Laboratory Combustion Research Articles

Speciation and Aqueous Dissolution of Macronutrients in Fire Ash: Variation across Ecosystems and the Effects on Nutrient Cycling.

This study investigated the speciation and aqueous dissolution of macronutrients in fire ash from diverse ecosystems and speciation of ash and smoke from laboratory burning, exploring the variations and their causes. The speciation of phosphorus (P), calcium (Ca), and potassium (K) in fire ash from five globally distributed ecosystems was characterized by using X-ray absorption spectroscopy and sequential fractionation. Aqueous dissolution of the macronutrients was measured by batch experiments at acidic and alkaline pHs. The results showed that P existed mainly as Ca phosphates, Ca as double carbonates, calcite, and sulfates, and most K was associated with Ca carbonates. Mineralogy and the relative abundance of the species were primarily controlled by elemental stoichiometry and fire temperature. Differences in Ca and P speciation existed between ash and smoke from laboratory burning, possibly caused by the temperature difference and/or mass fractionation during burning. The rates, extents, and pH dependencies of macronutrient dissolution differed among macronutrients and depended on their speciation, with K being highly soluble and the P and Ca regulated by solution pH. The variability in ash macronutrient chemistry and ecosystem-specific fire ash loads resulted in varying loads and availability of individual macronutrient from fire among ecosystems. This study provides a mechanistic understanding of how fires transform the chemistry of macronutrients and affect macronutrient returns to soils across different ecosystems, which is essential for evaluating the disturbance to ecosystem nutrient cycling by fires.

Cheatgrass alters flammability of native perennial grasses in laboratory combustion experiments

Abstract Background The invasive annual grass cheatgrass (Bromus tectorum) increases fuel continuity, alters patterns of fire spread, and changes plant communities in sagebrush shrublands of the Great Basin (USA) and adjacent sagebrush steppe, but no studies have contrasted its flammability to native perennial grasses. Understanding cheatgrass flammability is crucial for predicting fire behavior, informing management decisions, and assessing fire risk in invaded areas. This study aimed to determine the flammability of cheatgrass compared to two native perennial grasses (Columbia needlegrass [Achnatherum nelsonii] and bluebunch wheatgrass [Pseudoroegneria spicata]) across a range of fuel moistures. Results All three grass species had decreased flammability with increasing fuel moisture. Columbia needlegrass averaged 11% lower mass consumption than cheatgrass, and bluebunch wheatgrass had longer flaming duration and higher maximum temperatures than cheatgrass and Columbia needlegrass. The addition of cheatgrass to each perennial grass increased combined mass consumption, flaming duration, and flame heights. For these three attributes, the impact differed by the amount of cheatgrass in the mixture. Maximum and mean temperatures during perennial grass combustion were similar with and without cheatgrass addition. Some attributes of Columbia needlegrass flammability when burned with cheatgrass were higher than expected based on the flammability of each species, suggesting that Columbia needlegrass may be susceptible to pre-heating from combustion of cheatgrass. Conversely, the flammability of bluebunch wheatgrass and cheatgrass together had both positive and negative interactive effects, suggesting the impact on joint flammability from cheatgrass differs by perennial grass species. Conclusions This study provides experimental evidence supporting previous qualitative observations of cheatgrass flammability. Cheatgrass increased perennial grass sustainability and consumption, suggesting that cheatgrass poses a significant fire threat to native grasses regardless of moisture content. The study provides species-specific insights into flammability, which could be used to inform efforts to prevent or mitigate cheatgrass-induced wildfires.

Thicker or Shorter Bark Fragments of Eucalypt Tree Species Make More Densely Packed Fuel Beds, Which Slow Down Fire Spread

