Search Results (66)

A novel quinoline-containing benzoxazine resin, 8HQ-fa, has been successfully synthesized at room temperature using sustainable raw materials, such as 8-hydroxyquinoline and furfurylamine as the phenol and amine source, respectively. The chemical structure of the hereinafter referred to as quinolinoxazine is fully characterized by Fourier transform infrared spectroscopy (FT-IR), ¹H and ¹³C nuclear magnetic resonance spectroscopy (NMR), as well as by 2D ¹H–¹H nuclear Overhauser effect spectroscopy (NOESY) and ¹H–¹³C heteronuclear multiple quantum correlation (HMQC) NMR. Thermal properties and polymerization behavior of the monomer are studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The resulting polymer is also characterized in terms of its thermal and fire-related properties by DSC, TGA, and microscale combustion calorimetry (MCC). The resulting thermoset, poly(8HQ-fa), presents good thermal stability as evidenced by its T_g (201 °C), T_d5 and T_d10 (307 and 351 °C, respectively), and char yield (42%), and low flammability as determined by the LOI, heat release capacity, and total heat released values (34.3, 143 J/gK, and 10.8 kJ/g, respectively), making it a self-extinguishing thermoset. The combination of properties and advantages in the synthesis of 8HQ-fa, accompanied by a low polymerization temperature, suggests its great potential in the field of high-performance polymers. Full article

Chemical looping combustion (CLC) provides an inherently cost-effective method for carbon capture by employing a solid oxygen carrier (OC) to transfer lattice oxygen from air to fuel. The search for low-cost, high-performance natural OCs is crucial for the large-scale deployment of this technology. A natural iron ore containing 41.34% Fe₂O₃ was systematically evaluated as OC for the CLC of CO. Its redox performance was quantified in a fixed-bed reactor between 750 °C and 900 °C with CO concentrations of 10–20%. Multi-cycle tests were conducted to assess stability. Kinetic analysis of the initial cycles was performed using an integral model fitting method. Multi-cycle tests revealed that the fresh ore achieved peak conversions of 48.9% at 750 °C and 77.2% at 900 °C. However, severe sintering occurred beyond 850 °C after the first cycle, causing approximately a 50% drop in OC conversion. Interestingly, once sintered, a self-activation phenomenon was observed during subsequent cycles; the OC conversion slowly recovered from 32% to 37% from the second to the fifteenth cycle under the aggressive conditions (900 °C, 20% CO). Kinetic analysis of the initial cycles (before sintering) revealed low apparent activation energies, ranging from 15.93 to 19.13 kJ mol⁻¹, which are significantly lower than the typical literature values for iron-based ores. This work underscores the potential of natural iron ores as economical and sustainable OCs for CO-rich fuels. The observed self-activation ability of the sintered OC is a promising finding for long-term operation. The results also highlight the critical importance of operating conditions to avoid deep reduction and sintering, necessitating a high solids inventory and a moderate oxygen-to-fuel ratio in practical CLC systems. Full article

Efficient utilization of low-calorific-value gases reduces emissions but remains challenging. Self-heat-maintained combustion uses fuel’s exothermic heat to sustain stability without external heat, yet the feed gas typically requires preheating (typically 573–673 K). This study innovatively proposes a compact regenerative catalytic reactor featuring an integrated helical heat-recovery structure and replaces empirical preheating with a user-defined function (UDF) programmed heat transfer efficiency model. This dual innovation enables self-sustained combustion at 0.16 vol.% methane, the lowest reported concentration for autonomous operation. Numerical results confirm stable operation under ultra-lean conditions, with significantly reduced preheating energy demand and accelerated thermal response. Transient analysis shows lower space velocities enable self-maintained combustion across a broader range of methane concentrations. However, higher methane concentrations require higher inlet temperatures for self-heat maintenance. This study provides significant insights for recovering energy from low-calorific-value gases and alleviating global energy pressures. Full article

