant heat resistance exists, OH• is difficult to react with low-temperature hydrate components, but it can transform into O• to trigger the oxidation of methane. The H• generated has a sufficient lifetime to contact high-temperature oxygen molecules, converting oxygen into radicals that easily cross the water layer to achieve mass transfer. Therefore, finding ways to convert oxygen into various radicals is the key to solving the incomplete combustion of hydrates. Finally, the reaction pathways and microscopic reaction mechanisms of each species are proposed. [ABSTRACT FROM AUTHOR]

Large-scale multiphysics simulations are computationally challenging due to the coupling of multiple processes with widely disparate time scales. The advent of exascale computing systems exacerbates these challenges since these systems enable ever-increasing size and complexity. In recent years, there has been renewed interest in developing multirate methods as a means to handle the large range of time scales, as these methods may afford greater accuracy and efficiency than more traditional approaches of using implicit-explicit (IMEX) and low-order operator splitting schemes. However, to date there have been few performance studies that compare different classes of multirate integrators on complex application problems. In this work, we study the performance of several newly developed multirate infinitesimal (MRI) methods, implemented in the SUNDIALS solver package, on two reacting flow model problems built on structured mesh frameworks. The first model revisits prior work on a compressible reacting flow problem with complex chemistry that is implemented using BoxLib but where we now include comparisons between a new explicit MRI scheme with the multirate spectral deferred correction (SDC) methods in the original paper. The second problem uses the same complex chemistry as the first problem, combined with a simplified flow model, but runs at a large spatial scale where explicit methods become infeasible due to stability constraints. Two recently developed IMEX MRI multirate methods are tested. These methods rely on advanced features of the AMReX framework on which the model is built, such as multilevel grids and multilevel preconditioners. The results from these two problems show that MRI multirate methods can offer significant performance benefits on complex multiphysics application problems and that these methods may be combined with advanced spatial discretization to compound the advantages of both.

Despite the sudden burial to which they were subjected during the eruption of 79 AD, many of the soil samples from the Vesuvian area are poor or devoid of pollen. This research assesses whether a carbonization process may be responsible for the complete or partial loss of pollen grains or, at very least, for them going unrecorded during pollen analyses. The discovery of a certain number of pollen grains in plant material from Oplontis has made it possible to investigate which heating conditions they may have been subjected to. For this purpose, in this study, modern pollen grains were exposed to different temperatures for different time intervals in order to observe their modification. The data collected indicate that exposure to high temperatures, even for a short time, can significantly impact pollen grains to the point of making them undetectable during palynological analyses. Modern pollen grains similar to those of Oplontis are observed after exposure to 300 °C for 15 min. The state of preservation of the Oplontis reticulate grains makes prolonged exposure to 300 °C or higher temperatures unlikely. The temperature indications obtained are compatible with data from other studies. The hypothesis of combustion may also explain the small dimensions of many grains found in the Vesuvian sites. [ABSTRACT FROM AUTHOR]

Amidst the increasing deployment of renewable electricity, the demand for energy storage rises. To address medium to long-term storage needs, utilizing excess electricity for hydrogen production emerges as one of the most promising solutions. In the context of a modern energy grid characterized by intermittent power sources and challenges in constructing large power plants in densely populated areas, the concept of a Decentralised Energy Systems (DES) network appears practical. Consequently, there is an urgent need for research into efficient micro Gas Turbine (mGT) units fuelled by hydrogen. Most notably, it is important to assess the impact of several key combustor design parameters to minimise the NO x emissions. As a result, the study provides optimal values for both the momentum (3–4) and the primary equivalence ratio's (0.3–0.4) in order to optimise the hydrogen injection depth and minimise the high temperature zones near the combustor head wall, which will curtail NO x emissions. • Rising demand for energy storage with renewable electricity growth. • Low NO x hydrogen mGT in a Distributed Energy Systems (DES) framework. • Research on design and optimisation of micromix combustor. • Optimise design of nozzles to minimise hydrogen injection depth and wall temperature. • Optimal values of momentum (3–4) and equivalence ratio (0.4) decrease typical high NO x causes. [ABSTRACT FROM AUTHOR]

As a commonly applied ignition composition, Zr/KClO 4 has attracted various interests and plenty of efforts have been made to improve the combustion performance. In this study, Si nanoparticles were incorporated into Zr/KClO 4 by sonication. Around 2.5× peak pressure and 9.2× reactivity were achieved by Si/50%Zr/KClO 4 when compared to Zr/KClO 4. In addition, the peak pressure and pressurization rate of Si/Zr/KClO 4 ternary systems are all superior to ones of both Zr/KClO 4 and Si/KClO 4 binary systems. The synergetic effect of Si/Zr/KClO 4 is a combination of shorter ignition delay of Zr/KClO 4 and more gas production of Si/KClO 4 , which is also reflected on the higher flame propagation rate of Si/Zr-based thermites than composites with pure Si or Zr as the fuel. Meanwhile, the heat release during the redox reaction has been measured. The results show ∼700–1000 J/g higher energy release than Zr/KClO 4 , and higher combustion efficiency can be attained by ternary systems than binary ones. Thus, adding Si powders is an effective way to improve the energetic behavior of Zr/KClO 4 ignition composition, and Si/Zr/KClO 4 ternary composites can be a promising candidate for application in pyrotechnics. [ABSTRACT FROM AUTHOR]

This work aims to investigate the combustion characteristics, kinetics triplets, and thermodynamic parameters of microporous triazine-based organic polymers. The polymers were prepared by the incorporation of aliphatic and aromatic diamines (e.g., 1,4-hexane diamine (Hex) and 1,4-phenylenediamine (Bz)) with triazine core (Tr) via polycondensation polymerization. Both polymers Tr–Hex-diamine and Tr–Bz-diamine are microporous with a surface area of 212 and 524 m2/g, respectively. The successful synthesis was confirmed from FTIR and solid-state 13C CP-MAS. The combustion index (SN), kinetic triplets, apparent activation energy (Ea), pre-exponential factor (A), and thermodynamic parameters were estimated from the thermal degradation profiles of the polymers (TGA) at different heating rates. At the maximum heating rate (20 °C/min) the SN of Tr–Bz-diamine is 2.08, while it reached 4.2 for Tr–Hex-diamine, which indicates the high rate of combustion of the aliphatic hexyl chains. The other kinetic and thermodynamic parameters were determined by applying model-free isoconversional methods including Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (OFW), and Kissinger. From KAS, the average Ea for Tr–Bz-diamine and Tr–Hex-diamine are 163.4 and 147.8 kJ/mol, while 169.2 and 151.7 kJ/mol from OFW calculations. These values are higher in the case of the Kissinger method. The degradation mechanism and the rate of decomposition were determined from the Coats–Redfern method and by applying the master plot methods. Comparing the Ea values of the CR method with the integral method shows the possibility of the chemical reaction F3 mechanism beside multiple parallel reactions as shown by the master plot. The pre-exponential factor (A) along with the thermodynamic parameters (e.g., heat of enthalpy, entropy, and Gibbs free energy) were also determined and found to be within the same range of all methods. [ABSTRACT FROM AUTHOR]

