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The HIsmelt process uses pulverized coal and iron ore as raw materials, eliminating the need for coking and iron ore lumping compared to traditional blast furnace ironmaking processes, and significantly reducing CO2 and other pollutants emissions. However, as a new ironmaking process, the flow field, heat transfer, and combustion influencing factors of the main reactor are not resolved. Therefore, in this study, based on the consideration of fluid mechanics, heat conduction, and combustion reaction, a two-dimensional mathematical model was developed for the upper space of SRV (smelting reduction vessel), the main reactor of the HIsmelt ironmaking process, based on actual production data. The effects of hot air oxygen content and daily iron production on the velocity field, temperature field, and CO2 content field inside the SRV were investigated. The results show that as the oxygen content of hot air increases, the central airflow in the furnace develops downward, the gas temperature rises gradually, and the CO2 mass fraction generally shows a rising trend. When the daily output of iron increases, the velocity of airflow in the furnace decreases significantly, the gyratory zone moves upward; the high-temperature distribution zone in the furnace contracts; and the CO2 mass fraction decreases. [ABSTRACT FROM AUTHOR]

High energy composite films made from high explosives has important applications in pyrotechnics. In this study, electrostatic spraying was used to prepare energy-containing films based on 1,2,3,4-butanetetrol tetranitrate (ETN). The results show that all energy containing films are made of nanofibres. They have excellent hydrophobicity and combustion properties. In particular, monolayer films in which ETN is the main energy containing substance. Once ignited, the trace monolayer film generates a maximum pressure of 0.85 MPa and an adiabatic flame temperature of 2,855 °C. For single and double layer films, the heat of combustion can reach 9899 J/g and 11975 J/g respectively. The level of combustion heat can also be controlled by adjustment of the ETN content. The results of the thermo-properties performance evaluation show that by optimizing the nanostructure, the ETN-based energy-containing fiber membranes can meet the requirements of advanced pyrotechnic products. In particular, there is great potential in the metastable intermixed composites (MICs) field. [ABSTRACT FROM AUTHOR]

Balancing the enhancement of flame retardancy of epoxy resin while maintaining its mechanical capacities intact poses a significant challenge in the realm of flame‐retardant epoxy resins. To reach the above objectives, a COF‐based synergistic flame retardant with phosphorus, nitrogen, and silicon (PA‐COF@MT) was synthesized using phytic acid (PA), montmorillonite (MT), and covalent organic framework (COF). When PA‐COF@MT was added at 4 wt%, EP/PA‐COF@MT exhibited a reduction of 42.1% in peak heat release rate (PHRR), 45.84% in total heat release (THR), and 59.8% in total smoke production (TSP) compared with the pure EP. LOI increased by 30.5% and UL‐94 tested to V‐0 grade. flame‐retardant index (FRI) value of 3.03, achieving a "good" rating. Fire growth indices and mean effective combustion heat were increased while mechanical properties also improved. These findings suggest that the flame retarding mechanism of PA‐COF@MT is mainly through vapor phase and condensed phase actions. The combined effects of phosphorus, nitrogen, and silicon make the surface of carbon residue solid and dense, resulting in excellent heat insulation and smoke suppression effects. In simple terms, this study provides new insights into COF‐based flame retardants. Combining low‐cost and simple preparation methods, PA‐COF@MT has broad application prospects in flame‐retardant epoxy resin systems. [ABSTRACT FROM AUTHOR]

Using biogas fuel in a modern internal combustion engine equipped with gas equipment of the fourth and fifth generations can create several difficulties. This is due to the low heat of combustion of untreated biogas, the presence of moisture, and the specifics of the injectors. The main problem of the studies we considered is that there are no data on the operating parameters of biogas fuel injectors. Studies on the parameters of the Matrix, Barracuda, Valtek, Hana, and Keihin injectors in relation to biogas fuel were carried out according to performance indicators, the linearity of operation, the resistance of the injectors, the ability to maintain factory parameters, and service life. According to the indicators of performance and linearity of work, Valtek injectors have the highest deviation in productivity and linearity of work, with an average of 38.8%, and the lowest deviation of Barracuda injectors is 7.5%. Keihin (15.3%) and Hana injectors (19.1%) also showed good performance indicators, and therefore can be used effectively for biogas fuel systems. As a result of research on the response time of the injectors, it was established that the best indicators were found for Hana (1.75 ms) and Keihin (1.99 ms) injectors. Valtek injectors showed good response rates (2.07 ms), as did Barracuda injectors (2.19 ms), but the highest response time was found in Matrix injectors, with 2.44 ms. Keihin injectors had the lowest average resistance value of 1.25 ohms, and Valtek injectors had the highest resistance value of 3 ohms. According to the research results, Keihin, Matrix, and Barracuda injectors provide the best ability to maintain factory performance when using biogas fuel at 2 to 5%, and Valtek had the worst performance up to 20%. Keihin, Barracuda, and Hana experimental injectors had the highest service life, which is from 200 to 250 thousand km of car mileage. The lowest indicators were found for Valtek and Matrix injectors, the service life of which varies from 70 to 100 thousand km of mileage. [ABSTRACT FROM AUTHOR]

The study presents the potential use of winemaking residues, specifically grape pomace, for energy purposes. The pomace was obtained from the cultivation of the Regent grape variety on three different rootstocks—125AA, 161-49, and SO4—as well as a control group grown on its own roots. The research included determining the calorific value and combustion heat, conducting a technical and elemental analysis of the potential biofuel, as well as estimating emission indicators (CO, CO2, NOx, SO2, and particulate matter) and the theoretical volume of flue gases based on stoichiometric equations. The study revealed significant differences among the combustion heat, tested properties and calorific value, ash content, and the total volume of flue gases. The highest calorific value (17.7 MJ kg−1) and combustion heat (18.9 MJ kg−1) were obtained for pomace from the SO4SO4 rootstock, while the lowest values were observed in the control group (17.0 MJ·kg−1 and 15.8 MJ·kg−1, respectively). The highest ash content was also recorded for the SO4 rootstock (9.2%), with the lowest in the control group (6.7%). The control group exhibited the lowest CO2 emissions at 1390.50 kg·Mg−1, while the highest emissions were found in the pomace from the SO4 rootstock (1478.8 kg·Mg−1). Regarding the total flue gas volume, the highest volume was estimated for the pomace from the 125AA rootstock (7.8 m3·kg−1) and the lowest for the control group (7.3 m3·kg−1). The research demonstrated that grape pomace possesses favorable energy properties and could serve as a potential biofuel, contributing to the fuel and energy balance of agricultural production enterprises. The analyzed biomass exhibits properties similar to agrobiomass. [ABSTRACT FROM AUTHOR]

Soil contaminated with petroleum-derived products should be used to cultivate energy crops. One such crop is Zea mays. Therefore, a study was performed to determine the suitability of Zea mays biomass obtained from gasoline-contaminated soil for energy purposes. The analysis included determining the heat of combustion and calorific value of the biomass, as well as the content of nitrogen, carbon, hydrogen, oxygen, sulfur, and ash in the biomass. Additionally, the suitability of vermiculite, dolomite, perlite, and agrobasalt for the phytostabilization of gasoline-contaminated soil was evaluated. It was found that the application of sorbents to gasoline-contaminated soil significantly reduced the severe negative effects of this petroleum product on the growth and development of Zea mays. Gasoline contamination of the soil caused a significant increase in ash, nitrogen, and sulfur, along with a decrease in carbon and oxygen content. However, it had no negative effect on the heat of combustion or calorific value of the biomass, although it did reduce the energy production from Zea mays biomass due to a reduction in yield. An important achievement of the study is the demonstration that all the applied sorbents have a positive effect on soil stabilization, which in turn enhances the amount of Zea mays biomass harvested and the energy produced from it. The best results were observed after the application of agrobasalt, dolomite, and vermiculite on gasoline-contaminated soil. Therefore, these sorbents can be recommended for the phytostabilization of gasoline-contaminated soil intended for the cultivation of energy crops. [ABSTRACT FROM AUTHOR]

