Large Eddy simulations of premixed turbulent combustion

In the past two decades, Large-Eddy Simulation (LES) has become well established for modelling non-reacting flows. However, LES is still undergoing significant development for reacting flows. The most challenging topic in LES of combusting flows is modelling the reaction rate. To this end, several models have been proposed in the literature. Many of the models proposed so far are limited to corrugated flame (CF) regime. However, in many premixed combustion applications both CF and thin reaction zone (TRZ) regimes exist. There is, therefore, a need for accurate and robust physical modelling of the reaction rate across different regimes of premixed flames. In this thesis, a new flame wrinkling model is proposed based on fractal geometry concept requiring the modelling of an inner cut-off scale and fractal dimension. Damk¨ohler s limiting scaling laws are used to infer the cut-off and fractal dimension in limiting regimes. The assumptions made to obtain the fractal dimension in the proposed model are tested by analysing fractal characteristics of several thermochemical and thermo-nuclear direct numerical simulation (DNS) data sets featuring Damk¨ohler numbers. The fractal dimension is found to vary between 2.1 to 2.7 in the thermo-chemical hydrogen air turbulent premixed flames. The thermo-nuclear supernovae flames, which are in distributed regimes of combustion, yield fractal dimension about 2.7. The results for the maximum fractal dimensions are higher than previously reported in the literature and can be explained theoretically by a Reynolds number similarity argument which shows that the limiting value of the fractal dimension at low Damk¨ohler number is 8/3. To assess the performance of the new proposed model and also the models reported in the literature, a priori analysis of two DNS data sets are used. The sub-grid models are assessed using constant coefficient and dynamic coefficient versions using an approximate Germano identity. The effects of filter size on the performance of the models are also investigated. A priori assessments of the models show very good results for the models having power law form for all DNS data and filter sizes. In addition to this, a posteriori tests are conducted to assess these models in a slot Bunsen burner configuration in the TRZ regime. A combined progress variable and level set model has been used to model reaction rate. Chemistry is obtained from tabulated chemistry by solving strained and unstrained flamelets. The comparison of a priori and a posteriori results with the DNS data provides strong support for the validity of the proposed model

SENSIBLE EXPLORATION OF PAPERCRETE WITH DIVERSE RATIOS

A thorough examination on papercrete sampling of dimension 100 × 100 × 100 mm made with various components like sand, fly ash as well as glass fiber was performed after 28 days of air healing. Papercrete is a brand-new building product made with waste, concrete and also water. Papercrete had actually been made use of to construct inexpensive houses without much expertise of its architectural homes. The objective of this research is to get compressive stamina as well as mass thickness of papercrete by doing some test blends of papercrete with various components. From this research study it has actually been observed that the papercrete is a light-weight product and also it could be utilized as an infill product in high structures. Evaluating and also Analysis of the outcome given adequate information to show whether it is feasible to utilize Papercrete concrete as a building and construction product inning accordance with the information's the 14th & 28th day compressive stamina of the proportions 1:1:0.5, 1:1:1, 1:1:1.5 has actually ended up being 1, 0.5, 0.24 & 2.1, 0.98, 0.56 MPa specifically. For the water absorption examination 23.1%, 34.3%, 33.07% specifically for the weight 7.2 kg, 6.6 kg, 6.1 kg specifically and also in addition for the thickness examination 774.193, 709.677, 655.9139 kg/m3 specifically. Contrast in between the examples created was made use of to evaluate if it could be made use of in the future as a building aspects