Thermal decomposition of ammonium perchlorate (AP) typically requires high temperatures and activation energy, but the introduction of combustion catalysts will improve its thermal decomposition performance. Therefore, it is crucial to rationally design combustion catalysts for enhancing the thermal decomposition performance of AP. Herein, 3D NiO nanoflowers@2D graphite-phase carbon nitride (g-C 3 N 4) nanosheets (NiO@x%CN, x = 1, 3, 5, 7, 9) composite catalysts were constructed by solvothermal and calcination methods, and characterized by a series of analyses. NiO@5%CN displayed the best ability to catalyze the thermal decomposition of AP, which reduced the high decomposition temperature of AP by 113.8 °C and the activation energy by 21.67 kJ mol−1. The combustion rate of NiO@5%CN-CSP has increased by 118 % compared to that of composite solid propellants. This work provides a new insight for the design of NiO-based high-efficiency combustion catalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

The objective of this study is to evaluate the performance and emission characteristics of a diesel engine using metallic graphene oxide (GO) and nonmetallic zinc oxide (ZnO) nanoparticles in a Mahua biodiesel blend (B20). At a concentration of 75 mg/L, both GO and ZnO nanoparticles were considered and a surfactant (CTAB) and a dispersant (TWEEN 80) were added at a 1:1 ratio for surface modification. The nanofuel samples were analyzed for stability using a spectrophotometer. The nanoparticles mixed with dispersants and surfactants have shown improved stability. In addition, the injection pressure was varied from 200 to 250 bar. Dispersion of GO and ZnO nanoparticles in BD20 improved performance parameters such as BTE and BSFC. In addition, there was a significant decrease in CO, HC, smoke, and NOx emissions. TWEEN 80-added GO and ZnO nanoparticles in B20 achieved the best results, followed by the CTAB-added nanoparticles. In addition, the operating parameters showed a favorable trend toward improvement at higher injection pressures. At 250 bar, BTE was improved by 4.24% and BSFC was reduced by 3.59% compared to diesel. Also, the CO, UHC, NOx, and smoke opacity were reduced by 47.05%, 15.12%, 18.96%, and 37.09% for B20 + ZnO75 mg/L + TWEEN75 mg/L, respectively. [ABSTRACT FROM AUTHOR]

Porous silica was synthesized from cornhusk using the sol–gel polymeric route and compared with ash obtained from the direct combustion process under laboratory conditions. The unmodified ash from the direct combustion process was dissolved in NaOH for 1 h to form sodium silicate, which was subsequently hydrolyzed with citric acid to yield a silica xerogel. The obtained xerogel was characterized using inductively coupled plasma–optical emission spectrometry (ICP-OES), Fourier transforms infrared (FTIR) spectroscopy, X-ray diffraction (XRD), simultaneous thermal analysis (STA), gas sorption techniques to determine their elemental constituents, functional groups, crystalline phases, thermal stability, and porosity, respectively. The results showed that the synthesized silica xerogel exhibited porous network structures with a high-specific surface area and mesopore volume of 384 m2/g and 0.35 cm3/g, respectively. The pore size distribution revealed a complete transformation of the pore network structures of the unmodified ash from a monomodal to a bimodal pore system, with micro- and mesopore peaks centered around 1.5 and 3.8 nm, respectively. The ICP-OES results showed that the silica content significantly increased from 52.93 to 91.96 wt.% db after the sol–gel treatment. XRD diffraction confirmed the amorphicity of the silica particles obtained from the sol–gel extraction method. In addition, the STA data showed that the silica xerogel has high thermal stability compared to the unmodified ash, as the latter exhibited poor thermal stability and low textural properties. The high surface area and narrow pore cavity size distribution of the porous silica xerogel make it an ideal substrate for catalysts and an excellent template for growing other nanoparticles within the pores. [ABSTRACT FROM AUTHOR]

Buckwheat husks are a valuable source of carbon and show the potential to be used as an energy source. However, due to low bulk density and low susceptibility to compaction, it is beneficial to use them in the form of co-pellets. The study presents comprehensive research detailing buckwheat husks' potential for co-pelletization with oily (peanut husks) and dusty (senna leaves) agri-food wastes, whereas the effect of material parameters such as the amount of additive (10, 15, 20%) and the process parameters as the die rotational speed (170, 220, 270 rpm) on pellets' quality (kinetic durability, bulk and particle density, degree of compaction) and the energy consumption of the pelletization process were examined. Ten percent of potato pulp as a binder was added to each pelletized mixture. It was found that an increase in the senna leaf content affects positively the kinetic durability of pellets. The fatty peanut husks have a negative effect on the pellets' quality (measured by the kinetic durability and bulk density); however, both additions of senna leaves and peanut husks are lowering the energy consumption of the pelletizer. The highest quality pellets and the addition of 10% peanut husks to buckwheat husks (kinetic durability of 96%) and 20% of senna leaves to buckwheat husks (kinetic durability of 92%) obtained at 170 rpm were subjected to combustion in a fixed-bed unit, and the content of CO, CO2, NO, SO2, HCl, and O2 in the fuel gases was measured. The emission factors were higher than the Ecodesign limitations (CO > 500 mg·Nm−3, NO > 200 mg·Nm−3). The obtained results indicate that buckwheat husks can be successfully co-pelletized with other waste biomass; however, the pellets to be combusted require a boiler with improved air-supplying construction. [ABSTRACT FROM AUTHOR]

Titanium alloys can be ignited under extreme conditions including high pressure, high temperature, and high-speed friction. A theoretical description of the ignition conditions for titanium alloys is critical for their safe use in aerospace industries. In this study, a chemical-absorption-controlled ignition model for bulk TC17 alloy in oxygen-enriched atmospheres was developed based on Semenov's thermal ignition theory. The adsorption coefficient, reaction order, and activation energy for the ignition of TC17 alloy were obtained by fitting the model with the experimental critical oxygen pressure and critical ignition temperatures. The fitting results showed that the chemical-absorption-controlled ignition model fitted better with the experimental data compared with the diffusion-controlled ignition model, implying that the ignition process was controlled by chemical absorption rather than oxygen diffusion through the oxidation layer. Moreover, the activation energy for the ignition of TC17 alloy bars was obtained to be 50.01 kJ/mol, which was only less than one-fourth of that of non-isothermal oxidation (231.98 kJ/mol), indicating that the ignition requires much lower activation energy than oxidation. The chemical-absorption-controlled ignition model successfully predicted the ignition temperature of TC17 alloy bars with different diameters with the relative error within 4.41%, demonstrating the validity of the model. [ABSTRACT FROM AUTHOR]

