Numerical study on laminar burning velocity of ammonia flame with methanol addition

The combustion characteristics of ammonia/methanol mixtures were investigated numerically in this study. Methanol has a dramatic promotive effect on the laminar burning velocity (LBV) of ammonia. Three mechanisms from literature and another four self-developed mechanisms constructed in this study were evaluated using the measured laminar burning velocities of ammonia/methanol mixtures from Wang et al. (Combust.Flame. 2021). Generally, none of the selected mechanisms can precisely predict the measured laminar burning velocities at all conditions. Aiming to develop a simplified and reliable mechanism for ammonia/methanol mixtures, the constructed mechanism utilized NUI Galway mechanism (Combust.Flame. 2016) as methanol sub-mechanism and the Otomo mechanism (Int. J. Hydrogen. Energy. 2018) as ammonia sub-mechanism was optimized and reduced. The reduced mechanism entitled ‘DNO-NH3’, can accurately reproduce the measured laminar burning velocities of ammonia/methanol mixtures under all conditions. A reaction path analysis of the ammonia/methanol mixtures based on the DNO-NH3 mechanism shows that methanol is not directly involved in ammonia oxidation, instead, the produced methyl radicals from methanol oxidization contribute to the dehydrogenation of ammonia. Besides, NO_x emission analysis demonstrates that 60% methanol addition results in the highest NO_x emissions. The most important reactions dominating the NO_x consumption and production are identified in this study.     

Designing amorphous formulations of polyphenols with naringin by spray-drying for enhanced solubility and permeability

Naringin (NAR), a major flavanone (FVA) glycoside, is a component of food mainly obtained from grapefruit. We used NAR as a food additive to improve the solubility and permeability of hydrophobic polyphenols used as supplements in the food industry. The spray-dried particles (SDPs) of NAR alone show an amorphous state with a glass transition temperature (T_g) at 93.2 °C. SDPs of hydrophobic polyphenols, such as flavone (FVO), quercetin (QCT), naringenin (NRG), and resveratrol (RVT) were prepared by adding varying amounts of NAR. All SDPs of hydrophobic polyphenols with added NAR were in an amorphous state with a single T_g, but SDPs of hydrophobic polyphenols without added NAR showed diffraction peaks derived from each crystal. The SDPs with NAR could keep an amorphous state after storage at a high humidity condition for one month, except for SDPs of RVT/NAR. SDPs with NAR enhanced the solubility of hydrophobic polyphenols, especially NRG solubility, which was enhanced more than 9 times compared to NRG crystal. The enhanced solubility resulted in the increased membrane permeability of NRG. The antioxidant effect of the hydrophobic NRG was also enhanced by the synergetic effect of NAR. The findings demonstrated that NAR could be used as a food additive to enhance the solubility and membrane permeability of hydrophobic polyphenols.     

Experimental study of hydrogen explosion in repeated pipe congestion – Part 1: Effects of increase in congestion

Experimental studies were conducted with the objective of gaining a better understanding of the potential explosion hazard consequences that could be associated with a high-pressure leak from a hydrogen vehicle refuelling system. The first part of the study, described in this paper, was a series of experiments designed to establish hydrogen–air explosion overpressures in a well-defined and well understood 3 m × 3 m x 2 m (high) repeated pipe congestion. The results of the experiments are discussed in terms of the conditions leading to the greatest overpressures. It is concluded from the study that stoichiometric ratio in the range of 1.2–1.3 gives highest overpressure. Moreover, it was observed that increasing the congestion from 4-gate to 9-gate congestion leads to significant increase in the overpressure. In addition, it was concluded that, explosion in a hydrogen-air mixture is significantly more severe than the explosion in an ethane-air, methane-air or propane-air mixtures. This is attributed to higher laminar flame speed of hydrogen-air mixtures.     

Low dielectric constant polyimide mixtures fabricated by polyimide matrix and polyimide microsphere fillers

Polyimide microspheres were prepared via non‐aqueous emulsion polymerization by using pyromellitic dianhydride (PMDA) as anhydride monomer and 2,2‐bis(4‐(4‐aminophenoxy)phenyl)propane as amine monomer. The polyimide microspheres were well characterized by Fourier transform infrared spectroscopy, SEM and laser particle size analyzer. They were spherical in shape and monodisperse and their size was 31–33 μm. Polyimide mixtures formed by polyimide microspheres as fillers and polyimide composed of pyromellitic and dianhydride 4,4′‐oxydianiline (ODA) as matrix were investigated with regard to thermal properties, dielectric properties and mechanical properties. With 10%–50% polyimide microspheres in the polyimide mixtures, the dielectric constants were 2.26–2.48 (1 MHz) and the loss tangents were 0.00663–0.00857 (1 MHz), which were both significantly lower than the values for ODA‐PMDA polyimide. The decomposition temperature and glass transition temperature were above 440 and 290 °C. The polyimide mixtures possessed excellent thermal resistance. When the percentage of polyimide microsphere addition was 30%, the polyimide mixtures had the largest tensile strength (128.50 MPa) and elongation at break (9.01%). These results indicate that the polyimide microspheres were used as both low dielectric fillers and reinforcing fillers. © 2020 Society of Chemical Industry     

