Combustion Of Powders Research Articles

Synthesis of a Composite Material via Combustion of Titanium and Boron Powders and a Mechanically Activated Aluminum + Nickel Mixture

Synthesis of a Composite Material via Combustion of Titanium and Boron Powders and a Mechanically Activated Aluminum + Nickel Mixture

Simulation of Hydrogen Explosions in Closed or Vented Connected Vessels

ABSTRACT The aim of this work is to present an original numerical study of gaseous explosions with hydrogen in air inside a closed vessel and the chain propagation of an explosion in vented partitioned vessels. A fast calculation methodology, particularly interesting in the field of the risk assessment is developed mainly for lean mixtures. In addition to simulating the explosion in a closed environment, it takes into account the accidental transmission of the explosion from one compartment to another adjacent one by the means of the hot flow through the orifice common to both volumes. Finally, it is possible to generalize this novel methodology to a simple multi-partitioned structure. Some characteristics of the model have been initiated for the ignition and the combustion of propulsive powders in a one-compartment vessel and developed for gaseous mixtures with appropriate parameters linked to simplified kinetics. A simple representation of the combustion phenomena based on energy transfers and the action of specific molecular species is presented. The model allows the study of various parameters such as the initial thermodynamic conditions, the location of the ignition energy, and the size of the inner openings or the vent areas. The numerical results have been compared with data obtained by the means of experimental works in the laboratory or available in the literature and indicate correct preliminary trends.

Infiltration-controlled combustion of magnesium for power generation in space

Chemical heat integrated power systems can potentially provide high energy densities and long lifetimes compared to the best batteries. They are of interest for space missions where the use of solar or nuclear energy is impractical. In a new concept of such a system, a metal combustor is coupled with a chemical oxygen generator, and the metal powder bed inside the combustor burns with the infiltrated oxygen. However, the infiltration-controlled combustion of metal powders is not well understood. In the present work, a magnesium powder poured in a vertical quartz tube was ignited by a laser inside a chamber filled with oxygen at pressures of 44 – 90 kPa. The ignition resulted in the propagation of a thermal wave followed by a second ignition at the other end and propagation of a thermal wave backward. High-speed and infrared video recordings as well as thermocouple measurements were used for diagnostics. The results demonstrate that if a metal with a low Pilling-Bedworth ratio (0.81 for magnesium) is used, coflow combustion is possible. The coflow combustion wave propagates at incomplete conversion, with an axial velocity being as low as 0.1 mm/s and the zone of the highest temperature traveling along a helical path. An increase in the axial velocity of the combustion wave is accompanied by an increase in the flame thickness and a decrease in the extent of conversion.

Self-ignition temperature of the dust accumulations for sunflower and wood powders

Spontaneous combustion is a phenomenon that results from the heating of combustible organic powders by slow oxidation and which occurs through the air passage (created by an air depression) through the mass of dust. The oxidation phenomenon of combustible powders represents their reaction with atmospheric oxygen resulting in products of carbon dioxide, carbon oxide, water and other gases whose content depends on the temperature at which the oxidation takes place. The self-ignition of combustible dusts depends on their chemical composition, the properties of component substances, on the particle size and geometry of the material mass and, last but not least, on the temperature of the environment. Due to global worries of sustainability in construction engineering the trend is to use ecofriendly organic waste to various purposes as in construction materials. The challenge is that by using this kind of materials one should ensure the safety related to the process of such organic materials which are known to have combustible properties. The purpose of this work is to present the self-ignition behavior of combustible dusts such as sunflower and wood by means of drying tests under constant temperature conditions.