Background: The World Health Organization defined specific recommendations about digital tobacco cessation modalities as a self-management tool or as an adjunct to other support for adults. Objectives: The present umbrella review primarily aimed to assess the long-term (≥6 months) effectiveness and adherence of the different standalone digital tobacco cessation modalities (mobile text messaging, smartphone apps, Internet-based websites and programs, AI-based), administered individually or in combination; secondarily, the study aimed to assess the effect on smokers’ health. Methods: The present study (PROSPERO number: CRD42024601824) followed the PRISMA guidelines. The included studies were qualitatively synthesized and evaluated through the AMSTAR-2 tool. Results: Forty-five systematic reviews were included, encompassing 164,010 adult daily smokers of combustible tobacco. At 6 months, highly interactive or human-centered digital tools showed higher effectiveness (biochemically verified continuous abstinence rates (CARs) were 11.48% for smartphone apps and 11.76% for video/telephone counseling). In contrast, at 12 months, simpler, less interactive tools demonstrated higher effectiveness (self-reported CARs was 24.38% for mobile text messaging and 18.98% for Internet-based). Adherence rates were generally high, particularly with human-centered digital tools, amounting to 94.12% at 6 months and 64.08% at 12 months. Compared with individually administered digital tobacco cessation modalities, at 12 months, combined ones registered slightly higher effectiveness (self-reported CARs were 13.12% vs. 13.94%) and adherence (62.36% vs. 63.70%), potentially attributed to the multi-component nature and longer durations. Conclusions: Clinicians should prioritize combined digital tobacco cessation interventions that incorporate human-centered engagement initially, alongside simpler, sustained digital support to enhance long-term effectiveness and adherence. Future research should explore long-term medical and oral health benefits to assess the impact on overall health and well-being. Full article

This article presents the results of an experimental study focused on evaluating the potential to harvest electrical energy from vertical vibrations affecting a child car seat installed on an ISOFIX base with a support leg during real driving conditions. The objective was to measure vibration levels in the seat structure and assess the feasibility of converting this mechanical energy into electrical power. The study involved two child seat models, each tested under loads of 9 kg and 15 kg, while driving over smooth asphalt, damaged asphalt, and speed bumps. Acceleration data were collected at three key structural locations: the seat surface, the ISOFIX base, and the support leg. These measurements served as the basis for estimating the mechanical energy available and the resulting electrical output. Findings show that in poor road conditions, the system can generate enough energy to power a 10 µW sensor for more than 42 days. The results confirm the feasibility of using vibration energy harvesting to supply smart safety features such as presence detection, temperature monitoring, or posture sensing in child seats, without the need for batteries or a connection to the vehicle’s electrical system. Full article

This article examines the energy efficiency and climate impact of various heating methods commonly employed across industrial sectors. Fossil fuel combustion heat sources, which are predominantly employed for industrial heating, contribute significantly to atmospheric pollution and associated asset losses. The electrification of industrial heating has the potential to substantially reduce the total energy consumed in industrial heating processes and significantly mitigate the rate of global warming. Advances in electrical heating technologies are driven by enhanced energy conversion, compactness, and precision control capabilities, ensuring attractive financial payback periods for clean, energy-efficient equipment. These advancements stem from the use of improved performance materials, process optimization, and waste heat utilization practices, particularly at high temperatures. The technical challenges associated with large-scale, heavy-duty electric process heating are addressed through the novel innovations discussed in this article. Electrification and the corresponding energy efficiency improvements reduce the water consumed for industrial steam requirements. The article reviews new technologies that replace conventional process gas heaters and pressure boilers with efficient electric process gas heaters and instant steam generators, operating in the high kilowatt and megawatt power ranges with very high-temperature capabilities. Financial payback calculations for energy-optimized processes are illustrated with examples encompassing a range of comparative energy costs across various temperatures. The economics and implications of waste heat utilization are also examined in this article. Additionally, the role of futuristic, radical technical innovations is evaluated as a sustainable pathway that can significantly lower energy consumption without compromising performance objectives. The potential for a new paradigm of self-organization in processes and final usage objectives is briefly explored for sustainable innovations in thermal engineering and materials development. The policy implications and early adoption of large-scale, energy-efficient thermal electrification are discussed in the context of temperature segmentation for industrial-scale processes and climate-driven asset losses. Policy shifts towards incentivizing energy efficiency at the manufacturing level of heater use are recommended as a pathway for deep decarbonization. Full article

