正十烷简化机理的构建及其在发动机燃烧数值模拟中的应用

发动机燃烧室中燃料的能量释放与燃烧特性对于发动机设计具有重要作用，为了预测发动机点火包线和贫/富油极限等关键性能，迫切需要发展航空燃料及其典型组分的高精度化学动力学模型。本文针对燃料典型组分正十烷，采用自主开发的机理生成程序ReaxGen构建了其燃烧详细机理（1499种组分、5713步反应）。为了验证机理的合理性与可靠性，在当量比Φ=0.5-2.0，压力P=1-80 atm的宽工况条件下进行了点火延迟模拟验证，结果表明本文提出的正十烷详细机理在较宽的温度、压力和当量比条件下具有较高的模拟精度。为获得适用于发动机燃烧模拟的高精度简化机理，本文基于误差传播的直接关系图方法简化了正十烷燃烧详细机理，得到包含709种组分、2793步反应的正十烷半详细机理。进一步在高温范围（1000-1500 K），采用路径通量分析方法简化得到含77种组分、359个反应的骨架机理。获得的骨架机理能够合理描述正十烷在高温下的燃烧特性，且该骨架机理尺度规模可用于基于火焰面模型的燃烧数值模拟。基于此高精度的骨架机理模型，结合火焰面生成流形湍流燃烧模型，采用大涡模拟方法进行了航空发动机环形燃烧室单头部扇形的燃烧模拟，初步获得了非稳态流场结构，其中温度模拟结果与实验值基本符合。

Reduced Mechanism for n-Decane Combustion and Its Application in Numerical Simulation of Aeroengine Combustor

The energy release and combustion characteristics of fuel in aeroengines play an important role in the design of engines. In order to predict key performances such as engine ignition envelope and lean/rich fuel limit, there is an urgent need to develop high-precision chemical kinetic models of aviation fuel and its typical components. In this work, focusing on the typical component surrogate of n-decane in aviation fuel, a detailed mechanism for n-decane combustion including 1499 species and 5713 reactions is developed based on the automatic mechanism generation program of ReaxGen. In order to verify the reliability of the mechanism, the ignition delay simulation is carried out under the equivalence ratio of 0.5-2.0 and pressure of 1-80 atm. The results show that the detailed mechanism of n-decane has a good performance under a wide range of temperature, pressure and equivalence ratio. In order to obtain a high-precision simplified mechanism for aeroengine combustion simulation, the semi-detailed mechanism containing 709 species and 2793 reactions is generated through the method of directed relation graph with error propagation. Further, in the high temperature range of 1000-1500 K, the skeletal mechanism of 77 species and 359 reactions is developed by the paths flux analysis method. The skeletal mechanism reasonably describes the combustion characteristics of n-decane at high temperature, and the scale of the skeletal mechanism is suitable for the numerical simulation of combustion based on the flamelet generated manifold method. Based on the high precision skeletal mechanism, combining with the turbulent combustion model of flamelet generated manifold, the large eddy simulation method is used to simulate the single-head fan of the annular aeroengine combustor, and the unsteady flow field is preliminarily obtained. The results of temperature simulation are consistent with the experimental values.