Burning Grain Research Articles

Combustion behavior of discrete magnesium diboride particles in the state of motion

Magnesium diboride (MgB2) is regarded as a potential substitute for the amorphous boron (B) due to its excellent energy-release characteristics. In this work, the motion track, flame, and reaction process of discrete MgB2 particles were investigated in the state of motion to reveal their combustion mechanism. The effect of different gaseous mediums on the sustained combustion time and the ingredients and microstructure characteristics of combustion residues were also analyzed. Furthermore, the size distribution of grains in the initial MgB2 particles, MgO cluster particles, and burnt grains in the combustion residues was obtained using graphic analysis. Based on the different motion tracks and flame features obtained, three different combustion modes can be identified; single-stage combustion, two-stage combustion, and micro-explosion combustion. Among them, the single-stage combustion and the two-stage combustion exhibit similar sustained combustion times (12.1 ms and 12.3 ms, respectively), whereas the micro-explosion combustion exhibits a significantly shorter sustained combustion time (5.6 ms) due to the disintegration of particles. Besides, the average sustained combustion time of MgB2 particles was prolonged in the oxygen but shortened in the water vapor. The obtained X-ray diffractometer patterns showed that the combustion residues were composed of MgB2, MgO, Mg, B2O3, and MgBx (indicating an incomplete oxidation during the combustion), and that the burn-off rate of discrete MgB2 particles could still be improved. The scanning electron microscopy images showed a coating layer of condensed B2O3 and clusters of MgO particles on the surface of the combustion residues. The average diameter of burnt MgBx grains and MgO particles were calculated as 1.04 μm and 0.18 μm, respectively. The burnt MgBx grains were products obtained after the coagulation of liquid B2O3 layer and initial MgB2 grains and were larger than the initial MgB2 grains (diameter of 0.24 μm). The MgO cluster particles were condensed from gas-phase reaction and agglomerated to produce a porous structure.

THE “UZERLIKTAPA CULTURE” IN KARABAKH - AZERBAIJAN

İn the Middle Bronze period, primary city centers were formed in Azerbaijan – Karabakh, and progress was made in the economic sphere. This is a city whose wealth comes from the workers. This settlement is located in the MIL-Karabakh plain, east of the city of Agdam. The thickness of the cultural layer in this place of residence has reached 3 m. In the northern part, the remains of the defensive wall were discovered and the construction features were studied. In the north-western part of the excavation site, broken black-polished large bowl with wheat inside, lid, black-polished miniature plate fractures, grain stones, supports, 8 number of sickle teeth made of flint stone and a cudgel head were obtained. From the south side along the wall of the dwelling were obtained plastered floor remains, a hearth made of stone with burnt grain, a woman's statue of clay and broken clay objects. The materials of the upper layer of uzerliktapanon are large red-colored dishes, kitchen utensils, monochrome patterned dishes, barbecue and various stone models and smelters (weaving tool). Nakhchivan is considered the homeland of painted dishes in Azerbaijan. The acquisition of painted dishes in Karabakh gave researchers reason to say that there were economic and cultural relations between these two cultural centers.

Alginate-sepiolite-ammonium polyphosphate ternary hybrid gels for firefighting in grain and cotton reserves

An eco-friendly and bio-based ternary hybrid gel consisting of alginate, sepiolite, and ammonium polyphosphate (APP) was fabricated via a facile one-pot method. Rheological tests showed that this ternary hybrid hydrogel exhibited shear-thinning behavior. Firefighting experiments showed that a burning cotton bale extinguished by using water re-ignited, whereas the ternary hybrid gel effectively prevented smoldering and re-ignition of the cotton bale because of the firm adhesion of the hybrid gel to the surface of the cotton bale. Firefighting experiments also showed that the hybrid gel only covered the upper layer of a rice pile after firefighting efforts, whereas water ruined the grains completely, making them inedible and suitable for use only as a feed or for discard with the burnt grains. The firefighting mechanism of this hybrid gel involved multiple modes of action: volatilization of the large amount of water in the gel absorbed much heat (cooling the combustion zone), APP decomposed into non-flammable ammonia when heated (dilution of flammable volatiles and oxygen), and APP and sepiolite were conducive to forming a continuous and dense char layer (insulation of the exchange of combustible gas, heat, and oxygen). This work provides an environmentally friendly, cost-effective, and bio-based hybrid gel for firefighting in grain and cotton reserves.