Wildfire is a disturbance expected to increase in frequency and severity, changes that may impact carbon (C) dynamics in the soil ecosystem. Fire changes the types of C sources available to soil microbes, increasing pyrogenic C and coarse downed wood, and if there is substantial tree mortality, decreasing C from root exudates and leaf litter. To investigate the impact of this shift in the composition of C resources on microbial processes driving C cycling, we examined microbial activity in soil sampled from an Oregon burn 1 year after fire from sites spanning a range in soil burn severity from unburned to highly burned. We found evidence that postfire rhizosphere priming loss may reduce soil C loss after fire. We measured the potential activity of C‐acquiring and nitrogen (N)‐acquiring extracellular enzymes and contextualized the microbial resource demand using measurements of mineralizable C and N. Subsurface mineralizable C and N were unaltered by fire and negatively correlated with hydrolytic extracellular enzyme activity (EEA) in unburned, but not burned sites. EEA was lower in burned sites by up to 46%, but only at depths below 5 cm, and with greater decreases in sites with high soil burn severity. These results are consistent with a subsurface mechanism driven by tree mortality. We infer that in sites with high tree mortality, subsurface EEAs decreased due to loss of rhizosphere priming and that inputs of dead roots contributed to mineralizable C stabilization. Core Ideas: Postfire extracellular enzyme activity decreases were observed only in sub‐soils of higher burn severity sites.In high tree mortality burns, loss of rhizosphere priming may slow decomposition and mitigate carbon loss.This work challenges conventional views that fire affects only the surface of soils via direct heat and combustion. Plain Language Summary: Wildfires are expected to become more severe and frequent, which may change how much carbon is stored in the soil. Fire changes the relative amount of leaves, wood, and charcoal available for soil microbes to decompose, which may affect soil microbial activity and soil carbon as a result. In this study, we evaluated the effect of fire on soil microbial decomposition activity. We found burned areas had less microbial decomposition activity than unburned areas, but only below soil depths of 5 cm in areas where most trees died after the fire. This was a surprising result because fire heat and combustion only directly affects the surface soil. We attribute the lower activity in higher burn severity subsurface soils to greater dead roots and a loss of root secretions, which are known to boost decomposition. Reduced decomposition could partly offset fire‐caused carbon loss from the ecosystem. More research is needed to clarify the long‐term effect on soil carbon. [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]

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]

Purpose: Winter heating in rural areas of northern China requires about 200 million tonnes of standard coal, of which coal is used as the main heat source, causing serious air pollution and exacerbating the greenhouse gas effect. Abundant "zero-carbon" straw in rural areas is a viable strategy for replacing coal-fired heating. The purpose of this paper is to compare the environmental and economic performance of straw heating scenarios. Methods: The environmental impacts and economic costs of four straw heating models across household, village, township, and county scales were compared through life cycle assessment and life cycle cost methods. In this study, the 24-h heat demand of 1 m2 (5.18 MJ) was used as a functional unit. Results: The results showed that the county scale straw cogeneration (CSC) model exhibits the best environmental performance. The global warming potential (GWP) and primary energy demand (PED) of the CSC model are only 11.17% and 10.82% of the household heating model. Straw heating is preferable at the township scale to the village scale from environmental aspects, and direct combustion heating is superior to gasification. For economic aspects, fuel costs are the highest as a percentage of total costs, and the CSC model has the lowest economic costs, with an LCC of 47% of the HSP model. Replacing 20% of coal with straw for heating can reduce annual emissions by 128 million tonnes of CO2 equivalent and the energy conservation and emission reduction impact by 0.17 (19.97%) in rural areas of China. Conclusions: Straw heating reduces the environmental impact as scale increases. At the same scale, straw direct combustion for heating has better environmental and economic performance than gasification. The county scale straw heating model has 89% lower carbon emissions than household scale, and has the best overall performance. [ABSTRACT FROM AUTHOR]

This work assesses a chemical plant for the conversion of biogas into negative emission "emerald hydrogen" via electrified reforming and CO 2 separation. Electrification of the reformer allows for enhanced syngas production, compact reactor designs and flexible operation, thanks to the avoidance of combustion and heat transfer through pressure walls. The integration of the process with solar and wind power generation has been assessed by part-load process simulations and plant sizing and operation optimization through yearly simulations with hourly discretization. Different European locations with different wind and solar availabilities were assessed considering (i) short- and long-term cost scenarios for renewables and battery technologies and (ii) different plant size (from 390 to 3900 Nm3/h of biogas capacity). The overarching scope of the paper is to calculate the cost of the produced hydrogen and the economic value of flexibility for plants installed in different locations, under different cost scenarios. At design load, the assessed process consumes 17.7 kWh of electricity per kg H2 and retains 96% of the biogas chemical energy in the produced hydrogen. Additionally, 76% of the biogenic carbon is recovered as high-purity liquid CO 2 , achieving up to −9 kg CO2 /kg H2 negative emissions. When powered with 95% of renewable energy, hydrogen production cost ranges from 2.5 to 2.9 €/kg for a long-term REN cost scenario and large-scale flexible plant to 5.9–7.1 €/kg for a short-term REN cost scenario and small-scale inflexible plants. For small-scale plants, flexibility allows to reduce the hydrogen production cost by 11–16% with respect to the inflexible plant in the short-term renewables cost scenario and by 1–4% in the long-term cost scenario. For large-scale plants, the adoption of a flexible plant leads to a reduction of 17–23% of the hydrogen cost in the short-term scenario and of 6–22% in the long-term scenario. Operational flexibility of electrified reforming allows reducing the cost of negative-emission bio-hydrogen by 1–23%, depending on location and cost scenario. [Display omitted] • Process engineering study with off-design model. • Economic optimization of flexible process with PV, wind, BESS and gas storages. • 17.7 kWh/kg H2 of electric consumption and up to −9 kg CO2 /kg H2 negative emissions. • H 2 cost of 2.5–6.2 €/kg depending on location, REN cost scenario and plant capacity. • Flexibility reduces H 2 cost by 1–23% depending on location and REN cost scenario. [ABSTRACT FROM AUTHOR]

To investigate the combustion characteristics of non-stick coal and the formation patterns of main combustion products and radicals, this study initially conducted a TG-DSC experiment of non-stick coal. Subsequently, non-stick coal was characterized and analyzed using XPS and 13C NMR experiments, and a molecular model with the formula C208H199O23N3S was constructed. Subsequently, the ReaxFF MD method was employed to simulate the combustion molecular dynamics of the non-stick coal periodic mixing model under varying oxygen content and temperature conditions. The analysis focused on elucidating the formation patterns of free and primary products during combustion. Experimental findings indicate that the combustion of non-stick coal progresses through stages, including water evaporation and desorption (30–145.65 °C), dynamic equilibrium (145.65–181.76 °C), oxygen weight gain (181.76–263.56 °C), thermal decomposition (263.56–379.14 °C), combustion (379.14–562.04 °C) and burnout (562.04–800 °C). The ignition temperature of non-stick coal was determined to be 379.14 °C. The simulation results indicate that an increase in temperature and oxygen content further enhances the relatively stable peak production of CO2. The peak increase of CO production is weaker than that of CO2. The rise in temperature also promotes the formation of H2O, while the increase in oxygen content initially enhances and subsequently inhibits the peak production of H2O. H radicals, O radicals, and OH radicals are primarily generated through the decomposition reactions of small molecular compounds or other free radicals. Free radical polymerization and the decomposition of small molecular compounds represent the primary pathways for the formation of CO, CO2, and H2O. [ABSTRACT FROM AUTHOR]

