Composition Of Mixture Research Articles

Experimental Determination of the Temperature‐Dependent Broadening Effect of Water Vapour on the S‐Branch Raman Linewidths of Nitrogen

ABSTRACTThis work reports the S‐branch Raman linewidths of N2 broadened by H2O vapour at temperatures 870–1900 K determined using the picosecond time‐resolved pure rotational coherent anti‐Stokes Raman scattering (RCARS) approach. The coherent dephasing time constant of nitrogen in a binary mixture was determined from the time trace fitting of the RCARS signal. Raman linewidths of N2 for four different binary mixture compositions up to 20% H2O were obtained for each temperature and the N2‐H2O broadening coefficient was determined. The decay of nitrogen broadened by water vapour is faster than that of self‐broadened nitrogen for all temperatures leading to a higher Raman linewidth. Respectively, the S‐branch Raman linewidths of N2‐H2O deviate significantly in magnitude and slope from the Q‐branch Raman linewidth calculated by the modified energy gap (MEG) law. Therefore, taking into account the broadening effect of water molecules in nitrogen has the potential to significantly improve thermometry and species concentration determination. The determined S‐branch Raman linewidths and broadening coefficient will therefore find application in combustion and reactive flow diagnostics.

Hot Spot Induced Thermal Runaway Map for Polymerization Reactors

AbstractLow‐Density Polyethylene (LDPE) reactors have the potential for rupture because of thermal runaway from auto‐accelerating chemistry. Pockets of unmixed, highly reactive, LDPE constituents, called hot spots, are often generated by conditions within the reactor and are the main source of thermal runaway. Because of this, there is a need to define thresholds of hot spot conditions that produce runaway. Computational Fluid Dynamics is used to study an isolated LDPE sphere with varying initial temperature, initial catalyst concentration, and volume to determine which combinations promote thermal runaway. It is found that increasing both initial temperature and initial catalyst concentration increased thermal runaway likelihood, while, counter‐intuitively, hot spot volume has no effect. An LDPE runaway map is provided to quantify the combinations that result in safe reactor operation. This allows manufacturers to make more informed control actions and to determine safe reactor conditions based on local mixture composition and temperature alone.

Predictive Modeling of the Hydrate Formation Temperature in Highly Pressurized Natural Gas Pipelines

In this study, we aim to develop advanced machine learning regression models for the prediction of hydrate temperature based on the chemical composition of sweet gas mixtures. Data were collected in accordance with the BOTAS Gas Network Code specifications, approved by the Turkish Energy Market Regulatory Authority (EMRA), and generated using DNV GasVLe v3.10 software, which predicts the phase behavior and properties of hydrocarbon-based mixtures under various pressure and temperature conditions. We employed linear regression, decision tree regression, random forest regression, generalized additive models, and artificial neural networks to create prediction models for hydrate formation temperature (HFT). The performance of these models was evaluated using the hold-out cross-validation technique to ensure unbiased results. This study demonstrates the efficacy of ensemble learning methods, particularly random forest with an R2 and Adj. R2 of 0.998, for predicting hydrate formation conditions, thereby enhancing the safety and efficiency of gas transport and processing. This research illustrates the potential of machine learning techniques in advancing the predictive accuracy for hydrate formations in natural gas pipelines and suggests avenues for future optimizations through hybrid modeling approaches.

Ultralow thermal conductivity in Si–Ge nanograin mixtures: A cost-effective granular material for thermoelectric applications

This paper presents a theoretical study of the thermal conductivity of Si–Ge nanograin mixtures using a multiscale computational methodology based on solving the Boltzmann transport equation for phonons with first-principles techniques. A size-dependent correction factor is developed to account for the spatial dependence of the phonon distribution function on nanograin size, with parameters derived from the phonon properties of infinite Si and Ge crystals. This approach makes it possible to accurately calculate the thermal conductivity within a single nanograin, using force constants obtained from first-principles calculations. Thermal energy transport by phonons across grain boundaries is modeled by accounting for phonon transmission by two-phonon processes, weighting specular, and diffuse transmission for each phonon mode as a function of the root-mean-square roughness of the boundary relative to the phonon wavelength. The boundary thermal conductance model, previously validated against experimental data, is implemented using first-principles techniques. This approach excludes specular transmission for phonon modes with specific symmetries while ensuring conservation of the total number of modes in each symmetry class. The study examines the influence of grain size, nanograin mixture composition, temperature, and boundary asperities on the thermal conductivity of nanograin mixtures.