Solid rocket motor interior ballistics fluid-solid interaction simulation using level set method for 2D grains

The flow inside a solid rocket motor is considered taking into account the fluid-solid interaction between the combustion gases and the burning grain surface. An unsteady flow model is presented for the flow variables while the time-dependent burning surface is captured using the level set method. Then, a hybrid model is presented by coupling the flow model with the interface capturing technique. The proposed hybrid model is successfully tested against previously published experimental and numerical data. The use of the level set method enables the flow model to consider complex grain shapes like the star shapes. The proposed hybrid model is used to produce the pressure-time curves for cross-shaped grain and a star grain with five points.

THE HOUSEHOLD OF THE POPULATION OF THE SHYRIAIEVE HILLFORT

The Shyriaieve hillfort of the Scythian Age was excavated at the late of the 40s and in 1950. The site is located on the high right bank of the Seym River within Putyvl region. As a result, for the first time the information about the household of the local people was obtained. The researches at the site were resumed in 2017. During these four years, the identified material has become a basic to clarify some conclusions about agriculture, husbandry, hunting and fishing. During the comparative analysis the sources from the other fortified sites of the Scythian Age related to the Yukhniv culture of the Seym region and the ash-hill 10 of the Western Bilsk hillfort have been processed.
 In our days the information about agriculture of the population of Shyriaieve hillfort is extremely scarce. These are a few finds of agricultural tools, prints of cereals on the pottery (millet) and burnt barley grains.
 But the information about domestic animals and hunting species was processed. During four years of excavation, 3575 bones have been identified. The cattle breeding was predominant, as usual for the other settlements of the early Iron Age. Also, husbandry consisted of pig-, horse- and small cattle-breeding (with some differences).
 The results of comparative analysis of hunting species are different for the prevailing species on different sites. In most cases, the main object of hunting was a wild boar. This fact depends on the species diversity.
 As well as in whole population of the Yukhniv culture, in the Shyriaieve hillfort the fishing had been developed. The analysis of bone remains and fish scales ostends that the predatory fish was predominant. The complete absence of carp indicates the using the hook fishing. The nets were not used.
 It is not a final conclusion because the excavations are going on. However, based on the features of the local soils and the main hunting species of the population of the Shyriaieve hillfort the site was probably located in Scythian Age in the Forest zone not in the Forest-Steppe one according to modern geographical zoning.

Burnt grain and crop cleaning residues: an archaeobotanical contribution to the understanding of 3rd–6th century AD longhouses in Jutland and Funen (Denmark)

Burnt grain and crop cleaning residues: an archaeobotanical contribution to the understanding of 3rd–6th century AD longhouses in Jutland and Funen (Denmark)

Fires in the dark. Wood and charcoal analysis of the Early Medieval funerary deposits in the cave of Riocueva (Cantabria, Spain)

The results of the uncharred wood and charcoal analysis carried out on samples from the site are presented in this work. The assemblages comprised debris from combustion structures, remains related to the funerary burnings and torches, and also fragments of uncharred wood probably related to the funerary rite. The cave of Riocueva was used as a burial place at some point between the 7th and 8th centuries cal. AD. Archaeological work carried out between 2010 and 2014 has recovered the remains of at least eight young individuals and many associated objects: glass beads, rings, spindle hooks, knives and pot sherds, among others. As in other burial caves of similar chronologies from the Cantabrian region, rituals linked to the treatment of corpses have been detected. The destruction and burning of the skulls is the most stunning of them. Furthermore, burning grain beside the bodies, a custom forbidden by medieval penance books, has been tentatively suggested as a possible practice forming part of the rituals.