To clarify the influence of H2O thermal effect on the formation of ultrafine particulate matter (PM), Huangling coal char was burned in a high-temperature drop tube furnace at 1800 K under various O2/N2/H2O and O2/N2/H2O/Ar atmospheres. The introduction of Ar in the simulating atmosphere was designed to counteract the thermal effect of H2O. Results indicated that after eliminating the thermal effect of H2O, the yield of ultrafine PM continuously increased in higher H2O content. Compared with no H2O, the mass and number yield of ultrafine PM in O2/N2/H2O/Ar atmosphere with 30% H2O content increased by 35.5% and 58.9%, respectively. H2O thermal effect, gasification reaction, and char oxidation reaction during coal char combustion played a significant role in the formation of ultrafine PM. Oxidation reaction was the primary factor affecting the formation of ultrafine PM, and its relative contribution was more than 62.9%, whereas the thermal effect of H2O showed an overall negative net effect on the formation of ultrafine PM. With the H2O content varied from 5% to 30%, the contribution of H2O thermal effect to mass yield was in the range of −19.1% to −18.0%, while that to number yield was −33.1% to −30.6%. Once the H2O content reached 10%, the enhancing effect of H2O gasification reaction on the yield of ultrafine PM surpassed the negative contribution of H2O thermal effect. For a given H2O content, elevated O2 concentration weakened the negative contribution of H2O thermal effect. [ABSTRACT FROM AUTHOR]

Presently, the use of lean combustion has been growing in industrial furnaces, aero-engine, and rocket engine applications due to their low $$N{O_X}$$ N O X emission and minimum maintenance requirements. On the other hand, due to the excessively low combustion reaction rate, the operation at a low fuel–air ratio leads to the sudden shutdown of the engines, which is termed lean blowout (LBO). Therefore, to operate land-based and aircraft engines at an extremely lean fuel–air mixture, control of LBO has become indispensable. In the present work, we develop several feedback in-loop control strategies using a pixel-averaged intensity ratio between the red and blue components of the flame emission. During a lean operation, based on the quantification of the proximity of the combustion dynamics to the LBO limits using this color ratio, the control strategies make the solenoid valves active to inject a secondary pilot fuel and energize the flame base. We notice that a proper choice of the color ratio as a threshold enhances the stability of both premixed and partially premixed combustion using a low pilot fuel. Besides, we test $$N{O_X}$$ N O X emission for unpiloted and piloted operations and find that the emission is only marginally affected during a pilot injection. [ABSTRACT FROM AUTHOR]

Corner tangential and bias combustion technology have significant advantages in optimizing combustion and pollutant emissions. This paper combined the corner tangential, bias combustion and jet technology for the first time to control thermoacoustic oscillations and pollutant NOx emissions synchronously. The control feasibility was examined by three variables: widths of corner tangential slots, bias jets ratios, and jet flow rates. Results indicate that the widths of corner tangential slots and bias jets ratios significantly affect the suppression effectiveness of thermoacoustic oscillations and NOx emissions. The synchronous control effectiveness with larger widths of corner tangential slots and smaller bias jets ratios is better than that with smaller widths of corner tangential slots and larger bias jets ratios. The maximum damping ratio of dynamic pressure and CH* can achieve 90.1% and 82%, respectively. The dynamic pressure drops from 39.2 Pa to 3.9 Pa and CH* reduces from 0.006 arb.units to 0.001 arb.units. A lower oscillations frequency will form by the bias jets, which avoids the occurrence of high-frequency and high-amplitude thermoacoustic self-excited oscillations. Besides, the NOx emissions drop from 26.2 ppm to 13.9 ppm reaching a maximum reduction of 12.3 ppm. Meanwhile, a slimmer flame root and flatter flame front are triggered. Two flame modes are summarized as Model A and Model B. This research realized an efficient simultaneous control of thermoacoustic oscillations and pollutant NOx emissions, which could be a helpful guideline for designing lean premixed flames. [ABSTRACT FROM AUTHOR]

For the first of its kind, Cr 3 + -substituted calcium hexaferrite (CaCrxFe 1 2 − x O 1 9 (x = 1 , 3, 5 and 7)) nanoparticles (NPs) were synthesized via a facile, economical, eco-friendly lemon juice extract mediated green solution combustion method. The samples were calcined followed by characterization. The Bragg reflections confirm the formation of a single phase M-type hexaferrite crystal structure. No other impurity or mixed phases are observed even after the substitution of Cr 3 + to the host matrix. Meanwhile, the crystallite size decreases from 29.44 to 19.92 nm with an increase in the substitution of Cr 3 + ions. The surface morphological analysis shows the presence of agglomerated irregularly shaped NPs. The direct energy band gap estimated using Wood and Tauc's relation depicts the decrease in energy band gap from 2.98 to 2.74 eV with an increase in the substitution of Cr 3 + ions. These Cr 3 + -substituted calcium hexaferrite NPs were predicted to be useful in high-frequency applications based on structural, dielectric, and magnetic studies. [ABSTRACT FROM AUTHOR]

Motivated by her interest in fabric arts, late-eighteenth-century British chemist Elizabeth Fulhame experimentally investigated whether cloths of gold, silver, and other metals could be made by chemical rather than mechanical processes. In contrast to other women studying science at this time, she not only published an original monograph under her own name that challenged both the phlogistic and antiphlogistic views of combustion but also proposed an alternative explanation for oxidation and reduction. Although her contemporaries widely cited her innovative research, her history is not well known, yet a careful analysis of her work provides further insights into the reception of the antiphlogistic theory and the challenges and limitations experienced by women in chemistry during this period. [ABSTRACT FROM AUTHOR]

Fluorite-type nanocrystalline 5% iron-substituted ceria (Ce0.95Fe0.05O2−δ) was synthesized by the solution combustion method with an average crystallite size of 15 nm. The catalyst was well characterized by SEM, EDX, XPS, XRD, and H2-TPR studies, which confirmed the substitution of Fe3+ in the CeO2 lattice. This precious metal-free catalyst was developed for the selective conversion of various arylboronic acids to the corresponding biphenyls and phenols employing K2S2O8 and H2O2, respectively. This catalyst could be coated on cordierite monolith, which acts as a catalyst cartridge employed efficiently in recycling experiments up to seven cycles. The scale-up reaction was also carried out with a catalyst cartridge, affording a good yield of the desired product. [ABSTRACT FROM AUTHOR]