Mathematical Modelling of Tensile Mechanical Behavior of a Bio-Composite Based on Polybutylene-Succinate and Brewer Spent Grains

A model based on the fitting of stress–strain data by tensile tests of bio-composites made of a bioplastic (polybutylene succinate (PBS)) and brewer spent grain filler (BSGF) is developed. Experimental tests were performed for various concentrations of BSGF in the range from 2% to 30%. The model is suitable for describing the elastic–plastic behavior of these materials in terms of two mechanical parameters, tensile stress and tensile stiffness (or Young’s modulus), depending on the filler concentration. The mechanical characteristics, derived from the fit parameters, show good agreement with the experimental data. The mathematical model used here could be an important aid for the experimentation and manufacturing process as it allows the prediction of the mechanical tensile parameters of a mixture with different filler concentrations, avoiding the long and complex preparation cycle of bio-composites, as well as the specific mechanical tests. The physical properties required by the objects created with the PBS–BSGF bio-composite by the partners/stakeholders of the research project co-financing this research can be quite different; therefore, a mathematical model that predicts some of the mechanical properties in terms of the mixture composition may be useful to speed up the selection of the required amount of BSGF in the mixture.

Determination of steady-state for continuous powder mixing: Analysis of mixture properties and signal processing

Continuous powder mixing offers many advantages over batch processes, but its industrial implementation requires control of transient phases due to startup or variations in operating conditions. Detecting the steady-state by observing the mixture properties, obtained through in-line analysis of the mixture composition, is challenging due to the significant fluctuations in these properties. However, there is no quantitative method for identifying the steady-state for continuous powder mixing. We therefore propose in this work a methodology for steady-state detection by comparing several methods of mixture property analysis and signal processing. We show that conventional methods of mixture property analysis cannot reliably and accurately detect steady-state. We conclude that the best methodology is to perform signal processing on the content of the key component in the mixture. To do this, the signal of the content of the key component is first smoothed by the Savitzky-Golay filter. Then, the standard deviation of the filtered signal is compared with a tuning parameter to detect the beginning of steady-state. This method could be used to determine the mixing conditions leading to the smallest startup time, hence avoiding costly waste.

A Carbon Capture and Utilization Process for the Production of Solid Carbon Materials from Atmospheric CO2 - Part 2: Carbon Characterization.

This article is the second part of a study reporting the results of a novel carbon capture and utilization (CCU) process, which converts atmospheric CO2 into solid carbon materials. The CCU process combines direct air capture (DAC) with catalytic methanation, which is then followed by methane pyrolysis in a reactor filled with liquid tin. While Part 1 discussed the performance of the overall process and individual process steps regarding conversions and yields, Part 2 characterizes the solid carbon products obtained under various synthesis conditions. The effects of the pyrolysis temperature and the composition of the gas mixture from the methanation step on the solid carbon product are analyzed. Carbon powder is synthesized from methane with either H2 or CO2 as most important impurity. Carbon samples are characterized using SEM, TEM, Raman spectroscopy, XPS and XRD analysis. Very thin, disordered carbon flakes, soot aggregates and large carbon onions are identified as the main solid products of the process. Their formation mechanisms in the liquid metal-filled pyrolysis reactor are discussed.

Flame Speed Measurements of Ammonia-Hydrogen Mixtures for Gas-Turbines

Abstract Ammonia (NH3) is a promising sustainable fuel, as it has historically been shown to provide high energy potential and zero carbon emission. As a hydrogen (H2) carrier, NH3 serves as a possible solution to the U.S. Department of Energy?s Hydrogen Program Plan by providing efficient H2 storage and conservation capabilities. As a result, applied turbine-combustion research of NH3 and H2 fuel has been conducted to identify combustion performance parameters that aid in the design of sustainable turbomachinery. One of these key combustion parameters is the laminar burning speed (LBS). While abundant literature exists on the combustion of NH3 and H2 fuels, there is insufficient evidence in high pressure environments to provide a comprehensive understanding of NH3 and H2 combustion phenomena in turbine combustor settings. The effect of H2 addition to NH3 fuel was observed by comparing the LBS for various NH3-H2 mixture compositions. Experimental results revealed increased LBS values for H2 enriched NH3, with the maximum LBS occurring at stoichiometry. The experimental data were accurately predicted by the UCF NH3-H2 mechanism developed for this investigation, while NUI 1.1 simulations overestimated recorded LBS data by a significant margin. This study demonstrates and quantifies the enhancing effect of H2 addition to NH3 fuels via LBS and strengthens the literature surrounding NH3-H2 combustion reactions for future work.

