Internal Burning Research Articles

Numerical study on multiphase combustion characteristics of aluminum-based powder-fueled water ramjet engine

Powder-Fueled Water Ramjet Engine (PFWRE) is of great attraction for high-speed and long-voyage underwater propulsion, as well as air-water trans-media navigation applications due to its high energy density and thrust adjustability. However, the complex multiphase combustion process in the combustor significantly affects engine performance. In this study, a detailed model for aluminum particle combustion in water vapor is developed and validated via literature data as well as the ground direct-connected test we conducted. Thereafter, the numerical study on the multiphase combustion process inside the aluminum-based PFWRE combustor is carried out within the Euler–Lagrange framework using the developed model. Results show that a reverse rotating vortex pair before the primary water injection causes particles to flow back towards the combustor head and leads to product deposition. Aluminum particles external to the powder jet have shorter preheating time than internal particles and burn out in advance. The analysis of the particle combustion process indicates that the flame structure inside the combustor consists of the particle preheating zone, the surface combustion heat release zone, the gas-phase combustion heat release zone, and the post-flame zone. In the present configuration, as the particle size increases from 10 μm to 20 μm, the preheating zone length increases from 35 mm to 85 mm. Meanwhile, heat release from gas-phase combustion decreases, and the average temperature of the combustor head first increases and then decreases. This study not only provides insight into the multiphase combustion characteristics of the aluminum-based PFWRE combustor but also offers guidance for the design of the combustion organization schemes and engine structure optimization.

Medicolegal analysis of physical violence toward physicians in Egypt

This study analyzed physical violence against physicians in Egypt from a medicolegal perspective. 88%, 42%, and 13.2% of participants were exposed to verbal, physical, and sexual violence. Concerning the tools of violence, 75.2% of attackers used their bodies. Blunt objects (29.5%), sharp instruments (7.6%), and firearm weapons (1.9%) were used. The commonest manners of attacks were pushing/pulling (44.8%), throwing objects (38.1%), and fists (30.5%). Stabbing (4.8%) and slashing (2.9%) with sharp instruments were also reported. Traumas were mainly directed towards upper limbs (43.8%), trunks (40%), and heads (28.6%). Considering immediate effects, simple injuries were reported that included contusions (22.9%), abrasions (16.2%), and cut wounds (1.9%). Serious injuries included firearm injuries (4.8%), internal organs injuries (3.8%), fractures (2.9%), and burns (1.9%). Most (90.5%) of injuries healed completely, whereas 7.6% and 1.9% left scars and residual infirmities, respectively. Only 14.3% of physicians proceeded to legal action. The current study reflects high aggression, which is disproportionate to legal actions taken by physicians. This medicolegal analysis could guide protective measures for healthcare providers in Egypt. In addition, a narrative review of studies from 15 countries pointed to violence against physicians as a worldwide problem that deserves future medicolegal analyses.

Investigating the influencing factors and prediction models of skin burns for firefighters’ occupational safety

Relevant studies in the fields of fire safety, occupational health and firefighter clothing were analyzed in this study to address the high injury rate among firefighters during fire rescue and the complexity of factors affecting skin burns. The findings indicate that the degree of skin burns in firefighters is primarily influenced by the heat source (heat flux, type), firefighter clothing (fabric, pattern) and the under-clothing air gap (thickness, characteristics). Since skin burns cannot be directly measured, internal skin heat transfer and burn prediction models are commonly employed to assess the impact of external factors on skin burns. These models can predict the safe working distance or time for firefighters. Investigating the influencing factors and prediction models of skin burns among firefighters holds significant value in enhancing operating procedures, optimizing firefighter clothing design and effectively preventing skin burns.

Is multiple wavelength diode laser for facial contouring safe?

The multiple wavelength diode laser (MWDL) is a sophisticated device designed to target deeper skin layers by emitting various wavelengths. Its unique feature is the ability to deliver heat to specific depths within the tissue using different wavelengths while simultaneously cooling the skin surface. Recent research by Choi etal. suggests that wavelengths of 755 and 810 nm can induce carbonization in hair follicles, while the 1064 nm wavelength penetrates deeper into tissues. MWDL has been proposed for fat redistribution in aging, but concerns have been raised regarding ocular safety and potential tissue damage, particularly when used near the eyes. Studies have shown ocular injuries during cosmetic laser procedures, emphasizing the need for robust ocular protection and safety protocols. Additionally, there are reports of internal ischemic necrosis and burns, highlighting the importance of precise energy settings and parameter management. While MWDL shows promise, further research and comprehensive guidelines are needed to ensure safe and effective usage in clinical practice.

