Combustion Period Research Articles

Rapid Prediction of Hot-Air Temperature of Kalugin Top Combustion Hot Blast Stove by Means of Computational Fluid Dynamics Numerical Simulation

Based on the three-dimensional (3D) steady-state CFD numerical simulations conducted previously on an industrial Kalugin top combustion hot blast stove, a two-dimensional (2D) transient CFD numerical model for a single channel (hole) of a column of checker bricks in the regenerator of the same hot stove was established in the present work. The average mass flowrate and temperature of the flue gas flowing into the checker brick holes during the combustion period predicted by the 3D model were used as the inlet boundary conditions of the 2D model. Inside the hole of the checker bricks, processes of fluid flow and heat transfer of the flue gas during the combustion period and those of cold air during the hot-air-supply period were simulated using the 2D model for multiple operation cycles (combustion and hot-air-supply periods) of the hot stove, enabling rapid predictions of hot-air temperature under different operating conditions. The simulation results show that when the fuel gas flowrate and air consumption coefficient during the combustion period are controlled within the range of 80,000–100,000 Nm3/h and 1.02–1.28, respectively, a hot-air temperature in the range from 1273 °C to 1295 °C can be obtained during the hot-air-supply period. Applying this optimized operating condition to the industrial hot stove investigated in this study can achieve significant effects of reducing fuel gas flowrate by 8.6% and increasing hot-air temperature by 32 °C. In addition, a regression analysis on the numerical simulation results and the data measured from the industrial hot stove yields a roughly linear relationship between the dome temperature during the combustion period and the hot-air temperature during the hot-air-supply period, that is, the hot-air temperature would be increased by about 16 °C for every increment of 10 °C in the dome temperature, for instance. Therefore, the influences of the operating parameters on heat transfer characteristics in the regenerator and on hot-air temperature obtained in the present work provide a useful reference for guiding the hot stove operation optimization to achieve significant energy saving and emission reduction through facilitating more efficient combustion to minimize fuel gas consumption in steel plants.

Determination and analysis of macro-featured parameters based on kilogram-level coal spontaneous combustion experiment

The quantitative characterization of coal spontaneous combustion and the accurate determination of the dangerous degree are hot and difficult in the field of coal mine safety. In the paper, the experimental test analysis of Huangling No. 2 coal was carried out by a self-designed and built kilogram-level coal spontaneous combustion experimental device, and the macro featured parameters were obtained and analyzed, such as temperature field, index gas, weight, oxygen consumption rate and exothermic intensity, and spontaneous combustion limit parameters. The results show that the experimental spontaneous combustion period of Huangling No.2 coal is 34 days. When the coal temperature was below the critical temperature of 74.59 °C, the oxidation of coal samples was relatively slow, and the oxygen consumption and the production rate of gas products did not change much. After the coal temperature exceeded the critical temperature, the oxygen consumption rate and exothermic intensity increased faster and the oxidation accelerated. After reaching the dry cracking temperature of 104.93 °C, the oxidation degree accelerated sharply. CO starts to appear at the beginning of the experiment, and the increase of CO gas concentration during the heating process is exponential and can be used as an index gas. Under the temperature condition of 40 °C, the floating coal of 0.7 m needs 25.83% oxygen concentration, and the maximum air leakage intensity of the coal is negative, and no spontaneous combustion will occur. The test data and calculation results of the experiment are important for the prediction and forecast of natural fires and the determination of the risk of spontaneous combustion on site.

