Intense Burning Research Articles

Evaluation of electrognathography indicators in patients with decreased height of the lower part of the face and symptoms of intolerance to the structural materials of dentures

Purpose of the study: to conduct a comparative assessment of electrognathography indices in elderly patients with a decrease in the height of the lower part of the face with symptoms characteristic of intolerance to the structural materials of dentures, before and during the diagnostic and treatment stages of using occlusal-stabilizing devices. Material and methods. We examined 76 patients aged 61 to 74 years with a decrease in the height of the lower part of the face and the presence of symptoms characteristic of intolerance to the structural materials of dentures. Based on the results of a short “Hamburg” examination, 30 patients were selected with the possibility of dysfunctional disorders of the temporomandibular joint, for whom occlusal-stabilizing devices were made. Results. A study of elderly patients with a decrease in the height of the lower part of the face and symptoms characteristic of intolerance to the structural materials of dentures revealed the effectiveness of the use of occlusal-stabilizing devices at the treatment and diagnostic stages due to a decrease in complaints of dry mouth more than in twice, a decrease in the intensity of burning of the mucous membrane, a decrease in the number of complaints accompanying dysfunctional disorders of the temporomandibular joint, as well as an improvement in electrognathography indicators to physiological norms. Conclusion. The obtained results of treatment with occlusal-stabilizing devices for patients with a decrease in the height of the lower part of the face, presenting complaints characteristic of intolerance to the structural materials of dentures, at the treatment and diagnostic stages indicate the feasibility and effectiveness of their use in this category of people.

Longitudinal analysis of ARDS variability and biomarker predictive power in burn patients

Acute Respiratory Distress Syndrome (ARDS) is a severe complication in burn patients, characterized by rapid lung inflammation and hypoxemia. Managing ARDS is challenging due to its high mortality rates and the complex interplay of various pathophysiological factors. This study aims to investigate the heterogeneity of ARDS in burn patients admitted to the Intensive Care Unit (ICU) and evaluate the predictive efficacy of biomarkers in comparison to the PaO2/FiO2 (PF) ratio. A retrospective cohort study was conducted at the Burn Intensive Care Unit of Hangang Sacred Heart Hospital in Seoul, Korea, from July 2010 to December 2022, involving 2,318 patients. Longitudinal k-means clustering was employed to identify patient subgroups based on PF ratio trajectories. Biomarkers, including albumin, white blood cell (WBC) count, and lactate, were assessed for their predictive accuracy using multivariable logistic regression, area under the curve (AUC) analysis, net reclassification improvement (NRI), and integrated discrimination improvement (IDI). Four distinct patient clusters were identified. Cluster A exhibited the highest mortality rate at 54.9%, while Cluster D showed the lowest at 7.9%. Albumin demonstrated significantly higher predictive accuracy in Cluster A (AUC: 0.905, NRI: 0.421) and Cluster C (AUC: 0.915, NRI: 0.845), outperforming the PF ratio in both groups. However, in Clusters B and D, biomarkers did not significantly improve upon the predictive power of the PF ratio. Across all clusters, the integration of biomarkers with the PF ratio led to modest improvements but did not consistently outperform the PF ratio as a standalone predictor. This study reveals substantial heterogeneity in ARDS progression among burn patients, with varying mortality rates and biomarker efficacy across clusters. While biomarkers such as albumin showed potential in specific subgroups, their overall contribution to predictive accuracy was limited. Further multicenter, prospective studies are required to validate these findings and develop more refined predictive models. Personalized treatment strategies, based on biomarker profiles and traditional clinical metrics, could enhance ARDS management in burn patients.