Investigation of Ammonia/Hydrogen Mixtures and Pilot-Split Strategies in a Laboratory-Scale Radial Swirl Combustor

Abstract The transition to a decarbonized energy future relies on identifying the most suitable alternative fuels that can meet the needs of various energy sectors. While both ammonia and hydrogen are zero-carbon energy vectors, their physical properties and burning characteristics sit on either side of that of natural gas. Hence, mixtures of ammonia and hydrogen are being increasingly looked at as having the potential to fuel current energy systems without requiring significant combustor redesign. However, the combustion characteristics and operation limits for different ammonia/hydrogen mixtures still need to be evaluated. For gas turbine applications in particular, the effect of ammonia/hydrogen mixture composition and operating condition on flame behavior and stability is not well understood. The current work was carried out in a laboratory scale, radial swirl-stabilized turbulent combustor. A systematic study of two ammonia/hydrogen blend ratios (70:30 and 80:20 by volume) and a range of equivalence ratios were tested for different pilot-split ratios, to understand the effect on flame shape, stability and dynamics. Time-resolved pressure and integrated heat release fluctuations were measured to evaluate combustor dynamics, and NH2* chemiluminescence flame images were captured to understand spatial differences in flame structure. When comparing blend ratios, differences were observed in flame macrostructures and combustor dynamics, which could be largely attributed to the considerable difference in the laminar flame speeds of the blends. The addition of pilot generally improved the stability and lean operation for both blend ratios.

Study of patterns and mechanisms of combustion of powdered and granulated T-C-B system

Experimental studies of the combustion patterns of the ternary system (100 – x)(Ti + C) – x(Ti + 2B) of bulk density in powder and granular form used for the synthesis of composite ceramics TiC–TiB2 were carried out. The study shows that the dependence of the powder mixture combustion rate on the Ti + 2B content has a non-monotonic character, which is associated with the influence of impurity gas release on the combustion process. By removing the influence of impurity gas by granulation, a monotonic dependence with two characteristic sections was obtained. For the granulated mixture, an increase in the Ti + 2B content 60 wt. % leads to a change from the conductive combustion mode to the convective one, accompanied by a sharp increase in the combustion rate. For the conductive combustion mode, the combustion rate of the substance inside the granule and the combustion transfer time from the granule to the granule were determined, which allowed us to estimate the inhibitory effect of impurity gas release on the combustion rate of powder mixtures of different composition. For the convective combustion mode, it was shown that a decrease in the content of the gasifying additive in the mixture (granulation with ethyl alcohol) led to an unexpected result: an increase in the combustion rate of the mixture. For compositions with (Ti + 2B) 60 wt. % the combustion rate with counter filtration of impurity gases was determined for the first time, which made it possible to estimate the front rate increase according to the filtration combustion theory. According to XRD results, the combustion products of all compositions contain only two main phases TiC and TiB2.

Metal-organic frameworks with a sulfur-rich heterocycle: synthesis, gas adsorption properties, and metal exchange.

Three new three-dimensional (3D) metal-organic frameworks [M2(ttdc)2(dabco)] (M = Zn(II), 1-Zn; Cu(II), 1-Cu; and Zn/Cu, 1-ZnCu) based on thieno[3,2-b]thiophene-2,5-dicarboxylate (ttdc2-) were synthesized and characterized by a combination of physicochemical methods (single crystal X-ray diffraction, powder X-ray diffraction, chemical and thermogravimetric analyses and IR spectroscopy). 1-Cu demonstrated permanent porosity (Vpore = 0.790 cm3 g-1 and SBET = 1725 m2 g-1) and significant CO2, CH4, C2H2, C2H4 and C2H6 gas uptakes under ambient conditions. The adsorption selectivities for gas mixtures, calculated by IAST, were 10.8 (10.7), 14.6 (9.4), 1.7 (1.6) and 1.5 (1.6) for the equimolar gas mixture compositions CO2/N2, C2H6/CH4, C2H6/C2H4 and C2H6/C2H2 at 1 bar and 273 K (298 K), respectively. The mixed-metal compound 1-ZnCu was prepared by a crystal-to-crystal ion exchange metathesis reaction from 1-Zn with a 52% degree of ion substitution, confirmed by energy-dispersive X-ray spectroscopy, optical microscopy and single crystal X-ray diffraction analysis.