复合护色剂预处理及不同冻融条件对冷冻双孢蘑菇品质的影响

本实验针对冷冻双孢蘑菇在冻融过程中的品质劣变问题,研究了柠檬酸、L-半胱氨酸、抗坏血酸、异抗坏血酸钠等护色剂对双孢蘑菇褐变的影响,进一步分析了不同冷冻温度(-80、-40、-20℃)和解冻温度(25、4℃)对双孢蘑菇的汁液流失率、质构特征、微观结构、水分含量与分布及过氧化物酶活力等指标的影响。结果表明,复合护色剂配比为3.0 g/L异抗坏血酸钠、1.5 g/L L-半胱氨酸、0.4 g/L抗坏血酸、10 g/L柠檬酸时具有最佳护色效果;-80℃冷冻、4℃解冻的冻融条件下,双孢蘑菇汁液流失率为1.98%,显著低于其他各处理组;水分含量、质构特征值均高于其他冻融条件处理的双孢蘑菇;因此,-80℃冷冻、4℃解冻的冻融条件是较合理的冻融处理方式。本研究为冷冻双孢蘑菇产品的开发及冻融技术提供了参考。     

Experiments and Correlations of the Solubility of γ-DL-Methionine in Binary Solvent Mixtures

Antisolvents increase the supersaturation in the crystallization process which can enhance the product yield. The effect of an antisolvent on the solubility of γ-DL-methionine (γ-DL-met) in aqueous solution was investigated. The solubility of γ-DL-met was measured with various binary solvent mixtures. It improved with higher temperature but decreased with increasing the antisolvent mass fraction. Acetone showed the highest efficiency to reduce the solubility. The solubilities were correlated with the van't Hoff-Jouyban-Acree model and the modified Apelblat-Jouyban-Acree model. Both models fitted to the experimental results with high accuracy. Enthalpy, entropy, and Gibbs free energy of dissolution were determined by van't Hoff analysis. The thermodynamic properties indicated that the dissolution process is endothermic and entropy-driven.     

A miniature triaxial apparatus for investigating the micromechanics of granular soils with in situ X-ray micro-tomography scanning

The development of a miniature triaxial apparatus is presented. In conjunction with an X-ray micro-tomography (termed as X-ray μCT hereafter) facility and advanced image processing techniques, this apparatus can be used for in situ investigation of the micro-scale mechanical behavior of granular soils under shear. The apparatus allows for triaxial testing of a miniature dry sample with a size of \mathrm{8}\hspace{0.17em}\mathrm{mm}\times \mathrm{16}\hspace{0.17em}\mathrm{mm} (diameter \times height). In situ triaxial testing of a 0.4–0.8 mm Leighton Buzzard sand (LBS) under a constant confining pressure of 500 kPa is presented. The evolutions of local porosities (i.e., the porosities of regions associated with individual particles), particle kinematics (i.e., particle translation and particle rotation) of the sample during the shear are quantitatively studied using image processing and analysis techniques. Meanwhile, a novel method is presented to quantify the volumetric strain distribution of the sample based on the results of local porosities and particle tracking. It is found that the sample, with nearly homogenous initial local porosities, starts to exhibit obvious inhomogeneity of local porosities and localization of particle kinematics and volumetric strain around the peak of deviatoric stress. In the post-peak shear stage, large local porosities and volumetric dilation mainly occur in a localized band. The developed triaxial apparatus, in its combined use of X-ray μCT imaging techniques, is a powerful tool to investigate the micro-scale mechanical behavior of granular soils.     

Discrete element method study on hopper discharge behaviors of binary mixtures of nonspherical particles

This study is aimed at unveiling the influence of binary mixtures of nonspherical particles on hopper discharge behavior, which remains poorly understood. The discrete element method (DEM) is employed to simulate seven particle types with aspect ratios between 0 and 2 (namely, a sphere, two ellipsoids, two cylinders, and two cuboids) with the same volume. Seven monodisperse systems and twelve binary-shape mixtures are assessed. For the monodisperse systems, particle shape is the dominant factor dictating discharge rate, compared to other factors like aspect ratio, preferential orientation, and packing. Regarding the binary-shape mixtures, the discharge rates are similar for all twelve mixtures, reflecting a surprising lack of shape effects, which in turn means the negligible impact of solid volume fraction, aspect ratio, and segregation extent. Moreover, collision force is generally negatively correlated with discharge rate.     

铜渣球团还原-熔分工艺试验研究

在实验室条件下使用马弗炉模拟转底炉, 在1400 ℃下焙烧还原由铜渣、还原煤、石灰石等原料制备的含碳球团, 还原熔分生成粒铁和渣, 再通过人工挑选的方式实现渣和粒铁的分离。研究了焙烧时间、碱度、助熔剂种类和用量等因素对还原熔分效果的影响, 结果表明, 在焙烧时间40 min、球团碱度0.42、球团外配助熔剂CaF₂ 2%时, 可获得铁回收率91.71%、TFe品位95.22%、S含量0.37%的高品质粒铁。