A novel phosphorus-containing pyridinium porous organic framework with flame retardancy for enhancing efficiency and safety of solid-state polymer electrolyte

The development of solid-state polymer electrolytes (SPEs) is aimed to obtain electrolyte materials with higher ionic conductivity, better mechanical properties, and greater flame retardancy. Based on the above considerations, a phosphorus-containing cationic porous organic polymer (ZR-POF) is prepared through “one-pot” three-component polymerization and incorporated as a filler to prepare poly(ethylene oxide) (PEO)-based SPEs. By padding ZR-POF into PEO, the ionic conductivity of SPEs is significantly improved, especially the PEO-10 % ZR-POF electrolyte exhibits the highest ionic conductivity at 90 °C (1.26 × 10−3 S cm−1). And due to the nanosheet characteristics of ZR-POF, SPEs exhibit excellent mechanical properties, could form a more stable interface with the metal anode. It is worth noting that the introduction of phosphorus endows SPEs with excellent flame retardant properties, achieving rapid self-extinguishing within 12 s under intense combustion. Therefore, the resultant battery based on PEO-10 % ZR-POF electrolyte exhibits excellent electrochemical performance, with a capacity maintained at 591.8 mAh g−1 and a capacity attenuation rate of 0.027 % over 500 cycles at 1 C.

Indicators for Assessing the Combustion Intensity of Coal Particles Using a Single UV Sensor

This paper deals with the evaluation of the combustion intensity of coal particles on the basis of measurement data (UV radiation) from a scanning point photodiode. UV radiation is measured using a custom UV scanner at different distances from the burner in the vertical combustion chamber. The designed scanner uses a sensitive silicon carbide (SiC) photodiode, and its dynamical properties are investigated in the present work. Subsequently, experiments are performed for coal particles at different combustion temperatures and at different measuring locations of the scanner. The measurement data are processed in the frequency domain using the proposed algorithm, and two indicators for evaluating the combustion intensity are proposed. The obtained results show that the proposed indicators provide unequivocal information about the combustion intensity as a function of the combustion temperature.

A reliable combustion strategy for a throttling-assisted supersonic combustor with flight Mach 7

As the flight Mach number increases, scramjet engines struggle to achieve stabilized combustion. In the present investigation, a reliable combustion strategy is developed for a kerosene-fueled supersonic combustor. Assisted by air throttling, this enables the combustor to operate efficiently at a flight Mach number of 7. Various experimental measurement techniques are used to capture the combustion process and flow characteristics. A three-dimensional numerical method based on the Reynolds-averaged Navier–Stokes equations is employed to analyse the effects of air throttling on the non-reacting and reacting flow fields. The whole combustion test is effectively divided into five processes covering the establishment of non-reacting flow, ignition, flame stabilization, and flameout. Analysis of the experimental and numerical flow fields indicates that, as the origin of the initial flame in the combustor, the aerodynamic compression induced by air throttling promotes the kerosene/air sub-mixing region. The main mixing process is enhanced by the arrangement of ramps and cavity, which contribute to effective multi-channel injection. Two combustion modes are observed, namely combined cavity shear-layer/recirculation stabilized combustion and jet-wake stabilized combustion. In the reacting flow field, the additional injection of throttling gas improves the thrust augmentation at the cost of reduced combustion intensity. The outlet combustion efficiency and total pressure recovery coefficient are found to decrease by 8.49% and 28.79%, respectively.

Effect of Different Nozzle Arrangements on Combustion Flow Characteristics in a Swirl Coupling Multiple Direct Injection Combustor

ABSTRACT The influence of multiple direct injection nozzle arrangements with hexagonal, rhombus, and circular shapes on the combustion flow in gas turbines was numerically studied, and the combustion flow characteristics of swirl combustion combined with multiple direct injection combustion were analyzed, such as velocity and temperature distribution, vortex structure, NOX (nitrogen oxides) emission, flame stretch rate, etc. The result shows that for these different nozzle arrangements, the difference in velocity and temperature distribution is not obvious, but the difference in vortex structure is large. The hexagonal arrangement can form several counter-rotating vortex pairs (CVP) near the side wall, the rhombus arrangement can form several deflection vortex structures outside the center swirl, and the circular arrangement forms the least vortex structure. Furthermore, the circular arrangement is most effective in reducing the non-uniformity of the outlet temperature, OTDF is 0.00548, and it has a higher flame stretch rate, which means that it has a higher combustion intensity. However, the hexagon arrangement has the higher NOX emission, reaching 3.16 ppm.