Many eucalypt trees shed their bark annually. This bark becomes a component of the litter layer, which acts as fuel, especially during surface fires. The amount and quality of shed bark vary greatly among species, which might have important effects on forest surface fire behavior. In this study, we aimed to compare the bark fuel bed flammability of eight eucalypt tree species and tried to link their bark litter traits via the surface fuel bed structure to bark flammability. In controlled laboratory burns, three flammability parameters, the fire spread rate, total burning time, and maximum temperature, were measured. The bark litter traits included length, curliness, thickness, dry matter content, tissue density, carbon content, nitrogen content, and terpene content, while the litter bed packing ratio and packing density were also measured. We found significant differences in bark traits and flammability among species. Thicker bark fragments of the eucalypt tree species had higher packing densities in fuel beds, a slower fire spread, and a longer burning time. This relationship was strongly driven by the thick bark fragments of Eucalyptus punctata DC. Still, also within the other seven species, bark thickness was the strongest predictor of bark fuel bed flammability, with some additional explanatory power for bark length. For the first time, our study demonstrates that bark traits, particularly litter fragment thickness and length, drive bark litter flammability of eucalypt tree species through their effects on bark fuel bed structure. These findings contribute to our understanding and predictive power of wildfire behavior in forest stands dominated by different eucalypt species.

Analysis of a High-Speed Airbreathing Research Combustor for JP-7 Fuel-Cooled Design

The continuing maturation of high-speed airbreathing engines has driven an emerging need for a technology transfer from the laboratory into vehicle design. It is now desirable to convert robust, laboratory combustor designs intended for hours of combustion into lightweight, fuel-cooled engines ready for vehicle integration and flight. In a flight-ready combustor, the heat loss of the combustor must be optimized. To understand the heat loss requirement of a laboratory combustor and attempt to optimize it for flight, historical heat loss data of a water-cooled, axisymmetric research combustor are analyzed to inform the conversion of this combustor to a fuel-cooled, flight-like, high-speed airbreathing combustor. Historical data are analyzed at high (0.9) and low (0.3) fuel–air equivalence ratio (ER) values; the analysis shows that the JP-7 cooling flow rate of the combustor can be reduced by 90% (ER 0.3) and 89% (ER 0.9) compared to the baseline research combustor design. This analysis provides an important first look at the cooling design modifications required to convert a research combustor with this internal flow path into a fuel-cooled, flight-ready combustor for use onboard a flight vehicle.

Characterization of Waste Biomass Fuel Prepared from Coffee and Tea Production: Its Properties, Combustion, and Emissions

In order to reduce global warming, new energy fuels that use waste biomass to replace traditional coal are rapidly developing. The main purpose of this study is to investigate the feasibility behavior of different biomass materials such as spent coffee grounds (SCGs) and spent tea grounds (STGs) as fuel during combustion and their impact on the environment. This study involves using fuel shaping and co-firing methods to increase the fuel calorific value and reduce the emissions of pollutants, such as NOX and SO2, and greenhouse gas CO2. The produced gas content was analyzed using the HORIBA (PG-250) laboratory combustion apparatus. The results indicate that, among the measured formed particles, SCG:STG = 8:2, 6:4, and 4:6 had the lowest post-combustion pollutant gas emissions. Compared to using only waste coffee grounds as fuel, the NOx emissions were reduced from 166 ppm to 102 ppm, the CO emissions were reduced from 22 ppm to 12 ppm, and the CO2 emissions were reduced from 629 ppm to 323 ppm. In addition, the emission of SO2, the main component of acid rain, was reduced by 20 times compared to the combustion of traditional fuels. The SO2 emission of five different proportions of biomass fuels was 5 ppm, which is much lower than that of traditional coal fuels. Therefore, SCG and STG mixed fuels can replace coal as fuel while reducing harmful gasses.

The complex composition of organic aerosols emitted during burning varies between Arctic and boreal peat

AbstractPeatlands in the northern hemisphere are a major carbon storage but face an increased risk of wildfires due to climate change leading to large-scale smoldering fires in boreal and Arctic peatlands. Smoldering fires release organic carbon rich particulate matter, which influences the earth’s radiative balance and can cause adverse health effects for humans. Here we characterize the molecular composition of biomass burning particulate matter generated by laboratory burning experiments of peat by electrospray ionization 21 T Fourier-transform ion cyclotron resonance mass spectrometry, revealing a highly complex mixture of aromatic and aliphatic organic compounds with abundant heteroatoms including oxygen, sulfur and up to five nitrogen atoms. Primary organosulfur species are identified in the emissions of peat-smoldering, in part also containing nitrogen. Differences are observed when comparing structural motifs as well as the chemical composition of boreal and Arctic peat burning emissions, with the latter containing compounds with more nitrogen and sulfur.