Recurrent forest fires, emission of atmospheric pollutants (GHGs) and degradation of tropical dry deciduous forest ecosystem services

Forest fires threaten to biodiversity, ecosystem productivity, multiple ecosystem services, and it influences the emissions of large amounts of greenhouse gases into the atmosphere. This scientific study has been conducted at Ayodhya hill range of dry deciduous forest of Chota Nagpur plateau (India).The principal objectives of this research are (1) to measure the terrestrial ecosystem productivity by Vegetation Photosynthesis Model (VPM); (2) to estimate the greenhouse gases (GHGs) emission through forest fire following IPCC guidelines; and (3) to quantify the ecosystem service value and degradation of ecosystem services (ESs) by specific indices and focus group discussions (FGDs). Results show that biophysical, climatic and environmental factors notably affect the growth of ESs. A significant reduction of net primary production (NPP) and biomass has been measured in fire month (100.71 and 223.59 gC m−2 month−1) and values of spectral indices also show negative trend during fire month (-0.1279 to −0.2104) respectively. Total 294.15 g, 1.44 g, 21.03 g, 0.0099 g and 0.0231 g of CO2, CH4, CO, NO2, and NOX have been emitted respectively through forest fire from this hill range during forest burning period (March 2021). This study also revealed that average (18.50%) forest dependency or relative forest income (RFI) has been fallen in the recent years due to recurrent forest fires, execution of different developmental works and deforestation. The effective management of forest resources (through payment for ESs and willingness to pay approaches) is highly necessary in strengthening the rural economy and welfare of indigenous tribal people.

Therapeutic role of mesenchymal stem cells and platelet-rich plasma on skin burn healing and rejuvenation: A focus on scar regulation, oxido-inflammatory stress and apoptotic mechanisms

Cell-based therapies have great promise in accelerating and improving burn wound healing. It is a growing need to scale their competence to meet the clinical demands. In this study, the bone marrow mesenchymal stem cells (BMSCs) and platelet-rich plasma (PRP) were tested on the repair of induced burn wounds in a murine model. After the induction of thermal injury, rats were injected with BMSCs and/or PRP in the burn area. After 4 weeks of post-burn, our findings revealed that local treatment of burnt skin with BMSCs and/or PRP offered substantial outcomes when compared with the untreated group. Injected burn with BMSCs and/or PRP enhanced the wound contraction rate and decreased the burn area and period of epithelization. Significant increases in VEGF together with declines in MMP-9 and TGF-β1 were observed in burnt areas after being treated with BMSCs and/or PRP therapy that indicated improved angiogenesis, and re-epithelization. Furthermore, both MSCs and PRP modulated the burn's oxidative and inflammatory microenvironment as indicated by increases in SOD, CAT, and GSH besides declines in MDA, IL-6, TNF-α, NF-κB, NO, and iNOS. Notable increases in Bcl-2 levels and decreases in Cas-3 and Bax levels were recorded in burnt skin that received both agents concomitantly. Interestingly, the histopathological examination validates the healing power of BMSCs and/or PRP. Collectively, BMSCs and PRP have pioneered therapeutics candidates for clinical application in burn healing possibly via antioxidant, anti-inflammatory, and anti-apoptotic mechanisms along with regulating angiogenesis and scar formation.

The impact of fireworks burning on air quality and their health effects in China during Spring Festivals of 2015–2022

Ambient monitoring online data of six criteria air pollutants (PM2.5, PM10, SO2, NO2, O3 and CO) in 31 provincial capital cities in China during Spring Festivals from 2015 to 2022 were analyzed to estimate contributions of fireworks burning to PM2.5 and their health effects. It shows that daily average concentrations of PM2.5, PM10, SO2, NO2, and CO during Spring Festivals of 2015-2022 dropped remarkably by 36.5%, 48.9%, 70.6%, 29.7%, and 36.8%, respectively, while 8h O3 concentrations increased significantly by 21.6%. Average contributions of fireworks burning to PM2.5 during intensive fireworks burning periods from 2015 to 2022 were 44.8 ± 14.7 %, 56.2 ± 16.9 %, 50.1 ± 16.2 %, 46.0 ± 16.8 %, 44.3 ± 14.9 %, 33.2 ± 20.7 %, 44.5 ± 15.5 % and 35.2 ± 23.3 %, respectively. The total excess health risk (ERtotal) based on Chinese Ambient Air Quality Standards (CAAQS) and World Health Organization (WHO) air quality guidelines, and health-risk based air quality index values (HAQI) were estimated. Annual average values of ERtotal based on the WHO standard were 1.5–4.7 times as many as those estimated by CAAQS standards and annual average values of HAQI based on CAAQS Grade Ⅰ standard were higher than those based on CAAQS Grade Ⅱ standard. Main health risk factors were different under different air quality standards. It is necessary to further improve air quality to protect human health during Spring Festivals in China in the future.