Cellulose-based aerogel is an environmentally friendly multifunctional material that is renewable, biodegradable, and easily surface-modified. However, due to its flammability, cellulose serves as an ignition source in fire incidents, leading to the combustion of building materials and resulting in significant economic losses and safety risks. Consequently, it is essential to develop cellulose-based building materials with flame-retardant properties. Initially, a porous cellulose-based flame-retardant aerogel was successfully synthesized through freeze-drying, utilizing lignocellulose as the raw material. Subsequently, phosphorylation of cellulose was coupled with Ca²⁺ cross-linking via self-assembly and surface deposition effects to enhance its flame-retardant properties. Finally, the synthesized materials were characterized using infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, mechanical compression testing, and scanning electron microscopy. The aerogel of the phosphorylated cellulose nanofibrils cross-linked via 1.5% CaCl₂ exhibited the most effective flame-retardant properties and the best mechanical characteristics, achieving a UL-94 test rating of V-0 and a maximum flame-retardant rate of 90.6%. Additionally, its compressive strength and elastic modulus were recorded at 0.39 and 0.98 MPa, respectively. The preparation process is environmentally friendly, yielding products that demonstrate significant flame-retardant effects and are non-toxic. This product is anticipated to replace polymer-based commercial aerogel materials, representing a sustainable solution to the issue of “white pollution”. Full article

Fire is a combustion reaction where fuel reacts with oxygen in the presence of heat, releasing energy as light, heat, and flames. The main components of fire are fuel, oxygen, and heat. All three components must be present to cause a fire. Fire is a significant threat to residential and commercial buildings, often intensified by high fuel content in building materials such as wood and synthetics. This paper summarizes fire types and damages, loss of property and life, fuel content in building materials, and a method to reduce fire risk by minimizing the building material’s fuel content. This method uses minerals (coal combustion residual (CCR)), primarily inorganic oxides bonded with a small percentage of polyurethane binder, to manufacture a composite material moldable into multiple building products. The composite was tested as per the ASTM for mechanical, thermal, and fire safety performance. ASTM D635-based fire testing showed self-extinguishing behavior with significantly reduced burn rate and lengths (1–2 mm). A low calorific value of 6.6 MJ/kg was determined separately. The test results demonstrate that CCR-based mineral composites offer a fire-resistant, structurally sound, and eco-friendly alternative to wood products. This research supports recycling inorganic minerals into fire-resistant building products that enhance safety. Full article

The accurate identification of combustion status can effectively improve the efficiency of municipal solid waste incineration and reduce the risk of secondary pollution, which plays a key role in promoting the sustainable development of the waste treatment industry. Due to the low accuracy of the incinerator flame combustion state recognition in the current municipal solid waste incineration process, this paper proposes a Res-Transformer flame combustion state recognition model based on three feature enhancement strategies. In this paper, Res-Transformer is used as the backbone network of the model to effectively integrate local flame combustion features and global features. Firstly, an efficient multi-scale attention module is introduced into Resnet, which uses a multi-scale parallel sub-network to establish long and short dependencies. Then, a deformable multi-head attention module is designed in the Transformer layer, and the deformable self-attention is used to extract long-term feature dependencies. Finally, we design a context feature fusion module to efficiently aggregate the spatial information of the shallow network and the channel information of the deep network, and enhance the cross-layer features extracted by the network. In order to verify the effectiveness of the model proposed in this paper, comparative experiments and ablation experiments were conducted on the municipal solid waste incineration image dataset. The results showed that the Acc, Pre, Rec and F1 score indices of the model proposed in this paper were 96.16%, 96.15%, 96.07% and 96.11%, respectively. Experiments demonstrate the effectiveness and robustness of this method. Full article

