Gas turbines for power generation are optimised to run with fossil fuels but as a response to tighter pollutant regulations and to enable the use of renewable fuels there is a great interest in improving fuel flexibility. One interesting renewable fuel is syngas from biomass gasification but its properties vary depending on the feedstock and gasification principle, and are significantly different from conventional fuels. This paper aims to give an overview of the differences in combustion behaviour by comparing numerical solutions with methane and several different synthesis gas compositions. The TECFLAM swirl burner geometry, which is designed to be representative of common gas turbine burners, was selected for comparison. The advantage with this geometry is that detailed experimental measurements with methane are publicly available. A two-stage approach was employed with development and validation of an advanced CFD model against experimental data for methane combustion followed by simulations with four syngas mixtures. The validated model was used to compare the flame shape and other characteristics of the flow between methane, 40% hydrogen enriched methane and four typical syngas compositions. It was found that the syngas cases experience lower swirl intensity due to high axial velocities that weakens the inner recirculation zone. Moreover, the higher laminar flame speed of the syngas cases has a strong effect on the flame front shape by bending it away from the axial direction, by making it shorter and by increasing the curvature of the flame front. A hypothesis that the flame shape and position is primarily governed by the laminar flame speed is supported by the almost identical flame shapes for bark powder syngas and 40% hydrogen enriched methane. These gas mixtures have almost identical laminar flame speeds for the relevant equivalence ratios but the heating value of the syngas is more than a factor of 3 smaller than that of the hydrogen enriched methane. The syngas compositions used are representative of practical gasification processes and biomass feedstocks. The demonstrated strong correlation between laminar flame speed and flame shape could be used as a rule of thumb to quickly judge whether the flame might come in contact with the structure or in other ways be detrimental to the function of the combustion system.

用于发电的燃气轮机经过优化以使用化石燃料运行，但作为对更严格的污染物法规的回应，并允许使用可再生燃料，人们对提高燃料灵活性非常感兴趣。一种有趣的可再生燃料是来自生物质气化的合成气，但其性质因原料和气化原理而异，与传统燃料有很大不同。本文旨在通过比较甲烷和几种不同合成气成分的数值解来概述燃烧行为的差异。TECFLAM 旋流燃烧器的几何形状设计为代表普通燃气轮机燃烧器，被选择用于比较。这种几何形状的优点是可以公开获得详细的甲烷实验测量。采用两阶段方法，根据甲烷燃烧的实验数据开发和验证高级 CFD 模型，然后使用四种合成气混合物进行模拟。验证模型用于比较甲烷、40% 富氢甲烷和四种典型合成气成分之间的火焰形状和其他流动特性。发现合成气情况由于高轴向速度削弱了内部再循环区而经历较低的涡流强度。此外，合成气情况下较高的层流火焰速度对火焰前缘形状有很强的影响，通过使其远离轴向弯曲，使其更短并增加火焰前缘的曲率。火焰形状和位置主要由层流火焰速度控制的假设得到了树皮粉合成气和 40% 富氢甲烷几乎相同的火焰形状的支持。对于相关的当量比，这些气体混合物具有几乎相同的层流火焰速度，但合成气的热值比富氢甲烷的热值小 3 倍以上。所使用的合成气组合物代表了实际的气化过程和生物质原料。层流火焰速度和火焰形状之间显示出的强相关性可用作快速判断火焰是否可能与结构接触或以其他方式对燃烧系统的功能有害的经验法则。