Effect of ignition timing and hydrogen injection phase on HDI engine combustion and NOx emissions

ABSTRACT In order to improve the ITE and reduce NOx emissions in direct-injected hydrogen (HDI) engines under at medium and high loads, the effects of IT and hydrogen injection phase on the combustion and NOx emission characteristics of the HDI engine at high rpm and medium load were investigated numerically. The base engine is a four-cylinder turbocharged direct-injected gasoline (GDI) engine, which is modified into a HDI engine with direct-injected hydrogen fuel. The simulation is performed using GT-Power software. The operating condition of HDI engine is set to 5500 rpm and 50% load. Firstly, IT is optimized, and then based on the IT optimization results, the hydrogen injection phase is optimized. The results show that as the IT is advanced, the maximum pressure rise rate (MPRR) shows a gradual increasing trend, while the combustion intensity and the indicated thermal efficiency (ITE) increases firstly and then decreases, and the former reaches a maximum value at 25° CA BTDC, while the latter reaches a maximum value of 40.5% at 18°CA BTDC. In addition, the nitrogen oxide (NOx) emissions decrease as the IT is delayed. Based on 18°CA BTDC of IT, the results indicated that the later the moment of hydrogen injection, the higher the MPRR, resulting in the greater the knock intensity. The ITE is less affected by the hydrogen injection phase. When the hydrogen injection phase is delayed, NOx emissions increase slightly.

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

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

Elimination of an outbreak of carbapenem-resistant Acinetobacter baumannii in a burn unit

Carbapenem-resistant Acinetobacter baumannii (CRAB) is an opportunistic pathogen which has caused numerous healthcare-associated outbreaks particularly in intensive care and burn units. We describe an outbreak in a burn unit where 3 patients were identified as being colonized or infected with CRAB. A multi-faceted approach and rapid implementation of infection prevention measures were effective in identification and removal of potential environmental reservoirs resulting in the prevention of further transmission.

Advanced biomarker clustering analysis reveals mortality predictors in burn patients with sepsis

This study addresses the challenge of predicting mortality in sepsis among burn patients. Given the heterogeneity of sepsis, especially in the context of burn injuries, this study aims to identify reliable biomarkers for mortality prediction. The study is a retrospective review, focusing on the evaluation of various biomarkers and their changes over time in a burn patient cohort. Conducted in the Burn Intensive Care Unit of Hangang Sacred Heart Hospital, the study involved a retrospective review of 1,659 adult burn patients from January 2010 to December 2022. Key biomarkers analyzed include lactate levels, pH, platelets, procalcitonin, and others. Advanced clustering methodologies, such as dynamic time warping and hierarchical clustering, were utilized to classify patients into distinct groups based on their biomarker profiles and clinical outcomes. The study identified four patient clusters with unique lactate level trajectories. Significant findings include the identification of procalcitonin, pH, and platelets as key predictors of mortality, with varying degrees of efficacy across different clusters. For instance, in the “Persistent Rise” cluster, pH and platelet count showed Area Under the Curve (AUC) values of 0.756 and 0.753, respectively, indicating their strong predictive power. The study concludes that a combination of biomarkers, especially lactate dynamics, can effectively predict mortality in burn-induced sepsis. The results advocate for a more personalized approach in managing sepsis in burn patients, considering the specific biomarker trajectories. These findings are crucial for enhancing treatment strategies and improving patient outcomes in burn care.

Disentangling the spinal mechanisms of illusory heat and burning sensations in the thermal grill illusion.

The thermal grill illusion (TGI), a phenomenon in which the juxtaposition of innocuous warm and cold temperatures on the skin elicits a burning sensation, offers a unique perspective to how pain occurs in response to harmless stimuli. We investigated the role of the spinal cord in the generation of the TGI across 2 experiments (total n = 80). We applied heat and cold stimuli to dermatomes, areas of skin innervated by a single spinal nerve, that mapped onto adjacent or nonadjacent spinal segments. Enhanced warm and burning ratings during the TGI were observed when cold and warm stimuli were confined within the same dermatome. Furthermore, we found the spatial organisation of warm and cold stimuli within and across dermatomes affected TGI perception. Perceived warmth and burning intensity increased when the cold stimulus projected to the segment more caudal to the warm stimulus, whereas perceived cold during the TGI decreased compared with the opposite spatial arrangement. This suggests that the perception of TGI is enhanced when cold afferents are projected to spinal segments positioned caudally in relation to those receiving warm afferents. Our results indicate distinct interaction of sensory pathways based on the segmental arrangement of afferent fibres and are consistent with current interpretations of the spread and integration of thermosensory information along the spinal cord.