Internal combustion engines (ICEs) fuelled with hydrogen can play a major role in the short-term future transportation sector since they abate all criteria pollutants at engine-out reducing tailpipe CO2 emissions to near-zero levels. However, optimizing hydrogen ICEs is a challenging task that can be addressed through the development of a robust simulation tool capable to predict the H2 combustion process. In this study, a previously developed two-zone combustion model has been updated considering different laminar flame speed computations, both based on a detailed chemistry scheme: a polynomial correlation function and a tabulated approach. The predictive capabilities of the combustion model have been validated against experimental data coming from a 0.5L PFI single-cylinder engine under several operating conditions. The tabulated approach for laminar flame speed definition proved to be the best solution, leading to a combustion duration average error lower than 3 deg over a dataset containing more than 45 different operating conditions. • A predictive combustion model for hydrogen combustion was developed. • The air-hydrogen laminar flame speed calculated using detailed chemical kinetics. • Two approaches tested for implementing the laminar flame speed calculations. • Tabulated laminar flame speed provides high predictive capabilities. [ABSTRACT FROM AUTHOR]

Chemiluminescence of OH∗ is commonly employed as an optical indicator for the combustion process. It is widely recognized that the generation of OH∗ in hydrogen flames is primarily governed by the reaction H + O + M=>OH∗+M. In this study, the time histories of OH∗ chemiluminescence from the A→X band around 308 nm were recorded behind reflected shock waves for stoichiometric and lean H 2 /O 2 mixtures highly diluted in argon over the temperature range of 1130–3150 K and at the pressure of approximately 0.9 atm. Based on the time histories of OH∗ chemiluminescence, the best-fit reaction rate coefficient for the reaction H + O + M=>OH∗+M was determined as k = 3.17 × 1027exp(-121968 cal mol−1/RT) + 2.25 × 1017exp(-4246 cal mol−1/RT) cm6 mol−2 s−1 over the temperature range studied. Furthermore, by using the current rate coefficient in mechanism predictions, the predicted time histories and relative peak intensities of OH∗ chemiluminescence are in good agreement with experimental results reported in literature. • The time histories of OH∗ chemiluminescence up to 3150K are recorded. • The rate coefficient for H + O + M=>OH∗+M is determined. • The OH∗ sub-mechanism with the fitted rate coefficient has been verified. [ABSTRACT FROM AUTHOR]

Compared with pure NH 3 fuel, the lower NO emission conditions of NH 3 –H 2 mixtures under the oxygen-enriched combustion mode have been identified quantitatively. Furthermore, the effects of the H 2 addition on the NO productions of premixed oxygen-enriched NH 3 –H 2 flames are studied numerically, while the major reactions responsible for the variation of total NO are identified. Results show that the H 2 addition is eligible to reduce the NO emissions of the oxygen-enriched NH 3 combustion if the laminar burning velocity is fixed to a larger value (>23 cm/s). The quantitative equations are obtained to determine the optimum oxygen-enriched conditions of the NH 3 –H 2 mixture, aiming to achieve lower NO emission and similar or improved combustion stability compared to pure NH 3 fuel by restricting the minimum and maximum O 2 percentages for the NH 3 –H 2 mixtures. Based on the rate of production (ROP) analysis, for the oxygen-enriched NH 3 –H 2 combustion, R144 (HNO + H<=>H 2 +NO) is consistently the most significant NO production reaction, while R85 (NH + NO<=>N 2 O + H) and R91 (N + NO<=>O + N 2) play significant roles in the NO consumption. When the laminar burning velocity (S L) is kept to a lower value, the increased total NO of the oxygen-enriched NH 3 flames with the H 2 addition is ascribed to more efficient suppressions on the NO consumption reactions of R85, R91 and R77 (NH 2 +NO<=>NNH + OH). In contrast, thanks to the extra impact of the higher O 2 percentage on the H/O/OH radical pool at larger S L , the NO production reactions begin to suffer stronger suppressions of the H 2 addition, resulting in the reduced total NO of NH 3 –H 2 mixtures. Furthermore, R144 is identified as the key reaction influencing the variation trend of total NO at both lower and higher S L values. • NO emissions of oxygen-enriched NH 3 –H 2 combustion are investigated. • Lower NO emission conditions of NH 3 –H 2 mixture than NH 3 are identified. • H 2 addition leads to opposite change of NO emission at small and large S L. • Effects of H 2 addition on NO formations are analyzed at different S L. • R144 plays a decisive role in determining the opposite change of NO emission. [ABSTRACT FROM AUTHOR]

In this study, a three-dimensional, high fidelity LES of a fully premixed, lean hydrogen-air deflagration, in a confined and obstructed channel is performed. The experimental configuration studied is the GraVent explosion channel (L. Boeck et al., Shock Waves, 2016). A complete methodology to perform LES of lean hydrogen, strongly compressible deflagrations is presented. The capability of LES to quantitatively reproduce the main Flame Acceleration (FA) mechanisms of the fast deflagration is illustrated. The physics of FA are analysed and the contribution of the unburnt mixture flow aerodynamics to the absolute flame propagation speed, is evaluated. This is made possible by the access to the complete reactive flow fields, which are not available in the experiments. It is shown that the flow contraction, at fence-type obstacles, and the flame/vortex interaction, between the flame front and the turbulent structures in the wake of the obstacles, interact constructively, driving FA. [Display omitted] • 3-D Large Eddy Simulation of a fast deflagration in the GraVent BR30hS300 channel. • Methodology for LES of lean hydrogen explosions with Adaptive Mesh Refinement. • Excellent agreement with experimental measurements of flame velocity and overpressure. • Flow contraction at obstacles and flame/vortex interaction drive flame acceleration. [ABSTRACT FROM AUTHOR]

This work analyses two experiments that have a combustion reaction as their context. The production of this chemical reaction complicates to students the understanding of the final results, due to both the large number of concepts that they must consider and their use of causal linear reasoning that entails the functional reduction of the variables involved. This difficulty has led to their incorrect explanation not only by students of different academic levels, but also by preservice science teachers, textbook authors and even science education researchers. In order to mitigate the enormous cognitive demand involved in the understanding these two processes, a collection of previous experiments is proposed that allow to delimit their study. This initial lower understanding requirement may enable students to eventually focus their attention on the relevant conceptual elements, which is intended to make easier for them to use their prior knowledge concerning the physical behavior of gases. In any case, for their complete implementation in the science classroom, the role of teachers seems essential. This way, it would remain to be determined which grade of guided inquiry might be the most effective. [ABSTRACT FROM AUTHOR]

