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Modeling and simulation of cryogenic fluid injection and mixing dynamics under supercritical conditions.

机译：超临界条件下低温流体注入和混合动力学的建模与仿真。

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摘要

This research focuses on the modeling and simulation of cryogenic fluid injection and mixing processes under supercritical conditions. The objectives are: (1) to establish a unified theoretical framework that could accommodate full conservation laws, turbulence closure, and real-fluid thermodynamics and transport phenomena; (2) to systematically investigate the underlying physiochemical mechanism at near and supercritical conditions, and (3) to construct a quantitative basis for identifying and prioritizing the key design parameters and flow variables that exert strong influence on the injector behavior in different environments.; The theoretical formulation is based on the full conservation laws and includes real-fluid thermodynamics and transport phenomena over the entire temperature and pressure regimes of concern. Thermodynamic properties, such as enthalpy, internal energy, and heat capacity, are directly calculated from fundamental thermodynamics theories and a modified Soave-Redlich-Kwong (SRK) equation of state. Transport properties, such as viscosity and thermal conductivity, are estimated with an extended corresponding-state principle. Mass diffusivity is obtained by the Takahashi method calibrated for high-pressure conditions. Turbulence closure is achieved using a large-eddy-simulation (LES) technique, in which large energy-carrying structures are computed explicitly and effects of unresolved motions on the resolved scales are modeled. Modified Smagorinsky models extended to compressible flows is used to treat interaction with subfilter-scale. The resultant governing equations are calculated numerically using a preconditioned, density-based finite volume method along with a dual-time-stepping integration algorithm. All of the numerical relations, including the Jacobian matrices and eigenvalues, are derived from fundamental thermodynamics theories that can accommodate any equation of state. The resultant algorithm has been proven to be robust and efficient. Further numerical efficiency is achieved by utilizing a parallel computation scheme that involves the message-passing interface (MPI) library and multi-block treatment.; The theoretical model and numerical scheme were first validated against experimental data of cryogenic nitrogen fluid injection under supercritical conditions. Both two- and three-dimensional simulations were conducted. Reasonably good agreement was obtained in terms of the mean density distribution and the jet spreading angle, with a maximum deviation of 8%. The jet dynamics were largely dictated by the local thermodynamic state through its influence on the fluid thermophysical properties. When the fluid temperature transited across the inflection point on an isobaric density-temperature curve, the resultant rapid property variations might qualitatively modify the jet behavior compared with its counterpart at 1 atm. Increasing ambient pressure produced an earlier transition of the jet to the self-similar region in the simulations. (Abstract shortened by UMI.)
机译：这项研究的重点是在超临界条件下低温流体注入和混合过程的建模和仿真。目标是：（1）建立一个统一的理论框架，以适应完整的守恒定律，湍流闭塞以及实际流体的热力学和输运现象； （2）系统地研究在接近和超临界条件下的潜在理化机理，以及（3）构造定量基础，以识别和优先考虑对不同环境中的注射器性能产生重大影响的关键设计参数和流量变量。理论公式基于完全的守恒定律，并包括在整个关注的温度和压力范围内的真实流体热力学和传输现象。焓，内能和热容量等热力学性质可直接从基本热力学理论和改进的Soave-Redlich-Kwong（SRK）状态方程中计算得出。传输特性（例如粘度和导热率）是通过扩展的对应状态原理估算的。通过针对高压条件校准的Takahashi方法获得质量扩散系数。使用大涡模拟（LES）技术可实现湍流闭合，在该技术中，显式计算了大型的能量承载结构，并对未解析运动对解析尺度的影响进行了建模。扩展到可压缩流的改良Smagorinsky模型用于处理与子过滤器规模的相互作用。使用基于密度的预处理有限体积方法和双重时间步长积分算法，可以对所得的控制方程进行数值计算。所有的数值关系，包括雅可比矩阵和特征值，都是从可以适应任何状态方程的基本热力学理论中得出的。结果算法被证明是鲁棒和有效的。通过利用涉及消息传递接口（MPI）库和多块处理的并行计算方案，可以进一步提高数值效率。首先根据超临界条件下低温氮气注入实验数据验证了理论模型和数值方案。进行了二维和三维模拟。在平均密度分布和射流扩展角方面获得了合理的良好一致性，最大偏差为8％。射流动力学很大程度上受局部热力学状态影响，这取决于其对流体热物理性质的影响。当流体温度在等压密度-温度曲线上越过拐点时，与在1 atm时相比，所产生的快速特性变化可能会定性地改变射流的行为。在模拟中，环境压力的增加使射流更早地过渡到自相似区域。 （摘要由UMI缩短。）

著录项

  • 作者

    Zong, Nan.;

  • 作者单位

    The Pennsylvania State University.;

  • 授予单位 The Pennsylvania State University.;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2005
  • 页码 260 p.
  • 总页数 260
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;
  • 关键词

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