EXPERIMENTAL INVESTIGATION OF THE COMPRESSIVE STRENGTH OF CONCRETE-FILLED FRP TUBE CYLINDERS SUBJECTED TO FIRE

Concrete-filled fiber reinforced polymer tubes (CFFTs) are becoming an attractive system for many different structural applications, such as piles, columns, and piers. However, many engineers are hesitant to use FRPs in structure because of the lack of knowledge of their behavior when they are subjected to fire. This study presents test results of thirteen CFFT cylinders with tube thickness ranges from 1.9 to 4.3 mm subjected to direct fire for periods ranges from 2 to 15 minutes and compared to reference confined and unconfined concrete cylinder. The tubes are composed of filament wound E-class fiber immersed in polyester resin. The test results show almost no losses in compressive strength for 2 minutes burning period for all tested tube thicknesses. By increasing the burning period to 15 minutes, the residual compressive strength significantly deteriorated to 44%, 56%, and 74% of the referenced strength for the unburned tubes with thickness 1.9, 3.7, 4.3 mm, respectively. Further investigation and observations were recorded for the surface condition after exposure to fire.

Bioethanol Production from Two Varieties (Saccharum Officinarum and Saccharum Barberi) Of Sugarcane Peels

Provision of an alternative clean source of fuel with less cost, will reduce fossil fuel demand. Pollution is the major environmental problem. Air pollution is among the three types of pollution where harmful substances such as CO2 and CO are introduced to the environment and cause harm to humans and animals. Fossil fuel combustion from automobiles and industries causes this type of pollution. There is need to replace another source of fuel with renewable feedstock such as the peels of Saccharum officinarum and Saccharum barberi which are lignocellulose materials to produce bioethanol that has a lower impact on air pollution and the Ozone layer which causes Green-House effect than fossil fuels. Dilute H2SO4 at different concentrations of 1M,2M,3M,4M and 5M were replicated into three different parts respectively as hydrolysing solution. Saccharomyces cerevisiae was used as fermentation enzymes. Different pH values of 5, 6 and 7 was used for fermentation periods of 5, 6 and 7 days, respectively. The Bioethanol was distilled by the use of fractional distillation. Hydrolysed samples of 3M for 6th day of both Saccharum officinarum and Saccharum barberi produced the best yields of bioethanol at the pH of 5 and 5M hydrolysed samples of both Saccharum officinarum and Saccharum barberi produced the least bioethanol for all pH values and fermentation days. The Bioethanol produced was blended with kerosene fuel to create EK10 and EK20 kerosene-bioethanol blends for use as a fuel source in a kerosene lamp. EK10 blend took 126 hours to burn in a rotary kerosene lamp, while EK20 blend took 167 hours to burn-off in the same kerosene lamp. Hydrolysed H2SO4 of 3M, pH 5 and fermentation period of 6 days for both Saccharum officinarum and Saccharum barberi shows the best sample to produce bioethanol. The bioethanol kerosene blend EK10 and E20 was concluded to show long period of burning with clean soot in a rotary kerosene lamp, therefore the bioethanol kerosene blends can be used as substitutes for kerosene fuel.

