Burning Time Research Articles

PAM material that instantly gives ordinary fabrics excellent flame retardant and thermal insulation properties for fire rescue

To effectively reduce the damage caused by flame burns or heat transfer to the human body during fire, we used PAM aqueous solution as the matrix, XG as the thickener, HPMC as the water-retaining agent to form the basic material system, and added different functional particles (APP, PTW, HCB) to prepare a fire-proof and heat-insulating PAM flame-retardant material for fire emergency rescue. Ordinary cotton fabrics were impregnated into PAM flame-retardant materials using a simple impregnation process. After the impregnation, the test was performed in a non-dropping state (simulating the thermal protection effect of PAM flame retardant materials directly acting on the outside of the human body at the fire scene). The results show that the PAM flame retardant material prepared by adding 4 wt% HCB has the best comprehensive performance. TPP test shows that spraying PAM flame retardant material on the outside of the fabric can instantly give the fabric a higher thermal protection performance. Under the total heat flux of 84 kW/m2, the thermal performance protection value of the fabric is 2641.8 kW·s/m2, and the second-degree burn time can reach 31.45 s. PAM flame retardant material does not damage the fabric. After soaping, the air permeability of the fabric decreases slightly, the moisture permeability and wettability are improved, and the breaking strength is almost unchanged. The CCT test showed that the thermal radiation flux was 50 KW/m2, the PHRR value of PAM flame retardant material was 10.64552 KW/m2, the THR was 6.9 MJ/m2, and the flame retardant performance was excellent. The PAM flame retardant material prepared in this project can be applied to the fire scene and directly sprayed on the outside of the clothing of rescuers and recipients, giving the fabric a better thermal protection effect. It can also be used to extinguish fires in the external environment. This material offers a novel solution for enhancing fire rescuers' and victims' safety protection levels.

Investigation the Thermal Behavior of Lemon and Orange Peels Composite Fuel Diesel

Background: The aim of this research is to investigate the thermal behavior of a composite fuel prepared by mixing diesel fuel with citrus peel powder in the presence of activators and combustion accelerators. The study focused on utilizing abundant citrus waste, such as lemon and orange peels, as sustainable bioresources to reduce environmental pollution and optimize fuel efficiency. The research explored the thermal properties of the composite fuel and compared it with pure diesel through combustion experiments conducted at atmospheric pressure and combustion pressure in the engine. Methods: The study set the limits of the investigation to various proportions of lemon and orange peel powder mixed with diesel, ranging from 5% to 15% by mass of the total fuel composite. Two catalysts, sodium hydroxide (NaOH) and sulfuric acid (H2SO4), along with calcium oxide (CaO) powder were incorporated into the mixtures as activators to enhance combustion efficiency. The composite fuel characterization included thermogravimetric analysis (TGA) and thermographmetric station experiments to observe the combustion processes and assess the thermal behavior of the composite fuel. Results: The results revealed four distinct phases of combustion during the burning time of 60 seconds: volatile combustion, liquid combustion, combustion of solid materials, and the interaction of active substances with combustion residues. Using activators and catalysts significantly enhanced combustion efficiency and minimized the amount of residue produced during the process, resulting in thermal behavior that is more similar to that of pure diesel. Lemon peel powder with activators demonstrates better thermal behavior compared to orange peel powder. Conclusions: Based on the findings, some recommendations are proposed for further development such as the optimization of activator ratios, exploration of different proportions of lemon and orange peel powder, and investigation of other catalysts. Real-world engine performance tests and emission profile analysis can validate the thermal behavior results obtained from combustion experiments.

Enhancing the combustion of silicon nanoparticles via plasma-assisted fluorocarbon surface modification

