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A fire accident is one typical postulated accident in a nuclear fuel cycling facility. Safety-related data on a combustible fire are necessary to evaluate the safety of nuclear fuel cycling facilities under fire accident conditions quantitatively. Accurate and reliable data should be obtained by performing some demonstration tests. This study deals with the ignition and combustion characteristics of solvent involved at a nuclear fuel cycling facility and the fire behavior during a solvent fire. Small-scale and large-scale tests were conducted at the China Institute for Radiation Protection. The minimum ignition energy of the solvent under different temperatures was obtained. The test data were used to judge the possibility that the organic solvent ignited by a spark. Parameters such as combustion rate, smoke gas, aerosol release of solvent combustion, temperature distribution, and pressure change in the solvent fire cell were also obtained. The test results can be used as conservative estimates of the amount of aerosol release during a solvent fire. The experimental data also can be used to develop preventive and mitigation measures for solvent fire accidents. This paper puts forward information based on the experimental data and the recent international study. [ABSTRACT FROM AUTHOR]

High performance green propellant represented by ammonium dinitramide-based liquid propellant and its new ignition method are the research hotspots of space propulsion in the 21st century. Exploring the complex multi-scale physical properties of multi-component ammonium dinitramide-based liquid propellant droplets in the electrical ignition mode has wide application significance for spray, propulsion system design and combustion control. The droplet dynamics behavior and combustion characteristics of propellant droplets at different ignition voltages were studied experimentally. The droplet dynamics behavior during the evaporation process, including violent volume oscillation, approximate steady-state expansion, contraction, secondary expansion, puffing and micro-explosion, have been determined by the generation, growth, and discharge of vapor bubbles. In the initial evaporation process, the heterogeneous nucleation is dominant. As the droplet is continuously heated, homogenization nucleation gradually dominates. The main physical and chemical mechanisms of bubble evolution driven by temperature involve methanol boiling, water overheating, ammonium dinitramide decomposition and combustion reaction between vapor molecules. Increasing the ignition voltage increases the droplet dynamics behavior and the combustion, but promotes the combustion instability. Increasing the ignition voltage increases the ignition delay time, puffing delay time, droplet lifetime, maximum temperature of droplet, and reduces the ignition critical diameter. It is proposed that the method of suppressing the droplet breakup dynamics at decomposition area and enhancing the droplet breakup dynamics at the combustion area are conducive to the combustion control of the thruster in electrical ignition mode. This research provides novel insight into the study of the electrical ignition mechanism of liquid fuels. • The droplet dynamics behavior and combustion characteristics of HPGP droplets at different ignition voltages were studied experimentally. • Increasing the ignition voltage increases the droplet dynamics behavior and the combustion, but promotes the combustion instability. • Increasing the ignition voltage increases the ignition delay time, puffing delay time, and reduces the ignition critical diameter. [ABSTRACT FROM AUTHOR]

This study investigated the impact of injection strategy on combustion and emission characteristics of a partial premixed direct injection natural gas engine, using the Cummins ISX engine as a numerical model. Specifically, the influence of diesel injection timing and pressure on engine performance was analyzed with a fixed natural gas energy substitution ratio. It is found that advancing the diesel injection timing leads to longer the ignition delay time of diesel since temperature is lower than at top dead center. This resulted in a rapid initial heat release, which further increased the in-cylinder temperature at the beginning of combustion and shortened the combustion duration. Moreover, increasing the pilot diesel injection pressure resulted in longer diesel spray penetration and a higher proportion of natural gas consumption at the beginning of combustion, eventually leading to a faster in-cylinder temperature rise. The findings highlight that optimizing the combustion phasing and combustion temperature by adjusting the diesel injection parameters to avoid too high combustion temperature and negative work at compression end, which can effectively reduce nitrogen oxides emissions while maintaining high indicated mean effective pressure. [ABSTRACT FROM AUTHOR]