CUMITHERM®– современная керамика с нулевым расширением и ее применение

Carborundum Universal Limited – Industrial Ceramic (CUMI – IC) Division design, develop, manufacture and supplies technical ceramic products for industrial applications. The applications include wear-resistance, corrosion-resistance, electrical insulation, dielectrics, thermal and thermal shock resistance, ballistic protection etc. CUMI – IC division has recently developed through in-house R&D and launched CUMITHERM® which is a reaction-sintered aluminium titanate (Al2TiO5) products for thermal and thermal shock resistance applications. CUMITHERM® has near-zero/negative coefficient to thermal expansion, non-wettability to molten metal, excellent thermal insulation and very good mechanical and thermo-mechanical properties in this class of material. The mechanical performance improves with increase in temperature and gets double data round 900 °C. The unique properties like dimensional stability over a wide range of temperature and increase in strength with temperature are very rare in the field of material science. The reactions in tered aluminium titanate phases achieved by combining high-purity alumina and titania along with appropriate stabilizing agent and sintering additives in a precision controlled reactions in tering process and engineering a micro-fissures microstructure. Therefore, CUMITHERM® is ideally suited for non-ferrous molten metal handling and conveying applications like molten metal handling, conveying and in cast-house for primary processing of aluminium metals and secondary processing like non-ferrous foundries. The castings pouts and control rods, retainer rings,nozzles, launders, thimbles, dosing tubes, tapping plug and rings, insulation rings, riser tubes, sprue-bushes etc. Are the few example of CUMITHERM® application. CUMI has patent on a high-performance special designed Al2TiO5-tile lined launders products for non-ferrous cast-houses. The key benefits to the user sare (a) longer service life, (b) energy efficiency, (c) increased process reliability, (d) down-time reduction for reduced maintenance and (e) high-quality of process sed metalsКарборундум Юниверсал Лимитед – Подразделение Промышленной Керамики (CUMI – IC) – проектирует, разрабатывает, производит и поставляет продукцию из технической керамики для промышленного применения. В область применения решений данного подразделения входят износостойкие, коррозионно-устойчивые, электроизоляционные, диэлектрические, термоустойчивые и устойчивые к термическим ударам, баллистическая защита и т.д. Подразделение CUMI – IC, благодаря внутреннему отделу разработок, представило CUMITHERM®, являющийся реакционно-спечённым титанатом алюминия (Al2TiO5), применяемый в условиях, требующих термической устойчивости либо устойчивости к термическим ударам. CUMITHERM® обладает околонулевым/отрицательным коэффициентом термического расширения, несмачиваемостью по отношению к расплавленному металлу, отличными теплоизоляционными свойствами, а также очень хорошими механическими и термомеханическими свойствами среди материалов данного класса. Механические характеристики улучшаются при увеличении температуры, удваиваясь при 900 °C. Такие уникальные свойства, как геометрическая стабильность при широком диапазоне температур, а также увеличение прочности с увеличением температуры, очень редки в области материаловедения. Фаза реакционно-спечённого титаната алюминия достигается сочетанием сверхчистого глинозёма и титана при наличии подходящего стабилизирующего агента и спекающих добавок в точно контролируемой реакции процесса спекания, а также микроструктуры, содержащей микротрещины. В связи с этим CUMITHERM® идеально подходит для обращения и транспортировки расплавленных цветных металлов в литейных цехах во время первичной переработки алюминия, как и вторичной переработки, например, в литейных цехах цветных металлов. Сливные носки и регулирующие стержни, фиксаторы, разливочные стаканы, желоба, втулки, дозирующие трубки, выпускающие затворы и кольца, изоляционные кольца, подъёмные трубки, литниковые втулки и т.д. всего лишь малая часть примеров применения CUMITHERM®. CUMI запатентовали специально спроектированную высокопроизводительную литейную продукцию, футерованную плитами на основе Al2TiO5 для литейных цехов цветной металлургии. Ключевыми достоинствами для пользователей станут (а) более высокий срок службы, (б)энергоэффективность, (в) увеличение надёжности процесса, (г) уменьшение времени простоя во время плановых ремонтных работ и (д) высокое качество производимых металло