Daily detection and quantification of methane leaks using Sentinel-3: a tiered satellite observation approach with Sentinel-2 and Sentinel-5p

The twin Sentinel-3 satellites have multi-band radiometers which observe in methane-sensitive shortwave infrared bands with daily global coverage and 500 m ground pixel resolution. We investigate the methane observation capability of Sentinel-3 and how its coverage-resolution combination fits between Sentinel-5p and Sentinel-2 within a tiered observation approach for methane leak monitoring. Sentinel-5p measures methane with high precision and daily global coverage, allowing worldwide leak detection but with a coarse spatial resolution of 7 km × 5.5 km. The Sentinel-2 twin satellites have multi-band instruments that can identify source locations of major leaks (> 1 t/h) with their methane observations of 20 m resolution under favorable observational conditions, but these satellites lack daily global coverage.We show that methane enhancements can be retrieved from the shortwave infrared band measurements of Sentinel-3. We report the lowest emission detections by Sentinel-3 in the 8-20 t/h range, depending on location and wind conditions. We demonstrate Sentinel-3's capability of identification and monitoring of methane leaks using two case studies. Near Moscow, Sentinel-3 shows that two major short-term leaks, separated by 30 km, occurred simultaneously at a gas pipeline and appear as a single methane plume in Sentinel-5p data. For another Sentinel-5p leak detection near the Hassi Messaoud oil/gas field in Algeria, Sentinel-3 identifies the leaking facility emitting continuously for 6 days, and Sentinel-2 pinpoints the source of the leak at an oil/gas well. Sentinel-2 and Sentinel-3 also show the 6-day leak was followed by a four-month period of burning of the leaking gas, suggesting a gas well blowout to be the cause of the leak. We find similar source rate quantifications from plume detections by Sentinel-3 and Sentinel-2 for these leaks, demonstrating Sentinel-3's utility for emission quantification. We show that zooming in with Sentinel-3 and Sentinel-2 in synergy allows precise identification, quantification, and monitoring of the sources corresponding to methane plumes observed in Sentinel-5p's global scans.

Explosion behaviors of hydrogen-nitrous oxide mixtures with propane addition

In the present work, the explosion of hydrogen-propane-nitrous oxide mixtures with various equivalence ratios (ϕ=0.2-2.4), propane fractions (ωC=0-1.0) and initial pressures (P0=50-100 kPa) at ambient temperature (288 K, room temperature) was experimentally performed in a standard 3.375-L cubic vessel. The maximum explosion pressure (Pmax), maximum pressure rise rate ((dp/dt)max) and explosion time (te) were obtained in light of pressure–time curves, and the normalized maximum explosion pressure (Pmax/P0) and normalized explosion time (td/te) were analyzed as well. Moreover, the adiabatic pressure (Pad) and laminar burning velocity (SL) were also calculated for argumentation. The results indicate that with the increase of ωC, Pmax and (dp/dt)max both present three characteristic variation trends for different ϕ, while the inflections of Pmax-ϕ and (dp/dt)max-ϕ transient gradually from lean to rich mixtures. Besides, te and td/te are monotonously rising with ωC, illustrating that propane addition can remarkably decelerate the explosion process. In addition, with the increase of P0, Pmax/P0 raises monotonously and is asymptotic to Pad/P0 at ωC⩽0.2, demonstrating that heat loss decreases under higher P0. Linear dependence is also found between (dp/dt)max and P0 for any composition. Furthermore, te monotonically decreases with P0, due to the flame acceleration occurring in the combustion period. In general, the presence of nitrous oxide (N2O) with a large content makes the explosion extremely unstable, and a spot of propane can dramatically alter the explosion characteristics of H2-N2O mixtures. These results will be meaningful for the development of explosion-mitigation devices and technology in case of underlying explosion and fire hazards.

Fire spread in a large compartment with exposed cross-laminated timber and open ventilation conditions: #FRIC-01 – Exposed ceiling

Exposing cross-laminated timber (CLT) structures in buildings is increasingly popular in modern buildings. However, large timber surfaces, window facades, and different geometries can change the fire dynamics in a compartment. The effect of those parameters, therefore, needs to be studied. Two large-scale CLT compartment fire experiments (95 m2) have consequently been performed. The experiments were designed to represent a modern office building with an open-plan space and large window openings. In this experiment, #FRIC-01, the ceiling was exposed. The wood crib fire developed slowly and travelled approximately 1.5 m before the ceiling ignited at 32.5 min. Thereafter the fire spread rapidly across the ceiling and wood crib before it shortly after retracted. Three such cycles of rapid spread followed by a retraction occurred within 13 min, whereby the wood crib fire grew larger for each cycle. After the flames extended through the compartment for the fourth time, the fire remained fully developed. After a short period of intense burning, the CLT self-extinguished while the wood crib fire was still burning. The compartment withstood full burnout, and no reignition occurred despite some delamination and using an adhesive that lacks a demonstrated resistance against glue-line integrity failure.