Influence of Fuel Properties on the Light Absorption of Fresh and Laboratory-Aged Atmospheric Brown Carbon Produced from Realistic Combustion of Boreal Peat and Spruce Foliage.

Climate change has exacerbated fire activity in the boreal region. Consequently, smoldering boreal peatland fires are an increasingly important source of light-absorbing atmospheric organic carbon ("brown carbon"; BrC). To date, however, BrC from this source remains largely unstudied, which limits our ability to predict its climate impact. Here, we use size-exclusion chromatography coupled with diode array UV-vis detection to examine the molecular-size-dependent light absorption properties of fresh and photoaged aqueous BrC extracts collected during laboratory combustion of boreal peat and live spruce foliage. The atmospheric stability of BrC extracts varies with chromophore molecular size and fuel type: in particular, the high-molecular-weight fractions of both peat- and spruce-BrC are more resistant to photobleaching than their corresponding low-molecular-weight fractions, and total light absorption by peat-BrC persists over longer illumination timescales than that of spruce-BrC. Importantly, the BrC molecular size distribution itself varies with fuel properties (e.g., moisture content) and to an even greater extent with fuel type. Overall, our findings suggest that the accurate estimation of BrC radiative forcing, and the overall climate impact of wildfires, will require atmospheric models to consider the impact of regional diversity in vegetation/fuel types.

Experimental analysis and numerical simulation of ignition delay time of diesel fuel using a shock tube

The present work consisted in developing a computational routine for prediction and characterization ignition delay time, pressure, temperature generated and energy released in the combustion process in a shock tube. Mathematical modeling considered the high-pressure region of the shock tube known as the conducted section. The Lazarus code compiler was used to generate the unstructured triangular meshes and to implement the computational routines to simulate the propagation of shock waves inside the shock tube. The mathematical modeling used the geometric parameters of the shock tube of the combustion laboratory of the Federal University of Minas Gerais and was based only on the displacement of the shock wave after the diaphragm rupture. The main objective of the work was the development of computational routines to characterize the shock wave parameters of the ignition delay times of conventional diesel to validate the experimental tests carried out in the shock tube conducted by Santana et al. [3] and compare it with the experimental tests and numerical simulations carried out by other authors available in the literature. A linear regression of the experimental tests conducted by Santana et al. [3] with conventional diesel was performed to obtain the Arrhenius equation for numerical simulation of the ignition delay time of diesel under the following conditions: temperatures from 880 to 1300 K, pressures 24 bar and equivalence ratio 1. The results show good prediction between experimental tests and numerical simulations. Were found delay times ranging from 425 to 1890 μs. Considering all temperature range, the difference between the experimental and simulated test was approximately 15%, this difference also can be explained by the measurement in the shock tube, that the ignition delay time was calculated by the time difference between the passage of the shock wave by the pressure sensor and the start of the ignition detected by the luminosity detection sensor. This work is relevant because it was developed computational routine in open software and the results achieved in the simulation were considered satisfactory, since they are in the same order of magnitude as the results found in the experimental tests carried out by Santana et al. [3] and other works.

Molecular composition and the impact of fuel moisture content on fresh primary organic aerosol emissions during laboratory combustion of Ponderosa pine needles.