Global reliance on fossil fuel combustion for energy production has contributed to the rising concentration of atmospheric CO2, creating significant global climate challenges. In this regard, direct air capture (DAC) of CO2 from the atmosphere has emerged as one of the most promising strategies to counteract the harmful effects on the environment, and the further development and commercialization of this technology will play a pivotal role in achieving the goal of net‐zero emissions by 2050. Among various DAC adsorbents, metal–organic frameworks (MOFs) show great potential due to their high porosity and ability to reversibly adsorb CO2 at low concentrations. However, the adsorption efficiency and cost‐effectiveness of these materials must be improved to be widely deployed as DAC sorbents. To that end, this perspective provides a critical discussion on several types of benchmark MOFs that have demonstrated high CO2 capture capacities, including an assessment of their stability, CO2 capture mechanism, capture‐release cycling behavior, and scale‐up synthesis. It then concludes by highlighting limitations that must be addressed for these MOFs to go from the research laboratory to implementation in DAC devices on a global scale so they can effectively mitigate climate change. [ABSTRACT FROM AUTHOR]

In this paper, a heating device is implemented by considering two large factors in a 100 cmm RTO design. First, when the combustion chamber is used for a long time with a high temperature of 750–1100 °C depending on the high concentration VOC gas capacity, there is a problem that the combustion chamber explodes or the function of the rotary is stopped due to the fatigue and load of the device. To prevent this, the 100 cmm RTO design with a changed rotary position is improved. Second, an RTO design with a high-heating element is implemented to combust VOC gas discharged from the duct at a stable temperature. Through this, low-emission combustion emissions and energy consumption are reduced. By implementing a high heat generation device, the heat storage combustion oxidation function is improved through the preservation of renewable heat. Over 177 h of demonstration time, we improved the function of 100 cm by discharging 99% of VOC's removal efficiency, 95.78% of waste heat recovery rate, 21.95% of fuel consumption, and 3.9 ppm of nitrogen oxide concentration. [ABSTRACT FROM AUTHOR]

In this study, free‐standing composites consisting of 90 wt% nanoenergetic mesoparticles are fabricated and their combustion characteristics are investigated. The findings reveal that the integrity of the mesoparticles remains intact during the printing process and a reduction in sintering is observed for the composite of mesoparticles compared to the physical mixture. However, the composite of mesoparticles exhibits noncontinuous and oscillating propagation behavior at a steady frequency of ≈5 Hz. This is attributed to insufficient heat feedback from the flame to the unburnt material. To address this issue, carbon fiber (C.F.) is introduced into the composite to enhance heat feedback to the reaction front by intercepting hot agglomerates near the burning surface. Incorporating C.F. leads to steady propagation of the composite. Agglomerate residence time and characteristic heat transfer time analysis near the burning surface indicate that while the composite without C.F. has agglomerate residence time on the same order of magnitude as the characteristic heat transfer time, the composite with C.F. has significantly increased overall agglomerate residence time compared to the characteristic heat transfer time. This confirms the enhanced heat feedback through C.F. inclusion. This study demonstrates the crucial role of heat feedback in the combustion behavior of energetic composites. [ABSTRACT FROM AUTHOR]

To improve the energy conversion and efficiency, a micro-planar with arranged inlet-fins and bluff-bodies is proposed for H 2 -fueled micro thermophotovoltaic system. Effects of inlet-fins and bluff-bodies setting and combustor dimensions on combustion properties, heat transfer and energy conversion are investigated and analyzed under various operating conditions. The results illustrate that the flame stability and heat transfer in combustion chamber with arranged inlet-fins and bluff-bodies are enhanced, where heat recirculation is formed and radiation temperature is boosted. According to the field synergy analysis, coupling effects of inlet-fins and bluff-bodies on burning and thermal process can be improved by the optimization of bluff-bodies setting, and the flow limit is also expanded. There is a balance of the burner dimensions effects on the augment of radiation surface area and the reduction of radiation temperature for micro power generation. Particularly, the micro-planar with L a / L = 0.62 contributes to achieve a higher radiation density, and the highest electrical output P e = 3.16 W is adopted in combustor C2-0.62 at m f = 6.751 × 10−5 kg/s. It is beneficial to promote energy output of micro-planar and the energy efficiency of micro-thermophotovoltaic system. [Display omitted] • A micro-planar with arranged inlet-fins and bluff-bodies is proposed. • Combustion characteristics and heat transfer in the burner are analyzed. • Effects of burner setting on thermal performance are investigated. [ABSTRACT FROM AUTHOR]

Air injection technique for developing shale oil has gained significant attention. However, the ability of the heat front to consistently propagate within the shale during air injection remains uncertain. To address this, we investigated the heat front propagation within oiledetritus mixtures, shale cores, and fractured shale cores using a self-designed combustion tube (CT) and experimental schemes. By integrating the results obtained from high-pressure differential scanning calorimetry and CT, we developed a comprehensive reaction kinetics model to accurately analyze the main factors influencing the heat front propagation within fractured shale. The findings revealed that in the absence of additional fractures, the heat front failed to propagate within the tight shale. The flow of gases and liquids towards the shale core was impeded, resulting in the formation of a high-pressure zone at the front region of the shale. This pressure buildup significantly hindered air injection, leading to inadequate oxygen supply and the extinguishment of the heat front. However, the study demonstrated the stable propagation of the heat front within the oiledetritus mixtures, indicating the good combustion activity of the shale oil. Furthermore, the heat front successfully propagated within the fractured shale, generating a substantial amount of heat that facilitated the creation of fractures and enhanced gas injection and shale oil flow. It was important to note that after the heat front passed through the shale, the combustion intensity decreased. The simulation results indicated that injecting air into the main fracturing layers of the shale oil reservoir enabled the establishment of a stable heat front. Increasing the reservoir temperature (from 63 to 143 ℃) and oxygen concentration in the injected gas (from 11% to 21%) promoted notable heat front propagation and increased the average temperature of the heat front. It was concluded that temperature and oxygen concentration had the most important influence on the heat front propagation, followed by pressure and oil saturation. [ABSTRACT FROM AUTHOR]

The challenge of paper sludge disposal has become an important environmental issue; therefore, the combustion characteristics of paper sludge need to be examined. In this paper, the combustion of paper sludge particles under different atmospheres was analysed and investigated using a flat flame burner and optical observation techniques under fast temperature rise conditions. The combustion of paper sludge could be divided into a preheating stage, volatile combustion stage, and coke combustion stage. The changes in oxygen content had different effects on the different stages of combustion. The increase in oxygen content had no significant impact on the ignition time of the sludge particles; however, the flame brightness significantly increased. The CH* free radical appeared in the most intense stage of combustion and was depleted before the volatile flame disappeared. A higher oxygen content correlated to a faster CH* depletion. The influence of the oxygen content on the combustion rate and burnout degree of the sludge particles was investigated by comparing mass loss data and heating data. The maximum temperature and heating rate also increased with increasing oxygen content. The reduced oxygen concentration could not fully penetrate the ash layer on the surface of the particles and react with the interior sludge, resulting in a lesser degree of sludge particle burnout. [ABSTRACT FROM AUTHOR]

Air leakage rates are a crucial factor affecting the oxygen supply and heat storage capacity of coal spontaneous combustion (CSC) in goaf in underground coalmines. A suitable airflow rates in goaf can significantly promote CSC. To accurately reveal the effect of airflow rate on CSC, a bituminous coal was selected, and the thermogravimetric and differential scanning calorimetry were used to receive the mass loss characteristics and enthalpy changes for sample. Six characteristic temperatures and five reaction stages were identified under multiple airflow rates, the combustion characteristics were calculated, and apparent activation energy was obtained by Coats–Redfern, FWO and Starink methods. The results indicate that with the increasing airflow rate, the characteristic temperatures decreased firstly and then rose, of which all characteristic temperatures at 150 mL min−1 were the lowest. Meanwhile, the stability and combustion capability of sample were prominently enhanced, and its exothermic ability and heat release enlarged, and the reaction capability with oxygen was the highest at 150 mL min−1. Then, the Avrami–Erofeev equation (n = 3/2) was verified to be the most appropriate mechanism of the coal sample. In addition, apparent activation energy of sample was the lowest at 150 mL min−1, and the CSC ability was sensibly strengthened. The findings will serve as a theoretical basis for the initial stage on CSC in underground coalmines. [ABSTRACT FROM AUTHOR]