Study on Spontaneous Combustion Law and Prevention Technology of Abandoned Coal in Goaf of Coal Mine

The spontaneous combustion of coal in goaf areas is a significant natural disaster encountered during coal mining operations. To investigate the oxygen consumption characteristics of different coal types, we conducted TG experiments and closed oxygen consumption experiments using seven coal samples exhibiting various degrees of metamorphism. The findings revealed the following key observations: During the oxidation combustion process of coal, the absorbed heat originates from the physical and chemical adsorption of coal and oxygen. The first exothermic peak on the DSC curve represents the maximum combustion temperature of volatile matter and signifies the initiation of coal burning. Coal with higher ignition temperatures is less prone to spontaneous combustion. Analyzing the thermogravimetric curves, we observed that the ignition temperatures of 15# coal and 8+9# coal predominantly extracted from Duanwang Coal Mine are higher compared to the ignition temperature of the 4# coal seam (known for its susceptibility to spontaneous combustion) in Jiudaoling Coal Mine, Liaoning. This observation aligns with their nonspontaneous combustion characteristics. In the closed oxygen consumption experiment, we determined the volume oxygen consumption attenuation coefficients for the main mining areas’ 8+9# and 15# coal seams as 3.9001 × 10 − 4 and 3.83559 × 10 − 4 , respectively. Additionally, the critical oxygen consumption concentrations were measured as 15.71% and 16.78%. The shortest spontaneous combustion periods were determined to be 119.24 days and 121.25 days, respectively, for the aforementioned coal seams. To mitigate spontaneous combustion, the addition of inhibitors is necessary. The selection of an appropriate inhibitor depends on the increase in ignition activation energy. Notably, coal samples treated with a 15% MgCl2 inhibitor exhibited the highest increase in ignition activation energy. Hence, we concluded that a 15% MgCl2 inhibitor is the most suitable ratio for preventing spontaneous combustion.

Ambient air particulate total lung deposited surface area (LDSA) levels in urban Europe

This study aims to picture the phenomenology of urban ambient total lung deposited surface area (LDSA) (including head/throat (HA), tracheobronchial (TB), and alveolar (ALV) regions) based on multiple path particle dosimetry (MPPD) model during 2017–2019 period collected from urban background (UB, n = 15), traffic (TR, n = 6), suburban background (SUB, n = 4), and regional background (RB, n = 1) monitoring sites in Europe (25) and USA (1). Briefly, the spatial-temporal distribution characteristics of the deposition of LDSA, including diel, weekly, and seasonal patterns, were analyzed. Then, the relationship between LDSA and other air quality metrics at each monitoring site was investigated. The result showed that the peak concentrations of LDSA at UB and TR sites are commonly observed in the morning (06:00–8:00 UTC) and late evening (19:00–22:00 UTC), coinciding with traffic rush hours, biomass burning, and atmospheric stagnation periods. The only LDSA night-time peaks are observed on weekends. Due to the variability of emission sources and meteorology, the seasonal variability of the LDSA concentration revealed significant differences (p = 0.01) between the four seasons at all monitoring sites. Meanwhile, the correlations of LDSA with other pollutant metrics suggested that Aitken and accumulation mode particles play a significant role in the total LDSA concentration. The results also indicated that the main proportion of total LDSA is attributed to the ALV fraction (50 %), followed by the TB (34 %) and HA (16 %). Overall, this study provides valuable information of LDSA as a predictor in epidemiological studies and for the first time presenting total LDSA in a variety of European urban environments.

