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排序方式: 共有382条查询结果,搜索用时 15 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(9):6377-6387
This work is focused on the explosion characteristics of premixed gas containing different volume fractions of hydrogen in a narrow channel (1000 mm × 50 mm × 10 mm) under the circumstance of stoichiometric ratio. The ignition positions were set in the closed end and the middle of the pipeline respectively. The results showed that when the gas was ignited at the pipeline closed end, the propagating flame was tulip structure for different premixed gas. When the hydrogen volume fraction was less than 40%, the flame propagation speed increased significantly with the rise of hydrogen volume fraction, and the overpressure peak also appeared obviously in advance. However, when the volume fraction of hydrogen was more than 40%, the increase of flame propagation speed and the overpressure peak occurrence time varied slightly. Furthermore, when the ignition position was placed in the middle of the pipeline, the flame propagation speed propagating to the opening end was much faster than that propagating to the closing end, and there was no tulip shape when the flame propagates to the opening end. The flame propagating to the closed end appeared tulip shape under the influence of airflow, and high-frequency flame oscillation occurred during the propagation. This work shows that the hydrogen volume fraction and ignition position significantly affected the flame structure, flame front speed, and explosion overpressure. 相似文献
2.
Collocation methods are developed for the solution of some differential equation models for transport phenomena problems in one-and two-dimensions in co-axial annuli of spherical and cylindrical shapes. General formulae are developed to obtain orthogonal polynomials over an arbitrary interval using two types of weighting functions. The convergence and accuracy of the methods are demonstrated using two test problems, i.e., calculation of effectiveness factors in (a) a spherical pellet with peripherally deposited catalyst and (b) a Raschig ring type cylindrical catalyst pellet. Comparisons of results obtained from the present methods with analytic solutions for the first-order reactions indicate good agreement. Numerical solutions are also obtained for the second-and the third-order reactions for which analytic solutions are not available. Results obtained in terms of a new Thiele modulus involving the ratio of volume of peripherally deposited part of catalyst to exterior surface area indicate that this normalization brings effectiveness factor versus Thiele modulus curves close together for co-axial spherical and long cylindrical pellets, as it does for these geometries without the inner co-axial portion. 相似文献
3.
热轧窄带钢仿真系统及其应用 总被引:2,自引:0,他引:2
为适应窄带企业的可持续发展,成功开发出热轧窄带钢仿真系统工业软件。该软件基本涵盖了当前窄带生产中所涉及的诸如轧制负荷、尺寸精度、组织性能等主要技术问题,其中对窄带钢轧制压力的计算首次考虑了奥氏体再结晶软化程度的影响,使轧机负荷的预报精度明显提高;对轧制力矩的计算考虑了变形区几何参数对力臂系数的影响,使电机负荷的预报与实际更为接近。实际应用表明,对带钢头尾厚度差的预报以及给出的辊缝预设值均与现场实测非常接近,这对控制带钢的通条尺寸、提高窄带产品精度具有重要意义;对带钢轧后组织性能的预报与实测基本相符,这对改善窄带产品的组织性能具有重要参考价值。 相似文献
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大港减渣窄馏分族组成及结构参数 总被引:3,自引:0,他引:3
石油渣油的组成复杂,其合理利用应以充分了解其性质结构为基础。采用超临界流体精密分离(SCF)的方法,将大港渣油分离为11个窄馏分,通过对窄馏分的组成分布、化学结构研究,探讨渣油溶剂脱沥青的最佳方案。结果表明:随窄馏分收率的提高,饱和分逐渐降低,芳香分和胶质逐渐增加,当窄馏分的收率达50%以后,这种变化趋势加快。残炭和重金属的分布规律相似,收率达50%以后增加幅度变大。对各窄馏分平均分子结构参数的研究表明,平均分子中的总碳数和总环数的分布随收率的增大而增加,说明超临界流体对各组分的溶解是由非极性至极性、由小分子至大分子、由少环至多环和稠环的顺序进行的,这与各窄馏分的平均分子质量分布及碳氢原子比分布的规律一致。因此,若溶剂脱沥青以获得重油催化裂化原料为目的时,则适宜的萃取率应在46%~50%左右,此时的DAO不但具有较高的裂解活性,且残炭质量分数仅为2.65%,重金属质量分数为3.48μg/g,符合重油催化裂化对进料的要求。 相似文献
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基于窄带水平集的曲线演化与左心室MRI图像分割 总被引:2,自引:1,他引:2
文章研究了基于窄带水平集的曲线演化方法并应用于心脏的MRI图像分割。分析了窄带的生成技术,提出了基于模板的距离函数生成方法;针对MRI图像的特点,给出了一种分割MRI图像的水平集速度函数,以处理图像中出现的区域灰度不一致性以及弱边界现象。MRI图像的分割实验证明了该文算法的有效性。 相似文献
9.
A host material with high triplet energy based on dibenzofuran and triphenylamine interconnected through diphenylmethylene linkage was synthesized and photophysical properties of the host material were investigated. A high triplet energy of 2.90 eV was obtained due to complete separation of an electron donating triphenylamine and accepting dibenzofuran by diphenylmethylene linkage. It was found out that intermolecular charge transfer dominated the light emission of the host material. 相似文献
10.
A study of port plug distortion resulting from narrow gap combined GTAW & SMAW and Electron Beam Welding was carried out. Thermomechanical finite element analysis of port plug becomes virtually impossible because of the requirement of huge number of nodes and elements. Hence an analysis method based on the concept of inherent strain was used in this work. The computational time required was about 40-50 min only in a Core (TM) 2 Duo, 2.66 GHz computer with 2 GB RAM, which otherwise was not possible with other conventional computation techniques. As was expected the overall distortion due to EB welding was found to be less compared to that of narrow gap GTAW & SMAW. 相似文献