Development and Fidelity Evaluation of a Skeletal Ethylene Mechanism under Scramjet-Relevant Conditions

As one of the major short chain hydrocarbons resulting from the cracking process, ethylene is often used as a surrogate for cracked kerosene. In this study, a skeletal mechanism of ethylene was developed under the typical working conditions of scramjet combustors. The skeletal mechanism was reduced from a fully verified detailed mechanism under the desired working conditions. An integrated reducing method containing directed relation graph with error propagation method (DRGEP), sensitivity analysis (SA), and computational singular perturbation (CSP) was employed to obtain three skeletal mechanisms. A three-level fidelity validation of the skeletal mechanisms respectively comparing the kinetic properties, the global combustor performance, and the detailed flame structure was proposed to comprehensively evaluate the skeletal mechanisms. In the first-level fidelity validation, the three skeletal mechanisms all show good agreement with the detailed one in the autoignition delay and laminar flame speed over a wide range of working conditions. Then in the second-level fidelity validation, the smallest mechanism consisting of 24 species and 86 reactions (24S/86R) was further validated through incorporating with the large eddy simulation of a realistic scramjet combustor. Comparisons with the experimental data and the predictions by the detailed mechanism show that the global combustor performance (e.g., pressure, Mach number, and combustion efficiency) was accurately predicted by the 24S/86R mechanism. In the third-level fidelity evaluation, the flame structure characterized by the distribution of CO, OH, and heat release rate was analyzed through comparing the predictions by the 24S/86R mechanism with those by the detailed one during which the insufficiency of the skeletal mechanism was also recognized

Numerical Investigation on Flame Stabilization in DLR Hydrogen Supersonic Combustor with Strut Injection

<p>Flame stabilization in the DLR hydrogen supersonic combustor with strut injection was numerically investigated by using an in-house large eddy simulation code developed on the OpenFoam platform. To facilitate the comparison and analysis of various hydrogen oxidation mechanisms with different levels of mechanism reduction, the proposed 2D calculation model was validated against both the 3D simulation and the experimental data. The results show that the 2D model can capture the DLR flow and combustion characteristics with satisfactorily quantitative accuracy and significantly less computational load. By virtue of the flow visualization and the analyses of species evolution and heat release, the supersonic combustion in the DLR combustor can be divided into three stages along the streamwise direction: the induction stage where ignition occurs and active radicals are produced, the transition stage through which radicals are advected to the downstream, and the intense combustion stage where most heat release occurs. Furthermore, the sensitivity analysis of key reaction steps identifies the important role of chain carrying and heat release reactions in numerically reproducing the three-stage combustion stabilization mode in the DLR combustor.</p

Cytokines in human milk from Chinese women during day 3, 10, 30, and 90 after parturition (n = 24).

<p>Cytokines in human milk from Chinese women during day 3, 10, 30, and 90 after parturition (n = 24).</p

Positive association between levels of S100B and BDNF in human milk.

<p>The solid line represents the predicted regression line determined from repeated-measures analysis of S100B and BDNF concentrations 3 month after parturition. n = 24, P = 0.037<0.05.</p

Western blot analysis of BDNF and GDNF in human milk.

<p><b>A:</b> BDNF band at approximately 27 kDa. <b>B:</b> GDNF band at approximately 20 kDa.</p

Cytokines in the human milk from Chinese women during day 3, 10, and 30 after parturition (n = 42).

<p>*number of donors equal to 40.</p

S100B levels in human milk were closely correlated with BMI.

<p>The solid line represents the predicted regression line determined from measures analysis of human milk collected 3 days after birth. Pearson correlation coefficient (<i>r</i>) was 0.335. <i>P</i><0.05. n = 42.</p

Assignment of the main vibrational modes.(C_HCl:0.1mol/L,50mL).

<p>Assignment of the main vibrational modes.(C_HCl:0.1mol/L,50mL).</p

Selective adsorption experiments of REEs: (a) single solution, (b) mixed solution.

<p>Selective adsorption experiments of REEs: (a) single solution, (b) mixed solution.</p

Adsorption of Rare Earths(Ⅲ) Using an Efficient Sodium Alginate Hydrogel Cross-Linked with Poly-γ-Glutamate

<div><p>With the exploitation of rare earth ore, more and more REEs came into groundwater. This was a waste of resources and could be harmful to the organisms. This study aimed to find an efficient adsorption material to mitigate the above issue. Through doping sodium alginate (SA) with poly-γ-glutamate (PGA), an immobilized gel particle material was produced. The composite exhibited excellent capacity for adsorbing rare earth elements (REEs). The amount of La³⁺ adsorbed on the SA-PGA gel particles reached approximately 163.93 mg/g compared to the 81.97 mg/g adsorbed on SA alone. The factors that potentially affected the adsorption efficiency of the SA-PGA composite, including the initial concentration of REEs, the adsorbent dosage, and the pH of the solution, were investigated. 15 types of REEs in single and mixed aqueous solutions were used to explore the selective adsorption of REEs on gel particles. Scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy analyses of the SA and SA-PGA gel beads suggested that the carboxyl groups in the composite might play a key role in the adsorption process and the morphology of SA-PGA changed from the compact structure of SA to a porous structure after doping PGA. The kinetics and thermodynamics of the adsorption of REEs were well fit with the pseudo-second-order equation and the Langmuir adsorption isotherm model, respectively. It appears that SA-PGA is useful for recycling REEs from wastewater.</p></div