Mapping the Research Landscape on Poaching: A Decadal Systematic Review

Poaching is a widespread activity that affects wildlife management goals and undermines conservation efforts worldwide. Despite its complexity, poaching is still commonly addressed by researchers as a one-dimensional phenomenon. To deepen the scientific understanding of poaching, we conducted a systematic literature review in the Web of Science and Scopus databases for the last 10 years, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses methodology. We found that most studies were carried out in Africa, although 43% of all articles on poaching were published by researchers from the United States and the United Kingdom. The most studied species are elephants (22%), rhinos (19%), wolves (9%), and bears (6%). Although this study identified a wide range of motives and drivers behind poaching activities, more than half of the analyzed articles do not attempt to provide a deeper understanding of this phenomenon. Its understanding of poaching usually does not go beyond the environmental impact of illegal hunting. Our study’s potential limitations may relate to the focus on exclusively English-language articles and, among them, only those discussing mammal, bird, and reptile species. Our findings indicate that global scientific knowledge on poaching in the last 10 years is biased. There is an imbalance between the developed countries that mostly produce knowledge on poaching (usually from Northern America and Europe) and the developing countries commonly an object of interest. This bias is potentially challenging, as the global scientific knowledge on poaching comes from limited experience based on charismatic species and selective case studies. To overcome this gap and develop a deeper understanding of poaching, the scientific community needs to overcome this bias and address illegal hunting wherever it affects the environment and undermines conservation efforts

CUMITHERM®– современная керамика с нулевым расширением и ее применение

Carborundum Universal Limited – Industrial Ceramic (CUMI – IC) Division design, develop, manufacture and supplies technical ceramic products for industrial applications. The applications include wear-resistance, corrosion-resistance, electrical insulation, dielectrics, thermal and thermal shock resistance, ballistic protection etc. CUMI – IC division has recently developed through in-house R&D and launched CUMITHERM® which is a reaction-sintered aluminium titanate (Al2TiO5) products for thermal and thermal shock resistance applications. CUMITHERM® has near-zero/negative coefficient to thermal expansion, non-wettability to molten metal, excellent thermal insulation and very good mechanical and thermo-mechanical properties in this class of material. The mechanical performance improves with increase in temperature and gets double data round 900 °C. The unique properties like dimensional stability over a wide range of temperature and increase in strength with temperature are very rare in the field of material science. The reactions in tered aluminium titanate phases achieved by combining high-purity alumina and titania along with appropriate stabilizing agent and sintering additives in a precision controlled reactions in tering process and engineering a micro-fissures microstructure. Therefore, CUMITHERM® is ideally suited for non-ferrous molten metal handling and conveying applications like molten metal handling, conveying and in cast-house for primary processing of aluminium metals and secondary processing like non-ferrous foundries. The castings pouts and control rods, retainer rings,nozzles, launders, thimbles, dosing tubes, tapping plug and rings, insulation rings, riser tubes, sprue-bushes etc. Are the few example of CUMITHERM® application. CUMI has patent on a high-performance special designed Al2TiO5-tile lined launders products for non-ferrous cast-houses. The key benefits to the user sare (a) longer service life, (b) energy efficiency, (c) increased process reliability, (d) down-time reduction for reduced maintenance and (e) high-quality of process sed metalsКарборундум Юниверсал Лимитед – Подразделение Промышленной Керамики (CUMI – IC) – проектирует, разрабатывает, производит и поставляет продукцию из технической керамики для промышленного применения. В область применения решений данного подразделения входят износостойкие, коррозионно-устойчивые, электроизоляционные, диэлектрические, термоустойчивые и устойчивые к термическим ударам, баллистическая защита и т.д. Подразделение CUMI – IC, благодаря внутреннему отделу разработок, представило CUMITHERM®, являющийся реакционно-спечённым титанатом алюминия (Al2TiO5), применяемый в условиях, требующих термической устойчивости либо устойчивости к термическим ударам. CUMITHERM® обладает околонулевым/отрицательным коэффициентом термического расширения, несмачиваемостью по отношению к расплавленному металлу, отличными теплоизоляционными свойствами, а также очень хорошими механическими и термомеханическими свойствами среди материалов данного класса. Механические характеристики улучшаются при увеличении температуры, удваиваясь при 900 °C. Такие уникальные свойства, как геометрическая стабильность при широком диапазоне температур, а также увеличение прочности с увеличением температуры, очень редки в области материаловедения. Фаза реакционно-спечённого титаната алюминия достигается сочетанием сверхчистого глинозёма и титана при наличии подходящего стабилизирующего агента и спекающих добавок в точно контролируемой реакции процесса спекания, а также микроструктуры, содержащей микротрещины. В связи с этим CUMITHERM® идеально подходит для обращения и транспортировки расплавленных цветных металлов в литейных цехах во время первичной переработки алюминия, как и вторичной переработки, например, в литейных цехах цветных металлов. Сливные носки и регулирующие стержни, фиксаторы, разливочные стаканы, желоба, втулки, дозирующие трубки, выпускающие затворы и кольца, изоляционные кольца, подъёмные трубки, литниковые втулки и т.д. всего лишь малая часть примеров применения CUMITHERM®. CUMI запатентовали специально спроектированную высокопроизводительную литейную продукцию, футерованную плитами на основе Al2TiO5 для литейных цехов цветной металлургии. Ключевыми достоинствами для пользователей станут (а) более высокий срок службы, (б)энергоэффективность, (в) увеличение надёжности процесса, (г) уменьшение времени простоя во время плановых ремонтных работ и (д) высокое качество производимых металло