Study on the flame structure and flow field of hydrogen-enriched combustion in array micro-tube

Addressing climate change and reducing greenhouse gas emissions are critical priorities. Utilizing hydrogen-rich methane or pure hydrogen as fuels within gas turbines, facilitated by array micro-tube premixed combustion technology, is anticipated to markedly accelerate the decarbonization process of the energy sector. In this study, the flame structure of the array micro-tube premixed burner under various fuel compositions was examined using OH-Planar Laser-Induced Fluorescence and Particle Image Velocimetry measurement techniques. The effects of the equivalence ratio (φ) and the hydrogen power ratio (HPR) on the characteristics of the flame front, including its curvature, density, volume, and the associated flow field properties, were discussed. As φ and HPR increase, the wrinkled structure of the flame front is significantly enhanced, with a more pronounced effect on smaller scales. This enhancement leads to the separation of the unburned pockets from the main flame. Concurrently, both the flame length and the flame area decrease with the augmentation of φ and HPR, indicating a more concentrated combustion process and increased combustion intensity under hydrogen-enriched and pure hydrogen conditions. The study also observed a slight increase in both the negative and positive curvatures of the flame front, with a more notable increase in the negative curvature. The increased negative curvature results in an elevated degree of wrinkling and a higher value of Σ (flame surface density), reaching a maximum of 0.876 mm−1 under the conditions where φ is 0.8 and ⟨c⟩ (mean progress variable) is 0.5, resulting in the smallest observed flame volume of 100.6 mm3. Upon coupling the flame with the flow field, it was discovered that the exit flow field of the array micro-tube exhibits symmetry and a characteristic conical flame shape. The burning velocity of the side flame brushes increases, and the velocity peak shifts upstream. The aforementioned findings confirm that the addition of hydrogen increases the laminar flame velocity, enabling the flame to stably anchor to the microtube outlet and thereby enhance the flame's robustness and stability.

Optimizing poultry audio signal classification with deep learning and burn layer fusion

This study introduces a novel deep learning-based approach for classifying poultry audio signals, incorporating a custom Burn Layer to enhance model robustness. The methodology integrates digital audio signal processing, convolutional neural networks (CNNs), and the innovative Burn Layer, which injects controlled random noise during training to reinforce the model's resilience to input signal variations. The proposed architecture is streamlined, with convolutional blocks, densely connected layers, dropout, and an additional Burn Layer to fortify robustness. The model demonstrates efficiency by reducing trainable parameters to 191,235, compared to traditional architectures with over 1.7 million parameters. The proposed model utilizes a Burn Layer with burn intensity as a parameter and an Adamax optimizer to optimize and address the overfitting problem. Thorough evaluation using six standard classification metrics showcases the model's superior performance, achieving exceptional sensitivity (96.77%), specificity (100.00%), precision (100.00%), negative predictive value (NPV) (95.00%), accuracy (98.55%), F1 score (98.36%), and Matthew’s correlation coefficient (MCC) (95.88%). This research contributes valuable insights into the fields of audio signal processing, animal health monitoring, and robust deep-learning classification systems. The proposed model presents a systematic approach for developing and evaluating a deep learning-based poultry audio classification system. It processes raw audio data and labels to generate digital representations, utilizes a Burn Layer for training variability, and constructs a CNN model with convolutional blocks, pooling, and dense layers. The model is optimized using the Adamax algorithm and trained with data augmentation and early-stopping techniques. Rigorous assessment on a test dataset using standard metrics demonstrates the model's robustness and efficiency, with the potential to significantly advance animal health monitoring and disease detection through audio signal analysis.

