1. 浙江大学 能源清洁利用国家重点实验室,杭州,310027
2. 浙江大学 航空航天学院,杭州,310027
肖华林(1996-), 男, 重庆人, 博士生, 研究方向:航空发动机燃烧室内湍流燃烧机理.E-mail:HulonXiao@zju.edu.cn
罗坤(1977-), 男, 博士, 教授, 博士生导师, 研究方向:多相流燃烧的高精度数值模拟.E-mail:zjulk@zju.edu.cn
纸质出版:2020
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肖华林, 罗坤, 王海鸥, 金台, 樊建人. 环形模型燃烧室内不同Karlovitz数旋流预混火焰的直接数值模拟[J]. 空气动力学学报, 2020, 38(3): 611-618.
XIAO Hualin, LUO Kun, WANG Haiou, et al. Direct numerical simulations of swirling premixed flames in model annular combustors based on different Karlovitz numbers[J]. 2020, 38(3): 611-618.
肖华林, 罗坤, 王海鸥, 金台, 樊建人. 环形模型燃烧室内不同Karlovitz数旋流预混火焰的直接数值模拟[J]. 空气动力学学报, 2020, 38(3): 611-618. DOI: 10.7638/kqdlxxb-2020.0054.
XIAO Hualin, LUO Kun, WANG Haiou, et al. Direct numerical simulations of swirling premixed flames in model annular combustors based on different Karlovitz numbers[J]. 2020, 38(3): 611-618. DOI: 10.7638/kqdlxxb-2020.0054.
为了更好地理解航空发动机燃烧室内的旋流预混燃烧现象和机理,基于相关特征参数采用直接数值模拟方法研究了模型燃烧室内的旋流预混火焰。其中计算模型简化自环形燃烧室,包含两个相邻的贫燃旋流,参数尽可能接近实际航空发动机燃烧室工况。模拟中,采用了简化的煤油反应机理,设计了不同Karlovitz数(
Ka
)对应高低两种负荷。结果表明,在高压下火焰面极薄,小尺度湍流扰动对火焰面影响显著,燃烧室内湍流预混火焰位于薄反应区。在下游由于相邻旋流的作用而产生较为破碎的火焰结构,这一现象在高
Ka
时尤为明显。雷诺数
Re
和
Ka
较大时,旋流剪切作用所导致的下游中心回流效应增强,剪切层中的湍流扰动效应也更强。航空发动机燃烧室内主要反应物和生成物基本满足梯度输运关系,且在
Ka
较大时,梯度输运效应更显著。然而对于中间产物,梯度扩散假设在火焰面附近不成立,这对基于梯度扩散假设的相关计算模型提出了挑战。
In order to better understand the turbulent premixed combustion in aero-engine combustors
the turbulent premix flames in model combustors were studied by direct numerical simulations based on the relevant characteristic parameters. The calculation model is simplified from annular combustors that contains two adjacent lean premixed swirls with high inlet temperature and pressure to meet the aero-engine combustor conditions. In the simulation
the simplified kerosene reaction mechanism was used and different Karlovitz numbers (
Ka
) were designed corresponding to high and low loads. The simulation results show that the flame thickness under high pressure is extremely thin
so the flame surface is strongly affected by small scale turbulence. The turbulent premixed flame is located at thin reaction zone
which is distributed bilaterally along the shear layer
and a relatively broken flame structure is generated in the downstream due to the interaction of adjacent swirls
which is especially obvious when the
Ka
is high. From the upstream to the downstream
the average radial velocity increases due to the combustion expansion
while the average azimuthal velocity decreases due to the conservation of angular momentum. Turbulence pulsation in the downstream recirculation zone is stronger than that in the upstream. When the
Re
and
Ka
are larger
the downstream recirculation effect caused by the swirling shear action is more significant
and the turbulent disturbance effect in the shear layer is stronger. In addition
due to the limited space between the adjacent swirls
the expansion effect of the downstream flame of the double swirls is weaker than that of the single swirl. The correlation analysis of scalar flux and gradient shows that the main reactants and products basically satisfy the gradient transport
and the gradient transport effect is more significant when the number of
Ka
is large. However
for the intermediate products
the gradient diffusion hypothesis is not valid near the flame surface
which challenges the models based on the gradient diffusion hypothesis.
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