Wooden structures are prone to fire hazards, and studying their combustion properties is vital for their protection. Samples of fresh pine wood (FP) and pine subjected to artificially accelerated aging (treated at 240 circulation) were collected and prepared for analysis. The heat-release rate, smoke production, and yields of carbon monoxide (CO) and carbon dioxide (CO2) from both types of pine were assessed using conical calorimetry to determine their combustion characteristics. A historic building in Xi'an was modeled using PyroSim to serve as a representative case. The experimentally obtained combustion characteristics of the two pine wood types were inputted into the model, and the Fire Dynamics Simulator (FDS) software was utilized to simulate the development of fire in both newly constructed and aging historic buildings. The results suggest that aging impairs the wood's combustion properties and increases the susceptibility of pine to ignition. Consequently, this accelerates the spread of fire in wooden structures, leading to a rapid increase in temperature and swift smoke production during fires, thus amplifying the fire risk to historic wooden buildings. [ABSTRACT FROM AUTHOR]

The inherent drawbacks of biodiesel, particularly its poor performance in cold climates, necessitate the use of nano-additives to improve its cold flow properties such as the cloud point (CP), pour point (PP), and cold filter plugging point (CFPP). In this study, transesterification was employed to produce methyl esters from waste cooking oil, corn oil, and jatropha oil. These biodiesels were blended with diesel fuel at a 20% biodiesel and 80% diesel volume ratio and enriched with nano-Al2O3 at concentrations of 25, 50, and 100 mg/L. The aim of this study is to evaluate the impact of nano-Al2O3 on engine combustion, performance, exergy, and emissions of diesel engines using different biodiesel feedstocks. The addition of nano-Al2O3 to methyl ester mixtures (JB20A100, CB20A100, and WB20A100) resulted in enhancements in thermal efficiency by 8%, 11%, and 13%, respectively. CO emissions were reduced by 12%, 17%, and 22% for jatropha, corn, and waste cooking oil blends, respectively, with 100 ppm alumina. This reduction in CO emissions can be linked to the enhanced oxidation process facilitated by the high surface area of the nanoparticles, which act as catalysts, promoting more complete combustion. Similarly, UHC emissions decreased by 14%, 18%, and 23%, and smoke concentrations were significantly reduced by 14%, 17%, and 24% across the biodiesel blends. However, the introduction of alumina led to the rise in NOx emissions by 9%, 15%, and 19% for JB20A100, CB20A100, and WB20A100, respectively. The study also revealed increases in cylinder pressure by 2%, 4%, and 8%, and maximum heat release rates by 3%, 6%, and 10% for JB20, CB20, and WB20, respectively, upon the incorporation of 100 ppm Al2O3. Exergetic efficiencies improved by 6%, 17%, and 23% for JB20A100, CB20A100, and WB20A100, respectively, and the sustainability index showed enhancements of 2%, 4%, and 7%. Among the tested blends, WB20 with 100 ppm of nano-Al2O3 demonstrated the most promising results, significantly improving engine exergy, combustion, and performance while mitigating emissions to acceptable levels. This study underscores the potential of nano-additives to advance the sustainability and efficiency of diesel engine operations, particularly in cold climate. [ABSTRACT FROM AUTHOR]

Methane is a popular alternative fuel for internal combustion engines due to its availability in many forms such as methane hydrates, natural gas, biogas, compressed natural gas, liquid natural gas, synthetic natural gas, and pipe natural gas. Methane can be effectively used in existing diesel engines in dual-fuel mode with few modifications. Dual-fuel technology helps bridge existing conventional fuel and alternative gaseous fuel-powered conventional engines. The properties of methane, including its higher calorific value, abundant diffusion, and wider flammability limit make it a suitable fuel for improving the performance of compression ignition engine in dual-fuel mode. Methane-diesel dual-fuel engines are an effective technology for reducing vehicle pollution and partially replacing conventional fuels for transport applications. Therefore, a comprehensive review is needed to document the various pathways for the utilization of methane in dual-fuel engines. This study critically compared the combustion, noise, performance, and emission characteristics of various methane-fueled engines to identify the current challenges and future perspectives for the synergistic use of methane to reduce emissions from internal combustion engines. [ABSTRACT FROM AUTHOR]