In the current research, the rare earth‐doped magnesium aluminate (MgAl2O4:Eu3+) spinels were produced by the combustion synthesis method. The employment of thermodynamic calculations revealed that the combustion approach is a proper way to synthesize MgAl2O4:Eu3+ material by urea fuel, although this procedure was fulfilled at 500°C, the final temperature will be around 2030°C. The x‐ray and FT‐IR spectra confirmed the successful formation of spinels, while it was shown that the calcination procedure results in a significant increase of crystallinity. On the other hand, it was interestingly seen that the addition of large amounts of Eu3+dopant (10 wt%) suppresses the crystallinity. The MAUD calculations interestingly revealed that the increase of Eu3+ dopant from 1 to 10 wt% leads to the increase of MgO and Al2O3 impurities. The related microstructural evaluations revealed that the particle size of the synthesized powders is mostly less than 40 nm which shows the superiority of combustion synthesis over other commercial methods. Also, the broadening of XRD peaks confirmed the formation of nano‐sized powder. The photoluminescence (PL) characterizations showed that doping of MgAl2O4 with 7 wt% Eu3+ brings the most intensive emission properties at the wavelengths of 592 and 617 nm. [ABSTRACT FROM AUTHOR]

This work explores the theoretical and computational impacts of mixed‐type flux conditions and nonsmooth data on boundary/interior layer‐originated singularly perturbed semilinear reaction–diffusion problems. Such problems are prevalent in nonpremixed combustion models and catalytic reaction models. The inclusion of arbitrarily small diffusion terms results in boundary layers influenced by specific flux conditions normalized by perturbation parameters. We have demonstrated theoretically that the sharpness of the boundary layer is significantly reduced when this normalization is independent of the diffusion parameter. In addition, the presence of a nonsmooth source function gives rise to an interior layer in the current problem. We show that using upwind discretizations for mixed boundary fluxes achieves nearly second‐order accuracy if the first derivatives are not normalized concerning perturbation parameters. This outcome arises from the bounds of a prior derivative of the continuous solution. Furthermore, it is theoretically shown that nearly second‐order uniform accuracy can be attained for reaction‐dominated semilinear problems using a hybrid scheme at the discontinuity point. To ensure the uniform stability of the discrete solution, a transformation is necessary for the corresponding discrete problem. Theoretical results are supported by various experiments on nonlinear problems, illustrating the pointwise rates and highlighting both linear and higher‐order accuracy at specific points. [ABSTRACT FROM AUTHOR]

Conventional jet fuels derived from fossil sources contribute to greenhouse gas emissions and air pollution, leading to climate change. Recent studies have shown that biobased jet fuels from different feedstocks offer a more sustainable alternative to conventional fuels as they are derived from renewable biomass, reducing greenhouse gas emissions. The major feedstocks reviewed are jatropha curcas, camelina, karanja oil, waste cooking oil, and municipal solid waste. They offer diverse benefits for sustainable aviation fuel development. As a comparative analysis, this review examined jet fuel characteristics based on their physicochemical properties, namely energy content, viscosity, calorific value, cetane number, and freezing and flash points. The objective was to understand the influence of the properties on performance evaluation, environmental impact, and combustion characteristics. The properties of biojet fuels are compared with their fossil counterparts to validate their suitability as renewable alternatives and their benefits in terms of emissions reduction and engine performance. Biojet fuels perform better in terms of lower sulfur content, lower soot content, and a lower freezing point, their aromatic content, and their high cetane number. This study enhances the understanding of biojet fuels and their quality, and supports the development of sustainable fuel options. Overall, adherence to the American Society for Testing and Materials (ASTM) D7566‐18 standard is crucial for the acceptance and integration of biojet fuels into the aviation sector. Future research should explore feedstocks such as wood biomass, wastepaper, and agricultural residues for biojet fuels. It should also investigate the combustion and emission characteristics of biosourced aviation fuel at higher blending ratios (>50% by volume) with fossil Jet A‐1. [ABSTRACT FROM AUTHOR]

LiNi1/3Mn1/3Co1/3O2 (NMC 111) materials show promise as cathodes for lithium‐ion batteries (LIBs). However, their widespread use is hampered by various technical challenges, including rapid capacity fading and voltage instability. The cathode materials synthesized using the combustion method were annealed at various temperatures ranging from 650 to 900 °C for 24 h. In this study, we identified an optimal annealing temperature of 750 °C for LiNi0.3Mn0.3Co0.3Ti0.1O2 (NMCT) materials. NMCT‐750 exhibits an initial discharge capacity of about 140.1 mAh g−1 and retains the capacity of 91 % after 30th cycles. The good performance of NMCT‐750 is directly attributed to reduced cation mixing and the establishment of a stable structure with small particle sizes. In contrast, higher annealing temperatures (850 °C) lead to a rapid increase in primary particle size and result in poor cycling stability. Therefore, NMCT‐750, annealed at 750 °C, holds great potential as a cathode material for the next generation of LIBs. [ABSTRACT FROM AUTHOR]

This study aims to address critical challenges such as global warming and energy sustainability by targeting the reduction of high NOx emissions in diesel engines. The effects of acetone (AC) and magnesium oxide (MgO) nanoparticles (NPs) as additives in improving the physicochemical properties of biodiesel derived from renewable, nonedible Pistacia terebinthus oil, which is abundant in Turkey and has a high free fatty acid (FFA) content of 5.8%, were investigated. Due to the high FFA content, a two‐step (esterification followed by transesterification [TR]) method was used for biodiesel production. Additionally, a quantitative analysis of biodiesel obtained by both single (TR) and two‐step methods was performed to address a gap in the literature. The addition of AC and MgO NPs to B20 (80% diesel fuel and 20% biodiesel) fuel resulted in reductions in the rate of pressure rise, instantaneous energy release, cylinder pressure, mean gas temperature, and cumulative heat release rate. However, brake‐specific fuel consumption increased, and brake thermal efficiency decreased. Emissions analyses showed a reduction in CO emissions by 6.65% with AC and 2.10% with AC + MgO, and a reduction in NOx emissions by 41.64% with AC and 46.03% with AC + MgO. However, hydrocarbon emissions increased by 26.48%. The study highlights the synergistic benefits of AC and MgO additives in biodiesel, presenting a viable strategy for improving the environmental and performance metrics of biodiesel blends. It provides new insights into alternative fuel formulations. [ABSTRACT FROM AUTHOR]

The high-efficiency Sm3+doped La(OH) 3 nanoparticles are synthesized in developing orange-emitting phosphors. A hexagonal phase of pure and Sm3+doped lanthanum hydroxide nanoparticles can be obtained by urea-assisted auto-combustion after calcination at 900 °C for 4 h. The dopant concentration of Sm3+ ions varied as 2, 5, and 10 wt% in the host lattice. The X-ray diffraction pattern confirmed the formation of the hexagonal phase with space group P63/m (176). The phase formation of pure and Sm3+ion-doped La(OH) 3 nanoparticles was confirmed using Raman spectroscopy. The band gap energy is determined to be 5.6 eV. The photoluminescence spectrum under the excitation of 407 nm exhibits four emission bands centered around orange emissions 569 nm, 605 nm, 652 nm, and 711 nm corresponding to 4G 5/2 → 6H J (J = 5/2, 7/2, 9/2, 11/2) transitions—the CIE coordinate of the Sm3+doped La(OH) 3 samples positioned in the orange region. The lifetime of Sm3+ion doped La(OH) 3 is found to be 0.36 ms, 0.708 ms, and 0.185 ms for 2, 5, and 10 wt%. The results suggest that the prepared phosphors are valuable for orange emission optoelectronic devices. [ABSTRACT FROM AUTHOR]