Phase Transformations and Microstructure Evolution During Combustion of Iron Powder

Phase Transformations and Microstructure Evolution During Combustion of Iron Powder

IGNITION AND COMBUSTION OF TNT-DISPERSED ALUMINUM POWDER

IGNITION AND COMBUSTION OF TNT-DISPERSED ALUMINUM POWDER

METHOD OF CONTROLLING PRESENCE OF FOREIGN SUBSTANCES AND OBJECTS IN THE BORE OF THE BARREL USING MONOCHROME LIGHT

In the article, the authors propose a method for controlling the presence of foreign substances and objects inside the barrel. The problem of surface cleanliness control remains relevant in many areas, ranging from sanitary cleaning to nanoelectronics. In the military sphere, this becomes particularly important during the cleaning of cannon barrels. Both powder combustion products and cartridge cap and bullet shell particles are deposited in the barrel during firing from guns. Under the impact of high temperatures, the bullet particles are partially oxidized and cover the barrel channel with a thin layer of deposit of oxides, which are difficult to dissolve. As a result, the density of the bullet abuting the walls changes. This affects the characteristics of its motion inside the barrel. The accuracy of the shot is reduced, and subsequently the precision and accuracy of shooting in general decreases. The essence of the proposed method consists in the fact that a light source is placed in the bore of the barrel on one side, and an optical device is placed on the other side, with the help of which the presence of foreign substances and objects is monitored. Unlike the known methods, this method is characterized in that several monochrome light sources in addition are placed in turn in the bore of the barrel from the breech part, and in the bore of the barrel from the muzzle part there is equipment for receiving (detecting) monochrome light. Then, obtained monochrome light is analyzed, current value of its defined parameters is determined. At the next stage, parameter values of monochrome light fixed during control are compared with parameter values of reference signatures, which had been obtained before the barrel was put in service. These values are stored in equipment memory. If the values of at least one of the parameters from at least one of the monochrome light sources are found to be inconsistent with the parameters of the reference signatures, the equipment for receiving and analyzing monochrome light gives a signal about the presence of foreign substances and objects in the bore of the barrel.

Studies on aluminum powder combustion in detonation environment

The combustion mechanism of aluminum particles in a detonation environment characterized by high temperature (in unit 103 K), high pressure (in unit GPa), and high-speed motion (in units km/s) was studied, and a combustion model of the aluminum particles in detonation environment was established. Based on this model, a combustion control equation for aluminum particles in detonation environment was obtained. It can be seen from the control equation that the burning time of aluminum particle is mainly affected by the particle size, system temperature, and diffusion coefficient. The calculation result shows that a higher system temperature, larger diffusion coefficient, and smaller particle size lead to a faster burn rate and shorter burning time for aluminum particles. After considering the particle size distribution characteristics of aluminum powder, the application of the combustion control equation was extended from single aluminum particles to nonuniform aluminum powder, and the calculated time corresponding to the peak burn rate of aluminum powder was in good agreement with the experimental electrical conductivity results. This equation can quantitatively describe the combustion behavior of aluminum powder in different detonation environments and provides technical means for quantitative calculation of the aluminum powder combustion process in detonation environment.

Physicochemical Analysis of Wastewater Sludge in Yeosu National Industrial Complex

In 1987, the national industrial complex began to build wastewater treatment facilities, and the Yeosu National Industrial Complex is a large-scale industrial complex in which Korea''s representative heavy and chemical companies reside. In this study, in order to review the efficient sludge treatment method for the Jungheung Industrial Complex wastewater treatment plant as a research object, the physicochemical characteristics of the wastewater sludge were analyzed to examine ways to efficiently convert resources into resources. The Jungheung Wastewater Treatment Plant generated 9,200 tons/year of sludge in 2019, and the treatment cost was 1,253 million won per year. As a result of three components analysis of wastewater sludge, moisture was in the range of 70 to 91 %, and combustible matter was in the range of 5 to 19 %, and in the case of ash, it was in the range of 1 to 17 %. The average low calorific value of the subjects was 2,050 kcal/kg, and even within the same industry, the low calorific value was shown in the subjects with a low ratio of combustible powder and a relatively high content of ash. As a result of analysis of the five elements C, H, N, S, and O of wastewater sludge, the carbon value ranged from 3.17 to 49.72 %, and most subjects with high calorific value had high C content. There was no subject whose heavy metal content in the wastewater sludge exceeded the standard value. As a result of the analysis of inorganic elements, certain elements were found to be high depending on the characteristics of the industry, such as manganese cobalt (Co) being high in the petrochemical industry.