Mathematical thermo‐mechanical analysis on flame‐solid interaction: Steady laminar stagnation flow flame stabilized at a plane wall coupled with thermo‐elasticity model

AbstractA laminar stagnation flow flame stabilized at a plane wall is theoretically analyzed, coupled with a thermo‐elasticity model in the wall. Mathematical models for both the flame and the wall will be proposed, and corresponding analytical solutions based on their dimensionless forms will be obtained. The mathematical analysis of this flame‐solid interaction primarily focuses on the effect of the flame on combustion‐induced thermo‐mechanical stresses and the influence of wall material on flame properties such as flame temperature and stability against extinction. A sensitivity analysis is further performed to examine how thermo‐mechanical stress inside the wall is affected by changes in other combustion conditions (e.g., mixture composition, flame stretch rate). This study offers valuable insights into understanding the interaction between flames and solids, a relationship crucial in engineering applications such as the interaction between combustion processes and blades within gas turbine machinery.

Thermal Runaway of Na‐ion Batteries with Na3V2O2(PO4)2F Cathodes

The metal‐ion battery manufacturing growth rates increase attention to the safety issues. For promising sodium‐ion batteries, this topic has been studied in much less detail than for the lithium‐ion ones. Here, we explored the thermal runaway process of Na‐ion pouch cells with the Na3V2O2(PO4)2F (NVOPF)‐based cathode. The thermal runaway onset temperature for such cells is noticeably higher than that for the NMC‐based LIBs. We show that thermal runaway is triggered by the anode and the separator decomposition rather than by the processes at the cathode. The composition of the gas mixture released during thermal runaway process is similar to that for Li‐ion batteries. The results suggest that sodium‐ion batteries based on polyanionic cathodes can pave the way to safer metal‐ion energy storage technologies.

An Effective Method for Reproducing the Flow of a Gas-Liquid Mixture Using a Flow Standard

The appearance on the market of measuring equipment of multiphase flowmeters used in the oil and gas industry to measure the amount of extracted hydrocarbons directly at wells without preliminary separation and performing the function of operational accounting raised the question of their metrological support in accordance with the requirements of regulatory documents of the sphere of state regulation in this field of measurements. His decision was to create a reference base, the basis of which was the State primary special standard for units of mass flow of gas-liquid mixtures GET 195-2011 and a verification scheme for measuring multiphase flow rates, regulated by GOST 8.637-2013. When transmitting units of volume and mass flow of a multiphase mixture with the required accuracy, the main problem is the difficulty of reproducing and maintaining stability of several flow parameters at once – mass flow and content of liquid components (water and oil simulator) and volume flow of the gas phase. It should also be borne in mind that test programs for the purpose of approving the type of multiphase flow measuring instruments, as well as verification and calibration methods, provide for changing the modes of reproduction of a gas-liquid mixture, covering the measurement ranges of multiphase flowmeters. Such standards used in practice represent a very complex measuring system consisting of storage tanks for components, supply pumping and compressor units, control equipment, mixers and separators, measuring instruments for the physical parameters of multiphase flow components and an automated control system. Given the high cost of multiphase standards, when creating them, effective methods and methods should be used to reproduce the flow of a multiphase mixture with specified parameters, as well as to make a fairly rapid transition to the next mode provided by the program or methodology, which will reduce the time and production costs for the procedure of transferring units of measurement from the standard to the working measuring instrument. This article describes a method for reproducing the flow rate of a gas-liquid mixture according to the original technological scheme introduced during the development of the 1st category standard. Constructive solutions are presented that increase the efficiency of the liquid component separation apparatus to increase the dosing accuracy, as well as expand the range of reproduction of the flow rate and parameters of the multiphase flow, ensuring the consistency of the composition of the liquid mixture at a given regime. An original rational method of compressing and maintaining the pressure of the gas phase is described, which allows you to quickly switch to the next mode, confirmed by the results of experimental studies of the standard.

