Laminar diffusion flames have been employed extensively to investigate the effects of physical and chemical-related parameters on combustion phenomena. Attention has been given to improve combustion models while keeping the two-dimensional (2D) axisymmetric approach and simplified boundary conditions. The flow structure due to the discrete jet nature of the reactants claims a more realistic inlet boundary condition for the burner plate which can only be accomplished if the solution domain is 3D. In this work, we present a novel 3D simulation code for the analysis of non-premixed laminar flames of methane and air, considering detailed inlet boundary conditions. The code is based on the control volume finite element method, written in MATLAB environment. To accomplish that a novel flow-oriented upwind scheme was implemented for the advection terms of the conservation equations. Combustion modelling can be carried out by either an enhanced flame sheet model in which an enthalpy equation is integrated in combination with the mixture fraction equation or detailed reaction schemes. Radiative heat losses were accounted for in the added energy equation. Three-dimensional numerical predictions, based on the flame sheet model, were able to simulate the near-wall gas temperature and inflow velocity field of a set of perforated plate burner with different porosities. It was found that the discrete nature of the injection of fuel and oxidiser, inflow boundary condition, plays a significant role on flame shape and length. Much better agreement between published experimental data and numerical predictions was obtained, particularly regarding flame structure, species mass fractions and temperature distribution of non-premixed laminar flames regardless of the adopted simplified combustion model. It was observed that flame length decreased as the burner porosity increased, up to a certain limit. The modified flow-oriented scheme greatly improved solution stability and computational time of the reacting system predictions.

层流扩散火焰已广泛用于研究物理和化学相关参数对燃烧现象的影响。在保持二维（2D）轴对称方法和简化边界条件的同时，已经着重改善燃烧模型。由于反应物具有离散的射流特性，这种流动结构要求燃烧器板的入口边界条件更为实际，这只有在溶液域为3D的情况下才能实现。在这项工作中，我们考虑到详细的入口边界条件，提出了一种新颖的3D模拟代码，用于分析甲烷和空气的非预混合层流火焰。该代码基于在MATLAB环境下编写的控制体积有限元方法。为了达到这一目的，对守恒方程的对流项采用了一种新的面向流的迎风方案。可以通过将焓方程与混合物分数方程结合在一起的增强型火焰片模型或详细的反应方案来进行燃烧建模。在增加的能量方程中考虑了辐射热损失。基于火焰片模型的三维数值预测能够模拟一组不同孔隙度的多孔板式燃烧器的近壁气体温度和流入速度场。发现燃料和氧化剂的喷射的离散性，流入边界条件对火焰的形状和长度起着重要的作用。无论采用简化的燃烧模型如何，都获得了已发表的实验数据和数值预测之间更好的一致性，特别是在火焰结构，物质质量分数和非预混合层流火焰的温度分布方面。观察到火焰长度随着燃烧器孔隙率的增加而减小，直至达到一定极限。改进的面向流的方案极大地提高了反应系统预测的解稳定性和计算时间。