Experimental and LES investigation of flame propagation in a hydrogen/air mixture in a combustion vessel

This work presents an experimental and numerical investigation of premixed flame propagation in a hydrogen/air mixture in a closed combustion vessel. In the experiment, high-speed schlieren video photography and pressure sensor are used to examine the flame dynamics and pressure transient. In the numerical study, a large eddy simulation （LES） based on a RNG sub-grid approach and a LES combustion model is applied to reproduce experi- mental observations. The effects of four physical phenomena on the burning velocity are considered in the combustion model, and the impact of grid type on the combustion dynamics is examined in the LES calculations. The flame experiences four stages both in experiment and LES calculations with structured and unstructured grids, i.e., spherical flame, finger-shaped flame, flame with its skirt in contact with the sidewalls, and tulip-shaped flame. The flame speed and pressure in the vessel develop with periodical oscillations in both the experiment and LES simulations due to the interaction of flame front with pressure wave. The numerical simulations compare well with the detailed experimental measurements, especially in term of the flame shape and position, pressure build-up, and periodical oscillation behaviors. The LES combustion model is successfully validated against the bench-scale experiment. It is put into evidence that mesh type has an impact to a certain extent on the numerical combustion dynamics, and the LES calculation on structured grid canpredict the flame dynamics and pressure rise more accu- rately than that on unstructured grid with the same mesh resolution. The flame shape is more asymmetrical in the LES on an unstructured grid than that on a structured grid, and both the flame speed and the pressure rise at the later flame stage are underestimated in the LES on the unstructured grid.     

四元含锂铷氯化物水盐体系298.2 K介稳相平衡研究

采用等温蒸发法研究了四元含锂铷氯化物体系Li+,Na+,Rb+//Cl--H2O 298.2K下的相平衡关系,测定了平衡液相的溶解度、密度和折光率.基于实验数据,绘制了该四元体系的立体图、干基图、密度-组成图和折光率-组成图.该四元体系298.2K下的介稳相图由1个共饱和点,3条单变量曲线和3个结晶区(RbCl、NaCl、LiCl·H2O)组成.将研究的结果同LiCl+KCl+RbCl+H2O体系进行了对比和分析,总结Na+和K+对三元体系Li+,Rb+//Cl--H2O的影响.应用折光率计算的经验公式对实验测定的折光率进行了验证,其最大绝对误差小于-0.0090,从而证明了实验数据的可靠性.     

Phase stability and thermal conductivity of ytterbia and yttria co-doped zirconia

Rare earth oxides doping has been extensively investigated as one of the effective methods to lower thermal conductivity of 4.55 mol% Y2O3stabilized ZrO2(YSZ) thermal barrier coatings(TBCs).In the present work,5–6 mol% Yb2O3and Y2O3co-doped ZrO2ceramics were synthesized by solid reaction sintering at 1600 1C.The phase stability of the samples after heat treatment at 1500 1C was investigated.Yb2O3and Y2O3co-doped zirconia,especially when Yb2O3/Y2O3≥1,contained less monoclinic phase than single Yb2O3or Y2O3phase doped zirconia,indicating that co-doped zirconia was more stable at high temperature than YSZ.The thermal conductivity of the 3 mol% Yb2O3+3 mol% Y2O3co-doped ZrO2was 1.8 W m 1K 1at 1000 1C,which was more than 20% lower than that of YSZ.     

Hydrogen storage performances of the as-milled REMg11Ni (RE = Sm, Y) alloys catalyzed by CeO2

The addition of catalysts and rare earth elements is considered to be very effective methods to enhance the hydrogenation/dehydrogenation properties of Mg and Mg-based hydrides. In this paper, the REMg11 Ni+ 5 wt%CeO_2(RE = Sm, Y)(named REMg11 Ni-5 CeO_2(RE = Sm, Y)) alloys were fabricated through ball milling. The phase composition and structure of the as-milled alloys were investigated in detail. The isothermal hydrogen storage thermodynamics and kinetics of the as-milled alloys were measured by using an automatically Sievert apparatus. Non-isothermal dehydrogenation performance of the alloys was investigated by thermogravimetry(TG) and differential scanning calorimetry(DSC) at different heating rates. The results revealed that all the asmilled alloys were the nanocrystalline and amorphous structure. The RE = Y alloy had a faster hydriding rate and a lower onset hydrogen desorption temperature than the RE = Sm alloy. The superior property of the RE= Y alloy depended on the decrease of the dehydrogenation activation energy. By means of the measurement of Pressure-Composition-Isotherm(P-C-T) curves, the thermodynamic parameters of the REMg11 Ni-5 CeO_2(RE =Sm, Y) alloys were calculated, and the dehydrogenation enthalpy change was 74.86 k J/mol for the RE = Sm alloy and 73.75 k J/mol for the RE = Y alloy, respectively.     