In this paper, the characteristics of hydrogen-doped natural gas combustion in industrial boilers were investigated by means of numerical simulations. Initially, a jet flame test bench was constructed to conduct single-variable experiments at various hydrogen doping ratios and excess air coefficients, thus analyzing the impact on flame combustion patterns. Computational Fluid Dynamics (CFD) numerical simulations were performed using the Fluent software, focusing on the combustion zones within the burner and boiler chamber. Simulations were based on actual operating conditions to set parameters, employing the k-ε turbulence model. The SIMPLE algorithm facilitated examination of the effect of hydrogen doping ratios on the combustion temperature and concentration of pollutants, with a particular focus on the concentration of the flow field, temperature field, NOx generation rate, and the concentrations of O 2 and CO. The results show that: As the hydrogen doping percentage increases, the fuel flame propagation speed also increases, leading to a faster combustion process that yields a shorter, wider flame. Conversely, as the excess air coefficient rises, the flame becomes narrower, transitioning from a clearly-layered structure to a uniform one. Furthermore, an increase in the hydrogen doping ratio results in higher combustion temperatures and accelerated combustion reaction rates, accompanied by a decrease in CO concentration and an increase in NOx emission concentration. These results indicate that hydrogen doping enhances the combustion reaction and reduces pollutant emissions from gas combustion. This study provides a theoretical foundation for the practical application of hydrogen-doped natural gas in industrial boilers. • Experimental study of the effect of hydrogen doping ratio on flame morphology. • Effect of hydrogen doping ratio on combustion characteristics of natural gas. • Effect of excess air coefficient on combustion characteristics of natural gas. • Combining experimental and simulation to analyze combustion characteristics. • Analysis of combustion temperatures and pollutant generation characteristics. [ABSTRACT FROM AUTHOR]

In this study, the split-channel supercharge and fuel-air mixing technology (SCS-FAM) is firstly proposed for large-bore ammonia (NH 3)-hydrogen (H 2) engine, which involves the separation of fuel and air intake ports to mitigate the risk of H 2 backfire in intake system. We explored the activity stratification under different intake schemes and H 2 blend ratios through simulation, as well as how it affects the NH 3 –H 2 combined combustion characteristics including in-cylinder flow turbulence, temperature, concentration, and key intermediates distribution. The results show that in Scheme 2 when air entered the high swirl ratio intake 1 and fuel entered the low swirl ratio intake 2, a rich mixture was formed near the spark plug, accompanied by localized NH 3 thermal reforming phenomena, which improved the activity distribution of H 2. Additionally, the strong swirl promoted combustion in the squish zone and significantly shortened the post-combustion period. Scheme 2 achieved a higher indicated thermal efficiency (ITE) than Scheme 1 with a small amount of H 2 addition, with the highest ITE of 42.1% obtained at 15 vol% H 2 blend ratio. Notably, the addition of H 2 promoted NH 3 consumption and the generation of active radicals, resulting in reduced N 2 O emissions during the expansion stroke, but causing an increase in NO emissions. • Split-channel supercharge and fuel-air mixing technology is proposed to prevent H 2 backfire. • Different NH 3 –H 2 blend mixtures are compared and higher thermal efficiency is reached by lower H 2 fraction. • The localized ammonia-rich auto-thermal reforming improves the activity distribution of NH 3 –H 2 mixture. • Improved in-cylinder swirl could enhance the flame propagation in squish zone and reduce post-combustion. [ABSTRACT FROM AUTHOR]