The supersonic inflow passes through the shock train in the isolator of the scramjet to complete deceleration and pressurization, followed by combustion and energy release, providing strong thrust. When the back pressure generated by combustion is disturbed forward, the location of shock train leading edge (STLE) will also change accordingly. Once it moves to the entrance of the isolator, it will cause unstart. Accurately detecting STLE in the isolator of a scramjet is crucial for controlling the shock train and preventing the inlet from unstart. Therefore, based on the sparse reconstruction of compressive sensing and sensor compression coupling, a supersonic flowfield reconstruction model (POD-STLE) based on proper orthogonal decomposition (POD) was constructed to reconstruct the supersonic flowfield and detect the location of STLE in the supersonic isolator. The experiments were conducted on the shock oscillation under variable Mach numbers and back pressures, to construct the experimental dataset. Combining supersonic flowfield reconstruction and matrix decomposition, different sensor layouts were constructed, which can ensure accuracy and stability while saving sensor resources. The POD-STLE was applied to the flowfield reconstruction of the supersonic isolator, and the location of STLE was detected under variable and constant conditions, ultimately achieving the expected reconstruction effect and detection accuracy. This study provides a new research method for detecting the location of STLE in the supersonic isolator of a scramjet and provides technical for exploring supersonic flowfield. [ABSTRACT FROM AUTHOR]

In this work, we investigate the properties and stability of the combustion waves propagating in a system of layered solid fuel material in which the neighbouring fuel sheets can recuperate heat via thermal electromagnetic radiation. The analysis is undertaken within the flame sheet model, which allows to determine the combustion wave speed and structure and derive the dispersion relation characterising the stability of the reaction front. The proper choice of parameters leads to superadiabatic combustion temperature and significant increase of the combustion wave speed. In addition, the stable steady regimes of combustion can be substantially extended in the space of parameters. Such an enhancement of stability and ability to control the characteristics of the combustion wave propagation can be very attractive for the combustion synthesis of new layered materials, similarly to the chemical furnace technology proposed earlier. [ABSTRACT FROM AUTHOR]

Catalytic combustion, a highly efficient technique for reducing volatile organic compounds (VOCs), is the focus of this study. We investigate the improved catalytic efficiency of the physical mixing of nanosized Pt and atomically dispersed Co, supported on Al2O3 catalysts (Pt-Co)/Al2O3 (PM) for the catalytic combustion of VOCs. The catalyst efficiency is evaluated for the hydrogen-assisted catalytic oxidation of various VOCs, including aromatic and oxygenated VOCs such as benzene, toluene, methanol, and formic acid. Our study aims to understand the impact of hydrogen incorporation on the combustion process of various VOCs. The findings of this work underscore the potential of hydrogen-assisted catalytic ignition, which can achieve ignition at ambient temperature, a significant departure from conventional electric heating that typically requires additional energy to raise the temperature. Various characterization techniques, such as BET, STEM, and XRD, are employed to assess the structure–activity relationship of the catalyst. The optimal hydrogen concentration for complete VOC conversion is 3%. Notably, even at a lower hydrogen concentration of 2%, benzene and methanol reach an ideal ignition temperature of over 500 °C when introduced into the physically mixed catalyst. This study highlights the significant potential of hydrogen-assisted catalytic combustion, inspiring further research and offering a promising method to reduce VOCs effectively. [ABSTRACT FROM AUTHOR]

The flashover mechanism in an aircraft cargo compartment under low pressure was investigated in this study. A series of fire experiments were conducted in a scale model of a one-quarter volume FAA standard aircraft cargo compartment at 96 kPa and 60 kPa. The ignition of single-walled corrugated cardboard was chosen as the criterion of the flashover. The influence of different fire sizes and fuel types on the flashover was studied by comparing the average temperature of the smoke layer, the radiation heat flux at the floor level, and the heat release rate of the fire source. The critical condition and behavior of the flashover were analyzed. The results show that under low pressure, the flashover occurs at a higher temperature and radiation heat flux. Increasing the fire source size brings the flashover forward. At 60 kPa and 96 kPa, the cardboard ignites under a flashover when the average temperature of the smoke layer reaches 551 °C and 450 °C, and the average radiant heat flux at the floor level reaches 19.6 kW/m2 and 14 kW/m2, respectively. In addition, the minimum fire size for a flashover is directly proportional to the heat of evaporation and inversely proportional to the heat of combustion. [ABSTRACT FROM AUTHOR]

Coal-to-liquid technology is a key technology to ensuring national energy security, with the Fischer–Tropsch synthesis process at its core. However, in actual production, Fischer–Tropsch wax residue exhibits the characteristics of spontaneous combustion due to heat accumulation, posing a fire hazard when exposed to air for extended periods. This significantly threatens the safe production operations of coal-to-liquid chemical enterprises. This study primarily focuses on the experimental investigation of the oxidative spontaneous combustion process of three typical types of wax residues produced during Fischer–Tropsch synthesis. Differential Scanning Calorimetry (DSC) was used to test the thermal flow curves of the three wax residue samples. Kinetic analysis was performed using the Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) methods to calculate their apparent activation energy. This study analyzed the thermal behavior characteristics, exothermic properties, and kinetic parameters of three typical wax residue samples, exploring the ease of reaction between wax residues and oxygen and their tendency for spontaneous combustion. The results indicate that Wax Residue 1 is rich in low-carbon chain alkanes and olefins, Wax Residue 2 contains relatively fewer low-carbon chain alkanes and olefins, while Wax Residue 3 primarily consists of high-carbon chain alkanes and olefins. This leads to different thermal behavior characteristics among the three typical wax residue samples, with Wax Residue 1 having the lowest heat release and average apparent activation energy and Wax Residue 3 having the highest heat release and average apparent activation energy. These findings suggest that Wax Residue 1 has a higher tendency for spontaneous combustion. This research provides a scientific basis for the safety management of the coal chemical industry, and further exploration into the storage and handling methods of wax residues could reduce fire risks in the future. [ABSTRACT FROM AUTHOR]

Transitioning to low-carbon energy systems is crucial for sustainable development, particularly in oil-rich developing countries (ORDCs) that face intertwined economic and environmental challenges. This review uses the PRISMA methodology to systematically assess the current state and prospects of low-carbon thermal electricity generation and utilization technologies in ORDCs. The study emphasizes clean thermal technologies such as biogas, biofuels, biomass, hydrogen, and geothermal energy, focusing on solutions that are technically feasible, economically viable, and efficient in combustion processes. These nations face significant challenges, including heavy reliance on fossil fuels, transmission losses, and financial constraints, making energy diversification urgent. The global shift towards renewable energy and the need to mitigate climate change presents an opportunity to adopt low-carbon solutions that align with Sustainable Development Goals related to energy access, economic growth, and climate action. This review aims to (1) evaluate the current state of low-carbon thermal electricity technologies, (2) analyze the technical and economic challenges related to combustion processes and energy efficiency, and (3) provide recommendations for research and policy initiatives to advance the transition toward sustainable thermal energy systems in ORDCs. The review highlights practical approaches for diversifying energy sources in these nations, focusing on overcoming existing barriers and supporting the implementation of clean thermal technologies. [ABSTRACT FROM AUTHOR]