Spontaneous Combustion Characteristics and Critical Conditions of Spontaneous Combustion of Polished Aluminum Powder Based on F-K Theory

Spontaneous Combustion Characteristics and Critical Conditions of Spontaneous Combustion of Polished Aluminum Powder Based on F-K Theory

Endometriosis and Pelvic Pain in the Adolescent: Delayed Diagnosis Leading to Long-Term Suffering and the Need for Intervention

<h3>Study Objective</h3> To discuss the atypical presentation of endometriosis in adolescents, importance of decreasing delays in diagnosis and management and reducing long-term suffering in our adolescent population <h3>Design</h3> Narrative Review. <h3>Setting</h3> N/A. <h3>Patients or Participants</h3> N/A. <h3>Interventions</h3> N/A. <h3>Measurements and Main Results</h3> A database search was performed using MEDLINE/PubMed and CINAHL Plus. Keywords included, adolescent endometriosis, pelvic pain adolescents, secondary dysmenorrhea in adolescents, adolescent endometriosis presentation, adolescent endometriosis management. The committee opinion from the American College of Obstetrics and Gynecologists on dysmenorrhea and endometriosis in the adolescent was utilized. A manual search from reference lists of relevant articles was conducted. Endometriosis is the most common cause of secondary dysmenorrhea in adolescents. Delay in diagnosis of endometriosis in adolescents, continues to be a barrier in early intervention and management, leading to chronic pelvic pain and long-term suffering well into adulthood. Atypical presentation of endometriosis in adolescents contributes to the delay in diagnosis. In adolescents, endometriotic lesions present as red, clear, white, or glandular lesions rather than the powder burn lesions seen in adult women. Additionally, adolescents develop non-cyclical pain, not the classic cyclic pain associated with endometriosis. Pelvic ultrasounds and Magnetic Resonance Imaging are helpful in diagnosis, however laparoscopy remains the gold standard, even in adolescents, because the likelihood of discovering endometriosis in an adolescent presenting with dysmenorrhea and chronic pelvic pain refractory to medical therapy is at least 50%. Hormonal therapy, NSAIDs, GNRHa and, surgical management with postoperative hormonal therapy are the recommended treatments for adolescent patients. <h3>Conclusion</h3> Early intervention and management of endometriosis and pelvic pain in the adolescent population can decrease delay in diagnosis, long-term suffering, and potentially a reduction in disease progression. Diagnostic laparoscopy with biopsy and surgical therapy should not be delayed in the adolescent patients who are refractory to medical therapy; it still remains the gold standard in the diagnosis of endometriosis.

Fluorinated graphene improving thermal reaction and combustion characteristics of nano-aluminum powder

Two-phase flow loss is an important factor to reduce the combustion performance of aluminum-based solid propellants, which can be decreased if aluminum particles burn more rapidly and produce more gaseous products to crack their agglomeration. To reduce aluminum agglomeration and improve the combustion performance, fluorine-containing organic substances (FCOS) is used as a modified material for aluminum powder. Fluorinated graphene (FG) is a promising FCOS with both the physical and chemical properties of graphene and polytetrafluoroethylene, so we studied the effects of FG on the combustion and agglomeration of nano-aluminum powder. Specifically, the ignition, combustion, and agglomeration characteristics of FG modified nano-aluminum with ammonium perchlorate were studied. Results show that FG can promote the decomposition of ammonium perchlorate. An appropriate amount of FG has a positive effect on the ignition delay time and flame propagation velocity of nano-aluminum powder. The increase of FG content can reduce the size of aluminum agglomerates. These results can be useful for the applications of FG in aluminum-based solid propellants.