Due to their detrimental and persistent impacts on the environment, it is imperative to manage and dispose of hazardous wastes (HW) in a secure manner. This study investigates the combustion characteristics and environmental impacts of using HW as alternative fuels in clinker production. The HW categories analyzed include industrial hazardous waste (IHW), medical hazardous waste (MHW), and household hazardous waste (HHW). Specifically, IHW consists mainly of waste mineral oils, waste organic solvents, organic resin wastes, waste residues, and waste coatings. MHW primarily consists of medical plastic products. HHW mainly includes packaging from waste pharmaceuticals, waste pesticides, disinfectants, and waste paints. Compared to traditional pulverized coal, hazardous waste alternative fuel (HWAF) exhibits a lower fixed carbon content, with its heat generation primarily dependent on volatile substances, and a higher ash content, chemically similar to coal ash. The combustion process of HWAF involves three stages: moisture evaporation (0 °C–150 °C), volatile matter combustion (150°C–400 °C), and fixed carbon combustion (400 °C–550 °C). The primary emissions from this process include CO 2 , CO, trace amounts of SO 2 , NO 2 , H 2 O, and various complex organic compounds such as carboxylic acids, alcohols, ketones, and aldehydes. While HWAF ignites more readily than pulverized coal, it burns more slowly and less completely. The incorporation of combustion by-products into the cement clinker formulation does not interfere with the clinker's hydration processes or reactions. HWAF ensures a reduced heavy metal input rate in the firing system without significantly impacting the heavy metal content in the clinker. Mortar samples produced with this clinker meet the heavy metal leaching standards, affirming the environmental safety of the cement product. Increasing the proportion of HWAF results in a reduction in standard coal consumption and an increase in CO 2 reduction, achieving a maximum coal saving of 3.67 kgce/t.cl and a CO 2 emission reduction of 10.11 kg/t.cl. This study presents a clean production model for the co-processing of HWAF, effectively transforming waste into valuable resources by using hazardous waste materials as alternative fuels. [ABSTRACT FROM AUTHOR]

As the most prospective media material for porous media burners, silicon carbide reticulated porous ceramic (SiC RPC) is required to possess a high porosity to fulfill efficient combustion, as well as exceptional thermal shock resistance to withstand the thermal stress generated during the start-up and shutdown processes. To achieve the strengthening and toughening of highly porous SiC RPC, three-layered struts were constructed, and in-situ whiskers were formed in SiC RPC through vacuum infiltration and sintering under a nitrogen atmosphere in this work. The results indicated that the three-layered struts were formed after the preform was conducted with vacuum infiltration, encompassing a mullite coating, a silicon carbide layer and a mullite inner layer. When Si powder and flake graphite were incorporated into the SiC slurry, numerous SiC whiskers were formed in situ within the SiC skeleton. The formation of SiC whiskers was attributed to the enhancement of SiC RPC, resulting in an increase in CCS from 0.22 MPa to 0.55 MPa. Additionally, the residual strength retention rate after water quenching at 1100 °C was elevated from 41.6 % to 70.2 %. Moreover, the SiC RPC containing SiC whiskers exhibited an impressively high porosity of 83 %, leading to a surface temperature of 688 °C and a heating efficiency of 16.4 °C/min during the combustion process. [ABSTRACT FROM AUTHOR]

The characteristics of the multi-strut equipped large aspect ratio supersonic combustor fueled with liquid kerosene were observed to deepen understanding of the combustion characteristics. Some numerical simulations and experiments have been carried on at the condition of Tt = 1680K, Pt = 1.68Mpa, and Ma = 2.8. The mixing and combustion performances of liquid kerosene under the different fuel injection methods are studied by numerical calculation. The results show that with the multi-struts injection method, the fuel distribution can be optimized, and combustion performance is improved by 60%. Then, three different strut arrangement schemes are proposed by designing the relative position between the leading edge shock wave of the ignition strut and the injection strut. The shock field structure and total pressure loss in different cases are discussed, and a low-resistance strut arrangement scheme is obtained. The mixing efficiency of the liquid fuel is discussed, and the effect of the shock wave on the fuel vaporization process is analyzed by using the two-phase flow model. The results show that the process of fragmentation and atomization of the gaseous fuel is promoted by the shock wave, which improves the mixing efficiency. The influence of the arrangement scheme of the multi-struts on the combustion efficiency is analyzed. The degree of flame overlap increases rapidly at a small distance between struts, which makes the combustion efficiency drop by 30%. Finally, combined with the research contents of this paper, a design method of the multi-strut arrangement scheme is proposed, and the feasibility of the design method is verified by experiments. The results of this paper are beneficial for the future performance optimization of multi-strut combustors using liquid kerosene as fuel. [ABSTRACT FROM AUTHOR]