This paper presents the results of analytical studies of the combustion process of semi-coke, cedar sawdust, and their mixtures using the TGA method at three different heating rates with the determination of the main characteristics of heating: the presence of synergetic interaction between the components of the mixture affecting the maximum rate of combustion and kinetic parameters. Calculations of activation energy and pre-exponential multiplier of the Arrhenius equation by the Friedman and Ozawa–Flynn–Wall priori methods for initial combustibles and their mixtures have been carried out. Semi-coke was obtained by thermal treatment of brown coal at 700–900 °C to remove volatile substances, which makes it more environmentally friendly than the original coal. Semi-coke has a higher heat of combustion than biomass, and biomass has a higher reactivity than semi-coke. The combustion process of biomass occurs in a lower temperature range, and adding biomass to semi-coke shifts the combustion process to a lower temperature range than such for biomass. Adding at least 50% of biomass to semi-coke increases the combustion index by at least 1.1 times. Regardless of the heating rate of mixtures, synergetic interaction between the mixture's components increases the maximum combustion rate of coke residue by 20%. [ABSTRACT FROM AUTHOR]

To improve energy savings and emission reduction in industrial heating furnaces, this study investigated the impact of various molar fractions of hydrogen on natural gas combustion and compared the results of the Non-Premixed Combustion Model with the Eddy Dissipation Combustion Model. Initially, natural gas combustion in an industrial heating furnace was investigated experimentally, and these results were used as boundary conditions for CFD simulations. The diffusion flame and combustion characteristics of natural gas were simulated using both the non-premixed combustion model and the Eddy Dissipation Combustion Model. The results indicated that the Non-Premixed Combustion Model provided simulations more consistent with experimental data, within acceptable error margins, thus validating the accuracy of the numerical simulations. Additionally, to analyze the impact of hydrogen doping on the performance of an industrial gas heater, four gas mixtures with varying hydrogen contents (15% H2, 30% H2, 45% H2, and 60% H2) were studied while maintaining constant fuel inlet temperature and flow rate. The results demonstrate that the Non-Premixed Combustion Model more accurately simulates complex flue gas flow and chemical reactions during combustion. Moreover, hydrogen-doped natural gas significantly reduces CO and CO2 emissions compared to pure natural gas combustion. Specifically, at 60% hydrogen content, CO and CO2 levels decrease by 70% and 37.5%, respectively, while NO emissions increase proportionally; at this hydrogen content, NO concentration in the furnace chamber rises by 155%. [ABSTRACT FROM AUTHOR]

Although various hypergolic propellants like MMH/N2O4 (monomethylhydrazine/dinitrogen tetroxide) are widely used in small rocket engines, there remains a lack of in-depth study conducted on their chemical reactions and spray combustion behaviors. To fill this research gap, a simplified chemical kinetic model that is suitable for three-dimensional simulation was proposed in this paper for MMH/N2O4. Then, numerical investigation was conducted using the Volume of Fluid (VOF) model to explore the transient injection and atomization of MMH/N2O4 impinging jets in a small bipropellant thruster. Also, the instantaneous formation and evolution of the fan-shaped liquid film were analyzed. With the spray distribution determined, the proposed kinetic model and two existing mechanisms were applied to simulate spray combustion and heat transfer within the thruster, respectively, under the Euler–Lagrange framework. According to the research results, the liquid film covered nearly the entire chamber wall with a sawtooth pattern, which protected against the high temperatures of the engine wall. Notably, the two existing mechanisms showed significant errors in predicting temperature changes around the wall due to the excessively simplified reaction pathways. In contrast, the proposed model enabled the accurate prediction of the chamber pressure, wall temperature, and thrust with an error of less than 10%. Given the high accuracy achieved by the proposed numerical method, it provides a valuable reference for the development of advanced space engines. [ABSTRACT FROM AUTHOR]

Aluminized explosives are widely used in underwater explosives, and their energy release follows a typical time-varying process involving two stages: explosive detonation and afterburning of aluminum powder. Simulated deep-water explosion experiments of hexanitrohexaazaisowurtzitane (CL-20)-based explosives were conducted using a deep-water explosion pressure tank to study the effect of aluminum powder combustion on the shockwave propagation and bubble pulsation of deep-water explosions. The distribution mechanism of aluminum powder afterburning energy in the process of shockwave propagation and bubble pulsation under a high hydrostatic pressure was clarified, and the effect of aluminum contents on the bubble behavior of deep-water explosion was obtained by the proposed calculation method of bubble behavior. The results showed that the pressure of the shockwave of the CL-20-based aluminized explosive was lower, and the energy released by the combustion of aluminum powder increased the pressure in the middle and end of the shockwave's trailing edge, reduced the shockwave attenuation rate, and increased the first bubble pulse pressure and pulse period. The afterburning phenomenon of aluminum powder in the CL-20 aluminized explosive in explosion bubbles under high hydrostatic pressures was captured in the simulated deep-water explosion experiment for the first time. It was proven that the combustion time of the micro-aluminum powder was at the millisecond level, and the maximum radius of the bubble increased with the afterburning of aluminum powder. The characteristic parameters of the first pulsation of the CL-20-based explosive with different aluminum content in deep-water explosions calculated by the second-order Mach accuracy bubble dynamics equation and the equation of state of the explosion products were within 7% of the experimental values. The change of the afterburning process of the aluminum powder caused by the aluminum content has a great influence on the bubble behavior, and through the design of aluminum content, ideal deep-water explosion bubble characteristic parameters can be obtained. [ABSTRACT FROM AUTHOR]

The effects of compression ratio and injection timing on a direct injection spark ignition hydrogen engine under various excessive air ratios were analyzed using a 0.4-L single-cylinder engine in this study. The engine speed was set to 1500 rpm, and the excessive air ratio was changed by controlling the amount of injected hydrogen under wide-open throttle conditions. The compression ratio was changed from 10, 12, and 14 and the injection timing was varied from BTDC 200, 160, 120°CA. The results revealed that for a compression ratio 14 at a rich limit, late injection timing reduced knocking incidence by taking advantage of stratified mixtures combustion and increased indicated thermal efficiency by reducing combustion loss while producing lower NOx emissions. For compression ratio 14 at an excessive air ratio of 2.2, late injection timing increased indicated thermal efficiency by reducing both combustion and heat losses, achieving the higher indicated thermal efficiency of 42.3%. Although NOx emissions increased with the injection timing retardation, NOx emissions decreased to under 1 g/kWh under excessive air ratios above 2.5 conditions at all injection timings. [ABSTRACT FROM AUTHOR]

Boron is a potential fuel for energetic materials due to its high volumetric and gravimetric energy density. However, its application has long been constrained by ignition difficulties and insufficient combustion. In this study, a mixture of NGO and GF was introduced as an additive to boron particles. We prepared NGO/GF-coated B complexes and performed several characterizations, showing that NGO combined with GF had a good coating effect on B. The combustion heat was measured by an oxygen bomb calorimeter, while the combustion mechanism was proposed. Its effect on the thermal decomposition behavior of AP was also analyzed. The results showed that the combustion efficiency of NGO/GF-modified B was significantly improved, which was 14.34% higher than that of pure B. This enhancement was attributed to the synergistic effect of NGO and GF, which promoted ignition and combustion by releasing heat, gases, and fluorocarbon radicals. In addition, both boron and NGO/GF-modified boron accelerated the decomposition of AP, especially, in the presence of NGO/GF, the decomposition temperature of AP was advanced by 73.2 °C compared to that in the presence of boron alone. These findings may provide valuable theoretical guidance for the design and potential application of NGO/GF modified boron in energetic materials. [ABSTRACT FROM AUTHOR]

Bushfires pose a significant threat to numerous countries, often causing vast property damages and loss of lives. Efforts to combat and manage these fires heavily rely on predicting the fires' rate of spread and intensity. A significant component of these predictions involves understanding the thermophysical characteristics of vegetative fuels. The accuracy of predictive models (especially physical models) also depends on obtaining precise thermophysical and combustion parameters. This research aims to provide a comprehensive set of thermal degradation and combustion parameters for surface and near‐surface fuel samples collected during prescribed fire experiment conducted in April 2022 in Little Desert National Park, Victoria, Australia. Firstly, fuel properties like fuel height, moisture content, bulk density, fuel load and heat of combustion were meticulously characterized for both surface and near‐surface samples. Then activation energies for degradation reactions were determined using the Flynn–Wall–Ozawa method and for the determination of pre‐exponential factors, in most cases these reactions closely aligned with a Second order model. This was followed by determination of other parameters such as heat of reaction, specific heat and conductivity. It was found that the density, activation energy and heat of combustion did not vary significantly across the six samples under question. The comprehensive set of obtained parameters will likely help to facilitate better predictions in fire propagation modelling. [ABSTRACT FROM AUTHOR]