稀土离子在薄层色谱过程中的行为及展开剂的研究

本文从马丁方程出发对薄层吸附色谱过程中稀土离子的行为机理作了探索,在实验基础上研究五个展开体系对稀土元素 R_M 的影响,论证了展开剂各组分之间的竞争效应,协萃效应及反协萃效应对稀土元素 R_M 世和相邻稀土元素ΔR_M 的影响趋势,同时对如何选择展开剂最佳条件进行了讨论,对目前所用的一些方法作了比较和研究。     

稀土离子在薄层色谱过程中的行为及展开剂的研究

本文从马丁方程出发对薄层吸附色谱过程中稀土离子的行为机理作了探索,在实验基础上研究五个展开体系对稀土元素R_M的影响,论证了展开剂各组分之间的竞争效应,协萃效应及反协萃效应对稀土元素R_M和相邻稀土元素ΔR_M的影响趋势,同时对如何选择展开剂最佳条件进行了讨论,对目前所用的一些方法作了比较和研究。     

圆明园舍卫城遗址夯土崩解试验研究及保护建议

夯土的工程特性与夯土的抗风化能力息息相关,尤其夯土的矿物构成、颗粒密度和耐崩解性能决定了夯土城墙的稳定性与抗风化能力。本文首先对圆明园舍卫城遗址夯土的矿物成分进行了分析,然后根据土工试验方法等国家标准,对舍卫城夯土含水率、块体密度、开孔孔隙率、颗粒密度、总孔隙率、颗粒粒径进行了测试实验,并并开展了夯土耐崩解性实验。研究结果表明,舍卫城夯土主要由石英、方解石、斜长石、微斜长石、绿泥石,云母等构成。夯土本身富含粘土矿物及夯土颗粒分布级配不良是夯土城墙破坏的重要内因,水是舍卫城夯土城墙破坏的重要外因,而水的来源主要有储存的地下水及毛细作用,以及明显降雨,至夯土墙体饱和,使土体内部产生不均匀应力,导致土体沿着孔隙、裂隙方向崩解。在此研究基础上给予相应的保护建议。     

稀土对半钢碳化物形态与分布的影响

本文采用定量金相的方法研究了稀土变质处理后半钢中碳化物形态与分布的变化,适量的稀土可以破断晶界的网状碳化物。     

十四种具有公共阳离子的碱卤化合物二元系相图及其共晶点的理论计算

本文在二元溶体过剩焓和过剩熵都可以按组分的摩尔百分数展开成多项式的假设条件下,由热力学理论导出了确定二元系液一固两相平衡曲线的方程式。对于14种具有公共阳离子的碱卤化合物二元系,利用本文所导出的方程式,计算和讨论了它们的相图及其共晶点坐标,理论计算结果与实验结果能较好地吻合。     

硝酸稀土[R(NO_3)_3]和单一稀土(RGl_3)对小麦幼苗氮素代谢以及根系生长的影响

用不同浓度的硝酸稀土和氯化稀土处理小麦幼苗,发现低浓度可以促进干物质累积和根茎生长,高低浓度均对硝酸还原酶活性和氮素吸收有增加的趋势,但两者不是同步的关系。     

稀土有机配合物发光材料及电致发光器件的研究和设计

论述了稀土有机配合物的电致发光原理、器件结构、电致发光材料。介绍了目前研究状况及应用前景。     

茜素蓝S的极谱行为和稀土—茜素蓝S极谱络合吸附波研究

在pH 10.5的0.2mol/L乙二胺—盐酸底液中,用单扫极谱法可获得茜素蓝S的可逆的强吸附波和稀土离子—茜素蓝S的络合吸附波。茜紊蓝S在汞电极上的吸附符合Frumkim等温式。用该法测定了发光材料SrB_2O_7∶Eu中的铕含量,并研究了络合吸附波的电极过程。     

