A Priori Analysis of Subgrid Molecular Transport Effects on High Pressure Turbulent Combustion Modeling

米勒0965624这项建议解决了与现代柴油发动机、燃气轮机和火箭发动机相关的现实高压热力学条件下湍流火焰的亚网格统计。这项研究将利用大规模并行直接数值模拟(DNS)来分析几个高压火焰。在这些数值模拟中，湍流火焰的所有长度和时间尺度都是使用高精度技术完全求解的，而不使用湍流或亚网格模型。重点是分析与现代燃烧模型相关的术语，重点是大涡模拟(LES)和滤波密度函数(FDF)方法。高压实验是困难的，现有的对这些方法的DNS验证到目前为止还没有解决在真实火焰中非常重要的四个耦合现象：大压力、真实的化学成分、真实的财产模型以及广义的热和质量扩散。智力上的优点：假设局部亚格子分子混合效应可以对高压火焰动力学产生重大影响，这些效应通常被认为相对于湍流搅拌可以忽略不计。这是因为最终许多火焰是由物种和温度的扩散在局部控制的。熄火和重新点火事件对局部火焰条件高度敏感，在高压下，索雷特交叉扩散也会被高度放大。因此，将对氢-氧、氢-空气、庚烷-空气和甲烷-空气反应剪切层进行数值模拟。详细的和简化的化学动力学，真实的气体状态方程，真实的性质评估，以及完整的广义扩散模型都将被纳入其中。大规模并行模拟将为不同压力和雷诺数下的每个火焰产生一个数据库。然后，将以先验的方式探索该数据库，以分析与高压湍流燃烧的LES和FDF相关的次网格项和统计数据。需要建模的术语将被确定并进行适当的建模。广泛影响：这项研究有望增强社会对高压下湍流燃烧进行预测建模的能力。由于社会上使用的碳氢燃烧装置(包括柴油发动机、燃气轮机、火箭发动机和其他潜在的氢气技术)遇到的燃烧室压力不断增加，这一点势在必行。研究生和本科生都将参与其中。此外，教育计划的多学科部分涉及将参与这项研究的研究生与北卡罗来纳大学夏洛特分校的一群计算机工程师聚集在一起。域名系统代码将在赔偿委员会并行的现场可编程门阵列集群上共享和运行。本练习的目的是：在两个通常不相交的组之间共享知识，以及针对典型和高级并行体系结构进行代码优化。

Miller0965624This proposal addresses subgrid statistics of turbulent flames under realistic high pressure thermodynamic conditions relevant to modern diesel engines, gas turbines, and rocket engines. The research will utilize massively parallel direct numerical simulations (DNS), in which all length and time scales of the turbulent flame are fully resolved using high order accurate techniques and without the use of turbulence or subgrid models, to analyze several high pressure flames. The particular focus is on analyzing terms relevant to modern combustion models with emphasis on large eddy simulation (LES) and filtered density function (FDF) approaches. High pressure experiments are difficult and existing DNS validations of these approaches have thus far not addressed four coupled phenomena that can be highly important in real flames: large pressure, realistic chemistry, real property models, and generalized heat and mass diffusion.Intellectual Merit: It is hypothesized that localized subgrid molecular mixing effects, which are often assumed to be negligible relative to turbulent stirring, can have a substantial impact on high pressure flame dynamics. This is due to the fact that ultimately many flames are controlled locally by the diffusion of species and temperature. Extinction and re-ignition events are highly sensitive to local flame conditions and Soret cross-diffusion is also highly amplified at high pressures. DNS will therefore be conducted for hydrogen-oxygen, hydrogen-air, heptane-air, and methane-air reacting shear layers. Both detailed and reduced chemical kinetics, a real gas state equation, real property evaluations, and a complete generalized diffusion model will be incorporated. Massively parallel simulations will produce a database for each flame at various pressures and Reynolds numbers. The database will then be explored in an a priori manner to analyze subgrid terms and statistics related to LES and FDF of high pressure turbulent combustion. Terms requiring modeling will be identified and modeled as appropriate.Broader Impact: The research is expected to enhance society's ability to predictively model turbulent combustion at elevated pressures. This is imperative due to the ever increasing combustion chamber pressures encountered in hydrocarbon combustion devices utilized in society (including diesel engines, gas turbines, rocket engines, and other potential hydrogen technologies). Both graduate and undergraduate students will be involved. In addition, a multidisciplinary portion of the education plan involves bringing together the graduate students involved with this research with a group of computer engineers at UNC Charlotte. The DNS code will be shared and run on the UNCC parallel FPGA cluster. The purposes of this exercise are: knowledge sharing between two typically non-intersecting groups, and code optimization for both typical and advanced parallel architectures.