Oxidation of Geraniol on Vermiculite—The Influence of Selected Parameters on the Oxidation Process

Geraniol is a compound belonging to the group of monoterpenes that finds many applications in organic syntheses, medicine and cosmetics. The following properties of geraniol and its derivatives are of particular interest in medicine: its anti-inflammatory, antioxidant, antimicrobial and anticancer effects. The geraniol oxidation process was carried out using a mineral of natural origin—vermiculite. Vermiculite is a catalyst that perfectly fits into modern trends in the organic industry, where the aim is to use cheap, renewable and relatively easily available catalytic materials (vermiculite is found on continents including Africa, North America, South America, Australia and Asia). Preliminary studies on the oxidation process of geraniol on vermiculite was carried out in a glass apparatus using molecular oxygen supplied by means of a bubbler and magnetic stirrer with a heating function. During the oxidation process of geraniol on vermiculite, the influence of the following parameters was examined: the temperature, amount of catalyst and reaction time. The main parameters of the process, on the basis of which the most favorable process conditions were selected, were the selectivity of the transformation to 2,3-epoxygeraniol, citral and 2,3-epoxycitral, and the conversion of geraniol. The composition of the post-reaction mixtures was determined qualitatively and quantitatively using the gas chromatography method. In addition, vermiculite was subjected to instrumental tests, such as XRD, SEM, EDX, FTIR and UV-VIS. Moreover, the specific surface area, pore volume and pore volume distribution were estimated on the basis of N2 sorption at −196 °C and also the acid-site concentration in vermiculite was established.

Lattice Boltzmann Model for Rarefied Gaseous Mixture Flows in Three-Dimensional Porous Media Including Knudsen Diffusion

Numerical modeling of gas flows in rarefied regimes is crucial in understanding fluid behavior in microscale applications. Rarefied regimes are characterized by a decrease in molecular collisions, and they lead to unusual phenomena such as gas phase separation, which is not acknowledged in hydrodynamic equations. In this work, numerical investigation of miscible gaseous mixtures in the rarefied regime is performed using a modified lattice Boltzmann model. Slip boundary conditions are adapted to arbitrary geometries. A ray-tracing algorithm-based wall function is implemented to model the non-equilibrium effects in the transition flow regime. The molecular free flow defined by the Knudsen diffusion coefficient is integrated through an effective and asymmetrical binary diffusion coefficient. The numerical model is validated with mass flow measurements through microchannels of different cross-section shapes from the near-continuum to the transition regimes, and gas phase separation is studied within a staggered arrangement of spheres. The influence of porosity and mixture composition on the gas separation effect are analyzed. Numerical results highlight the increase in the degree of gas phase separation with the rarefaction rate and the molecular mass ratio. The various simulations also indicate that geometrical features in porous media have a greater impact on gaseous mixtures’ effective permeability at highly rarefied regimes. Finally, a permeability enhancement factor based on the lightest species of the gaseous mixture is derived.

Development and Manufacturing Method of Electrodes for a High Temperature Oxygen Sensor

The article discusses the use of zirconium dioxide stabilized with yttria as an electrolyte for the formation of a high-temperature ceramic oxygen concentration sensor. The fundamental possibility of using such a material is due to the high electrical conductivity caused by the mobility of oxygen ions in the vacancies of the solid electrolyte. The operating principle of such a sensor as an electrochemical concentration element is discussed. It has been shown that the use of such sensors is relevant for various industries (including chemical, metallurgical, oil and gas, energy and others). Options for forming electrodes of an electrochemical sensor using various materials and deposition methods are considered. A method for forming a platinum coating using a chemical method using isopropyl alcohol and subsequent pyrolysis was tested. It has been experimentally shown that the chemical method is applicable for the formation of electrodes of an electrochemical sensor. The electrical characteristics of the resulting coatings were measured. The optimal composition of the reaction mixture and the required number of layers to create a stable operating electrochemical sensor have been determined. The dependence of the potential of the formed electrochemical sensor from stabilized zirconium oxide on oxygen concentration in a wide temperature range has been studied. It has been shown that when using a scheme of sequential transformations, hydrolysis of platinum tetrachloride - deposition on a substrate - reductive pyrolysis, it is possible to obtain a high-quality conductive coating for the formation of gas sensor electrodes. The optimal composition of the reaction mixture for the formation of platinum electrodes has been selected. The optimal number of layers was determined to ensure the required level of electrical conductivity of the electrodes. It has been shown that an electrochemical element based on zirconium dioxide and platinum electrodes, formed according to the scheme developed in this work, can be used as a high-temperature oxygen sensor.