Flow field organization significantly influences the performance criterion of a scramjet combustor. Recently, DLR scramjet combustor with strut injector has been mostly used to alter the flow field. Researchers have used innovative strut injectors to enhance the performance of the DLR scramjet combustor. However, the effect of utilizing a strut with both parallel and normal injections of air and fuel in the DLR scramjet combustor has not been investigated till date. Hence, in this study, the DLR combustor is numerically investigated using a modified strut injector with both parallel and normal injections of air and fuel. The 2D numerical solver is validated with the experimental results having a maximum deviation of 7.3%. The analysis shows that the combustors with modified strut injectors produce better turbulence mixing compared to the DLR combustor, resulting in higher combustion performance. The modified strut combustors, i.e., CMSI-1, CMSI-2, and CMSI-3 produced a combustion efficiency of 76%, 79%, and 81%. In contrast, the maximum combustion efficiency produced by the DLR combustor is 50%. This improvement in the combustion performance of the combustors with modified strut injectors resulted in higher thrust force than the DLR combustor. The thrust force produced by CMSI-1, CMSI-2 and CMSI-3 are 3160 Pa.m2, 3200 Pa.m2 and 3216 Pa.m2, respectively. Finally, it has been found that the CMSI-3 has produced the maximum combustion efficiency and better thrust force among all the scramjet combustor models considered in the study. [ABSTRACT FROM AUTHOR]

Hydroxylamine nitrate (HAN)-based liquid propellants are characterized by high energy content and low toxicity ionic monopropellants, offering great potential application prospects in the space engine. This paper proposes an experimental system for electric ignition and combustion of HAN-based liquid propellant. The energy for decomposition, current, and combustion image of HAN-based liquid propellant are measured under different initial voltage, propellant volume, and the initial pressures in Ar and air atmospheres. The results show that the energy for decomposition decreased with an increase in initial voltage, propellant volume, and initial pressure. An increase in the initial voltage accelerates the reaction speed of HAN-based liquid propellant, and the energy for decomposition is approximately 3 J. An increase in the propellant volume decreases the equivalent resistance in the circuit, increasing the current and enhancing the thermal effect of the propellant. The accumulation of decomposition products and heat under high pressure reduced the energy for decomposition; the energy for decomposition is less than 1.5 J for the pressurization condition. Compared with the Ar atmosphere, the energy for decomposition of HAN-based liquid propellant shows better stability in the air atmosphere. The flow combustion device of HAN-based liquid propellant for the flow state is designed. The HAN-based liquid propellant is successfully ignited for different initial voltages and flow rates. The research results provide a reference for the design of space engine for HAN-based liquid propellant based on the electric ignition method. • Experiments for HAN electric ignition on different initial U , V , P were carried out. • The effects of initial conditions on the ignition energy of HAN was studied. • The comparison of ignition energy in air atmosphere and Ar atmosphere was analyzed. • The propellant flow combustion based-on the electric ignition method was achieved. [ABSTRACT FROM AUTHOR]

Safety of using hydrogen as fuel in aerospace applications is closely connected with hydrogen explosion safety during its transportation and stockpiling at launch places. In this paper, preventing the detonation propagation in the mixtures of hydrogen with air due to accidental hydrogen releases is studied in numerical experiments. Another fuel - hydrocarbon propylene – is studied as an optional inhibitor to be added in a small volume quantity to hydrogen-air mixture. The dependence of detonation wave cellular structure on the content of inhibitor is studied for different fuel-air ratios. The results make it possible determining the content of inhibitor sufficient for preventing the detonation onset or destroying the existing detonation wave. • Preventing the detonation propagation in the mixtures of hydrogen with air is studied numerically. • Another fuel - hydrocarbon propylene – is studied as an optional inhibitor. • The dependence of detonation wave cellular structure on the content of inhibitor is studied for different fuel-air ratios. • The content of inhibitor sufficient for preventing the detonation onset or destroying the existing detonation wave. [ABSTRACT FROM AUTHOR]

Adjusting injection and production parameters is an essential tool for studying the effect of reservoir heterogeneity on in-situ combustion (ISC) sweep and associated control strategies, as well as for achieving stable ISC. An asynchronous injection and production in-situ combustion (AIPISC) method through the coupling of the gas injector and producer in order to accomplish the balanced sweep of ISC. Using the Hongqian (HQ) ISC in Xinjiang as an example, numerical simulation was utilized to define the reservoir and investigate the sweep characteristics under various sedimentary models. The AIPISC technology was applied to several heterogeneous reservoirs, and the design scheme of AIPISC was created. Under the same heterogeneous reservoir circumstances as the conventional ISC approach, the oil saturation of the AIPISC wall increases from 0.65 to 0.72. The roundness of the combustion chamber was better, and balanced displacement can be achieved. Then the parameters of AIPISC were optimized to determine that the vertical permeability difference of the reservoir should be less than 15, the asynchronous time difference was 6 ∼ 8 months, and the gas injection amplitude was 1.5 ∼ 2.0. The results show that the experiment in HQ Oilfield was successful, and the usefulness of AIPISC was investigated using the electromagnetic approach. [ABSTRACT FROM AUTHOR]

The present study investigates the significance of the utilization of biodiesel derived from waste cooking oil in diesel engines and its impact on engine output and environmental pollution after blending with diesel and 1-pentanol. The higher values of the ignition index and comprehensive performance index of 4.34 × 10 − 4 mass/min°C2 and 13.71 × 10 − 6 mass2/min2 °C3, respectively, for D70B20P10 (70 % diesel, 20 % biodiesel & 10 % 1-pentanol by volume) indicate superior combustion performance. At full load, carbon monoxide and unburned hydrocarbon emissions from 1-pentanol blended fuels decrease significantly, ranging from 40 % to 52 % and 30.76–46.15 % compared to diesel. The D70B20P10 also showed an improved thermal efficiency of 28.68 % among all tested fuels at full load but slightly lower than diesel (29.56 %). Diesel demonstrated superior in-cylinder pressure (ICP) of 77 bar and heat release rate (HRR) of 41.1 J/ºCA owing to its excellent combustion characteristics. Introducing 5–10 % 1-pentanol in blend improved combustion, elevating ICP and HRR, attributed to enhanced fuel atomization and oxygen content. The sustainable process index value obtained for a global index per person is 0.002 × 10 − 4 cap Litre-1, which lies between 0 and 1, indicates sustainability and compatibility of biodiesel production demonstration by universal biofuels (Andhra Pradesh). [Display omitted] [ABSTRACT FROM AUTHOR]