Pine needles represent an important fuel source in coniferous forest systems in the western United States. During forest fires, they can be easily ignited and help sustain flame on the ground. In this study, a comprehensive chemical analysis was conducted to examine oxygenated organic compounds (OOCs) present in PM2.5 formed from burning dry and moist ponderosa pine needles (PPN) in the presence and absence of fine woody debris (FWD). The effect of fuel moisture content (FMC), a key parameter that influence smoke formation, has not received much attention. Therefore, we also investigated the effect of FMC on PM2.5 formation and its composition. Thirty three experiments were conducted at the US Forest Service Fire Science Laboratory. PM2.5 was collected onto 47 mm Teflon filters, and silylated extracts were analyzed by gas chromatography-mass spectrometry. More than fifty OOCs were identified, including levoglucosan and mannosan; n-dodecanoic acid and n-hexadecanoic acid; dihydroabietic acid, and dehydroabietic acid; and a series of intermediate volatile and semivolatile organic compounds. Mass spectra of a wide variety of compounds in electron and chemical ionization mode are provided. Most of these OOCs were identified in this study for the first time in PPN aerosol, although some were previously reported in pine wood and other biomass burning aerosol. Our results show significant changes in the composition and abundance of particles depending on the amount and type of PPN burned. When compared with dry PPN condition, moist PPN showed decreased emissions of PM2.5 and OOCs, due likely to the presence of water in the system that partially suppressed the production of OOCs. Incorporating pine needles in atmospheric models as a contributor to smoke particles generated during forest fires is an essential step towards reducing the current uncertainties regarding the influence of these aerosols on chemical/air mass characteristics, regional meteorology, and the climate.

Modification of the Rothermel model parameters – the rate of surface fire spread of Pinus koraiensis needles under no-wind and various slope conditions

Background The prediction accuracy for the rate of surface fire spread varies in different regions; thus, increasing the prediction accuracy for local fuel types to reduce the destructive consequences of fire is critically needed. Aims The objective of this study is to improve the Rothermel model’s accuracy in predicting the ROS for surface fuel burning in planted forests of Pinus koraiensis in the eastern mountains of north-east China. Methods Fuel beds with various fuel loads and moisture content was constructed on a laboratory burning bed, 276 combustion experiments were performed under multiple slope conditions, and the ROS data from the combustion experiments were used to modify the related parameters in the Rothermel model. Results The surface fire spread rate in Pinus koraiensis plantations was directly predicted using the Rothermel model but had significant errors. The Rothermel model after modification predicted the following: MRE = 25.09%, MAE = 0.46 m min−1, and R2 = 0.80. Conclusion The prediction accuracy of the Rothermel model was greatly enhanced through parameter tuning based on in-lab combustion experiments Implications This study provides a method for the local application of the Rothermel model in China and helps with forest fire fighting and management in China.

Chemically speciated air pollutant emissions from open burning of household solid waste from South Africa

Abstract. Open burning of household solid waste is a large source of air pollutants worldwide, especially in the Global South. However, waste burning emissions are either missing or have large uncertainties in local, regional, or global emission inventories due to limited emission factor (EF) and activity data. Detailed particulate matter (PM) chemical speciation data are even less available. This paper reports source profiles and EFs for PM2.5 species as well as acidic and alkali gases measured from laboratory combustion of 10 waste categories that represent open burning in South Africa. Carbonaceous materials contributed more than 70 % of PM2.5 mass. Elemental carbon (EC) was most abundant from flaming materials (e.g., plastic bags, textiles, and combined materials), and its climate forcing exceeded the corresponding CO2 emissions by a factor of 2–5. Chlorine had the highest EFs among elements measured by X-ray fluorescence (XRF) for all materials. Vegetation emissions showed high abundances of potassium, consistent with its use as a marker for biomass burning. Fresh PM2.5 emitted from waste burning appeared to be acidic. Moist vegetation and food discards had the highest hydrogen fluoride (HF) and PM fluoride EFs due to fluorine accumulation in plants, while burning rubber had the highest hydrogen chloride (HCl) and PM chloride EFs due to high chlorine content in the rubber. Plastic bottles, plastic bags, rubber, and food discards had the highest EFs for polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs as well as their associated toxicities. Distinct differences between odd and even carbon preferences were found for alkanes from biological and petroleum-based materials: dry vegetation, paper, textiles, and food discards show preference for the odd-numbered alkanes, while the opposite is true for plastic bottles, plastic bags, and rubber. As phthalates are used as plasticizers, their highest EFs were found for plastic bottles and bags, rubber, and combined materials. Data from this study will be useful for health and climate impact assessments, speciated emission inventories, source-oriented dispersion models, and receptor-based source apportionment.

