Development of tools for the numerical simulation of turbulent combustion

碳氢化合物的燃烧是许多工程应用中的重要现象。完全描述这些系统所需的化学动力学机制通常非常大，通常包括涉及数百种化学物质的数千个反应。实际上，在燃烧过程的所有实际应用中，发生燃烧的流动都是湍流的，并且在化学过程和流动过程之间存在复杂的非线性相互作用。 利用随机过程模拟燃烧过程的新发展已经开始为诸如化学反应等过程的离散性质提供新的见解。采用随机粒子模型（SPM）研究了离散反应对点火延迟时间的影响。 了解这些变化对于先进的新发动机概念（如HCCI发动机）的设计和操作至关重要。 我们将使用SPM在两种情况下研究点火： 1 -点火均匀性，通常假设整个均匀混合物同时点火，但有证据表明，可能存在一种点火发生在导致火焰传播的点的状态; 使用随机粒子模型的大涡模拟的湍流射流的2 -点火将用于产生独立的约化化学流形，这将使我们能够研究湍流和化学反应变化的独立影响。 我们还将使用线性涡模型，一个模型，近似的湍流混合的影响，在一维模拟的反应流，产生改进的预测的概率密度函数的反应过程变量在湍流预混燃烧，以期提高我们的预测湍流预混火焰。

Combustion of hydrocarbons is an important phenomenon in many engineering applications. The chemical kinetic mechanisms required to completely describe these systems are usually extremely large, often comprising thousands of reactions involving hundreds of chemical species. In virtually all practical applications of combustion processes, the flow in which the combustion takes place is turbulent and there is a complex, non-linear interaction between the chemical and flow processes. New developments in the use of stochastic processes to simulate combustion processes have begun to offer new insight into the discrete nature of processes like chemical reactions. A recent stochastic particle model (SPM) has been used to study the effects of discrete reactions on the shot-to-shot variations in ignition delay times. Understanding these variations is critical to the design and operation of advanced new engine concepts such as HCCI engines. We will use the SPM to study ignition in two contexts: 1 - ignition homogeneity, where it is often assumed that the entire homogeneous mixture ignites simultaneously, but evidence suggests that there may be a regime in which ignition occurs in spots that lead to propagating flames; and 2 - ignition of turbulent jets using Large Eddy Simulation with the stochastic particle model will be used to generate independent reduced chemistry manifolds that will allow us to study the independent effects of turbulence and chemical reaction variations. We will also use the Linear Eddy Model, a model that approximates the impact of turbulent mixing in one-dimensional simulations of reacting flows, to generate improved predictions of the probability density function of reaction progress variable in turbulent premixed combustion, with a view to improving our predictions of turbulent premixed flames.