As a new type of energy that can meet the requirements of carbon neutrality, biomass has received wide attention in recent years, and its rational and efficient thermal utilization can help reduce greenhouse gas emissions and establish an energy-saving, low-carbon energy system to promote sustainable development. In this paper, the current utilization and research status of plant-based biomass waste is comprehensively summarized from four aspects, namely component properties, industrial thermal utilization means, experiments and theoretical calculations. In addition, this paper summarizes the research progress in several aspects, such as microscopic experimental studies, macroscopic pyrolysis characterization, and multiscale theoretical model construction of biomass waste. However, due to the diversity and heterogeneity of biomass, there are still some challenges to extending the laboratory research results to large-scale industrial production, for which we also provide an outlook on future technological innovations and development directions in this research area. [ABSTRACT FROM AUTHOR]

Gasoline compression combustion engine has the advantages of low emission and high efficiency, which is very promising for research, but it is difficult to apply under low-load conditions. Gasoline has the characteristics of low reactivity; in the case of low thermodynamic state in the cylinder, the fire delay period of the fuel is longer, and the combustion phase is relatively lagging, which will lead to the increase of combustion cycle fluctuations, and even difficult to ignite and other adverse combustion phenomena. In order to improve the combustion stability of Gasoline Compression Ignition (GCI) engine under low-load condition and expand the limit of low-load combustion boundary, gasoline was reformed without catalyst under the boundary condition of reforming temperature of 488 K and reforming equivalent ratio of 8, and the concentration of reformed product was measured by a gas detection device. Subsequently, the coupling of the reformed product and spark plug with GCI engine under low-load condition was investigated to analyze the effect on engine combustion and emission. The results showed that the initial combustion timing of the low-load GCI engine was late, but the addition of reformed products could advance the combustion phase, shorten the combustion duration, reduce single-cycle NOx emission, and improve the small-load operation characteristics of GCI engine. Coupled spark plug ignition on the basis of adding reformed products could further improve the problem of combustion stability under low-load GCI engine. And the optimization effect became more obvious as the ignition position of the spark plug moves down. However, spark plug ignition would cause local high temperature areas, resulting in an increase in NOx emission. [ABSTRACT FROM AUTHOR]

The article "Analysis and management of herbicidal mixtures in a high‐intensity agricultural landscape in Belgium" discusses the impact of a stewardship program on reducing exceedance events for algae and macrophytes in Belgium. The authors identified a minor error in the data analysis programming but clarified that it did not affect the overall conclusions of the study. The study grouped sampling occasions into different risk groups and highlighted the compounds contributing to toxicity in algae and macrophytes. The stewardship program was credited with reducing exceedance events for both algae and macrophytes by 2013. [Extracted from the article]

Development of a model that allows performance and combustion characteristics for a supercharged diesel engine was the main objective sought by the present work. Thus, the developed model is used, to examine the impact of start combustion, combustion duration, compression ratio, and heat flux, as well as intake conditions such as pressure and temperature, on the combustion characteristics of the supercharged diesel. For this purpose, a one zone thermodynamic prediction model was adopted with Wiebe function for combustion sub-model. The heat transfer was correlated using Woschni correlation. A numerical simulation is developed considering the crankshaft angle as the independent variable. Validation of the computational code has been favorably evaluated using our experimental data. To give a more general aspect to the developed model, experimental data found in the literature, are also used for this purpose. The results show that the addition of a turbocharger increases low-speed airflow and hence fuel consumption. In addition, an increase in intake pressure contributes to the rise of the heat flux released during combustion, while an increase in intake temperature leads to a strong increase in combustion temperature. Moreover, an increase in the compression ratio leads in a remarkable increase in all parameters simultaneously. However, maximum combustion pressure limits must not be exceeded. This is because the pressure has an effect with the engine mechanical strength. [ABSTRACT FROM AUTHOR]

To clarify the mechanism of destructive knock combustion and piston ablation in heavy-duty diesel engines operating at low temperatures, CONVERGE simulation and wall temperature measurement were performed. The results show that as the initial temperature (intake valve closing instant) decreases from 380K to 307K, the spray wet-wall ratio increases from 12.8% to 22.2%. The fuel film evaporates slowly at low temperature before the hot flame, so the ignition is seriously delayed until the fuel injection ends, and the free-jet autoignition shifts to wall-attached combustion. However, the fuel film evaporation reverses after hot flame, and the maximum evaporation rate at 307K is about 54 times that at 380K. The wall temperature rises sharply to 350-450°C during wall-attached combustion. As the initial temperature decreases, the maximum pressure rise rate increases from 0.9MPa/°CA to 8.3MPa/°CA, and the pressure waves repeatedly oscillate along the end-center-end path in the cylinder. The highest pressure at the monitoring point is nearly an order of magnitude higher than the average, and the oscillation amplitude is as high as 6-10MPa, which far exceeds the failure threshold. The piston whose strength has been greatly reduced after thermal shock quickly undergoes ablation damage under strong pressure shock. [ABSTRACT FROM AUTHOR]

The stability of inverse nonpremixed oxygen (O2)/methane (CH4) coaxial jet flames near blowout limits in a model combustor is studied by analyzing signals for their local combustion phenomena using high-speed imaging and dynamic pressure. The power spectral analysis and the statistical analysis are conducted to delineate the stability of the inverse nonpremixed flames. Depending on the O2 to CH4 momentum flux ratio ((O/F)mom), two distinguished combustion phenomena which lead to different liftoff mechanisms are observed in the same burner configuration: the partial liftoff related to the aerodynamic mechanism and the local extinction related to the flame–turbulence interaction. The results of the power spectral density (PSD) show that on approaching the near-blowout limits, the local extinction or the partial liftoff occurs not in a specific frequency, but in a time-varying random distribution. The normalized root mean square (NRMS) based on the frame-integrated visible light signal (SVL) is found to be effective for quantifying the local extinction and the partial liftoff and particularly delineating the stability of the present inverse nonpremixed flames with the partial liftoff. [ABSTRACT FROM AUTHOR]