Nanostructured silicon has great potential as an energetic material due to its high energy density, close to that of aluminum; however, its combustion kinetics are strongly affected by the presence of a native oxide layer. As the particle size is reduced, the material behavior is dominated by surface effects, highlighting the need for new approaches to fabricate silicon nanoparticles and precisely control their surface chemistry. Here, we describe the use of low-temperature plasma to nucleate and grow < 10 nm silicon particles. The resulting aerosol is passed through a second plasma reactor, to which a fluorocarbon monomer is supplied. The second plasma initiates the growth of a polymeric shell onto the silicon particles, resulting in a highly conformal coating. Chemical analysis confirms that the polymer shell is compositionally similar to polyvinylidene fluoride (PVDF). We find that the fluorocarbon shell acts as an artificial passivation layer that significantly delays the onset of oxidation in air. In addition, the direct contact between the fluorocarbon shell and silicon core lowers the ignition temperature compared to the physical mixtures of silicon nanoparticles and PVDF. It leads to a higher pressurization rate and a lower combustion time when tested in a combustion cell. This is consistent with the combustion process being initiated by the exothermic interfacial reactions between the silicon core and the fluorocarbon shell. Mass spectroscopy confirms this hypothesis because silicon fluoride is produced only for the core–shell structure, and not for a physical mixture of silicon and PVDF. This study provides an example of a new processing technique capable of controlling the interfacial chemistry of small nanoparticles with beneficial effects on their combustion.

Evaluation of the reactivity of co-combustion of wheat straw and waste rubber thermolysis char

The co-combustion of wheat straw (WS) and waste rubber thermolysis char (WRTC) was examined with the perspective of utilizing WRTC as a high-calorific value fuel addition to agricultural biomass. The study investigated the effect of different proportions of WS-WRTC blends (10/15/25/49 wt% WRTC) and a maximum of 4 wt% binders, including potato starch and calcium oxide, on the reactivity of co-combustion and the distribution of products during the process. Thermogravimetric analysis with Fourier Transform Infrared Spectroscopy (TGA-FTIR) analyses was employed at a temperature range of 25–1000 ° C with a heating rate of 10 ° C/min. The kinetics of co-combustion were analyzed using the Fraser-Suzuki (FS) deconvolution method and a model-based kinetic modeling. The results indicate that a 10% addition of WRTC char reduces the intensity and rate of combustion and prolongs the combustion time. It was observed that the optimal addition to the blend is 25% WRCT, and it resulting in a reduction in activation energy and combustion indexes. However, it remains with no significant impact on process stability and efficiency. Kinetics of the decomposition of the WRTC25 mixture modeled by the deconvolution method indicates a 5-step reaction course, which is a combination of the characteristic combustion stages of both fuels. The main denoted functional group observed in the FTIR absorption spectra were C=O, C-O, O-H, and C-H related to the release of CO2, CO, H2O, CH4, aromatic compounds, and hydrocarbons.

Combustion behavior of solid waste fuels in the vertical tube reactor under different oxy-fuel environments

Oxy-fuel combustion technology has been recognized as one of the promising ways for cost-effective CO2 capture. The co-combustion characteristics of flax straw biomass/bituminous coal mixture (FS/BC) and flax straw biomass/sewage sludge mixture (FS/SS) under air, oxy-fuel (21%/79% O2/CO2) and oxygen-enriched oxy-fuel (30%/70% and 40%/60% O2/CO2) conditions were investigated in the vertical tube reactor. In particular, the study focused on the burning characteristics, the effect of blending ratio, and flue gas emissions. The findings indicated that flax straw biomass exhibited superior ignition performance compared to its blends with sewage sludge and bituminous coal. A higher O2 concentration from 21% to 40 led to a reduction in ignition delay time by 4s at 850 ℃ and by up to 10s at 950 ℃. Moreover, char combustion time was reduced by 50% for FS/SS blends due to the lower fixed carbon content compared to FS/BC blends. Additionally, increasing the O2 concentration resulted in lower emissions of CO by ∽40% and N2O by ∽45% for both blends. However, this also led to a slight increase in SO2 and NO emissions by ∽15% and ∽26%, respectively. The optimal conditions for the tested samples in oxy-fuel environment were found to be 30% O2/70 CO2, which enhanced combustion performance while lowering flue gas emissions.

Unraveling the Nanosheet Zeolite-Catalyzed Combustion of Aluminum Nanoparticles-Doped exo-Tetrahydrodicyclopentadiene (JP-10) Energetic Fuel.