Relationship between Slivering Point and Gas Generation Rules of 19-Perforation TEGDN Propellants with Different Length/Outside Diameter Ratios and Perforation Diameters

ABSTRACTIn order to investigate the relationship between the slivering point and burning progressivity, a set of 19-perforation propellants containing triethylene glycol dinitrate (TEGDN) with different lengths/outside diameter ratios and perforation diameters was prepared and tested in a closed vessel. The mass fraction of burnt propellant was derived from the recorded pressure–time history of 19-perforation TEGDN propellants in the closed vessel according to the gas state equation and the form function of tested propellants. Based on the form function calculation and the mass fraction of burnt propellant, instantaneous burning surface area and the burning rate were obtained. The influence of length/outside diameter ratios and perforation diameters on the progressive combustion performance is studied through the dynamic vivacity method. With an increase in the length/outsider diameter, the slivering point occurs earlier and the slivering process lasts longer. Further, the burning progressivity of surface area can be improved. For propellants with same length/outside diameter ratio, with a decreasing of perforation diameter, the slivering point lags behind and the burning progressivity becomes greater. The slivering point corresponds to the instantaneous burning area, which is related to the form function and total burning process as well. However, the total burning progressivity of propellant is a very comprehensive result of propellant under multiple actions, including the mass fraction of burnt propellant, grain size and burning rate at different pressure regions. The correlation between them can boost a better understanding on the interaction between grain size, slivering burning process and burning progressivity.

Enhancement of Aluminum Reactivity to Achieve High Burn Rate for an End Burning Rocket Motor

AbstractAluminum is used in solid propellants to increase the specific impulse (Isp). It is desirable to have high propellant loading in any stage as it reduces the structural coefficient and an end burning grain is known to be the one with the highest propellant loading. As aluminum combustion is a slow process, the time available for aluminum combustion in an end burning configuration will be very small at the start of the combustion process. This demands an increase in the reactivity of the aluminum. This study is built on the fact that mechanical activation of aluminum powder with PTFE (poly‐tetra‐flouro‐ethylene) enhances the reactivity of aluminum powder. This study also deals with the use of this activated aluminum powder in conjunction with various other methods to enhance the burn rates of the solid propellant. The temperature sensitivity was also measured. Based on these results, new designs with end burning grains for the third stage of Polar Satellite Launch Vehicle (PSLV) and for the second and third stage of Pegasus launch vehicle have been proposed to increase the payload capacity. With this new design, it is seen that the payload can be increased by 12.7 % and 17.6 % for PSLV and Pegasus, respectively. The novelty of this design is that with no changes to any other hardware of the above two systems the increase in payload can be achieved.

Structures with Bay-shaped Stoves in Ancient Slavs’ Husbandry (Based on Materials from Peresopnytsia in Pastivnyk Tract)

The article presents a comprehensive publication of small size structures with bay-shaped stoves from the excavations at the Early Slavs’ settlement in Pastivnyk Tract in Peresopnytsia of the Rivne Region and Oblast. There are three of them studied since 2002 during the period of active research: No 1 in excavation area 1, No 2 in excavation area 8, and No 1 in excavation area 9. There was the other stove to the left from the last mentioned. Based on the filling in the foundation pits, the structures are dated by the 10th century. Finds in the structures at Pastivnyk testify for their usage in work with «bread», or wider for cooking: fragments of millstones were found in structure 1/1; three types of various kitchen remains were found in No 2/8, and filling No 1/9 contained a significant admixture of burnt grains of cultivated cereals. The fact that such structures were not used as workshops (ceramic, ironworking, etc.) is indirectly evidenced by the planigraphy of the settlements: in cases where it was possible to trace, such structures were situated in immediate proximity to the dwellings, as well as in the residential area of the settlements.A review of similar structures is made which are situated mainly in Volyn. It is probable that such tradition of farmstead organization, in which structures for cooking were settled separately and outside the dwelling room, was spread at a very limited local territory, was appropriate for the annalistic Volynians, and was their own distinctive tribal peculiarity of farmstead organization.

Archaeology, baobabs and drought: Cultural proxies and environmental data from the Mapungubwe landscape, southern Africa

Ethnographic and archaeological data from the Mapungubwe landscape show that rainmaking deposits on hilltops, along with burnt grain bins in ordinary villages, represent cultural responses to severe drought by Iron Age agricultural communities. In ordinary villages, burnt granaries were the result of cleansing rituals, rather than violence or natural causes. A total of 13 episodes of severe droughts were previously documented in hilltop and village deposits. New climate proxy data from baobab trees provide a 1000-year-long regional record that helps to refine this drought sequence. Based on carbon isotope values, the baobab record documents additional episodes and confirms an early 14th-century drought associated with the abandonment of Mapungubwe. This abandonment, however, owed as much to cultural factors as to environmental pressures.