Deflector design to improve internal gas recirculation in a MILD combustion laboratory furnace

This study aims to investigate the governing conditions of a laboratory-scale methane-air MILD furnace equipped with a deflector. Implemented a deflector with arms to enhance the recirculation coefficient and analyzed the effect of increasing the arm's length on MILD combustion parameters. The arm's length was varied from zero to 110 mm. The results demonstrated that as the arm's length increased to 60 mm (Geometry No.3), both the region and intensity of the recirculation coefficient exceeded those observed in other geometries. This increase, up to 22.45 % compared to the armless geometry, is attributable to the expanded recirculation region. By examining the standard deviation of heat released, it was determined that Geometry No. 3 exhibited the smallest deviation (0.013 W). Consequently, heat was distributed more uniformly as the recirculation area in this geometry expanded, resulting in a larger reaction zone. This factor contributed to a more even distribution of heat released and, consequently, the temperature in Geometry No. 3. Moreover, there was an increase in NO pollutant emissions from 13.655 to 18.338 ppm with an increased arm's length. Ultimately, simulation results underscored that Geometry No.3 proved suitable for heat treatment applications regarding temperature uniformity, dilution levels, and reduced emissions of environmental pollutants.

Analyzing the Impact of Evolving Combustion Conditions on the Composition of Wildfire Emissions Using Satellite Data

AbstractWildfires have become larger and more frequent because of climate change, increasing their impact on air pollution. Air quality forecasts and climate models do not currently account for changes in the composition of wildfire emissions during the commonly observed progression from more flaming to smoldering combustion. Laboratory measurements have consistently shown decreased nitrogen dioxide (NO2) relative to carbon monoxide (CO) over time, as they transitioned from more flaming to smoldering combustion, while formaldehyde (HCHO) relative to CO remained constant. Here, we show how daily ratios between column densities of NO2 versus those of CO and HCHO versus CO from the Tropospheric Monitoring Instrument (TROPOMI) changed for large wildfires in the Western United States. TROPOMI‐derived emission ratios were lower than those from the laboratory. We discuss reasons for the discrepancies, including how representative laboratory burns are of wildfires, the effect of aerosols on trace gas retrievals, and atmospheric chemistry in smoke plumes.

Characterization of gas and particle emissions from open burning of household solid waste from South Africa

Abstract. Open burning of household and municipal solid waste is a frequent practice in many developing countries. Due to limited resources for collection and proper disposal, solid waste is often disposed of in neighborhoods and open-burned in piles to reduce odors and create space for incoming waste. Emissions from these ground-level and low-temperature burns cause air pollution, leading to adverse health effects among community residents. In this study, laboratory combustion experiments were conducted to characterize gas and particle emissions from 10 waste categories representative of those burned in South Africa: paper, leather/rubber, textiles, plastic bottles, plastic bags, vegetation (with three different moisture content levels), food discards, and combined materials. Carbon dioxide (CO2) and carbon monoxide (CO) were measured in real time to calculate modified combustion efficiencies (MCEs). MCE is used along with video observations to determine fuel-based emission factors (EFs) during flaming and smoldering phases as well as the entire combustion process. Fuel elemental composition and moisture content have strong influences on emissions. Plastic bags have the highest carbon content and the highest combustion efficiency, leading to the highest EFs for CO2. Textiles have the highest nitrogen and sulfur content, resulting in the highest EFs for nitrogen oxides (NOx) and sulfur dioxide (SO2). Emissions are similar for vegetation with 0 % and 20 % moisture content; however, EFs for CO and particulate matter (PM) from the vegetation with 50 % moisture content are 3 and 20–30 times, respectively, those from 0 % and 20 % moisture content. This study also shows that neglecting carbon in the ash and PM can lead to significant overestimation of EFs. Results from this study are applicable to emission inventory improvements as well as air quality management to assess the health and climate effects of household-waste open burning.