In this paper, the results of the technological combustion of SHS heat insulators based on mineral origins are presented. It is shown that after mechanochemical treatment of minerals—diatomite—the kinetic characteristics of the combustion process change, providing targeted formation of the phase composition, structure, and properties of the SHS composite. A positive effect of using various modifiers during the MCT of diatomite—the activation of the combustion process—was established. The selection of modifiers provides an increase in the strength of the synthesized SHS composites as a result of the formation of aluminate compounds in the synthesis products, and a decrease in thermal conductivity to 0.157 W/m*K due to the formation of the ultraporous structure of the samples. [ABSTRACT FROM AUTHOR]

This research involves the blending of readily accessible waste materials, namely diaper cellulose (DC) and sugarcane bagasse (SB), for a comprehensive thermodynamic and kinetic analysis during co-pyrolysis. Thermogravimetric analysis (TGA) has been conducted to undertake a co-pyrolysis investigation across different ratios of DC and SB. The analysis covered a temperature sequence of 20°C–800°C with varying heat flow rates of 10°C/min, 20°C/min, and 30°C/min. For activation energy determination, the Kissinger–Akahira–Sunose (KAS) and Ozawa–Flynn–Wall (OFW) methods were employed. The average activation energy, calculated using the OFW and KAS methods, was found to have values in the range of 209.46 and 226.109 kJ/mol for DC, 139.08 and 157.41 kJ/mol for 50DC-50SB, and 102.19 and 109.758 kJ/mol for SB, respectively. The activation energy data of the mixtures were shown to be decreasing from the pristine DC. Notably, the mixture exhibited a lower activation energy, indicating a positive synergistic effect resulting from co-pyrolysis. Thermodynamic parameters such as ΔH, ΔS, and ΔG for the mixture were also evaluated. The Gibbs free energy (ΔG) across samples varied between 288.71 and 123.05 kJ/mol for pure DC, DC-SB mixtures, and pure SB, demonstrating a notable influence on co-pyrolysis. The observed decrease in energy levels in the mixture suggests that the combination of sugarcane bagasse with diaper cellulose results in a reduced energy demand. Practical Applications: The activation energy, determined through thermogravimetric analysis (TGA), delivers valuable insights into the thermal decomposition behavior of materials. The TGA data help in illustrating the thermal constancy of materials, allowing researchers to assess the suitability of substances for specific applications. In industries such as pharmaceuticals, polymers, and chemicals, TGA with activation energy determination can be employed for quality control purposes. The calculated thermodynamic data are crucial in designing and optimizing pyrolysis and gasification processes. They aid in predicting the rate of thermal decomposition, optimizing reaction conditions, and improving the efficiency of these processes for bioenergy production or waste treatment. TGA with activation energy analysis is extensively used in the polymer industry. It assists in understanding the degradation kinetics of polymers, enabling the development of heat-resistant materials for specific applications. Also, these values are essential in catalyst design for chemical reactions. They guide the selection and optimization of catalysts for various processes, ensuring efficient and economical chemical transformations. Determining the activation energy of fuels provides critical information for combustion processes. This is useful in optimizing combustion conditions for energy production, as well as in assessing the stability and safety of fuel storage. [ABSTRACT FROM AUTHOR]

A phosphorus-nitrogen organic salt flame retardant (EP) was synthesized through a simple one-step reaction using etdronic acid as a phosphorus source (EA) and antiphenylenediamine (PPD) as a nitrogen source. Its structure was characterized by !H-NMR and FTIR spectroscopy. The flame-retardant TPU was prepared by mixing TPU with EP using a melt blending method, and its thermal stability, flame retardant performance, and mechanical properties were investigated. The results indicated that the addition of EP generated little effect on the thermal stability of TPU, and its flame retardancy was significantly improved. The flame-retardant TPU containing 3 wt. % EP (TPU-3% EP) obtained a limiting oxygen index of 28. 40 vol. % and also achieved a UL 94 V"0 classification in the vertical burn experiment. The residual carbon yield (CY) was more than twice that of pure TPU. Compared with pure TPU, the total heat release and peak heat release rate of TPU-3% EP were reduced by 22. 12% and 61. 85%, respectively, and its effective combustion heat was also reduced. EP can enhance the flame-retardant performance of TPU mainly by catalyzing the condensation phase to form charcoal and isolate thermal oxygen exchange. Moreover, the free radical quenching effectiveness in the gas phase also generates a certain flame-retardant effect. [ABSTRACT FROM AUTHOR]

Boron (B) powder is considered to be an excellent fuel for propulsion applications due to its remarkable energy density. However, B is severely affected by boron oxide (B2O3) on its surface. To solve this problem, polyvinylidene fluoride (PVDF) and copper oxide (CuO) coatings were applied onto B particles, leveraging their synergistic effects to enhance the ignition and combustion performance (ICP) of B. Various characterization methods and CO2 laser ignition experiments were used to determine how PVDF and CuO impact B combustion. PVDF and CuO are helpful to improve the ICP of B. Especially for the (B/CuO4)@PVDF16 sample, it exhibits 28.2% higher combustion heat, 46.4% shorter ignition delay, and flame expansion rate (FER) increases from 0.091 to 0.280 m s−1 versus unmodified B. Furthermore, PVDF suppresses B powder agglomeration during combustion. The present work provides a new idea for improving the combustion of B powder. [ABSTRACT FROM AUTHOR]

In recent years, ancient wooden building fires have been a hot issue that has not been properly solved. The existing ancient wood buildings objectively have serious natural ageing phenomenon, among which the dry and wet alternating ageing phenomenon of wood caused by water is the most serious. However, the phenomenon of dry and wet alternating ageing pays less attention to the influence of wood combustion. Therefore, this study took the typical wood species of ancient wooden buildings as the research object, based upon the natural ageing phenomenon of these buildings, determining the artificial acceleration of dry and wet alternate ageing method, to obtain dry and wet alternate ageing wood. The thermal diffusion coefficient of dry and wet ageing wood was analysed by thermal property experiments. Using differential scanning calorimetry experiment, we appraised the change law of heat flow in the combustion process of dry and wet ageing wood, determined the characteristic peak intensity and stage continuous temperature of dry and wet ageing wood, and mastered the change characteristics of wood in different thermal release stages affected by dry and wet alternating ageing. Finally, the apparent activation energy distribution of ageing wood in different exothermic stages was calculated and analysed by isoconversion method. The influence mechanism of alternating dry and wet ageing on wood combustion thermal release behaviour was revealed. The results show that the main thermal release of dry–wet ageing is the stage of volatiles precipitation. The alternate ageing of dry and wet has the greatest impact on the energy demand of thermal response in the accelerated thermal release stage. The influence of alternating dry and wet ageing on different types of wood in the rapid exothermic stage is quite different. [ABSTRACT FROM AUTHOR]