A study on the impact of fuel injection parameters and boost pressure on combustion characteristics in a diesel engine using alcohol/diesel blends

Engine researchers focused on alcohol fuels since the invention of diesel engines in the 1900s, and the rise in petrochemical costs in the 1970s triggered this concern. This study investigates the impacts of the injection start timing, pilot injection application, and boost air pressure increase, on combustion and exhaust emissions in a common rail diesel engine fueled with ethanol/butan-2-ol/diesel blends. The lowest combustion noise was obtained in the pilot injection application as 83.8 dB in E15B3. The results indicated that the peak point of cylinder gas pressure rose by more than 5 % in the application of pilot fuel injection and advanced injection timing, compared to conventional engine operating conditions. However, maximum CO2 and NOx were seen in the pilot injection application using FBDF as 5.7 % and 670 ppm, respectively. As alcohol rate increases in fuel blends, the average 1.3 °CA in the ignition delay period was increased, while the total combustion period was shortened more than 6 °CA. This result shows that the combustion reactions of alcohol/diesel fuels occur faster than pure diesel. However, the variation in the ignition delay and total combustion periods of the test fuels considerably reduced with pilot fuel injection application. These results indicates that pilot fuel injection may be applied very controlled according to changing engine conditions. It was calculated in statistical analysis that except for the coefficient variation of the maximum pressure increase rate, the other coefficient variation values were relatively stable and below 3 %. In addition, it was determined that the results of the finite element analysis are proportional to the pressure values obtained experimentally.

Light absorption properties of brown carbon aerosol after following the switch from coal to natural gas policy in China: A case study of winter particulate matter over Xi'an, northwestern China

To control haze pollution, the Xi'an city in northwestern China replaced coal by natural gas in industrial and household heating at the end of 2017. Following this change we studied here the light absorption properties of brown carbon (BrC)in atmospheric particulate matter (PM2.5) over Xi'an in 2018. PM2.5 samples were collected from November 15 to December 25, 2018, and the light absorption properties of brown carbon in methanol-soluble organic carbon (MSOC) and water-soluble organic carbon (WSOC) were analyzed. Compared to a previous study from the coal combustion period, the mass absorption efficiency (MAE) increased in the sampling period while the radiation-forced absorption fraction of brown carbon relative to elemental carbon reduced, indicating that the light-absorbing capacity and efficiency of brown carbon has improved. Furthermore, highly positive linear relationships (r > 0.80) occur between the absorption coefficient and typical products of biomass burning and vehicle emission, except for coal combustion (r = 0.57). Additionally, an estimation from the positive matrix factorization and multivariable linear regression model results showed that biomass burning, motor vehicle emission, and secondary source took up approximately 89.53% of AbsWSOC,365. The contribution of coal combustion to light absorption BrC was the lowest (7.36% for AbsMSOC,365 and 10.24% for AbsWSOC,365) in our study, which differs from previous studies in Xi'an. Therefore, the emission source of bulk coal combustion has a relatively small influence on the light absorption of BrC in Xi'an.

A novel multiple spark ignition strategy to achieve pure ammonia combustion in an optical spark-ignition engine