在Sr_3Ca_2(PO_4)_3Cl基质中Tb~(3+)和Dy~(3+)的发光及Ce~(3+)对它们的敏化作用

本文用高温固相扩散法合成了试样。研究了在Sr_3Ca_2(PO_4)_3Cl基质中,Tb~(3+)和Dy~(3+)离子的发光性质;Ce~(3+)对Tb~(3+)和Dy~(3+)离子发光的敏化作用;计算了Ce~(3+)→Tb~(3+)和Ce~(3+)→Dy~(3+)的能量传递效率;初步探讨了Ce~(3+)→Tb~(2+)和Ce~(3+)→Dy~(3+)之间的能量传递机理。     

稀土永磁同步电动机在油田抽油机上的应用与分析

在油田抽油机工况不变的条件下,分别采用稀土永磁同步电动机和Y系列异步电动机拖动抽油机进行现场试验,实测性能数据,计算并分析稀土永磁同步电动机相对Y系列异步电动机的节电率,说明稀土永磁同步电动机具有效率和功率因数高的特点。是一种节能产品,可以解决油田“大马拉小车”的难题。     

稀土肥料对秋苦荞麦生长发育及产量的影响

通过100mg／kg～400mg／kg不同稀土浓度对秋苦荞进行苗期处理,表明对生育时期和产量的影响差异均不显著。喷施稀土有降低株高的作用;分枝数以对照最高,达2．6个,其余各处理均有减少分枝的趋势,有随浓度的增大而增加的趋势。     

基于密度泛函理论的硬度均衡值与稀土氧化物超导性的关系

提出了确定稀土氧化物中元素硬度均衡值町ηcq的计算公式,用该式计算了252种稀土氧化物超导体的硬度均衡值ηcq。研究了稀土氧化物的超导性与稀土氧化物硬度均衡值之间的关系．结果表明,稀土氧化物超导体的硬度均衡值ηcq多数集中在4．511-5．343之间,而硬度均衡值在此范围之外的稀土氧化物一般不具有超导性．显然硬度均衡值ηcq。可作为稀土氧化物超导性的新的经验判据,这对进一步探讨稀土氧化物的超导机制有一定意义．     

乳酸酯的合成研究

报道了合成乳酸酯的新方法，即以乳酸和醇为原料，在对甲苯磺酸催化下以氧化钙为脱水剂，采用索氏提取器进行回流脱水合成乳酸酯．应用该方法，酯化反应时间缩短到３ｈ，收率高达８１％～９８％．同时对影响收率诸因素进行了考察，最佳反应条件为乳酸醇对甲苯磺酸的摩尔比为２４２０１     

稀土元素对党参幼苗生长发育及其生理效应影响的初步研究

本文探讨了稀土对党参幼苗生长发育及生理效应的影响情况。实验结果表明:采用适宜浓度及方法对党参施用稀土可增加其根长及根干重;提高根系活力,促进生长;增加叶绿素含量,提高光合作用效率;增加可溶性固性物含量;提高过氧化物酶同工酶活性,增强代谢作用。     

Two distinct roles of Al2Sm and Al11Sm3 phases on the corrosion behavior of the magnesium alloy Mg-5Sm-xAl

The roles of Al₁₁Sm₃ and Al₂Sm phases on microstructure evolution, mechanical properties and corrosion behavior of the Mg-5Sm-xAl system was investigated. The results showed that adding Al to Mg–5Sm binary alloy brought two Al–Sm phases, Al₁₁Sm₃ and Al₂Sm, which had two distinct roles regarding the microstructure evolution, mechanical properties and corrosion behavior of the Mg-Sm-Al alloy. Al₁₁Sm₃ produced a strong galvanic couple with the Mg matrix, and significantly accelerated the corrosion. The Al₂Sm particles promoted heterogeneous nucleation and refined the grains, which increased the tensile strength and ductility. Both types of Al–Sm particles provided strengthening effect for the alloy. With higher Al contents, Al₂Sm formed an Al oxide protective surface layer and increased corrosion resistance.     

钙钛矿型LaMnO3+λ的结构及对二甲苯氧化的活性研究

合成了系列稀土复合氧化物LaMnO3＋λ，并对其进行了XRD测试，用TREOR程序进行晶胞参数的计算并对二甲苯氧化的活性进行了测定。初步解释了其结构与性能的关系．