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The thermal safety of hydrophobic silica aerogels (SAs) is essential to thermal insulation applications. Herein, trimethylchlorosilane (TMCS), dimethyldichlorosilane (DMDCS), and methyltrichlorosilane (MTCS) were employed as surface modifiers to prepare three different methylsilyl-modified SAs (i.e., TSA, DSA, and MSA) and their combustion characteristics and thermal hazards were experimentally studied in detail. The cone calorimeter test found that the three SAs have similar combustion processes and the variations in ignition time and fire spread rate with the heat flux obey simple logarithmic and linear relationships, respectively. It further found that TSA has the most methylsilyl groups on silica skeletons and thus has the largest heat release, followed by DSA and MSA in turn, implying that TSA has the greatest fire hazard among the three SAs. These results further demonstrate that the type and quantity of methylsilyl groups on the skeletons of SAs significantly affect the thermal hazard of methylsilyl-modified SAs. In addition, the combustion mechanism of the methylsilyl-modified SAs is discussed. In total, this work experimentally studies the combustion characteristics of methylsilyl-modified SAs and compares their thermal hazards, clarifying the potential fire risk of methylsilyl-modified SAs in practical thermal insulation applications. [ABSTRACT FROM AUTHOR]

Under the background of achieving carbon dioxide peaking and carbon neutrality, the rapid development of renewable energy power generation poses new challenges to the flexible adjustment capabilities of traditional power plants. To explore the furnace combustion stability and optimal operation modes during deep peak shaving, a simulation of the combustion process under low-load conditions for a 600 MW wall-fired boiler is performed utilizing computational fluid dynamics (CFD) analysis. The impact of burner combination modes on the combustion process within the furnace is explored at 25% and 35% boiler maximum continuous ratings (BMCRs). This study investigates two configurations of burner combinations. One mode operates burners in layers A, B, and C, which include the lower layers of burners on the front and rear walls of the boiler, as well as the middle-layer burners on the rear wall, referred to as OM1. The other mode operates burners in layers A and C, which include the lower layers of burners on the front and rear walls of the boiler, referred to as OM2. The results indicate that OM2 exhibits superior capabilities in orchestrating the distribution of the airflow velocity field and temperature field under the premise of ensuring no more than a 1% decrease in the pulverized coal burnout rate. When OM1 is employed, the airflow ejected from the middle-level burners hinders the upward movement of pulverized coal sprayed from the lower-level burners, causing a larger proportion of pulverized coal to enter the ash hopper for combustion. Consequently, the ash hopper attains a peak mole fraction of CO2 at 0.163. OM2 delays the blending of pulverized coal with air by enhancing the injection quantity of pulverized coal per burner. As a result, the generation of CO in the ash hopper reaches a notable mole fraction of up to 0.108. The decreased furnace temperature promotes the formation of fuel-based NOx during low-load operation. Taking the 25% BMCR as an example, the NOx emissions measured at the furnace outlet are 743 and 1083 ppm for OM1 and OM2, respectively. This study focuses on the impact of combustion combinations on the combustion stability when the boiler is operating at low loads. The findings could enrich previous research on combustion stability and contribute to the optimization of combustion schemes for power plant boilers operating at low loads. [ABSTRACT FROM AUTHOR]

Electrical fires perennially rank first in fire occurrence types, with conductor overcurrent being one of the main inducements. This topic draws significant attention from scientific researchers and fire investigators. To understand the overcurrent fault and combustion characteristics of copper‐clad aluminum conductors, this paper examines 2.5 mm2 copper‐clad aluminum conductors that meet national standards, investigating morphological changes, temperature variations in the core and insulation layer, and flame propagation patterns under overcurrent conditions. Experiments using an electrical fault simulation device were conducted to study overcurrent failures of copper‐clad aluminum conductors under 52.5–105 A conditions. The results indicate that when the current exceeds 67.5 A, the conductor undergoes a series of changes during energization, including smoking, expanding, carbonizing, burning, and breaking; at 52.5 A, the insulation layer reaches thermal equilibrium at 150 s without combustion; for currents between 60–67.5 A, wire core temperature variations can be divided into three stages; at 75 A, the insulation layer reaches thermal equilibrium 10s before breaking; currents above 82.5 A see a sharp increase in temperature in both the core and insulation layer before the conductor breaks; above 97.5 A, the conductor first breaks and then burns. The research results have significant theoretical value in improving the scientific rigor of fire accident investigations and forensic evidence examinations. [ABSTRACT FROM AUTHOR]

