In this paper, the effects of variations in the fuel tube diameter and co-flow velocity in the combustion chamber on the non-premixed laminar flame are investigated. Methane gas, as a fuel, and the dry air, as an oxidizer. The size of the combustion chamber is constant and, by changing the fuel tube diameter and co-flow velocity, changes in the numerical values of temperature, velocity, density, and concentration of the species of reactants and products in the combustion chamber are evaluated. A finite volume method (FVM) with staggered grids is used for numerical solution. Equations of continuity, momentum, energy, ideal gas state and kinetic equations with thermodynamic and thermochemical information of chemical species are solved using numerical method of SIMPLE. The convective terms are discretized using Power Law scheme (PLS).The calculations are carried out using Dryer and Glassman’s three-stage chemical kinetics. Variable under relaxation factor dependent on temperature has been used to handle the solving chemical kinetic equations. Initially, the results of calculations are compared with the experimental and numerical results of other researchers, which show an acceptable agreement.. The results show that increasing the diameter ratio reduces the length of the flame. With the large ratio of the diameters, location of the combustion’s maximum temperature is at the chamber entrance and for the small diameter ratios, its location moves to nearly outlet of the chamber. In addition, the reduction of the ratio of the diameters increases the flame lift-off. Also the results show that the optimal of diameters ratio is 0.6 in order to prevent the lift-off flame and return the flame to inlet opening of combustion chamber. Also increasing the fuel tube diameter, increases the amount of oxygen due to the return flow formation and decreases the volumes of water vapor and carbon dioxide in the centerline of the combustion chamber. The flame length attains the maximum possible value with respect to diameter ratio of 0.6 at inlet air velocity of 0.3 m/s. In addition, it is shown that increasing the air velocity increases the total flame lift-off and flame length until the air velocity reaches the value of around 0.3 m/s and by increasing the air velocity more than 0.3 m/s, the total flame lift-off and flame length decreases.

在本文中，研究了燃料管直径和燃烧室内同流速度的变化对非预混层流火焰的影响。甲烷气体作为燃料，干燥的空气作为氧化剂。燃烧室的尺寸是恒定的，并且通过改变燃料管的直径和并流速度，可以评估温度，速度，密度以及燃烧室中反应物和产物的种类的数值的变化。带有交错网格的有限体积法（FVM）用于数值求解。利用SIMPLE的数值方法求解了连续性，动量，能量，理想气体状态和动力学方程，以及化学物种的热力学和热化学信息。对流项使用幂律方案（PLS）离散化。使用Dryer和Glassman的三阶段化学动力学进行计算。取决于温度的弛豫因子下的变量已用于处理化学动力学方程式。最初，将计算结果与其他研究人员的实验和数值结果进行了比较，这表明了可接受的结果。结果表明，增加直径比会减少火焰的长度。对于较大的直径比，燃烧最高温度的位置位于燃烧室的入口，对于较小的直径比，燃烧的最高温度几乎移至燃烧室的出口。另外，直径比的减小增加了火焰剥离。结果还表明，最佳直径比为0。为了防止火焰升起，将火焰返回燃烧室的入口，请参见图6。同样增加燃料管的直径，由于形成回流而增加了氧气的量，并减少了燃烧室中心线中水蒸气和二氧化碳的体积。在进气速度为0.3 m / s时，火焰长度相对于直径比0.6达到最大可能值。另外，显示出增加空气速度会增加总火焰升空和火焰长度，直到空气速度达到约0.3 m / s的值，并且通过将空气速度增加超过0.3 m / s，总火焰会增加升起和火焰长度减少。由于回流形成而增加了氧气量，并减少了燃烧室中心线中水蒸气和二氧化碳的体积。在进气速度为0.3 m / s时，火焰长度相对于直径比0.6达到最大可能值。另外，显示出增加空气速度会增加总火焰升空和火焰长度，直到空气速度达到约0.3 m / s的值，并且通过将空气速度增加超过0.3 m / s，总火焰会增加升起和火焰长度减少。由于回流形成而增加了氧气的量，并减少了燃烧室中心线中水蒸气和二氧化碳的体积。在进气速度为0.3 m / s时，火焰长度相对于直径比0.6达到最大可能值。另外，表明增加空气速度会增加总火焰升空和火焰长度，直到空气速度达到约0.3 m / s的值为止，并且通过将空气速度增加超过0.3 m / s，总火焰会增加升起和火焰长度减少。