RP-3航空煤油高温骨架机理构建及验证

依据RP-3航空煤油的成分,考虑平均分子量及碳氢摩尔比等性质,本文提出其三组分替代燃料模型,其中正癸烷74.24%、1,3,5-三甲基环己烷14.11%和正丙基苯11.65%(质量分数)。采用机理生成程序ReaxGen得到详细化学反应机理;采用机理简化程序ReaxRed,运用直接关系图法与主成分分析法获得高温骨架机理(79物种,311反应)。该机理针对多个工况进行了点火延迟时间与层流火焰速度的验证,能较好地预测实验结果。路径分析结果表明高温下替代燃料通过氢提取反应、单分子裂解反应及β-断键反应消耗。敏感性分析表明高温点火过程由多种小分子自由基(H、CHO、C2H3等)的氧化及分解反应和大分子燃料的氢提取反应控制;影响火焰传播过程的关键反应来源于C0-C3的小分子核心机理。本文所提出的这个尺寸较小但精度较高的骨架机理可用于发动机燃烧过程的高保真数值模拟。     

Vaporisation characteristics of methanol,ethanol and heptane droplets in opposed stagnation flow at low temperature and pressure

A computational model is developed and applied to study the vaporisation behaviour of three liquid fuels. This fundamental study is motivated by a need to understand how the performance of direct-injection-spark-ignition (DISI) engines may be affected by changes in fuel composition, especially alcohols. Currently, most DISI engines are designed for homogeneous-charge combustion, where the in-cylinder fuel injection, vaporisation and mixing is accomplished during the intake and early in the compression process. Thus the temperature and pressure are low, compared to post-compression conditions. The two-phase axisymmetric model is based upon an ideal opposed stagnation flow field. Liquid droplets are carried in one air stream that is met by an opposed air flow. Because of stagnation-flow similarity, the mathematical model can be represented as a one-dimensional boundary-value problem. Results show significant differences between methanol, ethanol and heptane fuels, which have potentially important impacts on the design and modification of fuel-injection systems for direct-injection engines with alternative fuels.     

Evaluation of the fuel cell performances of TiO2/PAN electrospun carbon-based electrodes

Electrocatalytic effect of the untreated and TiO₂+polyacrylonitrile (PAN) modified discarded battery coal (DBC) and pencil graphite electrodes (PGE) were evaluated in fuel cell (FC) applications. TiO₂+PAN solution is coated on PGE and DBC electrodes by electrospinning. According to the FESEM and EDS characterizations, TiO₂ and PAN nanofibers are found to be approximately 40 and 240 nm in size. TiO₂+PAN/PGE showed the best FC performances with 2.00 A cm^–2 current density and 5.05 W cm^–2 power density values, whereas TiO₂+PAN/DBC showed 0.68 A cm^–2 current density and 0.62 W cm^–2 power density values. Electrochemical characterizations of PGE and TiO₂+PAN/PGE electrodes were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Finally, long-term FC measurement results of developed electrodes exhibited very reasonable recovery values. Along with the comparison of the electrode performances, the recovery of DBCs as electrodes for renewable energy production has been achieved.     

PtMo催化剂抗SO2中毒机理的DFT研究

空气中的杂质气体如SO2能使燃料电池阴极催化剂Pt中毒,降低催化剂的活性和稳定性,而Mo原子的掺杂则能有效提高Pt催化剂的活性和抗SO2中毒性.据此我们采用密度泛函理论分析Mo掺杂提高Pt催化剂抗SO2毒性的原因,Pt与掺杂Mo之间的原子比为8：1.首先,分别计算SO2及解离中间物种S和SO3在Pt（111）和PtMo（111）表面的吸附构型,获得各物种的几何、电子构型.然后,通过比较各吸附物种在Pt（111）和PtMo（111）面的吸附能、键长、键角变化,分析吸附前后Pt（111）和PtMo（111）面分态密度、d带中心以及差分电子密度的变化.结果发现：Mo的掺杂明显减弱了Pt-S间的相互作用,降低SO2、S、SO3在PtMo（111）表面的吸附能;Mo减弱了SO2吸附对PtMo（111）体系电子构型的影响,使催化剂尽量保持原有的电子构型及活性.     

RuxCoySez纳米簇合物对阴极氧还原反应的催化性能

以Ru3（CO）12、Co4（CO）12和Se为原料,采用低温回流技术在1,6-己二醇中合成了RuxCoySez纳米簇合物.利用SEM和XRD测试表征了催化剂的微观形貌和相结构,催化剂粉末以六方结构的Rux簇为主相,同时形成无定形相,呈现高度均匀聚集的纳米颗粒.利用旋转圆盘电极研究了催化剂对氧还原反应电催化活性.在0.5molL-1H2SO4溶液中,RuxCoySez催化剂对氧还原的催化活性和电化学稳定性明显高于RuxSey,开路电位达到0.91V（vs.NHE）.     

Ln_2MO_4 cathode materials for solid oxide fuel cells

One of the major challenges to develop intermediate temperature solid oxide fuel cells is finding a novel cathode material, which can meet the following requirements: (1) high electronic conductivity; (2) chemical compatibility with the electrolyte; (3) a matched thermal expansion coefficient (TEC); (4) stability in a wide range of oxygen partial pressure; and (5) high catalytic activity for the oxygen reduction reaction (ORR). In this short review, a survey of these requirements for K2NiF4-type material wi...     

Sulfonated polyaniline/vanadate composite as anode material and its electrochemical property in microbial fuel cells on ocean floor

A unique sulfonated polyaniline/vanadate composite was synthesized and utilized as a composite anode in microbial fuel cells on ocean floor (BMFCs). X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were employed to characterize its chemical composition and morphology. Wettability of the composite anodes decreases due to the addition of polytetrafluoroethylene (PTFE). The electrochemical behavior of the composite anodes was investigated by means of linear sweep voltammetry and Tafel plot measurem...     

Catalytic performances of kaoline and silica alumina in the thermal degradation of polypropylene

Polypropylene was cracked thermally and catalytically in the presence of kaoline and silica alumina in a semi batch reactor in the temperature range 400℃～550℃ in order to obtain suitable liquid fuels.The dependencies between process temperatures,types of catalyst,feed compositions and product yields of the obtained fuel fractions were found.It was observed that up to 450℃ thermal cracking temperature,the major product of pyrolysis was liquid oil and the major product at other higher temperatures(475℃～550℃) ...     

微波功率和微波作用时间对脉冲微波辅助化学还原合成的Pt/C催化剂性能的影响

采用脉冲微波辅助化学还原法制备了质子交换膜燃料电池(PEMFC)用Pt/C催化剂.通过X射线衍射(XRD)和高分辨透射电镜(HRTEM)等分析技术对催化剂的微观结构和形貌进行了表征.利用循环伏安(CV)法计算了催化剂的电化学比表面积.在此基础上制备了膜电极(MEA)并组装成单电池,考察了制备的Pt/C催化剂作为单电池阴...     

燃油氧化脱硫

综述了燃油的氧化脱硫,包括一些具有吸引力的氧化脱硫方法,如H2O2/有机酸,H2O2/杂多酸,H2O2/含钛分子筛和其它非过氧化氢体系(如叔丁基过氧化物等).对本课题组开发的新型乳液催化氧化脱硫体系进行了详细的介绍.在乳液体系中,界面问的传质限制被大大降低.在温和条件下,双亲性乳液催化剂可以将柴油中的含硫化合物选择氧化...