Response of cool‐season turfgrass monocultures and two‐way mixtures to sequential acute drought periods

AbstractTurfgrass seeds are often sold as mixtures of several species to increase the probability of positive responses toward abiotic and biotic stresses, a response to drought being one of these. Several species of turfgrass are already thought to be better suited for drought, such as hard fescue (Festuca brevipila Tracey) and tall fescue [Schedonorus arundinaceus (Schreb.) Dumort]. However, little is known about the benefit of these species in mixtures with drought‐intolerant and/or drought‐avoiding species during drought. Understanding species mixture composition during establishment, before and after drought stress periods, could help develop more resilient mixtures for this stress condition. We compared monocultures and mixtures of hard fescue, Kentucky bluegrass (Poa pratensis L.), and perennial ryegrass (Lolium perenne L.) during sequential short drought and recovery periods in controlled conditions. We observed that the composition of most mixtures remained similar during drought and recovery periods; however, perennial ryegrass was often less prevalent after drought stress. We found that hard fescue monocultures had better green leaf coverage than Kentucky bluegrass and perennial ryegrass during drought stress. However, the presence of hard fescue in mixtures was not an indicator of greater drought tolerance, and variable fluorescence to maximal fluorescence data indicated that hard fescue was just as physiologically stressed as perennial ryegrass and Kentucky bluegrass during the drought periods. These results indicate that while hard fescue seems visually drought tolerant, it is still physiologically stressed and improved drought tolerance could be achieved through focusing on physiological indicators of stress in this species rather than visual indicators.

Domain growth kinetics in active binary mixtures.

We study motility-induced phase separation in symmetric and asymmetric active binary mixtures. We start with the coarse-grained run-and-tumble bacterial model that provides evolution equations for the density fields ρi(r⃗,t). Next, we study the phase separation dynamics by solving the evolution equations using the Euler discretization technique. We characterize the morphology of domains by calculating the equal-time correlation function C(r, t) and the structure factor S(k, t), both of which show dynamical scaling. The form of the scaling functions depends on the mixture composition and the relative activity of the species, Δ. For k → ∞, S(k, t) follows Porod's law: S(k, t) ∼ k-(d+1) and the average domain size L(t) shows a diffusive growth as L(t) ∼ t1/3 for all mixtures.

Unraveling the Source of Self-Induced Diastereomeric Anisochronism in Chiral Dipeptides.

Mastering of analytical methods for accurate quantitative determinations of enantiomeric excess is a crucial aspect in asymmetric catalysis, chiral synthesis, and pharmaceutical applications. In this context, the phenomenon of Self-Induced Diastereomeric Anisochronism (SIDA) can be exploited in NMR spectroscopy for accurate determinations of enantiomeric composition, without using a chiral auxiliary that could interfere with the spectroscopic investigation. This phenomenon can be particularly useful for improving the quantitative analysis of mixtures with low enantiomeric excesses, where direct integration of signals can be tricky. Here, we describe a novel analysis protocol to correctly determine the enantiomeric composition of scalemic mixtures and investigate the thermodynamic and stereochemical features at the basis of SIDA. Dipeptide derivatives were chosen as substrates for this study, given their central role in drug design. By integrating the experiments with a conformational stochastic search that includes entropic contributions, we provide valuable information on the dimerization thermodynamics, the nature of non-covalent interactions leading to self-association, and the differences in the chemical environment responsible for the anisochronism, highlighting the importance of different stereochemical arrangement and tight association for the distinction between homochiral and heterochiral adducts. An important role played by the counterion was pointed out by computational studies.