摘要燃烧在能源与动力工程领域里的应用非常普遍。在各种动力设备，例如内燃机，锅炉，燃气轮机等中都存在着燃烧。在这些燃烧过程中通常都存在着湍流燃烧，湍流流动与化学反应过程相互影响，使得燃烧变得十分复杂。通过对湍流燃烧的研究与分析，进而实现提高燃烧效率，降低污染物的排放，发展新型燃烧技术。87042

直接数值模拟不需要对湍流燃烧建立近似模型，就能够分辨精细的时间尺度和空间尺度，并且最后的模拟结果具有良好的精确度。本文基于FDS软件，运用直接数值模拟方法来对甲烷燃烧火焰反应羽流进行研究分析。分析了甲烷燃烧过程中火焰结构形态、密度、温度场、速度场、热释放率、甲烷的质量分数等物理量的变化规律，其结果认为：

（1）在甲烷燃烧过程中，流场中会产生大涡结构。大涡结构在轴线方向上的运输会使整个流场发生周期性运动变化。

（2）反应流场中心的密度较低，外侧密度较高。流场下游的温度差较大，大涡结构中的温度分布比较复杂。羽流中最大速度区域沿着中心轴线发生变化，流场中心的速度比外侧要大。

（3）由于外界没有产生干扰，反应流场的密度场，温度场，速度场分布都是关于几何中心对称。

（4）热释放率最终稳定在一定范围内波动。火源位置附近的甲烷质量分数最高。

毕业论文关键词：甲烷燃烧；反应羽流；火焰；直接数值模拟

Abstract The combustion is very widely used in the field of energy and power engineering。 Combustion is in all kinds of power equipment, such as internal combustion engines, boilers, gas turbines, etc。 In the combustion process usually involves turbulent combustion。 Interaction between turbulent flow and chemical reaction process makes the combustion very complicated。 The purpose of research and analysis of turbulent combustion is to improve combustion efficiency and reduce the emission of pollutants, and to develop new types of combustion technology。

Direct numerical simulation does not need to establish an approximate model for turbulent combustion, it is able to distinguish the fine time scale and spatial scale, and finally the simulation results have good accuracy。 In this paper, based on the FDS software, a direct numerical simulation method is used to study the flame reaction plume of methane combustion。 The changes of flame structure shape, density, temperature field, temperature field, velocity field, heat release rate and mass fraction of methane in methane combustion process were analyzed。 The result is that:

(1) In the process of methane combustion, large eddy structure will be generated in the flow field。 The transport of large eddy structure in the axial direction will cause the whole flow field to be changed periodically。

(2) The density of the centre of the reaction flow field is relatively low and the density of outside is relatively high。 The temperature difference in the downstream of the flow field is very large, and the temperature distribution in the large eddy structure is more complicated。 The maximum velocity region of the plume changes along the central axis, and the velocity of the center of the flow field is larger than that of outside。

(3) The heat release rate is stable in a certain range The highest concentration of methane was near the fire source。

(4) The heat release rate is stable in a certain range The highest concentration of methane was near the fire source。

Keywords: methane combustion; reactive plume; flame; direct numerical simulation

目  录

第一章 绪论 1

     1。1研究目的及意义 1