Experimental and numerical simulation of effects of CO2/N2 concentration and initial temperature on combustion characteristics of biomass syngas

Biomass syngas is a form of renewable energy with very broad application prospects, and it has different combustion characteristics according to the fuel composition and processing technology of biomass syngas. The influence of combustion composition, diluent and temperature variation on combustion characteristics were studied in this paper. The FFCM-1 mechanism was used to investigate the combustion characteristics of CO/CH₄/H₂ under varied diluents CO₂/N₂ and temperature by using spherical expansion flame method and ANSYS CHEMKIN-PRO. The experimental laminar burning velocity was compared with the simulation results of FFCM-1 mechanism. The results reveal that the experimental data are in good agreement with the simulation results, which are somewhat different under the condition of rich fuel. The laminar burning velocity decreases significantly with the increase of diluent CO₂/N₂, with the effect of diluent CO₂ being more significant. The laminar burning velocity increase dramatically with the increase of initial temperature, and the adiabatic flame temperature also decreases with the increase of diluent. The reduction caused by diluent CO₂ is much larger than that caused by diluent N₂. The change of initial temperature also affects the adiabatic flame temperature, but the range of variation is not as pronounced as that of diluent. Not only was the interaction between the combustion characteristics of CO/CH₄/H₂ under different diluents and temperature changes explored in this paper, but the influence mechanism was also revealed in depth.     

Cyclohexane‐1,3‐dione as a derivatizing agent for the analysis of aldehydes by micelar electrokinetic chromatography with diode array detection

Aldehydes are important compounds in a large number of samples, especially food and beverages. In this work, for the first time, cyclohexane‐1,3‐dione (CHD) was used as a derivatizing reagent aiming aldehyde (formaldehyde, acetaldehyde, propionaldehyde, and valeraldehyde) analysis by MEKC‐DAD. The optimized separation of the derivates was performed using a voltage program (+20 kV, 0–15 min.; +23 kV, 15–17 min.) at a temperature of 26°C, and using as the running buffer a mixture containing 100 mmol/L of sodium dodecyl sulfate and 29 mmol/L of sodium tetraborate at pH 9.2, with maximum absorbance at 260 nm. CHD was compared with two other derivatizing agents: 3‐methyl‐2‐benzothiazolinone hydrazone and phenylhydrazine‐4‐sulfonic acid. The CHD‐aldehyde derivatives were also characterized by LC‐MS. The calibration curves for all aldehydes had r² above 0.999 and LODs ranged from 0.01 to 0.7 mg/L. The optimized methodology was applied in sugar cane brandy (cachaça) samples successfully. CHD showed to be an alternative derivatization reagent due to its stability, aqueous solubility, high selectivity and sensitivity, reduced impurities, and simple preparation steps.     

Investigation on the effect of density ratio on the convergence behavior of partitioned method for fluid–structure interaction simulation

In order to investigate the effect of density ratio of fluid and solid on the convergence behavior of partitioned FSI algorithm, three strong-coupling partitioned algorithms (fixed-point method with a constant under-relaxation parameter, Aitken’s method and Quasi-Newton inverse least squares (QN-ILS) method) have been considered in the context of finite element method. We have employed the incompressible Navier–Stokes equations for a Newtonian fluid domain and the total Lagrangian formulation for a non-linear motion of solid domain. Linear-elastic (hyper-elastic) model has been employed for solid material with small (large) deformation. A pulsatile inlet-flow interacting with a 2D circular channel of linear-elastic material and a pressure wave propagation in a 3D flexible vessel have been simulated. Both linear-elastic and hyper-elastic (Mooney–Rivlin) models have been adopted for the 3D flexible vessel. From the present numerical experiments, we have found that QN-ILS outperforms the others leading to a robust convergence regardless of the density ratio for both linear-elastic and hyper-elastic models. On the other hand, the performances of the fixed-point method with a constant under-relaxation parameter and the Aitken’s method depend strongly on the density ratio, relaxation parameter selected for coupling iteration, and degree of deformation. Although the QN-ILS of this work is still slower than a monolithic method for serial computation, it has an advantage of easier parallelization due to the modularity of the partitioned FSI algorithm.     

基于Retinex理论与概率非局部均值的红外图像增强方法

针对传统红外图像增强算法中细节模糊及过度增强的问题,提出了一种基于Retinex理论与概率非局部均值相结合的红外图像增强方法.首先通过单尺度Retinex方法调整图像中过暗与过亮部分的灰度级;然后利用概率非局部均值对图像进行分解处理得到基本层与细节层,对基本层采用直方图均衡化拉伸对比度,对细节层采用非线性函数进行增强;最后,将不同层次的结果融合得到对比度与细节增强的红外图像.用该方法对多组不同场景的红外图像进行仿真实验,并将其与多种增强方法进行主、客观对比分析,结果表明所提方法在红外图像的细节及对比度增强方面都获得了更好的效果.     

柱面微通道板的制备及其性能研究

针对未来空间天文学应用的超分辨率光谱成像仪器的需求，对低噪声柱面微通道板（MCP）的制备方法及其性能进行了研究. 提出了一种将光学抛光与热成型相结合的新的柱面MCP制备方法，利用不含放射性元素的低噪声MCP玻璃，制备出曲率半径为400mm、尺寸为30mm′46mm、长径比为80:1、通道直径12.5mm、通道间距15mm的柱面MCP，并将其与感应电荷楔条形阳极（WSA）组成光子计数探测器，对其暗计数率、分辨率进行了检测，暗计数率约为0.1counts/cm2×s.