Powder-fueled ramjets show great potential due to their unique advantages. How to further improve ramjet performance through methods such as fuel improvement is also an important focus. In this paper, a 14 km, Ma 3.0, ground test of a powder-fueled ramjet using boron–aluminum composite powder fuel (B–Al composite powder fuel) was conducted. The feasibility and combustion performance of B–Al composite powder fuel were verified. Under the condition of an air–fuel ratio of 19.39, the ramjet achieved independent self-sustaining combustion for 10 s, and the characteristic exhaust velocity efficiency (${\eta }_c^{*}$) reached 81.84%. Through SEM-EDS, XRD, and XPS, this study systematically analyzed the surface morphology, composition, and chemical state of the wall deposits in the combustion chamber after the test. The combustion behavior of the B–Al composite powder fuel in the ramjet was clarified. The composite powder fuel could be converted into smaller and more combustion-favorable reaction basic units during the combustion process. However, the imbalance and unevenness of Al and B in the combustion reaction and the non-reaction or reaction termination of B particles remain significant issues. This study shows that B–Al composite powder fuel has a good application basis and potential, and provides experimental data support for the subsequent improvement and optimization of the B–Al composite powder fuel system. Full article

The production of Ti₃AlC₂ was investigated by self-propagating high-temperature synthesis (SHS) using the sample compacts composed of elemental powders with or without TiC and TiH₂ additions. The influence of Al, carbon, TiC, and TiH₂ was explored on the combustion sustainability, combustion velocity and temperature, and phase composition and microstructure of the product. The experimental results indicated that the elemental sample with an Al-excess composition increased the combustion velocity and improved the formation of Ti₃AlC₂, but the sample with a carbon-deficient composition produced the opposite effect. Although both TiC and TiH₂ additions decreased combustion exothermicity, an appropriate amount of TiC enhanced the yield of Ti₃AlC₂. However, the incomplete decomposition made TiH₂ unsuitable as a source of Ti and resulted in a low yield of Ti₃AlC₂. In this study, the final product containing the highest content of Ti₃AlC₂ was synthesized from the Al-excess and TiC-added sample of 2.5Ti + 1.2Al + 1.5C + 0.5TiC, and the product was composed of 89.3 wt.% Ti₃AlC₂, 5.9 wt.% Ti₂AlC, and 4.8 wt.% TiC. A reaction mechanism was proposed for the formation of Ti₃AlC₂ by SHS, which involved three exothermic reaction steps sequentially producing TiC, Ti₂AlC, and Ti₃AlC₂. The as-synthesized Ti₃AlC₂ grains were in the shape of thin platelets with a thickness of about 1.0 μm, and a layered structure formed by closely stacked platelets was clearly observed. Full article

The increasing need for sustainable waste management and abundant availability of banana tree waste, a byproduct of widespread banana cultivation, have driven interest in biomass conversion through clean fuels. This study investigates the oxidative pyrolysis of banana tree waste to optimize process parameters and enhance bio-oil production. Experiments were conducted using a fluidized bed reactor at temperatures ranging from 450 °C to 550 °C, with oxygen to biomass (O/B) ratios varying from 0.05 to 0.30. The process efficiently converts this low-cost, renewable biomass into valuable products and aims to reduce energy intake during pyrolysis while maximizing the yield of useful products. The optimal conditions were identified at an O/B ratio of 0.1 and a temperature of 500 °C, resulting in a product distribution of 26.4 wt% for bio-oil, 20.5 wt% for bio-char, and remaining pyro-gas. The bio-oil was rich in oxygenated compounds, while the bio-char demonstrated a high surface area and nutrient content, making it suitable for various applications. The pyro-gas primarily consisted of carbon monoxide and carbon dioxide, with moderate amounts of hydrogen and methane. This study supports the benefits of oxidative pyrolysis for waste utilization through a self-heat generation approach by partial feed combustion providing the internal heat required for the process initiation that can be aligned with the principles of a circular economy to achieve environmental responsibility. Full article