Investigation of biomass powder as a direct solid biofuel in combustion engines: Modelling assessment and comparisons

Early studies have shown that biofuels in powder form burn like a gas. In addition, they are less pollutants and renewable source. In this study, powder biofuel is investigated as a direct solid fuel in internal combustion engine. The biofuel is applied in a cylindrical shape and micron-size, with length between 75–5800 μm and diameter 30–1380 μm. Several mathematical models were investigated including different stages of biomass powder combustion in the engine. The mathematical models include drying, shrinkage, and volatilization processes. The modelling tools also investigated the movement of the fuel powder in the cylinder upon injection, how it is distributed, and its performance before combustion. The proposed models are simulated using computational fluid dynamics (CFD) tools and validated against experiments. The results showed that all models can represent the biomass powder combustion reasonably. However, some models are least expensive in calculations and time. Results also displayed that the powder are traced in different groups based on sizes and flow responses and that takes about 0.2 s. The biomass powder gasification is completed at temperature 1050 K and extra temperature has no meaning.

Promotional effect of silica on the combustion of nano-sized aluminum powder in carbon dioxide

This paper presents how the combustion performance of nano-sized aluminum (nAl) powder in carbon dioxide are affected by silica. The ignition and combustion performance of nAl powder with silica addition were studied by a high-temperature tube furnace. An s-type thermocouple and a high-speed motion acquisition instrument were performed to evaluate the ignition temperature, maximum combustion temperature, maximum change of rate of temperature, and combustion propagation speed. The combustion efficiency and combustion products were measured and analyzed by a gas-volumetric method and an X-ray diffraction. The results show that silica added into nAl powder can enhance its maximum combustion temperature and maximum change of rate of temperature, while its ignition temperature increases slightly. The nAl powders with addition of 6.00 wt.% and 12.00 wt.% silica present high combustion propagation speeds, especially for the latter, it has high combustion efficiency. The effect mechanism of silica on the combustion of nAl powder in carbon dioxide was discussed.

Field efficacy of ethnomedicinal plant smoke repellency against Anopheles arabiensis and Aedes aegypti

The repellency effect of smoke from burning Azadirachta indica, Eucalyptus camaldulensis and Ocimum forskolin plants to reduce human-mosquito biting activity. Ground mixed powders of the plant leaves produced smoke by direct burning and thermal expulsion on the traditional stoves in experimental huts against An. arabiensis and Ae. aegypti. A four-by-four Latin-square design was used to assign treatment and control experimental huts over different nights. In the treatment huts, the percent repellency of the smoke produced by burning powdered plant mixtures of the plants were determined by reduction mosquito density. There was a reduction on An. arabiensis (93.75%, P < 0.001) and Ae. aegypti (92%, P < 0.001) respectively, for huts with burning powder versus no treatment. Overall, plant mixed powders tested by both methods of application offered significant protection (>90%) against both mosquito species tested and has the potential to be used as an alternative mosquito control method.

Combustion of aluminum powder using CO2 laser in O2/CO2 atmosphere under different pressure conditions

Combustion of aluminum powder using CO2 laser in O2/CO2 atmosphere under different pressure conditions

Establishing the interface layer on the aluminum surface through the self-assembly of tannic acid (TA): Improving the ignition and combustion properties of aluminum

Aluminum powder is widely used in the field of propellants and explosives due to its high energy density. However, the dense oxide film on its surface will hinder the combustion of aluminum powder. Herein, Al@TA-Fe with core-shell structure was prepared by self-assembly of tannic acid (TA) and Fe(III) ion on the surface of aluminum, and was characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and thermogravimetry-differential scanning calorimetry (TG-DSC). The results show that the TA-Fe interface layer in Al@TA-Fe can effectively promote the ignition of aluminum powder, which can make the aluminum powder be ignited at the temperature far below the melting point of aluminum. Meanwhile, the carbides formed by the decomposition of tannic acid are beneficial to the cracking of the alumina on the surface of the aluminum powder, which can promote the internal aluminum to participate in the reaction and improve the reaction efficiency of aluminum. The TA-Fe layer can inhibit the agglomeration of molten aluminum during the combustion of aluminum and can effectively improve the corrosion resistance of aluminum powder. The iron ions in the TA-Fe interface layer can successfullycatalyze the thermal decomposition process of ammonium perchlorate (AP). In addition, Al@TA-Fe can effectively increase the burning rate of the propellant compared with pure aluminum powder.