On the fractal characteristics of low Damköhler number flames

Knowledge of the fractal properties of premixed flame surfaces can potentially be used to help develop turbulent combustion models. Here, direct numerical simulations of low Damköhler number flames are used to analyse the fractal nature of the flames. Two sets of data are considered: (i) thermochemical hydrogen–air turbulent premixed plane-jet flames with detailed chemistry and (ii) thermonuclear flames in type Ia supernovae. A three-dimensional box counting method is used to investigate fractal dimension of the flame surface, characterising the self similarity of flame fronts. In the premixed flames, the fractal dimension is found to vary in time between 2.1 and 2.7. The supernovae flames in distributed combustion regimes yield fractal dimension about 2.7. The results for the maximum fractal dimensions are higher than previously reported. They are explained theoretically by a Reynolds number similarity argument which posits that the high Reynolds number, low Damköhler number limiting value of the fractal dimension is 8/3. Also tested is Mandelbrot’s fractal additive law which relates the fractal dimension determined in two dimensions, which is typical of experimental measurements, to that in three dimensions. The comparison of the fractal dimension in both two-dimensional and three-dimensional spaces supports the additive law, even though the flames considered do not formally satisfy isotropy. Finally, the inner-cut off is extracted from the hydrogen flames and found to be consistent in order of magnitude with Kolmogorov scaling

Heavy-Oil Surrogate Formulation Based on FT-ICR MS Analysis

Surrogate molecules are commonly employed to represent complex mixtures to predict properties and develop chemical kinetic models. The objective of a surrogate formulation is to emulate the chemical and physical properties of a complex matrix by using either a single molecule or multiple molecules. The proposed surrogate molecule’s chemical kinetic model can be used to simulate the behavior of oil in various scenarios, such as pyrolysis and oxidation. However, creating surrogates for heavy oils demands a meticulous characterization involving numerous chemical analytical techniques, which are not only resource-intensive but also time-consuming, with their interpretation posing challenges. This study introduces a novel approach to formulate surrogate molecules for heavy oils, specifically relying on high-resolution mass spectrometry. This method facilitates the creation of one or more surrogate molecules for residual oils in a semiautomatic manner. The foundation of this methodology lies in the derivation of structure descriptors from FT-ICR MS data. The presented approach is explained in detail and successfully applied to identify both single surrogate molecules and multicomponent surrogate molecules within two residual oils obtained from Saudi Arabia. The results show that the surrogates obtained can effectively approximate the elemental composition and align well with estimated functional groups using nuclear magnetic resonance. Additionally, these surrogate molecules can predict physical properties, such as heating values, for both oils through quantitative structural property calculations. This study is expected to streamline the process of estimating surrogate molecules for heavy oils without the need for multiple analytical techniques. Consequently, this will reduce the time, cost, and subjectivity associated with conventional approaches