The flexible control in burning rate and stable combustion of solid propellants over a broad range of pressures essentially determine the performance of solid rocket motors. The nanoscale metals and their oxides are usually utilized as the traditional burn rate modifiers in adjusting the combustion behaviors of solid propellants, but the energy characteristics of propellants are greatly compromised owing to the inert nature of additives used. In this paper, a series of metal complexes of triaminoguanidine-glyoxal polymer (TAGP-Ms) with high nitrogen content were synthesized and employed as energetic burn rate inhibitors in tunning the combustion properties of composite modified double-based (CMDB) propellants. The influences of prepared TAGP-Ms on the thermal decomposition and combustion of CMDB propellants were comprehensively investigated based on thermal analysis technique and combustion characterization methods. It was found that the peak temperatures of the second exotherm displayed for the propellants containing TAGP-Ms inhibitors were significantly increased by more than 30°C (except for TAGP-Cu), indicating the TAGP-Ms is capable of suppressing the thermal decomposition of CMDB propellants. More importantly, the heat releases of CMDB propellants were substantially enhanced by 16%~34% determined by DSC analysis. In comparison to the blank reference, the energetic TAGP-Ms inhibitors could promote the heat of combustion for the involved CMDB propellants by 5%~9%. The burning rates of CMDB propellants were notably reduced over a wide range of pressures by adding TAGP-Ms, whereas the calculated pressure exponents at pressures ranging from 10 to ~ 22 MPa appear to be relatively high due to the accelerated HMX decomposition. The measured combustion wave temperatures suggest that the CMDB propellants with TAGP-Ms undergo a three-stage combustion process with the highest temperatures in the range of 2160 ~ 2230°C. [ABSTRACT FROM AUTHOR]

The impact of pyrolysis gas composition and the underlying reaction kinetics on the burning characteristics of a leaf was computationally investigated. The computational configuration resembled a previous experimental setup where vertically oriented manzanita (Arctostaphylos glandulosa) leaves were burned. Different compositions and reaction kinetics for the pyrolysis gas released during the leaf thermal decomposition were examined. The most detailed composition included $${\rm{C}}{{\rm{H}}_4}$$ C H 4 , $${\rm{CO}}$$ CO , $${\rm{C}}{{\rm{O}}_2}$$ C O 2 , and $${{\rm{H}}_2}$$ H 2 , which was suggested by the previous experimental study of pyrolysis products of different plant species. The least involved compositions only included either $${\rm{C}}{{\rm{H}}_4}$$ C H 4 or $${\rm{CO}}$$ CO . In all considered compositions, in addition to pyrolysis gas, the release of the heavy gas, i.e. tar, was accounted for. Tar breakdown was represented by a single-step reaction with the light gases above and soot as the products where the stoichiometric coefficients were determined by an optimization technique for consistency with the measurements for the tar molecule. The burning simulation results agreed best with the previous experimental data when a mixture of $${\rm{C}}{{\rm{H}}_4}$$ C H 4 , $${\rm{CO}}$$ CO , $${\rm{C}}{{\rm{O}}_2}$$ C O 2 was used. The least agreement was noted when pyrolysis gas was represented by only $${\rm{C}}{{\rm{H}}_4}$$ C H 4 . Inclusion of tar breakdown reaction appreciably increased the overall heat release due to combustion of its products above the leaf. [ABSTRACT FROM AUTHOR]

Lab scale combustion of solid fuels, such as biomass, is mostly performed using fixed bed combustors. Steady state data detailing various progress variables (temperature and emissions) are widely available within the literature. However, there is very little information available on how the onset of the steady state operation is identified especially in relation to batch operation, which is subject to depleting fuel bed. This paper uses experiments coupled with a systemic post-processing approach based on MATLAB in order to identify the onset of the steady state operation. The results show that by using both the percentile mean deviation and slope of certain measured progress variables (including the fuel bed temperature, freeboard temperature, fuel mass loss, and emissions) the steady state regime can be accurately predicted. The use of freeboard temperature data alone is not sufficient. Based on the methods developed, radiation error in thermocouple data was found to be significant in both non-staged and staged air combustion modes of fixed bed combustor. Moreover, the radiation error was lower for downstream thermocouples in contrast to upstream thermocouples. [ABSTRACT FROM AUTHOR]

A char cone, whose shape is similar to Bunsen flame and varies with oxidation conditions, was found in steady smoldering of biomass rods. In this short communication, characteristics of this char cone in natural downward smoldering of char rods with different diameters (2 – 7 mm) and ash contents (30–46%) were investigated via measuring propagation velocity and analyzing shape of char cone. Results showed that smoldering propagates steadily in all prepared char rods and the propagation velocity decreases with increasing diameter and ash content of char rods. Height of char cone is proportional to the mass flowrate of carbon, similar to the relationship between flame length and volume flowrate of gas fuel in laminar jet diffusion flame. It implies that oxygen diffusion through ash plays a dominant role in natural smoldering of char rod. This work provides some experimental basis for further investigation on mechanism of steady smoldering. [ABSTRACT FROM AUTHOR]

In this work, a Mg-based energetic composites, commonly known as pyrotechnic tracer composition (Mg-PC), was successfully fabricated by a mechanical milling method. The influence of the impact of artificial heat- or moist-aging on the combustion heat, ignition characteristics, and the thermal decomposition behavior of the as-prepared composite were investigated. Results show that the total energy output has decreased by 16% and 51% for the heat- and moist-aged samples, respectively. Microcalorimetric studies revealed shorter induction times and higher heat flow magnitudes for the different aged samples. Compared with the unaged composition, the ignition time of heat- and moist-aged samples are distinctly increased by 2.2 and 14.3 times, respectively. The thermogravimetric analysis demonstrated that humidity and thermal agings have a catalytic effect and accelerate the decomposition reaction, reducing the onset temperature decomposition by about 4–6°C after aging. The kinetic deconvolution analysis (KDA) indicated a multistep reaction comprising the resin decomposition, partial decomposition of the oxidizer, and the combustion of the Mg-PC. The activation energy of the first two decomposition steps was lower than that of the as-prepared mixture. Furthermore, the combustion process, corresponding to the third step exhibited slightly higher activation energy compared to the unaged formulation and is assigned to the fuel oxidation and the pre-decomposition of the oxidizer under heat- or moist-aging. [ABSTRACT FROM AUTHOR]

Numerical simulations are used to study effects of ozone (O3) and thermal enhancement on autoignition and subsequent burning characteristics of isolated n-heptane droplets in microgravity conditions. Particular focus is given to effects of O3 on low temperature combustion, or cool flames. Levels of ambient O3 mole fraction and ambient temperature are varied from 0 to 0.03 and 400 K to 750 K, respectively. A comparison between two low temperature chemistry enhancement strategies – O3 addition and temperature increase – are investigated on an equivalent energy addition basis to evaluate relative effects on combustion characteristics. Results of this study are analyzed using physical and mixture fraction approaches because of unique insights offered by these frameworks. Ignition and ensuing flame propagation are investigated via a most reactive mixture analysis, evaluated using homogeneous reactor simulations of mixture compositions and temperatures surrounding the droplet. Lastly, a Damköhler number analysis is performed to explore oscillatory ignition dynamics. [ABSTRACT FROM AUTHOR]