Вплив термогазодинамічних властивостей часток твердого ракетного па-лива на швидкість його горіння

The aim of this work is to eliminate the explosion possibility of a rocket engine that operates on a fast-burning solid propellant. The problem is considered by analogy with experiments conducted earlier. Various ways to increase the propellant combustion rate are presented. Examples of how the solid propellant combustion rate depends on the metal fuel and the oxidizer particle size are given. It is shown that unstable combustion of a solid propellant at high combustion chamber pressures is due to unstable combustion of the gas phase in the vicinity of the bifurcation point. Zeldovich’s theory of nonstationary powder combustion is applied to analyzing the explosion dynamics of the Hrim-2 missile’s solid-propellant sustainer engine. This method of analysis has not been used before. The suggested version that this phenomenon is related to the aluminum particle size allows one to increase the combustion rate in the combustion chamber of a liquid-propellant engine, thus avoiding the vicinity of the bifurcation point. The combustion of solid propellants differing in aluminum particle size is considered. The metal fuel and the oxidizer particle sizes most optimal in terms of explosion elimination are determined and substantiated. The use of submicron aluminum enhances the evaporation of ammonium perchlorate due to the infrared radiation of aluminum particles heated to an appropriate radiation temperature. This increases the gas inflow into the charge channel, thus impeding the suppression of ammonium perchlorate sublimation by a high pressure, which is important in the case where the engine body materials cannot withstand a high pressure in the charge channel. This increases the stability and rate of solid propellant combustion. It is shown that the Hrim-2 missile’s solid propellant cannot be used in the Hran missile. The combustion rate is suggested to be increased by using fine-dispersed aluminum in the solid propellant.

Particle formation during suspension combustion of different biomass powders and their fast pyrolysis bio-oils and biochars

The fly ash formation during suspension combustion of five different biomass powders (stem wood, bark, forest residue, willow, and reed canary grass) and the corresponding products from fast pyrolysis (bio-oil and biochar) of the powders was investigated. The fifteen fuels were burned in a drop tube furnace under normal (20 vol-% O2) and oxygen-enriched combustion conditions (40 vol-% and 60 vol-% O2). The trends in the data were used to discuss differences in combustion behavior and devise recommendations for the use of the fuels. There was a general difference in fly ash formation mechanism between the solid fuels (biomass and biochar) and the bio-oil fuels, which was attributed to parts of the ash-forming elements in bio-oil being dissolved in the oil. Oxygen-enrichment did not affect the release of inorganic elements to the gas phase for bio-oil combustion. Since the bio-oils generate lower fly ash during combustion, ~100 times compared to the original biomasses, they should be reserved for combustion technologies demanding fuels with very low ash content, whereas the biochar should be used in large scale combustion facilities with advanced gas cleaning technology operated by teams with experience of handling ash related operational problems.

Fire hazard potential of non-metallic powder layers induced by deposit surfaces

Combustible dust may result in a catastrophic dust explosion with much larger accident consequences than that of combustible gas or vapors. By considering the significant contribution of dust layer fire to dust explosion, fire hazards of dust layer were investigated to clarify the possible worsening situation induced by the properties of deposit surface. The results showed that the effect of thermal conductivity of deposit surface on layer fire hazard was complex even for the same powder material, which depended on the contribution of conductivity to the layer flame spreading. Good permeability of the deposit surfaces (e.g., metal gauze) could contribute to a bottom fire with high flame height and temperature. For whatever deposit surfaces (i.e., ceramic and metal plate, or metal gauze), the inclination angle of the dust layer could result in a high flame spread velocity (FSV). As a result, good permeability deposit surfaces coupled with a large inclination angle would significantly enhance the fire hazard of the dust layer, which should be taken enough consideration in the powder process industries or public activities where combustible powders were used.