甲醇与蓖麻油混合物运动粘度的实验研究

利用改型的乌别洛特毛细管粘度计,本文对243～353K温度范围内对质量配比为98.8:1.2的甲醇与蓖麻油混合物的运动粘度进行了实验研究,运动粘度测量结果的不确定度为1.06%,利用得到的实验数据拟合了甲醇 蓖麻油二元混合物的运动粘度方程.方程与实验数据最大偏差为3.31%,平均偏差为1.11%.     

碳酸二甲酯黏度和密度的实验测量

采用振动弦黏度/密度计对碳酸二甲酯的黏度与密度进行了实验研究,测量的温度范围为283～353 K,压力范围为0.1～20 MPa.实验系统黏度和密度测量的不确定度分别为±2%和±0.2%.利用得到的实验数据,分别拟合了碳酸二甲酯黏度和密度的关联方程.黏度实验数据与方程的平均绝对偏差为0.47%,最大绝对偏差为2.06%;密度实验数据与方程的平均绝对偏差为0.04%,最大绝对偏差为0.14%.最后将实验数据与文献数据进行了比较.为碳酸二甲酯作为替代燃料等研究提供了基础数据.     

生物柴油及与正丁醇混合物的热物性实验研究

本文测量了常压下生物柴油及其与正丁醇混合物的密度、黏度和表面张力数据,温度范围分别为278~363K、313~363 K、293~353 K。对于密度测量,生物柴油的质量分数分别为80%、60%、50%、40%、20%;对于黏度测量,生物柴油的质量分数分别为80%、50%。同时采用不同模型对生物柴油及其与正丁醇二元混合物的密度、黏度、表面张力实验数据进行拟合,结果显示良好,拟合模型与实验数据的最大标准偏差分别为0.01%、1.56%、0.14%。     

稠密流体导热系数和粘度计算的新方程

根据热力学面上流体无量纲化剩余迁移性质曲线与对比密度曲线的相似性,通过关联无量纲化剩余导热系数和粘度与对比密度的方程,提出了一个推算卤代烃制冷工质稠密流体迁移性质状态方程。在常压下迁移性质计算的基础上,应用该方程只要已知物质的临界参数、分子量和偏心因子便可以计算稠密流体（气相或液相）的导热系数和粘度。该方法的提出使得迁移性质的计算像平衡性质一样通过状态方程便可以求出。与实验数据比较,本方法计算导热系数的总平均偏差为 4.8％,最大偏差为18.0％;计算粘度的总平均偏差为4.4％,最大偏差为 15.6％。     

添加碳酸二甲酯改善正丁醇汽油热物性的研究

正丁醇是一种非常有潜力的替代性汽油,本文采用碳酸二甲酯改善其热物理性质,以提高其燃烧效率。利用毛细管法和流动型量热法分别测量了碳酸二甲酯和正丁醇二元混合物的密度、黏度和比定压热容,温度测量范围为313.2～333.3K,压力测量范围为0.1～18.0 MPa。实验结果表明,DMC可以大幅降低正丁醇的黏度和比定压热容、提高其密度,有利于改善其燃烧效率。进而提出了该混合物密度、黏度以及比定压热容的计算模型,平均绝对相对偏差分别为0.09%、2.58%、0.17%。     

柴油、乙醇和水三组元乳化液流变特性的研究

研究了柴油、乙醇和水三组元乳化液的流变特性。实验发现乳化液在本文的组分配比下近似为牛顿流体,而且乳化剂的种类、含量以及乳化液的组分等均对乳化液的流变特性具有显著的影响。对于组分相同的乳化液,乳化液的粘度随着乳化剂含量和粘度的增加而增加;当乳化剂的含量和粘度相同时,若乙醇和水之间的相对质量分数保持不变,减少乳化液中柴油的含量(柴油不少于50％),乳化液的粘度随之增加。但是,柴油、乙醇和水三组元乳化液的粘度要比柴油、甲醇和水三组元乳化液的粘度大2到3倍。     

液体混合物新的粘度方程

液体混合物粘度是很重要的基础数据之一,但直到现在还没有可靠的理论方法来预计这些粘度,多数体系的粘度是靠实验直接测试.本文是基于Eyring的纯液体粘度理论,并应用了溶液的局部浓度理论,来建立一个新的半理论方程,以便关联和预计液体混合物的粘度.经过对方程中的参数估值及对方程的适用性进行检验,结果表明该方程是令人满意的.     