Soot particles undergo in-cylinder oxidation again via EGR recirculated gas: Analysis of exhaust soot particle characteristics

Exhaust gas recirculation (EGR) is one of the effective methods to control NOx emission from diesel engine. The present study focused on the amount of soot particles that are back into the engine cylinder via EGR recirculated gas, to explore its influence mechanism on exhaust soot particle characteristics. A DPF (diesel particulate filter) was integrated in EGR loop, which was employed to remove recirculated soot particles and reduce PM emissions. A comprehensive set of experimental techniques were used to characterize the morphology, nanostructure, surface functional groups and oxidation behaviors of soot particles. Results revealed that when soot particles underwent in-cylinder oxidation again via EGR recirculated gas, exhaust soot particles had smaller primary particle size (dp), longer fringe length (La), smaller separation distance (Ds) and tortuosity (Tf), as well as lower relative amount of aliphatic C–H group and oxidation reactivity. Due to higher graphitization degree of recirculated soot particles, the internal burning was conducted earlier during oxidation processes, which resulted in hollow structure at 50% and 75% burn-off stages.

Accretion of substellar companions as the origin of chemical abundance inhomogeneities in globular clusters

ABSTRACTGlobular clusters exhibit abundance variations, defining ‘multiple populations’, which have prompted a protracted search for their origin. Properties requiring explanation include the high fraction of polluted stars (∼40−90 per cent, correlated with cluster mass), the absence of pollution in young clusters, and the lower pollution rate with binarity and distance from the cluster centre. We present a novel mechanism for late delivery of pollutants into stars via accretion of substellar companions. In this scenario, stars move through a medium polluted with asymptotic giant branch (AGB) and massive star ejecta, accreting material to produce companions with typical mass ratio q ∼ 0.1. These companions undergo eccentricity excitation due to dynamical perturbations by passing stars, culminating in a merger with their host star. The accretion of the companion alters surface abundances via injected pollutant. Alongside other self-enrichment models, the companion accretion model can explain the dilution of pollutant and correlation with intracluster location. The model also explains the ubiquity and discreteness of the populations and correlations of enrichment rates with cluster mass, cluster age, and stellar binarity. Abundance variations in some clusters can be broadly reproduced using AGB and massive binary ejecta abundances from the literature. In other clusters, some high companion mass ratios (q ≳ 1) are required. In these cases, the available mass budget necessitates a variable degree of mixing of the polluted material with the primary star, deviations from model ejecta abundances, or mixing of internal burning products. We highlight the avenues of further investigation that are required to explore some of the key processes invoked in this model.

Numerical study on combustion efficiency of aluminum particles in solid rocket motor

The combustion of aluminum particles in solid rocket motor plays an important role in energy release of propellants. However, due to the limited residence time, aluminum particles may not be burned completely, thus hindering the improvement of specific impulse. This study aims to explore the characteristics of aluminum combustion efficiency and its influencing factors by experiments and numerical simulations, providing a guideline for engine performance improvement. As an input of simulation, the initial agglomerate size was measured by a high pressure system. Meanwhile, the size distribution of the particles in plume was measured by ground firing test to validate the numerical model. Then, a two-phase flow model coupling combustion of micro aluminum particle was developed, by which the detailed effects of particle size, detaching position and nozzle convergent section structure on aluminum combustion efficiency were explored. The results suggest that the average combustion temperature in the chamber drops with increasing initial particle size, while the maximum temperature increases slightly. In the tested motors, the aluminum particle burns completely as its diameter is smaller than 50 μm, and beyond 50 μm the combustion efficiency decreases obviously with the increase of initial size. As the diameter approaches to 75 μm, the combustion efficiency becomes more sensitive to particle size. The combustion efficiency of aluminum particle escaping from end-burning surfaces is significantly higher than that from internal burning surface, where the particle combustion efficiency decreases during approaching the convergent section. Furthermore, the combustion efficiency decreases slightly with increasing nozzle convergent section angle. And theoretically it is feasible to improve combustion efficiency of aluminum particles by designing the convergent profile of nozzle.