Optimising Processes in a Severe Burn Intensive Care Unit through the Implementation of a Digital Management System

The treatment of severely burned patients is demanding and necessitates specialised centres capable of providing adequate therapy over several months. The establishment of digital management systems in intensive care units signifies a substantial advancement in modern healthcare. Introducing such a system in a specialised intensive care unit for severe burn patients presents opportunities for optimisation but also potential obstacles. This study aims to provide insights into the perception of change from the perspective of staff and discuss the implementation of digital systems in the field of intensive care medicine. After a selective sample was established, the impacts of the digital management system were examined across various categories. The data collected through a questionnaire and brief interviews were evaluated in terms of average values within each category, with interpretations taking into account characteristics such as professional group and work experience. Overall, the digital management system is considered suitable for use in the intensive care unit for severe burn patients by both medical and nursing staff. The continuous monitoring of vital parameters and the reduction of errors in medication administration are highlighted as positive aspects. However, negative points include the inferior documentation of burn wounds and specialised documentation for burn patients. In due consideration of various factors such as experience, team size, and patient clientele, which impact the usability of the program, some aspects in need of improvement were identified. In summary, however, it can be said that there was a positive and favourable consensus regarding the introduction of such a system in the intensive care unit. Additionally, it can be concluded that the system is described as significantly more effective for a general surgical intensive care unit than for a specialised intensive care unit, e. g. an intensive care unit for severe burn patients.

Comparative experimental study on the co-firing characteristics of water electrolysis gas (HHO) and lean coal/lignite with different injection modes in a one-dimensional furnace

Zero-carbon fuels (H2/NH3) replacing coal co-firing is a promising way to address carbon emissions. Hydrogen co-firing helps improve combustion stability at low loads and control pollutant emissions. This study used a safer water electrolysis gas (HHO) for the multi-coal co-firing adaptability test. The effects of HHO injection mode and flow rate on combustion intensity, flue gas emissions, and fly ash characteristics were investigated. The results showed that HHO and lean coal/lignite co-firing could significantly increase the combustion temperature. The maximum temperature increases after co-firing were 108 °C and 95 °C. As the HHO increased, the CO2 in lignite co-firing increased, and CO and unburnt carbon decreased, while the opposite results were observed for lean coal (LC). At the 2200L/h HHO co-firing, CO2 decreases by 14.46 % and 27.22 % for LC premixed co-firing (PC) and staged co-firing (SC). Compared to SC, PC is more conducive to promoting the complete combustion of coke. The NOX emissions of HHO/LC co-firing are lower than those of pure coal, reaching the lowest value of ∼ 9 ppm under SC. As the HHO increases, the NOX of Lignite-PC first increases and then slowly decreases, while Lignite-SC has the opposite effect. Although various NOX emission trends are observed under different conditions, the results are dominated by a common mechanism − the competition between NOX reduction caused by HHO gas and the increase in co-firing temperature on NOX generation. The NOX of SC is all lower than that of PC. The SO2 emission from the LC co-firing decreases with the increase of HHO, while the SO2 from lignite increases. The SO2 of LC-SC can be reduced from ∼ 142 ppm to 0 ppm. HHO gas injection inhibits the release and oxidation of sulfur in lean coal. The differences in coal types lead to different changes in SO2 of co-firing. HHO gas reduced the SO3 content of lignite fly ash by 38.01 %. The high-temperature reduction atmosphere promotes the decomposition of sulfates and increases SO2 emissions. HHO co-firing refines the particle size of fly ash. The ultra-fine and micron particle matter (PM) increases, and the content of PM>100μm in Lignite-SC decreased by 10.32 %.

Assessing turbulence–flame interaction of thermo-diffusive lean premixed H2/air flames towards distributed burning regime