Nanosheet MFI zeolites (Zeolite Socony Mobil, five) have grown in popularity in cracking catalysis considering their tunability in porous topologies, acidic sites, and sheet thickness, thus allowing them to selectively adsorb molecules of specific sizes, shapes, and polarities, resulting in improved cracking performance for a specific fuel. Five different MFI zeolites in the form of a mesoporous nanosheet structure with a controlled concentration of acidic sites denoted as NSMFI(y), where y is Si/Al ratio, have been synthesized. The effects of the relative acidity content of these NSMFI(y) samples on the zeolite-catalyzed combustion of aluminum nanoparticles (AlNPs)-aided exo-tetrahydrodicyclopentadiene (JP-10) mixed energetic fuel droplets levitated in an oxygen-argon atmosphere were investigated using time-resolved imaging (optical and thermal infrared) and spectroscopic techniques (UV-vis and FTIR). The addition of 1.0 wt % of NSMFI(y) zeolites to AlNPs-JP-10 fluid fuel results in critically reduced ignition delays (9 ± 2 ms), elevated ignition temperatures (2800 ± 170 K), and prolonged burning times (60 ± 10 ms) with an enhanced combustion efficiency. The NSMFI(y) zeolites, which possess high acidity and significant mesoporosity, play a crucial role in improving the combustion efficiency by effectively catalyzing the chemical activation of JP-10 and prolonging the burning of the igniting droplet. The NSMFI (60) variant with the highest acidic site content achieved a maximum combustion efficiency of 80 ± 6%. A comprehensive catalytic combustion mechanism has been elucidated based on the detected reactive intermediates such as hydroxyl radical (OH) and aluminum monoxide (AlO). These findings will help to critically advance the development of next-generation, sustainable, and innovative mixed nanofluid fuels.

Karakteristik Pembakaran Droplet Campuran Metil Oleat – Etanol dengan Penambahan Multi -Walled Carbon Nanotubes

This research intended to investigate the combustion characteristics of methyl oleic – ethanol blend with OH functionalized multi-walled carbon nanotubes (MWCNT-OH) addition. Methyl oleic is an unsaturated fatty acid methyl ester, which is a constituent of various biodiesels. The observed fuel was a mixture of Methyl oleic with 20% vol of ethanol. MWCNT-OH content was varied by 100 ppm, 200 ppm, 300 ppm, 400 ppm, and 500 ppm (wt based). The presence of ethanol in the droplets is intended to promote the microexplosion phenomenon, generating smaller droplets and a shorter burning time. The experimental results show that the MWCNT-OH addition on the droplet of Methyl oleic – ethanol blend decreased the ignition delay and droplet burning time, while the constant burning rate and droplet temperature (and flame temperature) were increased. Reducing ignition delay time due to the higher thermal conductivity of nanofluid droplets results in more effective heat absorption from the environment and better heat transport inside the droplet. Hence, droplet vaporization, flammable mixture formation and ignition occur in a shorter time. Furthermore, this condition encourages a higher burning rate and a lower droplet burning time. The higher droplet and flame temperatures are related to the higher heating value of the methyl oleic – ethanol – MWCNT-OH mixture and higher droplet burning rate, which results in a higher heat release rate.

Numerical Study of High-g Combustion Characteristics in a Channel with Backward-Facing Steps

High gravity (high-g) combustion can significantly increase flame propagation speed, thereby potentially shortening the axial length of aero-engines and increasing their thrust-to-weight ratio. In this study, we utilized the large eddy simulation model to investigate the combustion characteristics and flame morphology evolution of premixed propane–air flames in a channel with a backward-facing step. The study reveals that both the increase in centrifugal force and flow velocity can enhance pressure fluctuations during combustion and increase the turbulence intensity. The presence of centrifugal force promotes the occurrence of Rayleigh–Taylor instability (RTI) between hot and cold fluids. The combined effects of RTI and Kelvin–Helmholtz instability (KHI) enhance the disturbance between hot and cold fluids, shorten the fuel combustion time, and intensify the dissipation of large-scale vortices. The increase in fluid flow velocity can raise the flame front’s hydrodynamic stretch rate, thereby enhancing the turbulence level during combustion to a certain extent and increasing the fuel consumption rate. When a strong centrifugal force is applied, the global flame propagation speed can be more than doubled. Within a certain range, the increase in high-g field strength can enhance the intensity of RTI and accelerate the transition of RTI to the nonlinear stage.