Effect of nanostructure, porosity and extent of oxidation on soot reactivity

Oxidation evolutions of structure, porosity and reactivity properties of four model carbons (PU, S160, N330 and R250) with different initial reactivity were studied. Results showed that changes in the porosity and nanostructure properties instead of initial properties significantly affected the soot reactivity during the soot oxidation process. Two high-reactivity soot surrogate samples, i.e., PU and S160, initially presented turbostratic disordered crystallites, resulting in higher reactivity at the early oxidation stage. Oxidation mainly proceeded inwardly in a peeling fashion, and more disordered internal crystallites were exposed after oxidized, slightly increasing the reactivity of PU and S160. Two low reactivity soot surrogate samples, i.e., N330 and R250, initially exhibited the typical core–shell structure. The oxidation rates of N330 and R250 were lower than that of PU and S160 due to more ordered exterior crystallites and less surface oxygen content at the early oxidation stage. Once oxygen penetrated the particle core, many pores were generated. Next, the particle became hollow through internal burning of the more reactive internal carbon at the late oxidation stage. After 40% burnoff, these hollow structures promoted oxidation in both outward and inward directions. Therefore, oxidation rates of N330 and R250 significantly increased.

The role of volatile organic compounds in the oxidation-driven fragmentation of soot particles

In this work, the role of volatile organic compounds (VOCs) in soot oxidation and fragmentation was investigated in a lean, premixed CH4 flame. An aerosol generator was used to homogeneously disperse soot with and without VOCs (termed Soot-W and Soot-WO, respectively) into the flame. Because minimal soot was formed in the flame itself, information on the fragmentation of the Soot-W and Soot-WO during the oxidation process was readily captured to determine the role of VOCs in soot fragmentation. The integrated number concentration of fine mode particles and the degree of particle aggregation show that the presence of VOCs suppresses soot aggregate fragmentation, primarily by the mitigating consumption of the neck sites between primary particles due to the decreased specific surface area. The actual oxygen diffusion route and effective pore width between the crystallite structures were determined using the image analysis technique. To determine the characteristic regime of oxygen diffusion, the distribution of effective pore width was studied using high-resolution transmission electron microscopy and image analysis. The estimated effectiveness factor indicates that the presence of VOCs lowers the propensity of internal burning via intra-particle oxygen diffusion, and reduces the extent of primary particle fragmentation, as evidenced by a relatively smaller peak of ultrafine particles. The analysis of the nanostructure of neck sites vs. the bulk discovers significantly more disordered and thus reactive structure at neck sites, explaining the prevalence of aggregate fragmentation over primary particle fragmentation. The finding of the role of VOCs in oxidation-driven fragmentation is beneficial to the optimization of existing models for predicting the number concentration of fine and ultrafine particles. Furthermore, a better understanding of this role may aid in the control of the most harmful fine and ultrafine particle emissions.

Effect of the oxidation-induced fragmentation of primary particles on soot oxidation reactivity

Experiments were performed on a CH4 lean premixed flame to better understand the effect of the oxidation-induced fragmentation of primary particles on soot oxidation reactivity. An aerosol generator was used to homogeneously disperse diesel soot into the flame. Because minimal soot was formed in this flame itself, the information about diesel soot fragmentation was readily obtained. The thermophoretic and probe sampling techniques were used to obtain soot particles at various heights above the burner. The particle size distribution, oxidation reactivity, nanostructure and carbon chemical state of each sample were characterized. The soot reactivity was evaluated in terms of activation energy. The results indicate a higher extent of aggregate fragmentation occurs at moderate soot burnout percentages and that the internal structure in soot is not destroyed during aggregate fragmentation. At higher soot burnout percentages, the internal burning produces more primary particle fragmentation, so that the soot particles exhibit an increase in fringe tortuosity and decreases in fringe length and sp2/sp3 hybridization ratio. These variations in physicochemical properties increase the oxidation reactivity of the soot particles.

"INTERNAL BURN TO MOVE ON" MILLENNIAL LEADERS’ CHALLENGES AND RESOURCES AT WORK

"INTERNAL BURN TO MOVE ON" MILLENNIAL LEADERS’ CHALLENGES AND RESOURCES AT WORK

Analysis of Biodiesel Spray Combustion in Internal-Combustion Engine using Multidimensional Models

With the rapid scale expansion of the first generation of bio-liquid fuels, its impact on the prices of agricultural products, food security and the environment has begun to emerge and attracted extensive attention from governments and academia. A new multi-dimensional model of biodiesel spray combustion in an internal combustion (IC) engine is designed. Firstly, the BP neural network mining model is used to extract the spray combustion data of the IC engine. Then, based on the combustion data of biodiesel load in an internal combustion engine, burning rate and heat release, the principle of spray combustion of biodiesel is analyzed. Finally, from the two aspects of gas-phase control and liquid phase control, a multi-dimensional model of biodiesel spray combustion in IC engine is established and the spray combustion characteristics of biodiesel in IC engine are analyzed. The research results show that the model can effectively analyze the effect of load and fuel temperature on the spray combustion characteristics of biodiesel and the results of the model are almost the same as the actual data and the calculation accuracy is high. It is an effective method for studying the spray combustion characteristics of biodiesel.