Simultaneous laser-induced fluorescence of OH radicals and particle image velocimetry, and quasi-simultaneous 1D Raman/Rayleigh and 2D Rayleigh scattering measurements are used to investigate the effects of Karlovitz number (by varying the equivalence ratio) and residence time (by varying the axial measurement location) on the internal flame structures of lean premixed hydrogen/air turbulent jet flames. The turbulent flow fields, instantaneous macroscopic flame structures, and thermochemical states of a set of lean premixed hydrogen/air turbulent flames with varying initial equivalence ratio of 0.3, 0.4, and 0.45 at a constant bulk velocity of 100m/s are discussed. With an increasing equivalence ratio, the Karlovitz number derived from the turbulent flow fields decreases rapidly from 7690 to 260 and 100, determined at a downstream location of x/D=7. At the highest Karlovitz number (i.e., the lowest equivalence ratio), a distributed burning is observed in the jet flame as turbulent transport dominates over molecular mixing, and the effects of differential diffusion and flame curvature are suppressed. With decreasing Karlovitz number, intense burning regions characterized by elevated local equivalence ratio, high water mole fraction, and super-adiabatic flame temperatures are observed in association with positive flame curvature. The same combustion diagnostics are applied to another lean premixed hydrogen/air turbulent flame with an initial equivalence ratio of 0.4 and a bulk velocity of 200m/s at selected downstream locations of x/D=3.5, 7, 10.5, and 14 to assess the effects of developing turbulence and residence time. Corresponding Karlovitz numbers are 680, 730, 775, and 690, as the local turbulent intensity changes along downstream locations. While flame structures reveal characteristics towards distributed burning at lower x/D, a locally intense burning region appears at higher x/D together with positive curvature. This is mainly because the turbulence develops with increasing x/D and the flame surface is more disturbed and curved by turbulent eddies with increasing turbulence length scales. The highly diffusive hydrogen is locally concentrated by positively curved flame surfaces, resulting in fuel-rich burning regions at a higher temperature. This indicates that, as velocity fluctuations increase in axial direction, turbulence can also promote thermo-diffusive instabilities to a certain extent, increasing the mixture inhomogeneity in temperature space by interacting with the differential diffusion effect of hydrogen at atmospheric pressure.Novelty and significanceThe novelty of the current work is the focus on turbulence–chemistry interactions of premixed hydrogen/air jet flames at high turbulence and ultra lean conditions. Comprehensive experimental results including the turbulent flow fields (particle image velocimetry), instantaneous flame structures (laser-induced fluorescence of OH radicals) and internal thermochemical states (quasi-simultaneous 1D Raman/Rayleigh and 2D Rayleigh scattering imaging) of hydrogen/air jet flames are analyzed and discussed. The data sets with well-characterized boundary conditions and high measurement accuracy, are crucial for validation and development of numerical simulation models.

Combustion modes of kerosene spray in a scramjet combustor with different injection schemes

Combustion modes of kerosene spray in a scramjet combustor condition with different injection schemes are experimentally investigated at Mach 2.52. The study is based on two single injectors with nozzle diameters of 0.79 and 1.14 mm and two dual injectors with nozzle diameters of 0.56 and 0.72 mm, respectively. The results show that the weak combustion mode has little effect on the flow field, while the intensive combustion mode has the opposite effect. The dual injector can promote evaporation and mixing of the kerosene spray. Compared with the dual injector, intensive combustion cannot occur when a single injector is used, and the flame stability range is also narrower. As the nozzle diameter of the injector increases, the distribution and oscillation of kerosene spray change significantly, transition from the weak to intensive combustion mode occurs at a higher equivalence ratio, and the flame stability range increases. However, change in the nozzle diameter does not affect the overall process of combustion mode transition. For the single injector, intensive combustion still cannot occur when the nozzle diameter changes. In addition, change in the nozzle diameter has little effect on combustion heat release when the combustion mode remains unchanged.

Experimental study of rotating direction for dual-axial swirlers on the flow field and combustion characteristics of aero-engine combustor