Inertial Confinement Fusion Propulsion for the Massive Ra World Ship Model – Part 2

A strategy for sending humans around other stars will be to acquire the ability to construct large World Ships which are of order ~1011-1012 tons in mass, ~100 km in length and host large populations of millions of people over many generations of lifetime. This paper presents such a concept but driven by inertial confinement fusion engines utilising very large pellets of order 230 g in mass augmented with 4.85 kg/pellet of expellant propellant for increased mass flow rate and thrust generation. A mission architecture is constructed for a 1 million population carrying capacity growing to 10 million, based on an original 1984 published model which achieved a cruise speed of 1,500 km/s or 0.5% for a 1,000 year trip time. Calculations show that propulsion of such a vast construction will require hundreds of engines operating in parallel thrust mode and at moderately high pulse frequency for an elongated burn time of order half a century. The purpose of this study was to examine whether it was possible to drive an interstellar world ship using ICF engines using similar assumptions to a 1984 study for a Mk2A design. The conclusion of this study is that although an architecture does appear to be possible, there are practical reasons why it may be better to pursue alternative propulsion methods for this specific application such as via external nuclear pulse propulsion as adopted for the original studies. This paper is a follow-up to an earlier one which discussed some of the assumptions of the study. Keywords: World Ships, Interstellar Studies, Fusion Propulsion

Study on Synergistic Radiation Yellow Light of Strontium Nitrate/Barium Nitrate-Based Illuminant

ABSTRACT In order to change the problem of a single yellow light color emitted by sodium salt illuminant. Based on the principle of color-light mixing and the mechanism of synergistic radiation of double-dyeing flame agents, four groups of strontium nitrate/barium nitrate-based yellow light illuminant formulations with different ratios were designed, which were calculated and comparatively analyzed by REAL and MATLAB software through experiments. From the experimental results, it can be seen that the virtual main wavelength of strontium nitrate/barium nitrate-based yellow light illuminant was adjusted in the range of 579 nm-591 nm, and the color ranged from light yellow to golden yellow, among which the best formulation was strontium nitrate/barium nitrate/magnesium/worm gum/polyvinyl chloride with the ratio of 50.25/16.25/13.5/2.5/17.5. The oxygen balance of this formulation was −0.130 g-g-1, and the combustion temperature was 2790.88 K. The color light emitters were Sr, SrO, SrOH, SrCl, Ba, BaO, BaOH, BaCl, the color coordinates were (0.5256, 0.3988), the virtual dominant wavelength was 591 nm, the color purity was 0.79, and the luminescence intensity was 247,893.18 cd, and the combustion time was 6.8s.

Integrated Optimization of Quality Control and Maintenance Policies for Light-Emitting Devices

This research represents a comprehensive exploration of optimization policies pertaining to burn-in, quality control, and preventive maintenance for light-emitting devices. Utilizing a MATLAB-based computational model, we embarked on an in-depth investigation of the complex interplay and dependencies between these policies. Our findings illustrated that, with optimal burn-in time, cut-off threshold, and replacement interval, the total cost per usage duration was significantly reduced. Additionally, we investigated the system performance with and without quality control. It was observed that an increase in burn-in time corresponded to an increase in cost. The absence of quality control resulted in a similar pattern with the replacement period, where the cost remained constant after a certain replacement period. Conversely, the implementation of quality control indicated a direct relationship between burn-in time and cost, and an inverse relationship between replacement period and cost.

Coke breeze combustion and emission behaviors of CO and NO during iron ore sintering

CO emission reduction, especially the coordinated emission reduction of CO and NO in sintering flue gas, has attracted widespread attention in the world. The effects of different sintering raw materials, temperature and atmosphere on coke breeze combustion and CO and NO emission behaviors were studied. The results show that, sintering raw materials significantly improved the combustion performance of coke breeze, and promoted the simultaneous reduction of CO and NO emissions. Among them, Dolomite had the strongest catalytic effect, which reduced the apparent activation energy of coke breeze combustion reaction from 99.35 kJ/mol to 56.11 kJ/mol, and the emission reductions of CO and NO were as high as 47.84 % and 73.25 %, respectively. The catalytic ability of the raw materials components was CaO ＞ MgO ＞ Fe2O3. However, during the combustion process of coke breeze without raw materials, the reduction of NO by CO was affected by the atmosphere of the boundary layer, the conversion of N element was negatively correlated with the content of CO. When the temperature increased from 600 ℃ to 1 050 ℃, the combustion performance was improved, the thickness of the combustion zone was reduced by 47.92 %, the total emission of CO was decreased by 65.39 %, and the total emission of NO was increased by 23.05 %. The O2 concentration decreased from 21 % to 10 %, the combustion rate decreased, the combustion zone thickened by 90 %, incomplete combustion was promoted, the total emission of CO increased by 101.15 %, and NO decreased by 21.09 %. The CO2 concentration increased from 5 % to 15 %, the gasification reaction was enhanced, the combustion time was extended, the combustion zone thickened by 45.9 %, the total emission of CO increased by 87.12 %, and the reducing atmosphere was enhanced, which was conductive to the reduction of NO by CO, and the total emission of NO decreased by 50.59 %.