Accurate Computation of Grain Burning Coupled with Flow Simulation in Rocket Chamber

In this paper, we present a novel numerical approach for predicting the fluid flow in a solid rocket motor chamber with burning propellant grain. We use a high-order technique to track the regressing grain surface. Spectral convergence toward the exact burning surface is achieved thanks to Fourier differentiation. For the computation of the internal chamber fluid flow, we make use of a body-fitted volume mesh deforming with the grain surface. We describe several methods to deform the volume mesh and to keep good mesh element quality without global remeshing. We then couple the surface and volume approaches and integrate them into a complex code for compressible, multispecies, turbulent flow simulations. Thanks to these methods, we are able to exhibit one of the first three-dimensional simulations of the internal flow in a realistic solid rocket motor coupled to complex grain surface regression. In prior work, burning grain surface methods have only been coupled with one-dimensional internal ballistics solvers.

Robust Design Optimization of Dual Thrust Solid Propellant Motors due to Burning Rate Uncertainties

Solid rocket motor design becomes a clamant task where fusion of design and non-design parameters may lead to various design configurations, especially under uncertainties. This paper proposes a robust design optimization method for the performance of a dual thrust solid rocket motor under investigation of the propellant burning rate and grain geometry uncertainties. It was found that due to uncertainties, the burning rate varies erratically during burning surface area regression, which may lead to catastrophic failure. The present approach aims at uncertainty quantification associated with burning rate and its influence on dual thrust motor performance. A first-order orthogonal design is applied to estimate the worst case deviation coupled with motor internal ballistics. The robustness assessment is measured directly by a mean-variance and average difference approach. A sensitivity analysis of performance parameters is performed to analyze the effects of variation of the design parameters. A hybrid genetic algorithm and simulated annealing approach is used as optimizer. The robust design solution obtained in the form of insensitive design and performance parameters shows the effectiveness and efficiency of the proposed methodology.

An archeomagnetic analysis of burnt grain bin floors from ca. 1200 to 1250 AD Iron-Age South Africa

Recognition of the rapid decay of Earth’s magnetic field over the last 150 years, chronicled in magnetic observatory and satellite data, highlights the need for a higher resolution record of geomagnetic field behavior over the past millennium. Such a record would help us better understand the nature of the recent dramatic changes. A limitation of the existing database is undersampling of the Southern Hemisphere. Here we investigate the potential of obtaining archeomagnetic data from Iron-Age burnt grain bins from southern Africa. These structures preserve oriented material that can record both paleodirections and paleointensity information. Directional data collected from three sites (ca. 1200–1250 AD) fall 9–22° to the East of predictions. Thellier–Coe and Shaw paleointensity results differ from model values by ∼15%. The consistency of results between the three sites suggests that further investigations of these materials with different ages could markedly improve the current spatial distribution of the archeomagnetic database.

Influence of Mollusk Species on Marine ΔR Determinations

Radiocarbon ages were measured on replicate samples of burnt grain and 5 mollusk species collected from a single sealed layer at an archaeological site (Hornish Point) on the west coast of South Uist, Scotland. The aim was to examine the impact of using different mollusk species on ΔR determinations that are calculated using the paired terrestrial/marine sample approach. The mollusk species examined inhabit a range of environments and utilize a variety of food sources within the intertidal zone. Several authors have suggested that these factors may be responsible for observed variations in the14C activity of mollusk shells that were contemporaneous in a single location. This study found no significant variation in the14C ages of the mollusk species, and consequently, no significant variation in calculated values of ΔR. The implication is that in an area where there are no carboniferous rocks or significant local inputs of freshwater to the surface ocean, any of a range of marine mollusk species can be used in combination with short-lived terrestrial material from the same secure archaeological context to accurately determine a ΔR value for a particular geographic location and period in time.