To avoid increasing the dilution gas to achieve higher temperatures for rapid compression machines (RCM) at the end of compression, this study introduced an oil-bath heating system designed to precisely improve the initial temperature of the mixture, thereby enabling ammonia-hydrogen ignition at practical fuel concentrations for internal combustion engines (ICEs). Using this oil-bath heated RCM, the ignition delay times (IDTs) of ammonia-hydrogen under conditions relevant to ICEs were measured. The ammonia-hydrogen combustion mechanism proposed by Stagni et al. (10.1016/j.proci.2022.08.024) was then validated against these measured IDTs and subsequently optimized. Guided by a comprehensive review of the existing literature on ammonia-hydrogen chemistry, the optimization involved updating 42 reaction rate coefficients and adding 9 new reactions. The optimized mechanism, comprising 31 species and 214 reactions, demonstrated accurate predictions of ignition delay time, laminar flame speed, and species mole fractions across a wide range of experimental setups and conditions for ammonia-hydrogen, confirming the mechanism's robust performance and its suitability for high-precision simulations in ammonia-hydrogen ICE applications. • An oil-bath heating system was developed to elevate the mixture temperatures of an RCM. • The NH 3 –H 2 ignition delay times (IDTs) at engine relevant conditions were measured. • An NH 3 –H 2 kinetic model was constructed with reliable reaction rate constants. • The model well predicts the NH 3 –H 2 IDTs, laminar flame speed, and species mole fractions. [ABSTRACT FROM AUTHOR]

To achieve zero carbon emissions, replacing conventional fuels in combustion engines and gas turbines with carbon-free fuel is of utmost important. While hydrogen is effective in mitigating climate change, the cost challenges in liquefaction and transportation persist. Ammonia (NH 3), a carbon-free fuel with its higher volumetric energy density and cost advantages, emerges as a potential substitute. This review reports the most recent studies on NH 3 as a fuel for micro gas turbine (MGT), highlighting both advantages and limitations. The performance and emissions in gas turbines are discussed. The main obstacles to a widespread usage of NH 3 blends as fuel for MGT power generation are addressed, along with the current stage of commercialization. The review explores all the numerical and experimental works on NH 3 blend in combustion system of MGT, and further presents ways to overcome the limitations associated with the combustion, such as high NO x emissions and low burning velocity. [Display omitted] • A comprehensive analysis of ammonia blend reactive fuels for micro gas turbine power generation is presented. • Advantages and limitations of ammonia combustion in micro gas turbine over hydrocarbon fuels are summarized. • The issues that hinder a widespread usage of ammonia and ammonia/blend as fuel for micro gas turbine are addressed. • The current stages of commercialization are discussed. • Possible approaches to overcome ammonia combustion barriers in micro gas turbine are highlighted for future research. [ABSTRACT FROM AUTHOR]

The design of novel energetic compounds constitutes a pivotal research direction within the field of energetic materials. However, exploring the intricate relationship between their molecular structure and properties, in order to uncover their potential applications, remains a challenging endeavor. Therefore, employing multi-molecule assembly techniques to modulate the structure and performance of energetic materials holds immense significance. This approach enables the creation of a new generation of energetic materials, fueling research and development efforts in this field. In this study, a series of coordination compounds are synthesized by utilizing tetranitroethide (TNE) as an anion, which possesses a high nitrogen and oxygen content. The synthesis involves the synergistic modification between metal ions and small molecule ligands. Characterization of the obtained compounds is carried out using various techniques, including single crystal X-ray diffraction, IR spectroscopy, elemental analysis, and simultaneous TG–DSC analysis. Additionally, the energy of formation for these compounds is calculated using bomb calorimetry, based on the heat of combustion. The detonation performances of the compounds are determined through calculations using the EXPLO 5 software, and their sensitivities to external stimuli are evaluated. [ABSTRACT FROM AUTHOR]

Introduction: Fuel cell technology is a harbinger of the future for generating electricity due to their high efficiency and low emissions achieved through the direct conversion of chemical energy into electrical energy without combustion. Methods: To optimize the design and performance, a fuel cell model is essential to predict its behaviour in different conditions. This technical note presents a novel physics-based approach, the Young's Double-slit Experiment Optimizer (YDEO), for identifying parameters in Proton Exchange Membrane Fuel Cells. A performance metric is established by formulating an objective function that relies on the summation of squared errors between experimental and estimated values. Results and discussion: The effectiveness of this approach is evaluated through the analysis of four benchmark test cases: Horizon 500 W, BCS500 W, NedstackPS6, and 250 W. The corresponding objective function values for these test cases are 0.011243, 2.065557, 0.011698, and 5.250849, respectively. The simulation results demonstrate the efficacy of the proposed YDEO algorithm when compared with other existing popular and contemporary algorithms in the literature. [ABSTRACT FROM AUTHOR]

The phenomenon of spontaneous combustion during the release of high-pressure H 2 is critical to the safe storage and transportation. Besides physical methods to suppress self-ignition, the approach of mixing low-reactivity gases has gained increasing attention. Previous work has mainly focused on the flow, physical heating effects, and boundary conditions of self-ignition in mixed gases, while the intrinsic chemical reaction mechanisms of spontaneous combustion remain underexplored. To clear this issue, this work uses the ReaxFF MD simulation method to study the spontaneous combustion process of H 2 /CO and H 2 /CH 4 mixtures with various concentrations. The results indicate that: (1) in pure H 2 , H 2 /CO, and H 2 /CH 4 systems, the primary initial reaction mechanism is H 2 +O 2 HO 2 +H. Additionally, in some mixed systems, CO + O 2 CO 2 +O and CH 4 +O 2 CH 3 +HO 2 may also serve as initial reaction mechanisms. (2) Under fuel-lean combustion conditions, the RIDTs of the systems decrease, supporting the viewpoint that self-ignition typically occurs first in fuel-lean regions. The addition of CO and CH 4 increases the RIDTs, which helps inhibit the development of self-ignition. (3) In H 2 -rich environments, CO combusts to CO 2 through the formation of HOCO, while CH 4 undergoes dehydrogenation and oxidation processes through intermediates such as CH 3 , CH 3 O, and HCHO, leading to the formation of CO and CO 2. The combustion of H 2 is also influenced by these processes. (4) The addition of CO and CH 4 increases the activation energy of H 2 combustion, raising the reaction energy barrier that must be overcome for spontaneous combustion. This effectively helps to suppress the occurrence and development of self-ignition during the release of high-pressure gases. • Clear initial reaction mechanism of pure H 2 , H 2 /CO, and H 2 /CH 4 combustion systems. • RIDTs of H 2 , H 2 /CO, and H 2 /CH 4 systems are statistically analyzed and compared. • Reaction pathways of H 2 , CO, and CH 4 in mixed systems have been identified. • Combustion activation energies of H 2 in mixed systems are calculated. • Explained the inhibition of self-ignition from a molecular reaction perspective. [ABSTRACT FROM AUTHOR]

To reduce fossil fuel consumption, blending sludge pyrolysis gas and ammonia (NH 3) for combustion enables the energy utilization of sludge pyrolysis gas while improving combustion characteristics of NH 3. This study employs chemiluminescence to investigate the structure of sludge pyrolysis gas/ammonia/air flame for the first time. A thorough investigation was conducted into the impacts of various swirl structure parameters on the stable combustion range and pollutant emissions. To further reduce pollutant emissions, staged combustion was used, and the effects of ammonia doping ratio, secondary air equivalence ratio, and secondary air inlet height on pollutant emissions were analyzed. The findings demonstrate that increasing the ammonia ratio narrows stable combustion equivalence ratio range. Additionally, at a thermal power of 5 kW, stable combustion was observed in the equivalence ratio range of 0.41–1.70, an improvement of 95.5%. Notably, staged combustion significantly reduced NO emissions, achieving concentrations as low as 32.7 ppm under stoichiometric conditions, compared to 1912.6 ppm in non-staged pure NH 3 combustion. This study provides valuable insights into the stability and emission characteristics of sludge pyrolysis gas/ammonia swirl burners for efficient and cleaner low-carbon fuels utilization. • First study on the stability and emissions of pyrolysis gas/NH 3 swirling flames. • Ammonia addition reduces OH* radiation intensity, particularly in lean combustion. • Increasing ammonia narrows the stable combustion equivalence ratio. • The optimal swirl parameters for stable combustion are proposed. • Staged combustion at 150 mm height reduces NO emissions to 32.7 ppm. [ABSTRACT FROM AUTHOR]