Parametric study of solid propellant slotted grain

One of the goals in solid rocket motor design is to have as large volumetric loading as possible keeping the basic requirements unaffected. Slotted grain can achieve this goal as it has the advantages of sliver-free and no stress-concentration regions that occur in other internal burning grains as star grain and wagon wheel grain. It has the disadvantage of exposing the motor wall to hot gases. In this paper, the geometry of slotted grain is discussed and the effect of design parameters (e.g., number of slots, dimensions of the slot, etc.) of slotted grain on grain burn back is explained. Also, a comparison between results and experimental data is performed.

Effect of Modified Combustion Chamber on Performance Characteristics by using Blends of Simarouba Biodiesel

This work aims to study combustion chamber geometry on combustion, performance and emissions of a biodiesel (Simarouba) fuelled modified piston diesel engine. In the existing consequence, biodiesels have established a lot of consideration as an alternate fuel for internal combustion engines. In accumulation, the biodiesels have poor atomization individualities due to diminished CA at the time of fuel injection. However, biodiesel properties are not similar to conventional CI engine fuels, predominantly their higher value of viscosity and lower volatility. This paper emphasizes adapting the internal burning engine combustion chamber structure to promote whirl to better the mixture burning. An assessment of works indicates that investigational studies have not accompanied a specially modified piston for appraising at a constant speed of 1500 revolutions per minute and a compression ratio (CR) of 17.50 at different injection pressure (IP) and different injection timing too. The performance considerations viz... Specific fuel consumption (SFC), brake thermal eff. (BTH), carbon monoxide (CO), oxides of nitrogen (NOx) and unburnt hydrocarbons have been studied. This effort aims to analyze the effect of cylinder structure on burning and exhaust gas emissions of a biodiesel (Simorouba) fuelled specially modified piston conventional diesel engine. It is observed that the IC engine with personalized piston contributes to optimal performance. This exertion is to overview the effect of the specially modified piston on burning, performance parameters and engine exhaust emissions of a biodiesel (Simorouba) fuelled specially modified piston conventional diesel engine. The internal combustion engine under contemplation with specially modified piston gives optimal performance for the internal combustion engine. It has been noticed that the engine under consideration with threaded piston gives optimum performance.

Dynamic X-Ray Imaging of Additively Manufactured Reactive Components in Solid Propellants

A variety of methods have been developed to enhance solid propellant burning rates, including adjusting oxidizer particle size, changing the formulation, modifying the propellant core geometry, and adding catalysts or wires. Fully consumable reactive wires embedded in propellant have been demonstrated to increase the burning rate by increasing the surface area; however, the observation of this effect has been limited to viewing via an intrusive window next to the wire. Here, dynamic X-ray radiography is employed to analyze the evolution of the internal burning profile of propellant embedded with additively manufactured reactive components. This avoids heat loss at the window and allows analysis of the three-dimensional volumetric consumption of strands with internal branching geometries. Printable reactive wires made of aluminum/polyvinylidene fluoride were embedded as single wires, pitchforks, and U- and V-shaped geometries. The nano-aluminum-based formulation produced cone-shaped burning surfaces at 1 atm without the ejection of unburned propellant, even for multiple wires burning in close proximity. The results demonstrate a route to preferentially tailor the internal burning profile of propellants with embedded printable reactive wires and a dynamic X-ray imaging technique to qualitatively and quantitatively characterize the complex internal perforation development.

Experimental study of impact of lubricant-derived ash on oxidation reactivity of soot generated in diesel engines

The objective of the present study was to understand how the lubricant-derived ash-loaded diesel particulate filter (DPF) impacted the soot oxidation reactivity during the regeneration process. Four major commercial lubricant additives (i.e. Ca, Zn-P, Ca-Zn-P, and Mo-P) were heated up in a muffle furnace to generate ash particles, which were mixed with diesel soot in a loose-contact pattern for further analysis. Thermogravimetric analysis (TGA) was employed for both non-isothermal and isothermal conditions to examine the oxidation reaction parameters, including ignition temperature, peak temperature and burnout temperature. In the meantime, the sizes and nanostructures of the primary soot particles during the oxidation process were characterized by high-resolution transmission electron microscopy (HRTEM). Results showed that lubricant-derived ashes accelerated the oxidation of soot particles as indicated by the reduced oxidation characteristic temperatures and increased oxidation rate. Based on the analysis of HRTEM images, both surface and internal burning phenomena existed in the oxidation processes of pure soot conditions and soot-ash mixtures conditions. The structures of shell-core, onion- and capsule-like, hollow and carbonization fragments appeared sequentially through the entire oxidation processes. Comparing to the pure soot conditions, the tendency of surface burning of the soot particles was notably increased by the lubricant-derived ashes. It was thus concluded that, the lubricant-derived ash components played the role as catalyst to promote soot oxidation and favor the whole regeneration process, even though the ashes may deteriorate performance of DPF by increased backpressures.