Study of the diesel fuel drop vaporization and combustion at a hydrogen-diesel fuel dual fuelled diesel engine

Abstract The present paper shows the analysis of the results of the theoretical model developed by authors for diesel fuel drops vaporization study, air-diesel fuel-hydrogen mixture forming estimation and diesel fuel drops combustion in the presence of air-hydrogen mixtures set in the cylinder before the start of conventional fuel injection. The model is applied to a single cylinder diesel engine fuelled with diesel fuel and hydrogen, in dual mode by diesel gas method, at the engine speed of 900 rev/min. For a diesel fuel drop the vaporization speed, mixture formation speed, combustion speed, flame radius are presented and analysed. At hydrogen use, the cyclic amount of diesel fuel is reduced and the vaporization duration of the diesel fuel drop is reduced comparative to classic fuelling. At dual fuelling, the combustion of the burning of air-hydrogen mixtures in the vicinity of diesel droplets leads to reduced vaporization time, with 43%, an increased vaporization rate, with 26.9% and an accelerated formation of the mixture between diesel fuel and air-hydrogen mixture. Further, the combustion speed increase with 6.9%, the combustion time is decreased with 6% and the flame radius increase with 6.7%.

Understanding post‐fire vegetation recovery in southern California ecosystems with the aid of pre‐fire observations from long‐term monitoring

AbstractAimsPost‐fire vegetation recovery is often determined by the similarity of post‐burn with unburned sites because of a lack of in situ information on pre‐fire communities. The inclusion of pre‐fire data can help account for pre‐existing differences and explore recovery also in terms of return to pre‐fire conditions. We used long‐term monitoring data in coastal sage scrub and grasslands to: (a) examine vegetation cover recovery of different functional groups; and (b) determine whether vegetation composition in burned areas has recovered in 4 years after fire with burned to unburned and pre‐ to post‐fire comparisons.LocationOrange County, California, USA.MethodsWe analyzed long‐term vegetation monitoring (2007–2021) data from 39 grassland and 58 coastal sage scrub transects in southern California, including observations before and after the 2017 Canyon 2 fire. Linear mixed‐effect models were used to determine whether forb, grass, and shrub covers differed between burned and unburned sites while considering the effects of year and repeated monitoring. We used canonical analysis of principal coordinates to analyze vegetation composition based on burn status and time of sampling.ResultsWhereas vegetation cover in grassland recovered quickly, native vegetation cover in burned coastal sage scrub remained lowered 4 years after fire, though forb and non‐native grass cover were higher in some post‐fire years. Community composition in burned coastal sage scrub was still in recovery 4 years after fire when compared with unburned or pre‐fire composition. Although burned and unburned grassland differed after fire in dominant grass species, inclusion of pre‐fire data showed that this was a pre‐existing difference.ConclusionsCoastal sage scrub had not recovered pre‐fire vegetation cover and composition by 4 years after fire, whereas grassland cover rebounded quickly, albeit with shifts in composition over time; patterns that were detected only by having pre‐ and post‐fire data from long‐term monitoring efforts.

SiO2 decorated wood nanocomposite with enhanced mechanical performance, flame and water resistance

Development of lightweight and strong structural material using fast-growing poplar wood is promising for green and sustainable engineering. Herein, the overall performances of fast-growing natural poplar wood (NPW) are significantly enhanced via delignification, in situ growth of SiO2 followed by densification. The SiO2/compressed-delignified-wood (SiO2/CDW) nanocomposite obtained exhibits outstanding mechanical properties including a bending strength of 395.6 ​MPa, a tensile strength of 253.4 ​MPa, and a toughness of 7.1 ​MJ/m3, which is improved by 1548 ​%, 240 ​% and 590 ​%, respectively compared with NPW. In addition, the ignition time and burning time of SiO2/CDW nanocomposite are prolonged by 700 ​% and 112 ​% compared to those of NPW. Moreover, the specific wear rate of SiO2/CDW is 18 ​× ​10−6 mm3/Nm, which is 72.6 ​% lower than that of NPW. Moreover, the spring-back ratios of SiO2/CDW in 95 ​% and in water are 45.2 ​% and 66.7 ​%, which are lower than those of CDW (64.6 ​% and 92.4 ​%). The SiO2/CDW nanocomposite with enhanced mechanical, flame/water retardant and wear performances are promising to meet the needs of modern engineering as green and sustainable materials.