高密度和高粘度比率下气液两相流动的数值模拟

本文在VOF方法的基础上,采用粗细两套网格对高密度和高粘度比率下的气液两相流动模拟进行了研究分析.在细网格中求解流体体积函数方程,在粗网格中采用交错网格求解动量方程和压力修正方程,通过粗细网格间的数据传递获得求解动量方程时需要的准确的界面密度和粘度及控制体密度,克服了高密度和高粘度比率下通过插值方法计算界面密度和粘度及控制体密度带来较大误差的困难,保证了质量和动量同时守恒.高密度和高粘度比率下气液两相流动中气液交界面处密度、速度和压力急剧变化,为了保证格式的有界性和稳定性,采用稳定的有界高阶组合格式STOIC.最后模拟了不同工况下气泡在液体中的运动,并通过实验和模拟结果验证了方法的可行性及准确性.     

非共沸混合工质热泵循环的理论计算和分析

本文提出的计算方法,可避免比热方程,而主要利用已有的纯工质物性数据和少量混合工质实验数据,包括汽液平衡数据和PVTx数据,以拟合Redlich-Kwong方程混合规则中的二元相关因子k和Wilson方程常数,对非共沸混合工质的焓、熵进行计算。文中以R12(1)-R142b(2)二元混合工质热泵循环为例作了热力计算及比较了不同组成配比下对热泵循环性能的影响。     

半经验反演方法计算两个二元气体混合物的粘度和扩散系数

利用粘度碰撞积分方程的直接反演方法计算了两个二元气体混合体系即苯-甲醇和甲烷-四氟甲烷的低密度势能．另外利用动力学理论以及对应态原理计算了两种体系不同温度和不同比例的粘度系数和扩散系数．计算结果和实验数据具有较好的一致性.     

Dielectric constants of binary mixtures of propylene carbonate with dimethyl carbonate and ethylene carbonate from molecular dynamics simulation: comparison between non-polarizable and polarizable force fields

Using non-polarizable and polarizable molecular dynamics simulations, binary mixtures of propylene carbonate?+?dimethyl carbonate and propylene carbonate?+?ethylene carbonate with various compositions were investigated. The polarizable model produces more reasonable estimation of dielectric constants than the non-polarizable model; however, combining the electronic continuum model with the non-polarizable MD improves the comparison between the two models. Fair agreement was found between the results from these simulations and available experimental data. In addition, for a better understanding of the mixing behaviour, the excess dielectric constants over the entire composition were calculated. By comparison of the two mixtures in various mole fractions, distinctive mixing behaviours of propylene carbonate?+?dimethyl carbonate (poorly symmetric mixture) and propylene carbonate?+?ethylene carbonate (highly symmetric mixture) were observed.     

液体合金NaK的粘滞性

我们曾用振球法在约300℃的温度范围内测定了液体合金NaK三种样品(K:49%,51%,74%)的粘滞性。结果表明,此类液体合金相当满意地遵守安德兰规律(η=Be^b/T)。在本文中,除对实验设计及测量的叙述外,并对某些有趣问题作了讨论。     

Thermophysical properties of binary mixtures (dimethyl carbonate + ketones) at T = (303.15, 308.15 and 313.15) K

The densities ρ, viscosities η, and refractive indices n_D of binary mixtures of dimethyl carbonate (DMC) with acetophenone, cyclopentanone, cyclohexanone, and 3-pentanone have been measured over the entire range of composition at the temperatures 303.15, 308.15 and 313.15 K and at atmospheric pressure. The density values were used to calculate excess molar volumes V^E, and other excess functions of interest such as deviations in viscosity Δη, excess Gibb's free energies of activation of viscous flow ΔG^E and deviations in molar refraction ΔR. The measured viscosities were compared with those predicted using the Grunberg-Nissan, Eyring-Margules, Soliman-Marshall, and McAllister four body models. Furthermore the refractive indices data have been correlated using Lorentz-Lorentz, Weiner, Newton, Gladstone-Dale, Eykman, and Eyring-John equations and a satisfactory agreement was found for all the binary systems studied in the present work.     

Rotational Diffusion of Coumarins in Aqueous DMSO

The rotational dynamics of four structurally similar polar molecules viz., coumarin 440, coumarin 450, coumarin 466 and coumarin 151 has been studied in binary mixtures comprising of dimethyl sulphoxide and water at room temperature using the steady state fluorescence depolarization method and time correlated single photon counting technique. The binary mixtures are characterized by the fact that at a particular composition the viscosity (η) of the solution reaches a maximum value that is higher than the viscosities of either of the two co-solvents. The dielectric properties of the solution change across the composition range and the qualitative features of the solvent relaxation dynamics in complex systems are known to differ from those in simple solutions. A hook type profile of rotational reorientation time (τ _r ) vs viscosity (η) is obtained for all the solutes in dipolar aprotic mixture of dimethyl sulphoxide-water, with the rotational reorientation times being longer in organic solvent-rich zone, compared to the corresponding isoviscous point in water-rich zone due to strong hydrogen bonding. Fluorescence lifetimes as well as rotational reorientation times are sensitive to the composition of the binary solvent system under study than to the viscosity suggesting the importance of local structure. The results are discussed in the light of hydrodynamic and dielectric friction models. Dedicated to Professor M.I. Savadatti on his 77^th Birthday.     