Eficiência dos dessecantes paraquat e diquat na antecipação da colheita do milho

O uso de dessecantes na cultura do milho pode trazer benefícios para os agricultores, especialmente visando a disponibilização antecipada do solo para implantação de uma nova cultura, assim como o oferecimento antecipado do produto colhido ao mercado. Dentre os dessecantes disponíveis comercialmente, os herbicidas paraquat e diquat merecem destaque. O objetivo deste trabalho foi avaliar a eficiência dos herbicidas paraquat e diquat, aplicados como dessecantes em diversos estádios de desenvolvimento da cultura de milho, sobre parâmetros produtivos e incidência de doenças nos grãos de milho. O ensaio foi conduzido na Embrapa Milho e Sorgo, Sete Lagoas, MG, utilizando-se os seguintes tratamentos: aplicação de paraquat e diquat aos 14 e 7 dias antes e aos 7 dias depois do ponto de maturação fisiológica (MF), assim como na própria MF. Ambos os produtos foram aplicados na dosagem de 400 g ha-1. O cultivar de milho utilizado foi o BRS 3101. Aos 0, 3, 6, 9, 12 e 15 dias após a aplicação dos produtos foram coletados 30 grãos de seis espigas aleatórias, para determinação da umidade dos grãos e peso da matéria seca. Na colheita foram avaliados: altura da planta e da espiga, índice de espigas, produção de grãos e espigas e sanidade dos grãos. Os produtos testados não apresentaram diferenças de eficiência para a maioria dos parâmetros avaliados, embora visualmente tenha sido constatado que o paraquat age mais rapidamente do que o diquat na secagem do tecido foliar verde. Apesar disso, quando se detectou alguma diferença entre os dois produtos químicos, o diquat foi superior ao paraquat. Com relação às épocas de aplicação dos produtos, foi constatado que a aplicação dos dessecantes aos 14 dias antes da MF resultou em redução na produção de grãos, devido à diminuição no peso da matéria seca dos grãos, apesar de ter antecipado em dois dias a MF e em quatro dias a colheita. Esse fato ficou mais bem evidenciado com a aplicação do paraquat. A produção de grãos verificada nos tratamentos testemunhas se igualou à dos melhores tratamentos com os dessecantes. O uso do paraquat resultou em grãos com maior porcentagem de infecção por Fusarium subglutinans, patógeno causador dos grãos ardidos em milho. Com relação à época de aplicação dos dessecantes, 14 dias antes da MF foi a que tornou o milho mais suscetível ao ataque desse fungo.

Experimental Methods for Studying the Combustion of Granular Powders in a Broad Range of Process Parameters

The combustion of granular powders is studied in a broad range of loading densities. The nontraditonal design of manometric bombs and the model ballistic installations on which the conditions close to a real detonation were simulated were used. It was established experimentally that the instability of a shot from a light–gas gun is caused by poor reproducibility of the ignition and combustion of powders fired at a loading density of Δ≲ 0.5 g/cm3. It is shown that the differences between the specific features of gas formation upon combustion of fine tubular and multiperforated powders under conditions of a classical manometric bomb (Δ≤ 0.3 g/cm3) and in a real shot (Δ≥ 0.6 g/cm3) are connected not only with the nonstationary character of combustion, but also with the dependence of the shape of a burning grain (area of the burning surface) on experimental conditions and, in particular, on the loadng density. It is shown that the use of a stepwise dependence of the factor in a geometrical law of combustion allows one to obtain a good agreement between the experimental and calculated pressure curves, including the ignition period, which makes it possible to describe the combustion of combined charges more correctly.

Une sépulture à incinération sur l'oppidum de Mourrel-Ferrat à Olonzac (Hérault) (fin premier âge du Fer - début second âge du Fer)

A cremation was discovered during a programme of trial trenching that aimed to ascertain the chronology of the Mourrel-Ferrat oppidum (Hérault) and to date the walls and embankments. The cremation was found in a pit dug into the gelifracted limestone. In the upper layers of the deposit the following elements were discovered : a handful of burnt human bones, plus splinters of animal bones, a deer bone, burnt grain, an iron knife, a fragment of an massaliete amphorae handle plus some shards of hand-thrown pottery. This discovery could indicate that there was cemetery within the fortifications, thus supplying us with some interesting perspectives vis a vis funerary practices at the end of the early and the beginning of the late Iron Ages.

Characteristic Properties of an End Burning Grain with Smoke Reduced Ferrocene Containing Composite Propellant

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Characteristic Properties of an End Burning Grain with Smoke Reduced Ferrocene Containing Composite Propellant

Characteristic Properties of an End Burning Grain with Smoke Reduced Ferrocene Containing Composite Propellant