Fine and ultrafine particle emission factors and new diagnostic ratios of PAHs for peat swamp forest fires

Peatland fires are one of the major global sources of atmospheric particles. Emission factors for fine (PM1 and PM2.5) and ultrafine (PM0.1) particles and particle-bound polycyclic aromatic hydrocarbons (PAHs) from plants in the peat swamp forest (PSF), including Melaleuca cajuputi leaves, M. cajuputi branches, M. cajuputi bark, Lepironia articulata (Retz.) Domin, forest leaf litter and peat were measured in a laboratory combustion chamber. From these measurements, new PAH diagnostic ratios for fine and ultrafine particles were proposed for identifying the forest burning source. The new emission factors for PM were PM0.1: 0.03–0.33, PM1: 0.69–2.11 and PM2.5: 1.12–4.18 g/kg; for PM-bound PAHs, the factors were PM0.1: 5.7–166.0, PM1: 31.5–1338.9 and PM2.5: 36.3–3641.1 μg/kg. The predominant PAHs for PSF burning were Pyr, BbF, DBA (in PM0.1), Flu, DBA, BghiPe (in PM1), and BbF, DBA and BghiPe (in PM2.5). We also presented new diagnostic ratios for PSF burning, including BaP/(BaP + Chr): 0.39–0.75, BaP/(BaP + BbF): 0.21–0.47 and BaA/(BaA + Chr): 0.36–0.53. Moreover, the physical and chemical characteristics of ambient fine and ultrafine particles in the Kuan Kreng forest during the 2019 forest fire (FF) and 2021 non-forest fire (NFF) periods were investigated. The mean PM0.1, PM1 and PM2.5 concentrations during the FF period were approximately 3.5–4.4 times as high as those during the 2021 NFF period. New PAH diagnostic ratios of BaP/(BaP + BbF) versus BaP/(BaP + Chr) were able to identify PAH burning sources in PM1 and PM2.5 but were less clear for PM0.1, which was dominated by a single source – M. cajuputi. Chemical mass balance studies identified peat forest burning emissions as the main source of fine and ultrafine particles during the FF period. This study suggests that the new PAH diagnostic ratios can be used to identify the burning source for more precise source apportionment.

Leaf litter combustion properties of Central European tree species

AbstractTemperate forests of Central Europe are exposed to increasing fire risk. However, little is known about combustion properties of leaf litter, which plays an important role in the spread of surface fires. We used cone calorimetry to compare combustion properties of leaf litter samples from seven common tree species of Central European forests by reconstructing a litter layer of original depth in sample holders with a size of 10 cm × 10 cm. In addition to mono-specific leaf litter beds, combustion experiments included mixtures of different litter types, mixtures of litter and bryophytes and one mixture of litter and fine woody debris, totalling to 13 different setups (i.e. litter types). Recorded combustion properties included ignitability, flaming duration and heat release. Differences in combustion properties were analysed using analyses of variance followed by pairwise post-hoc tests. Combustion properties mainly differed between different litter types (broadleaf, pine needle, short needle). Highest total and peak heat release were observed for Scots pine (Pinus sylvestris), while peak heat release rates showed only minor differences for litter of the remaining species. Broadleaf litter was characterized by highest ignitability. For short-needle litter, we observed long flaming duration and incomplete combustion, resulting in the lowest total heat release on a sample mass basis. For litter mixtures of pine and broadleaf litter, we observed lower peak heat release rates in comparison to mono-specific pine litter. Mosses reduced peak heat release rates and increased the proportion of unburned biomass. However, the magnitude of this effect differed between bryophyte species included in the mixtures. The addition of fine woody debris strongly increased total heat release, highlighting the importance of fine woody fuels for fire behaviour. The results of this study provide valuable baseline information on combustion behaviour of leaf litter from Central European forests. Due to the limitations of laboratory combustion experiments to reproduce conditions of real forest fires, there is a need for future field studies investigating fire behaviour under natural conditions.

Issue Information

New PhytologistVolume 237, Issue 4 p. 1067-1070 Cover and Issue InformationFree Access Issue Information First published: 19 January 2023 https://doi.org/10.1111/nph.18232AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract Cover Legend Pinus ponderosa sapling exposed to fire under a controlled environment at the University of Idaho combustion laboratory. Image courtesy of Raquel Partelli-Feltrin. (Partelli-Feltrin et al., pp. 1154–1163). Volume237, Issue4February 2023Pages 1067-1070 RelatedInformation

