激光散射法流体近临界区互扩散系数和黏度实验研究

The popularization and application of fluid working in the subcritical and supercritical thermodynamic state would be difficult to be carried out without the understanding of the transformation rules and the available experimental data of the transport properties of working fluid. However, the transport properties would show the un-normal and dramatical variation in the near-critical thermodynamics region. This project is aimed at the measurement of the mutual diffusion coefficient and viscosity of working fluid in this special thermodynamic region, and the laser light scattering method based on the microscopic fluctuation theory will be investigated for measurement. The acting mechanisms between microscopic fluctuation, mutual diffusion coefficient and viscosity, frequency characteristics of scattered light will be identified. The influencing mechanisms of the unnormal mutual diffusion coefficient and viscosity in the near-critical thermodynamic state on the laser light scattering method will be developed. The key technologies such as photon correlation calculation, frequency coupling etc will be researched. The experimental system will be established and the measurement of mutual diffusion coefficient and viscosity of gases and liquids will be carried out by the same experimental system. The experimental uncertainty in mutual diffusion coefficient and viscosity are less than 1.5%, and 1.0%, respectively. The experimental system can be used in temperatures up to 800 K and pressures up to 40 MPa. The combined standard uncertainty of temperature and pressure are less than 15mK and 0.02Mpa. Using the new light scattering system, the mutual diffusion coefficient and viscosity of fluids which the current researches were focused on such as biofuel were investigated, and the transformation rules of the mutual diffusion coefficient and viscosity in the near-critical thermodynamic region will be proposed, which will be aimed to present the correlations for estimating the mutual diffusion coefficient and viscosity with better applicability and higher precision.

跨/超临界技术的推广应用离不开对其工质迁移性质变化规律的认识和精确实验数据的掌握，而流体在近临界热力学不稳定区域内的迁移性质多呈现超常急剧变化。本项目将利用基于物质微观涨落机理的激光散射法，专门针对这一特殊热力学区域内的互扩散系数和黏度开展实验研究。探明微观涨落、互扩散系数和黏度、散射光频率特征间的作用机理；揭示近临界区域内非常规互扩散系数和黏度变化对光散射法的影响机理；查明光子相关运算、频谱耦合等关键技术内涵；建立可以同时开展气/液相态下流体互扩散系数和黏度测量的光散射实验平台，互扩散系数和黏度测量不确定度分别达到：<1.5%、<1.0%，温度、压力工作范围和测量不确定度：~800K(<15mK)和~40Mpa(<0.02Mpa)；获取近临界区内生物燃料等热门工质高精度互扩散系数和黏度实验数据，揭示其特殊的变化规律，并给出具有一定普适性和较高精度的计算关联式。

本项目重点围绕激光散射法流体互扩散系数和黏度测量展开研究，构建了散射光频谱特征参数与二元互扩散系数、颗粒粒径和液体黏度之间的数学物理模型；确立了动态光散射法流体互扩散系数和黏度测量的实验原理；搭建完成了国内首套动态光散射法流体扩散系数和黏度测量实验系统，温度和压力适用范围为293 ~ 653 K和常压 ~ 10 MPa，互扩散系数、黏度、温度和压力测量不确定度分别小于1.3 %、1.4%、0.016 K和0.019 MPa。实验台各项关键技术指标均达到或超过国际同类实验平台水平。利用该实验系统实现了互扩散系数和黏度的实验测量，并在此基础上测量获得多种烷烃、生物燃料、燃料添加剂和气体等的热扩散率以及音速实验数据，填补了上述物质热扩散率以及音速实验数据的空白，揭示了热扩散率以及音速在探测区域内随温度/压力的变化规律。

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