This study explores the impact of compression ratio (CR) and fuel blends on the combustion properties of a diesel engine fueled by conventional diesel and biodiesel derived from Moringa oleifera. The research was conducted on a single-cylinder diesel engine with variable compression ratio (VCR) and common rail direct injection (CRDI), utilizing diesel and Moringa oleifera biodiesel blends MB10, MB20, and MB30. The experimental conditions included varying the CR between 15:1 and 18:1, maintaining an injection timing of 23°before top dead center, injection pressure set at 600 bar, and an engine speed of 1500 rpm under 100% load. The findings revealed that increasing the CR raises cylinder pressure (CP), cumulative heat release rate (CHRR), and rate of pressure rise (ROPR) for all the tested fuel blends. Notably, the diesel exhibited the highest CP of 70.83 bar, CHRR of 1.36 kJ, and ROPR of 6.42 bar/°CA (degree per crack angle) at a CR of 18:1. Among the biodiesel blends, MB30 showed the highest CP of 69.21 bar, while MB10 displayed highest CHRR and ROPR of 1.5 kJ and 6.17 bar/°CA, respectively. Furthermore, the net heat release rate (NHRR) and mean gas temperature (MGT) decreased with rising CR for all tested fuels. At a lower CR of 15:1, the diesel showcased the highest NHRR and MGT of 69.75 J/°CA and 1303.69 °C, respectively, whereas, in the case of biodiesel blends, MB20 demonstrated the highest values of 67.53 J/°CA and 1287.39 °C, respectively, at the same CR. Meanwhile, the ignition delay (ID) and combustion period diminish with a rise in the CR for all tested fuel blends. At a higher CR of 18:1, the minimum ID and combustion duration for diesel were reported as 17°CA and 15°CA, respectively. For the biodiesel blends, MB10 and MB30 showed a minimum ID of 16°CA, while MB10 and MB20 exhibited minimum combustion duration of 15°CA at the same CR.

The inherent drawbacks of biodiesel, particularly its poor performance in cold climates, necessitate the use of nano-additives to improve its cold flow properties such as the cloud point (CP), pour point (PP), and cold filter plugging point (CFPP). In this study, transesterification was employed to produce methyl esters from waste cooking oil, corn oil, and jatropha oil. These biodiesels were blended with diesel fuel at a 20% biodiesel and 80% diesel volume ratio and enriched with nano-Al2O3 at concentrations of 25, 50, and 100 mg/L. The aim of this study is to evaluate the impact of nano-Al2O3 on engine combustion, performance, exergy, and emissions of diesel engines using different biodiesel feedstocks. The addition of nano-Al2O3 to methyl ester mixtures (JB20A100, CB20A100, and WB20A100) resulted in enhancements in thermal efficiency by 8%, 11%, and 13%, respectively. CO emissions were reduced by 12%, 17%, and 22% for jatropha, corn, and waste cooking oil blends, respectively, with 100 ppm alumina. This reduction in CO emissions can be linked to the enhanced oxidation process facilitated by the high surface area of the nanoparticles, which act as catalysts, promoting more complete combustion. Similarly, UHC emissions decreased by 14%, 18%, and 23%, and smoke concentrations were significantly reduced by 14%, 17%, and 24% across the biodiesel blends. However, the introduction of alumina led to the rise in NOx emissions by 9%, 15%, and 19% for JB20A100, CB20A100, and WB20A100, respectively. The study also revealed increases in cylinder pressure by 2%, 4%, and 8%, and maximum heat release rates by 3%, 6%, and 10% for JB20, CB20, and WB20, respectively, upon the incorporation of 100 ppm Al2O3. Exergetic efficiencies improved by 6%, 17%, and 23% for JB20A100, CB20A100, and WB20A100, respectively, and the sustainability index showed enhancements of 2%, 4%, and 7%. Among the tested blends, WB20 with 100 ppm of nano-Al2O3 demonstrated the most promising results, significantly improving engine exergy, combustion, and performance while mitigating emissions to acceptable levels. This study underscores the potential of nano-additives to advance the sustainability and efficiency of diesel engine operations, particularly in cold climate.