A novel meso-scale 3-channel 5-turn Swiss-roll type combustor was designed and tested. The non-catalytic combustion of lean ethanol–air mixtures was experimentally investigated in relation to the oxygen excess ratio (α), which varied from 1.5 to 7. Depending on the control parameters used, two distinct regimes of combustion were experimentally observed: one with a combustion zone within the central chamber and another with a combustion zone in the inflow channel. The combustion temperature was virtually independent of stoichiometry. For richer mixtures and lower flow rates, the combustion zone is established in the inflow channel, thus limiting the combustion temperature. A qualitative model was proposed for the process and solved analytically; it described how the combustion regime self-adjusted, with the reaction zone moving into the inflow channel from the central chamber. This study confirmed the possibility of the sustainable combustion of ultra-lean fuel mixtures in a Swiss-roll combustor. Full article

The self-propelled straw pickup baler in agricultural work is responsible for collecting and compressing straw to facilitate transportation and storage, while reducing waste and environmental pollution. Like other agricultural equipment, the straw pickup baler is a complex mechanical system. During operation, its excitation characteristics under multi-source stimuli and the coupling characteristics of various components are not yet clear. This paper analyzed the excitation mechanics property of each component of the self-propelled straw pickup baler and established balance equations. Based on the balance equations, the coupling characteristics of the structures were studied. Through experiments collecting excitation signals from multiple devices under different operating conditions, the vibration excitation signals of each component were obtained. The experiments revealed that the excitation and coupling signals in the Z direction are particularly evident. Based on experiments, the effective Z-direction vibration signal value on the left front of the chassis exceeds 7 m·s², while on the right front it increases from 1.995 m·s² to 7.287 m·s², indicating the most intense vibration direction. It was also found that, at the driver’s cab, the effective Z-direction vibration signal values at two response points, 11 and 12, both exceed 7 m·s². The data indicate significant vibrations occur in both the longitudinal and vertical directions. Using the Signal Analyzer module in MATLAB for signal processing, it was found that the prominent filtered signals consist of combustion excitation harmonics and continuous low-frequency vibrations from the compression mechanism. The periodic reciprocating compression motion of the crank-slider mechanism causes sustained impacts on the frame, leading to periodic changes in the vibration amplitude of the chassis. Thus, the vibration reduction of the compression mechanism’s periodic motion is key to reducing the overall vibration of the machine. Full article

Minimum ignition energy (MIE) has been extensively studied via experiments and simulations. However, our literature review reveals little quantitative consistency, with results varying from 0.324 to 1.349 mJ for ϕ = 1.0 and from 0.22 to 0.944 mJ for ϕ = 0.9. Therefore, there is a need to resolve these discrepancies. This RANS study aims to partially address this knowledge gap. Additionally, it presents other flame evolution parameters essential for robust combustion design. Using the reactingFOAM solver, we predict the threshold energy required to ignite the fuel mixture. For this, the single step using the Arrhenius law is selected to model ignition in the flame kernel of stochiometric and lean CH₄/air mixtures, allowing it to develop into a self-sustained flame. The ignition power density, an energy quantity normalised with volume, is incrementally varied, keeping the kernel critical radius r_s constant at 0.5 mm in the quiescent mixture of two equivalence ratios ϕ 0.9 and 1.0, for varied operating pressures of 1, 5, and 10 bar at the constant initial temperature of 300 K. The minimum ignition energy is validated with twelve independent 1-bar datasets both numerically and experimentally. The effect of pressure on MIEs, which diminish as pressure rises, is significant. At ϕ = 1.0 (and 0.9), the flame temperature reached 481.24 K (457.803 K) at 1 bar, 443.176 K (427.356 K) at 5 bar, and 385.56 K (382.688 K) at 10 bar. The minimum ignition energy was validated using twelve independent 1-bar datasets from both numerical simulations and experiments. The results show strong agreement with many experimental findings. Finally, a mathematical formulation of MIE is devised; a function of pressure and equivalence ratio shows a slightly curved relationship. Full article