The dynamics of an axisymmetrical swirling jet is studied via global linear stability and resolvent analyses. The modeled flow represents a combustor-like swirling jet, that is turbulent, compressible, non-parallel, and enclosed. In particular, the computational domain embeds a realistic axisymmetrical swirler model to resolve the mode conversion process. Swirl fluctuations are non-negligible on this configuration representative of a swirl burner, and match the analytical mode shapes of inertial waves of an inviscid uniform flow as obtained from global stability analysis. The stability map presents two eigenvalues driving a modal amplification. These eigenmodes couple a standing acoustic wave sustained in the mixing duct and the combustion chamber with the Kelvin-Helmholtz mechanism at the mixing duct exit and the acoustic-vorticity mode conversion process at the swirler, and act as a frequency selection criterion. Finally, the most amplified forcing from the resolvent analysis is similar to an unsteady heat source in the combustion chamber, and the identified optimal amplification mechanism is likely to be triggered in reacting flow with unsteady heat release rate. [ABSTRACT FROM AUTHOR]

The transition to cleaner energy sources, particularly in hard-to-abate industrial sectors, often requires the gradual integration of new technologies. Hydrogen, crucial for decarbonization, is explored as a fuel in blended combustions. Blending or replacing fuels impacts combustion stability and heat transfer rates due to differing densities. An extensive literature review examines blended combustion, focusing on hydrogen/methane mixtures. While industrial burners claim to accommodate up to 20% hydrogen, theoretical support is lacking. A novel thermodynamic analysis methodology is introduced, evaluating methane/hydrogen combustion using the Wobbe index. The findings highlight practical limitations beyond 25% hydrogen volume, necessitating a shift to "totally hydrogen" combustion. Blended combustion can be proposed as a medium-term strategy, acknowledging hydrogen's limited penetration. Higher percentages require burner and infrastructure redesign. [ABSTRACT FROM AUTHOR]

Sustainable technologies to replace current fossil solutions are essential to meet future CO2 emission reduction targets. Therefore, this paper compares key performance indicators of a hydrogen- and a methane-flame-fired crucible furnace with computational fluid dynamics simulations at identical firing powers, aiming to fully decarbonize the process. Validated numerical models from the literature were used to compare temperatures, radiation fields, radiation parameters and heat transfer characteristics. As a result, we observed higher combustion temperatures and a 19.0% higher fuel utilization rate in the hydrogen case, indicating more efficient operating modes, which could be related to the increased radiant heat flux and temperature ranges above 1750 K. Furthermore, higher scattering of the heat flux distribution on the crucible surface could be determined indicating more uneven melt bath temperatures. Further research could focus on quantifying the total fuel consumption required for the heating up of the furnace, for which a transient numerical model could be developed. [ABSTRACT FROM AUTHOR]

Combustion modes of kerosene spray in a scramjet combustor condition with different injection schemes are experimentally investigated at Mach 2.52. The study is based on two single injectors with nozzle diameters of 0.79 and 1.14 mm and two dual injectors with nozzle diameters of 0.56 and 0.72 mm, respectively. The results show that the weak combustion mode has little effect on the flow field, while the intensive combustion mode has the opposite effect. The dual injector can promote evaporation and mixing of the kerosene spray. Compared with the dual injector, intensive combustion cannot occur when a single injector is used, and the flame stability range is also narrower. As the nozzle diameter of the injector increases, the distribution and oscillation of kerosene spray change significantly, transition from the weak to intensive combustion mode occurs at a higher equivalence ratio, and the flame stability range increases. However, change in the nozzle diameter does not affect the overall process of combustion mode transition. For the single injector, intensive combustion still cannot occur when the nozzle diameter changes. In addition, change in the nozzle diameter has little effect on combustion heat release when the combustion mode remains unchanged. [ABSTRACT FROM AUTHOR]

This study introduces an empirical model designed to predict the maximum values of time-dependent data across four turbulence-related fields: hydrogen combustion in renewable energy systems, urban microclimate effects on cultural heritage, shipping emissions, and road vehicle emissions. The model, which is based on the mean, standard deviation, and integral time scale, employs two parameters: a fixed exponent 'ν' (0.3) reflecting time scale sensitivity, and a variable parameter 'b' that accounts for application-specific uncertainties. Integrated into the Computational Fluid Dynamics (CFD) framework, specifically the Reynolds-Averaged Navier–Stokes (RANS) methodology, the model addresses the RANS approach's limitation in predicting extreme values due to its inherent averaging process. By incorporating the empirical model, this study enhances RANS simulations' ability to predict critical values, such as peak hydrogen concentrations and maximum urban wind speeds, which is essential for safety and reliability assessments. Validation against experimental and numerical data across the four fields demonstrates strong agreement, highlighting the model's potential to improve CFD-RANS predictions of extreme events. This advancement offers significant implications for future CFD-RANS applications, particularly in scenarios demanding fast and reliable maximum value predictions. [ABSTRACT FROM AUTHOR]

Warsaw is among European cities with the worst atmospheric air quality, mainly due to very high pollution emitted by the residential sector and road traffic. This results in high concentrations of particulate matter and nitrogen oxides, often exceeding WHO standards. The paper discusses the current and expected effects of actions taken by the Warsaw authorities, to significantly improve air quality in the city. The policy directly addresses one of the UN Sustainable Development Goals (SDG 11, Sustainable Cities and Communities). The analysis presented in the paper consists of two stages. The first, covering the years 2018–2029, deals with the ongoing Clean Air Program, which assumes primarily the reduction, and ultimately the complete elimination, of coal combustion in all heat sources of the residential sector. This sector is widely identified as the main source of urban air quality degradation, especially in Polish cities due to the dominant share of coal in the fuel mix. The second part of the corrective measures, covering the period 2024–2034, primarily concerns the reduction of nitrogen oxide pollution, mainly from traffic. The latter takes into account the expected effects of the introduction of a Low-emission Zone (LEZ) in the city center (launched in July 2024) and implemented in five two-year stages, in which car emission limits will be gradually tightened. According to the analysis results, the implementation of the Clean Air Program can result in about a 20% reduction in annual average PM2.5 concentrations by 2024, with a small (about 9%) reduction in NOx. At the same time, a significant reduction in NOx levels can be achieved by full implementation of the LEZ, especially within the zone boundaries (more than 50%). An important factor here is the size of the zone. The paper compares the effectiveness of two being considered versions, differing in size zones. [ABSTRACT FROM AUTHOR]

Low-temperature combustion (LTC) concepts, such as homogeneous charge compression ignition (HCCI) and partially premixed combustion (PPC), aim to reduce in-cylinder temperatures in internal combustion engines, thereby lowering emissions of nitrogen oxides (NOx) and soot. These LTC concepts are particularly attractive for decarbonizing conventional diesel engines using renewable fuels such as methanol. This paper uses numerical simulations and a finite-rate chemistry model to investigate the combustion and emission processes in LTC engines operating with pure methanol. The aim is to gain a deeper understanding of the physical and chemical processes in the engine and to identify optimal engine operation in terms of efficiency and emissions. The simulations replicated the experimentally observed trends for CO, unburned hydrocarbons (UHCs), and NOx emissions, the required intake temperature to achieve consistent combustion phasing at different injection timings, and the distinctively different combustion heat release processes at various injection timings. It was found that the HCCI mode of engine operation required a higher intake temperature than PPC operation due to methanol's low ignition temperature in fuel-richer mixtures. In the HCCI mode, the engine exhibited ultra-low NOx emissions but higher emissions of UHC and CO, along with lower combustion efficiency compared to the PPC mode. This was attributed to poor combustion efficiency in the near-wall regions and engine crevices. Low emissions and high combustion efficiency are achievable in PPC modes with a start of injection around a crank angle of 30° before the top dead center. The fundamental mechanism behind the engine performance is analyzed. [ABSTRACT FROM AUTHOR]