Ammonia is an attractive carbon-free fuel that has the potential to reduce the need for conventional hydrocarbons (HC) and reduce emissions of undesirable pollutants such as CO, CO2, particulates, and unburned hydrocarbons. However, ammonia has different combustion characteristics than conventional HC fuel. Ammonia is difficult to ignite and has a low combustion rate, resulting in large cyclic variations. In addition, nitrogen oxides (NOx) emissions in the exhaust tract are a major challenge when using ammonia as a fuel directly in engines. In this study, the effect of multiple spark ignition sites on the combustion of pure ammonia in an optical spark ignition engine (SI) was investigated. The experiment was conducted with four spark plugs mounted equidistantly on a special metal liner and one spark plug fitted at the top of the cylinder head. The multiple flames emitted from the different spark ignition sites were captured by natural flame luminosity (NFL) imaging. In the results, the conventional single spark ignition is compared with multiple ignitions. It was found that single spark ignition resulted in lower in-cylinder pressure, longer combustion duration, and higher combustion instability due to the poor ammonia fuel combustion rate. However, firing multiple spark plugs significantly improved combustion stability, increased engine power, and shortened the combustion period under the same operating conditions. In addition, the flame kernels produced by multiple ignition sites resulted in higher NOx emissions in the exhaust tract due to the higher temperatures in the cylinder. In addition, this study also investigated the effect of three different air–fuel equivalence ratios (λ) of 1.0, 1.2, and 1.4 on the combustion characteristics of ammonia fuel. The maximum NOx level was obtained for λ: 1.2 because the excess air in the mixture oxidizes the ammonia and provides abundant oxygen to generate more NOx. Further reducing the ammonia fuel and increasing the excess air to λ: 1.4 dramatically reduced NOx emissions due to the lower pressures and temperatures in the cylinder resulting from the longer combustion period.

Burning of Municipal Solid Waste: An Invitation for Aerosol Black Carbon and PM2.5 Over Mid–Sized City in India

Waste management is the main concern of most cities in developing countries. The proper procedure is needed to reduce Municipal solid waste, that’s why burning is the cheaper way to decrease solid waste. The main aim of this study is to assess the concentration of Black Carbon and PM2.5 during the MSW burning sites in Jamshedpur. The continuous measurement was taken during the burning period in three phases at Industrial, Urban, and Rural waste burning sites having respective average BC concentrations observed as 145 ± 46, 101 ± 33 & 95 ± 33 μg m−3, and PM2.5 as 1391 ± 358, 998 ± 319, 957 ± 313 μg m−3. BC and PM2.5 concentrations show significant diurnal variations with maximum average concentration at the midnight phase due to large temperature fluctuation (lower mixed layer height) in the atmosphere. This evaluation during burning period exceeds regular day estimates by around 5–6 times. The rate distinction of BC by the Aethalometer model indicates that source apportionment of BC is more sensitive in assessing BCBB (biomass burning) with an average fraction of 82% at 880 nm because waste trash burning in the dump yard was mostly solid. Pearson correlation analysis shows strong correlations between BC and PM2.5 concentration that is primarily attributable to well-known nearby sources such as vehicular emissions.

NBR Index-Based Fire Detection Using Sentinel-2 Images and GIS: A Case Study in Mosul Park, Iraq

Forest fires lead to severe damage to the environment and human health. Monitoring can be applied using remotely sensed data and in combination with Geographical Information Systems (GIS) based spatial analysis. Lately, Iraq subjected to many forest fires. In this study, the aim was to monitor and detect the burned areas in Mosul Park during the latest period which happened in June 2022. The hypothesis of the study was based on using Sentinel-2 images and the Normalized Burn Ratio (NBR) index. Two images have been used to compare burned areas; one during the fire events and another postfire. as well as, Normalized Difference Vegetation Index (NDVI) map has been used to identify the Park's characteristics. Moreover, Pearson's correlation (r) with Air Quality Index (AQI) was determined during the burning period. GIS-based processes resulted in detecting the area of burning where the burned area was 16.76 hectares and lay in the eastern part of the study area. Pearson correlation with AQI has resulted in 0.92, while the collinearity between the burned areas and AQI was 0.84. Accurate and prompt planning for fire-affected regions is essential for supporting fire affect assessment, calculating environmental losses, determining planning strategies, and monitoring vegetation recovery.