Numerical Simulations of Spray Combustion in Jet Engines

The aviation sector is facing a massive change in terms of replacing the currently used fossil jet fuels (Jet A, JP5, etc.) with non-fossil jet fuels from sustainable feedstocks. This involves several challenges and, among them, we have the fundamental issue of current jet engines being developed for the existing fossil jet fuels. To facilitate such a transformation, we need to investigate the sensitivity of jet engines to other fuels, having a wider range of thermophysical specifications. The combustion process is particularly important and difficult to characterize with respect to fuel characteristics. In this study, we examine premixed and pre-vaporized combustion of dodecane, Jet A, and a synthetic test fuel, C1, based on the alcohol-to-jet (ATJ) certified pathway behind an equilateral bluff-body flameholder, spray combustion of Jet A and C1 in a laboratory combustor, and spray combustion of Jet A and C1 in a single-sector model of a helicopter engine by means of numerical simulations. A finite rate chemistry (FRC) large eddy simulation (LES) approach is adopted and used together with small comprehensive reaction mechanisms of around 300 reversible reactions. Comparison with experimental data is performed for the bluff-body flameholder and laboratory combustor configurations. Good agreement is generally observed, and small to marginal differences in combustion behavior are observed between the different fuels.

Emission characteristics and influencing mechanisms of PAHs and EC from the combustion of three components (cellulose, hemicellulose, lignin) of biomasses

Biomass burning is an important source of polycyclic aromatic hydrocarbons (PAHs) and elemental carbon (EC), but the formation mechanisms are still unclear. Cellulose, hemicellulose, and lignin are the three major components of biomass. In this study, the three-components extracted from three typical biomass raw materials were used for laboratory combustion experiments, to investigate the differences in the emission factors and chemical compositions of PAHs and EC. The average emission factors of the 16 kinds of PAHs were showing as lignin (135 ± 180 mg/kg) > cellulose (97.8 ± 124 mg/kg) > hemicellulose (48.9 ± 65.2 mg/kg), and the average emission factors of EC presented in the descending order of cellulose (1.65 ± 3.02 g/kg), lignin (1.30 ± 1.04 g/kg), and hemicellulose (0.450 ± 0.480 g/kg), respectively. The proportion of naphthalene emitted from cellulose and hemicellulose combustion is higher, while fluoranthene and pyrene accounted significantly higher proportion for lignin. Moreover, the influence of ignition temperature and oxygen content on the emission characteristics of PAHs and EC were also discussed. The influence of ignition temperature on the emission of EC and PAHs is more significant compared to oxygen content, because it obviously promoted the PAHs and EC formations through resonance-stabilized hydrocarbon-radical chain reaction (RSR) pathway. However, correlation analysis combined with cluster analysis showed that the RSR-pathway probably had different effects on PAH growth for the three-components, as the indene-involved RSR-pathway were mainly related to 4–6 ring PAHs for cellulose and lignin (except fluoranthene and pyrene), but 2–4 ring PAHs for hemicellulose. We also found that the fitted results according to the proportion of three-components were significantly higher than the measured values of raw materials for indene, medium-molecular-weight PAHs, and soot-EC. These results presented the different formation pathways for medium-molecular-weight PAHs and the two EC components emitted by biomass combustion, which are worthy of further studies in exploring the generation mechanisms of PAHs and EC.

Comparative Analysis of Combustion of Qualified Composite Fuel for the Transitional Period in the Household and Communal Sector in Poland

Abstract The article presents the results of laboratory combustion tests of the microbriquette obtained from useless coal (grain class of < 5 mm) generated in the production of “eco-pea” (eko-groszek) coal. The briquettes of 1.5 and 2.5 cm3 were made in a roller press of crushed coal granulation down to 2 mm, mixed with a binder and/or catalytic additives and sorbents, then dried to final moisture of about 7%. The tests were carried out on a specially designed stand enabling to determine the differential curve of the weight loss of samples heated to the ignition temperature and then burnt with laminar airflow by natural chimney draft. Comparative tests were carried out with ecopea coal from the “ZG Sobieski” mine. The results indicate that composite fuels, in the form of microbriquette, ignite faster, burn at a higher temperature and leave less ash when burned than lump coal. The greater reactivity of the briquette concerning the lump coal allows for minimizing the air rate by about 10%, which also reduces the exhaust gas volume by the same amount and the stack losses. It reduces the velocity of dust lifting, which leads to the reduction of their emission.