Density functional theory calculations for ethylene carbonate-based binary electrolyte mixtures in lithium ion batteries

The density functional theory (DFT) calculations have been performed to investigate the interaction of Li⁺ with various organic solvents widely used as Li ion rechargeable battery electrolytes such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC); and their EC-based binary mixtures at the level of B3LYP/6-31G (d). The interaction of Li⁺ with these solvents has been calculated in terms of electronic structures of clusters of the mixtures of organic solvents including a lithium ion. The main objective of our investigation is to help in understanding a stable and enhancing ionic transfer at graphite/electrolyte interface assisted by the mixtures of the solvents. The calculated results favor the stability of EC-based binary mixtures and high EC-content binary mixture systems. In infrared (IR) vibrational spectra, the IR active modes of the solvent show significant changes due to the cation-solvent interaction.     

Phase studies and thermal stability of binary systems of cholesteric liquid crystals

The binary mixture of cholesteryl oleyl carbonate (COC) and cholesteryl nonanoate (CN) with different ratios has been characterized by differential scanning calorimetry (DSC) to determine the phase diagrams. Their normal shelf-life and accelerated stability studies were also examined. A novel microscopic Fourier-transform infrared (FT-IR) spectrometer equipped with DSC was also used to measure simultaneously the chemical structural variation and the thermal response of these liquid crystals. The results indicate that the binary mixture might transform from smectic to cholesteric and then to isotropic liquid (CN composition <50%); from solid to cholesteric and then to isotropic liquid (CN composition >50%). Therefore, the 50% CN composition might play a critical role in the phase transition of the binary COC-CN mixture. The microscopic FT-IR/DSCsystem could also confirm the phase transition, but could measure the phase trasition temperature of liquid crystals more easily and sharply than the DSC method. The long-term accelerated thermal stability of the COC-CN mixture seemed to be more constant when stored at 4 °C than in any other temperature conditions.     

Viscosity and diffusivity in melts: from unary to multicomponent systems

Viscosity and diffusivity, two important transport coefficients, are systematically investigated from unary melt to binary to multicomponent melts in the present work. By coupling with Kaptay’s viscosity equation of pure liquid metals and effective radii of diffusion species, the Sutherland equation is modified by taking the size effect into account, and further derived into an Arrhenius formula for the convenient usage. Its reliability for predicting self-diffusivity and impurity diffusivity in unary liquids is then validated by comparing the calculated self-diffusivities and impurity diffusivities in liquid Al- and Fe-based alloys with the experimental and the assessed data. Moreover, the Kozlov model was chosen among various viscosity models as the most reliable one to reproduce the experimental viscosities in binary and multicomponent melts. Based on the reliable viscosities calculated from the Kozlov model, the modified Sutherland equation is utilized to predict the tracer diffusivities in binary and multicomponent melts, and validated in Al–Cu, Al–Ni and Al–Ce–Ni melts. Comprehensive comparisons between the calculated results and the literature data indicate that the experimental tracer diffusivities and the theoretical ones can be well reproduced by the present calculations. In addition, the vacancy-wind factor in binary liquid Al–Ni alloys with the increasing temperature is also discussed. What’s more, the calculated inter-diffusivities in liquid Al–Cu, Al–Ni and Al–Ag–Cu alloys are also in excellent agreement with the measured and theoretical data. Comparisons between the simulated concentration profiles and the measured ones in Al–Cu, Al–Ce–Ni and Al–Ag–Cu melts are further used to validate the present calculation method.     

生物制气-柴油双燃料发动机燃烧特性研究

各种农林废弃的生物质,经气化炉热解气化产生可燃生物制气,作为柴油为引燃燃料的双燃料发动机主要燃料,测量该发动机及柴油机在运转范围内的燃烧过程,并分析燃烧始点、最高燃烧压力及相位的变化规律。双燃料发动机与燃用纯柴油时的发动机相比,燃烧始点较迟,在低速大负荷时比柴油机气缸最高燃烧压力及最大压力升高率要大,在其余工况比柴油机要低。     

振动管密度计研制及二甲醚液相密度实验研究

本文研制了一套高精度的金属振动管密度计,测量不确定度小于土0．5 kg／m3。用新研制的密度计,对233．15-323．15 K温度区间内的二甲醚饱和液相密度进行了实验研究,实验结果最大相对扩展不确定度为0．34％(包含因子k=2)。利用本文实验数据和文献数据拟合了一个新的二甲醚饱和密度方程,新方程和实验数据的平均和最大相对偏差分别为0．13％和0．37％,可以满足工程实际应用。