The flow field structure for aero-engine combustor is one of the most important factors for combustion performance. To investigate how the rotating direction of dual-axial swirlers affects the flow field and combustion characteristics, particle image velocimetry (PIV) experiments were conducted in the primary combustion and intermediate zones. Additionally, planar laser induced fluorescence (PLIF) was used to map the distribution of kerosene and OH in the primary combustion zone. The results show that the swirling jets in co-swirl exhibit greater jet momentum, resulting in a longer primary recirculation zone and a larger deflection angle of the primary jets. This ultimately leads to a higher recirculation rate compared to counter-swirl. The primary jets define the boundary of the flow field structure. The rotating direction primarily affects the flow field structure upstream of the primary jets, exerts a relatively weaker influence on the intermediate zone, which is mainly affected by the deflection direction of the primary jets, and essentially has no impact on the dilution jets. Co-swirl has a relatively stable flow field than counter-swirl, whereas the flow field in counter-swirl is more chaotic, featuring a greater number of vortex cores in the primary recirculation zone. The coupling between the primary and swirling jets affects the mass transfer direction in the intermediate zone, which is reflected in the fact that the mass transfer is from top-left to bottom-right in co-swirl, while it is in the opposite direction in counter-swirl. OH is predominantly found in the swirling shear layers, the primary and secondary combustion zones, whereas kerosene is mainly concentrated in the shear layers of swirling jets. The kerosene distribution in co-swirl shows a larger and more concentrated expansion angle compared to counter-swirl. In contrast, the OH distribution downstream of counter-swirl is broader, with more intense combustion due to enhanced kerosene decomposition and fuel-air mixing. The smaller primary recirculation zone in counter-swirl forces the primary combustion zone to extend downstream, leading to a more intense reaction in the secondary recirculation zone.

Experimental and numerical study of H[formula omitted] enrichment on swirl/bluff-body stabilized lean premixed n-butane/air flame

This study focused on the stabilization of lean premixed flames of n-butane/H2/air with swirl/bluff-body. The research explored four different hydrogen fractions (0, 20%, 40%, and 80%) at a constant equivalence ratio and Reynolds number. The turbulent reacting flow was resolved using a combination of Delayed Detached Eddy Simulation (DDES) and Flamelet Generated Manifold (FGM) model. The velocity fields and reaction zones were obtained through Particle Image Velocimetry (PIV) and OH* chemiluminescence measurements respectively. H2 addition to n-butane significantly enhanced flame characteristics. The chemiluminescence imaging showed that the flame base became stronger with increasing hydrogen addition, reducing the risk of flame lift-off. Hydrogen addition not only increased the overall reaction rate but also changed the combustion intensity at the nozzle exit from weak to strong, which is crucial for flame stabilization. Interestingly, no flashback was observed even at 80% H2 addition to n-butane at the same level of power rating. The flow strain rate analysis of the PIV measurements showed that the inclusion of hydrogen skewed the strain rate probability density functions towards the positive side, indicating an increase in the burning rate. The results demonstrate a progressive increase in preferential diffusion of H2 from reactants to products as the H2 enrichment in the fuel rises and resulted in a more intense flame. Also, the present simulation results were validated with the PIV data, and they showed good agreement. Specifically, an 80% H2 blend exhibited a 16% peak enhancement in flame surface density compared to pure n-butane while concurrently reducing CO2 emissions by 23.2%. The incorporation of H2 also led to the increased vortex strength and strain rate within the flame.

Deactivation of iron particles during combustion and reduction

Iron is a promising carbon-free renewable energy carrier to replace fossil fuels. However, during a redox cycle, iron may experience deactivation due to structural changes, which can shorten the cycle lifetime. In this work, deactivation of iron particles in terms of changes in reactivity and morphology during the oxidation and reduction process was investigated, under both fixed-bed and suspension conditions. Simple thermal treatment in an inert atmosphere at 1200 °C had no influence on the reactivity of particles towards oxidation, even at long exposure resulting in mild agglomeration. In fixed-bed oxidation at 600 to 1100 °C, solid sintering was found to be rapid and severe at higher temperatures. However, the sintering showed no influence on the reactivity of particles towards H2 under slow-heating conditions in a TGA. In pulverized-fuel combustion in a drop tube reactor, the intensive combustion and heat release led to melting of particles and morphology change from irregular to spherical. As the reactor temperature was increased from 800 to 1200 °C, the particle reactivity in terms of reduction degree (fractional conversion from Fe2O3 to Fe) slightly decreased from 78 % to 72 %, possibly related to a minor loss of surface area. TGA experiments involving successive redox cycles showed a steady decline in reduction reactivity (750 °C, 2.5 % H2), slightly enhanced by agglomeration, while the oxidation degree (950 °C or 1200 °C, 21 % O2) remained constant. The present work indicates that both deactivation and loss of iron due to evaporation may serve to limit the energy release in iron combustion over extended cycles.