Impacts of advanced diesel combustion operation and fuel formulation on soot nanostructure and reactivity

Advanced diesel combustion, accomplished via a single pulse fuel injection and high levels of exhaust gas recirculation (referred to as “PCCI”, partially-premixed charge compression ignition), is shown to be a path to reduce oxides of nitrogen and particulate matter simultaneously. This is well established in the literature. Less established is the extent to which such dilute combustion processes influence soot formation and affect soot that is emitted from diesel engines under such combustion modes. This work focuses on characterization of the nanostructure and oxidative reactivity of soot generated by a light-duty turbodiesel engine operating under a PCCI combustion mode, a dilute, low-temperature combustion process. Previous work on a type of PCCI combustion, referred to as high-efficiency clean combustion (HECC), showed soot samples having a fullerenic nanostructure, characterized by high levels of tortuosity of the fringe layers as seen in transmission electron micrograph images and as quantified using an image processing algorithm. Thermogravimetric analysis of the HECC mode soot samples showed that they displayed higher rates of oxidation than soot samples from a conventional diesel combustion mode. The present work returns to PCCI combustion, considering the timing of the main fuel injection, and the effects of operating on fuels rich in n-alkanes, particularly a fuel produced from a low temperature Fischer-Tropsch process (LTFT) and a renewable diesel fuel (RD) produced via hydrodeoxygenation of a plant oil. PCCI combustion conditions yield soot that shows higher reactivity compared to soot from the conventional combustion mode regardless of fuel type. LTFT and RD fuels produce soots with lower reactivity compared to ULSD. Soots produced from PCCI combustion have higher surface oxygen concentration and higher proportion of amorphous carbon. In addition, TEM images show that PCCI soots from all three fuels have smaller primary particle and particle aggregate sizes, and smaller graphene layers. These properties explain the higher reactivity of soot from PCCI combustion. The less reactive soots, which are produced from LTFT and RD fuel under conventional combustion, show internal burning during oxidation. However, soots with higher reactivity which are produced from late injection PCCI combustion and ULSD show shrinking core oxidation, likely because of their overall amorphous structure.

Modernization of a tractor motor for diesel combustible and methanol

When carrying out research to improve the environmental performance of motors, attention should be paid to reducing the nitrogen oxide content of the effluent gases, since they are the most toxic components among the entire range of polluting chemical compounds contained in exhaust gases, since they are formed in the burning process as a result of chemical reactions atmospheric oxygen and nitrogen. The most effective way of using methanol in internal burning engines is now to feed it directly to the diesel cylinder using a dual combustible supply system, which allows replacing up to 80% of the diesel combustible. The ignition of methanol in this case is due to the supply of a seed portion of diesel combustible. This method, with some changes and additions to the design of the motor, can be implemented on engines already in operation. In this paper, the effect of methanol application on the volumetric content and mass concentration of nitrogen oxides in exhaust gases calculated on the basis of the results of experimental studies of a motor of 2H 10.5 / 12.0 air cooling with a hemispherical burning chamber in a piston using a dual combustible delivery system and injection of diesel combustible (ignition) through a multi-jet nozzle, depending on the change in load.

Inadvertent Internal Skin Burn Caused by Radiofrequency Electrodes During Ablation Procedures.

Inadvertent Internal Skin Burn Caused by Radiofrequency Electrodes During Ablation Procedures.

Smokeless flare tips failure investigation: case study

ABSTRACTFlare tip is an important safety feature of most oil and gas producing and processing facilities. They are used extensively in the hydrocarbon and petrochemical industries as a system to achieve safe and reliable gas release during a plant upset or emergency situation. In this study, a detailed metallurgical investigation of failed smokeless flare tip stack drums at natural gas liquid fractionation plant was performed. Environmental scanning electron microscopy coupled with energy-dispersive X-ray microanalysis and Vicker's microhardness measurement analysis showed severe intergranular cracking damage initiated from the edge of the barrel. Formation of non-protective oxide and Ni-rich sulphide was detected along with the formation of corrosion products and scale primarily at cracks. These findings suggested that the flare tip stack drums have experienced frequent flame impingement or internal burning which promoted microstructural changes in the material and high-temperature corrosion, leading to crack initiation and growth and subsequently resulted in failure.