Experimental study of dynamic combustion behavior and heat transfer of heptane pool fire with burning time under thin fuel thickness (2.0 mm–14.0 mm)

A dynamic combustion period occurs after the liquid fuel ignition, but the combustion mechanism is complicated and unclear due to dynamic heat transfer between the fuel and the substrate. This work uses a method of experimental research and theoretical analysis to study the dynamic combustion behaviour and heat transfer of pool fire with burning time (t) under thin fuel thickness (δ). Research contents include the relation of flame height (Z), burning rate (m˙), heat transfer between fuel and substrate with t, and the evolution mechanism of the output composition of total heat feedback with δ. The research found Z and m˙ increase with t until maintaining constant, whereas δ is different. Heat convection loss increases rapidly, then increases slowly, and finally keeps constant because thin-layer fuel is quickly heated. Heat radiation loss firstly surges, then fluctuates due to the combined effect of the flame shape and necking effect. Total heat loss tends from radiation to convection. The heat for heating fuel and the heat radiation reflected from the substrate are considered in the dynamic combustion stage. The fractions of heating fuel, vaporization heat, heat loss and heat reflection were calculated and studied. This work adds theoretical knowledge of fire dynamics

Indoor air pollution from the household combustion of coal: Tempo-spatial distribution of gaseous pollutants and semi-quantification of source contribution

Coal is a widely used solid fuel for cooking and heating activities in rural households, whose incomplete combustion in inefficient household stoves releases a range of gaseous pollutants. To evaluate the impact of coal combustion on indoor air quality, this study comprehensively investigated the indoor air pollution of typical gaseous pollutants, including formaldehyde (HCHO), carbon dioxide (CO2), carbon monoxide (CO), total volatile organic compounds (TVOC), and methane (CH4), during coal combustion process in rural households using online monitoring with high tempo-spatial resolution. The indoor concentrations of gaseous pollutants were considerably elevated during the coal combustion period, with the indoor concentrations being significantly higher than those in courtyard air. The levels of several gaseous pollutants (CO2, CO, TVOC, and CH4) in indoor air were much higher during the flaming phase than the de-volatilization and smoldering phases, while HCHO peaked in the de-volatilization phase. The gaseous pollutant concentrations mostly decreased from the room ceiling to the ground level, while their horizontal distribution was relatively uniform within the room. It was estimated that coal combustion accounted for about 71 %, 92 %, 63 %, 59 %, and 21 % of total exposure to indoor CO2, CO, TVOC, CH4, and HCHO, respectively. Improved stove combined with clean fuel could effectively lower the concentrations of CO2, CO, TVOC, and CH4 in indoor air and reduce the contributions of coal combustion to these gaseous pollutants by about 21–68 %. These findings help better understand the indoor air pollution resulting from residential coal combustion and could guide the development of intervention programs to improve indoor air quality in rural households of northern China.

Numerical analysis for optimizing combustion strategy in an ammonia-diesel dual-fuel engine

Due to the stringent environmental regulations, the use of ammonia, a carbon-free fuel, as a fuel for internal combustion engines is attracting attention. It is necessary to understand the characteristics of engines using ammonia to replace diesel engines. Therefore, in this study, the combustion characteristics of an ammonia-diesel dual-fuel engine were investigated through numerical simulation to optimize the combustion strategy. A reaction mechanism was constructed for the simulation. Ammonia energy fractions ranging from 40 to 90% and diesel injection timings from −80 to −15 crank angle degrees (CAD) were considered. When the diesel injection timing was advanced, the combustion period was shortened, and the premixed combustion characteristics were shown. An increase of the efficiency of up to 11.0% compared to diesel combustion was obtained under advanced injection timing and high ammonia energy fraction. This is because the slow flame propagation of ammonia was compensated for by the effect of premixed combustion. Therefore, the advance of the injection timing resulted in a reduction in unburned ammonia emissions. Also, the combustion temperature increased due to the premixed combustion effect. So, the nitrous oxide emission was greatly reduced by thermal decomposition. And carbon dioxide emission was proportional to diesel quantity. As a result, greenhouse gases were reduced by up to 80.6% compared to diesel combustion in advanced injection timing and high ammonia energy fraction. However, nitric oxide emissions increased as the ammonia energy fraction increased and injection timing advanced under the influence of fuel and thermal nitrogen oxides. It was significant compared to diesel engines.