Construction and combustion behavior of horizontal two-dimension combustion networks of boron-metal oxides

In order to break through the top-down combustion mode brought by the traditional pillars, it is explored to explore the exploration of delay composition array construction in two-dimensional dimensions. In this study, B-CuO, B-Bi2O3, B-Fe2O3 sticks and combustion networks with good forming properties were prepared with the help of a micro-pen direct ink writing device by dispersing the above materials in DMF with boron and metal oxides as the main body of the charge and F2602 as the binder. The sticks were thermally ignited using a nichrome wire, and the flame propagation behaviors of the sticks with different formulations, spacings and heights were tracked with a high-speed camera, and a series of combustion networks were designed on the premise of not leaping into flames. Results show that the B-CuO stick has the fastest ignition speed level (19.71–29.02 mm ·s−1) at equivalence ratios of 1.0–4.0, followed by B-Bi2O3 (5.99–16.01 mm ·s−1) and B-Fe2O3 is the slowest (1.91–4.94 mm ·s−1). The sticks burned best at an equivalence ratio of 1.0–1.5. A variety of combustion networks were constructed on 50 × 50 mm glass slides by selecting B-CuO, B-Bi2O3, and B-Fe2O3 at the equivalence ratios of 1.0, 1.5, and 1.5, respectively, among which B-CuO had the shortest combustion time (5.17 s), the shortest total combustion network length (252 mm), and 400 mm network could be realized for B-Bi2O3. Construction and 19.85 s, and B-Fe2O3 can realize 608 mm network length and 130.7 s combustion time. Through these studies, the two-dimensional combustion network construction of boron-metal oxides was realized, which provides a new idea for the delay action in small size.

Combustion visualization analysis of alternative fuels in the pulverized coal injection raceway through laminar flow reactor

Currently, the steelmaking process uses a pulverized coal injection (PCI) system that serves as the heat source and reductant for ironmaking (blast furnace and FINEX) where system uses expensive high-grade coal and high operating costs. Hydrogen steelmaking is currently being developed to achieve carbon-free operation. To achieve a soft-landing during this phase of rapid change, the use of biomass and inexpensive, thermal coal, and coke dust is necessary. Research on their combustion characteristics is necessary to apply these alternative fuels to PCI. Therefore, this study analyzed the combustion characteristics of ignition delay, devolatilization, and char combustion using a laminar flow reactor visualization equipment that simulates blast furnace (BF) and FINEX PCI tuyere, using flame image data processing. The ignition time were generally longer in BF than in FINEX, and the char combustion length and time also showed the same trend due to the high oxygen rate which indicate under 2 ms on ignition delay, under 16 ms on char combustion. Also, the volatile cloud was qualitatively shown in the image to be highest in thermal coal and biomass with high volatile matter. Based on the correlation and theoretical calculation with proximate analysis and the results, ignition delay time had a combined effect of volatile matter and moisture except coke dust, and char combustion time affected unburned carbon. The combustion chemical characteristics were discussed with chemical percolation devolatilization (CPD) model parameter. Through SEM image and BET analysis, the surface area has been increased more than 10 times after combustion. Consequently, the biomass and high moisture thermal coal could cofired within 10 % and coke dust could be cofired within 9 %, respectively.

A quantitative theory for heterogeneous combustion of nonvolatile metal particles in the diffusion-limited regime

The paper presents an analytical theory quantitatively describing the heterogeneous combustion of nonvolatile (metal) particles in the diffusion-limited regime. It is assumed that the particle is suspended in an unconfined, isobaric, quiescent gaseous mixture and the chemisorption of the oxygen takes place evenly on the particle surface. The analytical solution of the particle burn time is derived from the conservation equations of the gas-phase described in a spherical coordinate system with the utilization of constant thermophysical properties, evaluated at a reference film layer. This solution inherently takes the Stefan flow into account. The approximate expression of the time-dependent particle temperature is solved from the conservation of the particle enthalpy by neglecting the higher order terms in the Taylor expansion of the product of the transient particle density and diameter squared. Coupling the solutions for the burn time and time-dependent particle temperature provides quantitative results when initial and boundary conditions are specified. The theory is employed to predict the burn time and temperature of 10–100 μm iron particles, which are then compared with measurements, as the first validation case. The theoretical burn time agrees with the experiments almost perfectly at both low and high oxygen levels. The calculated particle temperature matches the measurements fairly well at relatively low oxygen mole fractions, whereas the theory overpredict the particle peak temperature due to the neglect of evaporation and the possible transition of the combustion regime.Novelty and significance statementFor the first time, we present a comprehensive and quantitative analytical theory elucidating the heterogeneous combustion of nonvolatile (metal) particles in the diffusion-limited regime. This novel theoretical model exhibits a remarkable capacity for quantitative prediction, obviating the need for supplementary information from numerical simulations or experimental data. The derivation process of analytical solutions for burn time and time-dependent particle temperature from conservation equations is elaborated, offering transparency and insight into the model’s foundations. To demonstrate the practical utility of the theory, we apply it to analyze the combustion of iron particles, providing valuable mathematical perspectives on the underlying processes. The model’s predictions for burn time and temperature align closely with experimental results, offering a partial validation of the theory within the realm of its applicable assumptions. This pioneering work contributes a robust and versatile analytical framework, advancing our understanding of diffusion-limited combustion phenomena of nonvolatile particles.

Effect of natural agents on the mechanical and flame retardant properties of cotton fabrics – finishing technique

The current study carefully examines the antibacterial finished cotton fabric materials in terms of enhanced flame-retardant capability by eco-friendly herbal extracts to cotton fabrics while concurrently analysing their tensile strength qualities. Because active compounds have been incorporated into the fabric’s structure, the treated fabrics’ tensile strength has changed less over time than untreated fabrics. The plain weave cotton fabric with a specification of 140 g/m2 and a 15% finished concentration had a tensile strength of 238.92 kg/cm2, while cotton fabrics with specifications of 240 g/m2, terry weave with a 15% finished concentration, had a tensile strength of 294.43 kg/cm2. The finishing process has betterment in comparison to the untreated cotton fabrics had tensile strengths of of 140 g/m2 plain and 240 g/m2 terry weaves fabric which has 238.38 kg/cm2 and 288.47 kg/cm2, indicating that the ashwagandha-finished cotton fabrics performed better. The burning period increases from 35 sec for untreated 140 g/m2 plain cotton fabric, according to the flame reaction studies. According to tests on flame reaction, fabrics treated with a combination of banana peels and casein have a burning time rise from 35 s for untreated 140 g/m2 plain cotton fabric to 100 s, and up to 60 s for Ashwaganda and Ginger completed fabrics. The findings of the Limited Oxygen Index (LOI) test revealed that the completed fabrics made from a mixture of banana peels and casein had significantly higher LOI values of 23 than the other treated samples, which had an average LOI of 19 and 20, compared to the untreated cotton fabrics’ LOI of 18.

Numerical simulation of the thermo-mechanical coupling behavior of skin tissue exposed to repetitive pulse laser irradiation

A thorough understanding of the thermo-mechanical coupling behavior during the interaction between pulsed laser and skin tissue is a prerequisite for successful application of pulsed laser technology in the treatment of various skin diseases and injuries. Taking into account the complex physiological structure of skin tissue, a theoretical model is established to characterize the thermo-mechanical response of multi-layer skin tissue with variable physical properties, in which the non-linear governing equations of bio-thermo-mechanics with dual-phase lag mechanism and Henrique burn equation are involved. The finite difference method was employed to obtain the time-space distribution of skin temperature, displacement and stress under repeated pulse laser action, and the incidental thermal damage was further evaluated on this basis. The numerical results stated that: i) repeated pulse laser can significant reduce the peak temperature of skin tissue and further reduce or even eliminate thermal damage under the premise of required energy threshold, ii) the thermo-mechanical coupling response and potential thermal damage will be inhibited when the temperature dependence of physical parameter is considered, in which the thermal stress is more sensitive to the temperature dependence than others, iii) the thermal damage is more sensitive to the input parameters than that of thermo-mechanical response, and the burn time can be effectively delayed or even avoided for appropriate input options.