The flame in a gas turbine model combustor close to blow-off is studied using large eddy simulation with the objective of investigating the sensitivity of including different heat loss effects within the modelling. A presumed joint probability density function approach based on the mixture fraction and progress variable with unstrained flamelets is used. The normalised enthalpy is included in the probability density function to account for heat loss within the flame. Two simulations are presented that use fixed temperature boundary conditions, and use adiabatic and non-adiabatic formulations of the combustion model. The results are compared against the previous fully adiabatic case and experimental data. The statistics for the simulations are similar to the results obtained from the fully adiabatic case. Improved statistics are obtained for the temperature in the near-wall regions. The non-adiabatic flamelet case shows the average reaction rate values at the flame root are approximately 50% smaller in comparison to the adiabatic flamelet cases. This causes the lift-off height to be overestimated. The time series of the lift-off height and the volume integrated heat release rate show that including non-adiabatic flamelets causes the flame to be highly unstable. A higher enthalpy deficit is seen in the near-field regions when the flame root is not present and experiencing some lift-off, suggesting that the flame is more dynamic when including heat loss.

中文翻译：

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在稀薄涡流稳定火焰的大涡模拟中模拟热损失效应

使用大涡模拟研究燃气轮机模型燃烧器中接近排气的火焰，目的是研究在建模中包括不同热损失效应的敏感性。使用基于混合分数和无应变小火焰的进展变量的假定联合概率密度函数方法。归一化焓包含在概率密度函数中，以说明火焰内的热损失。提出了两种模拟，它们使用固定温度边界条件，并使用燃烧模型的绝热和非绝热公式。将结果与之前的完全绝热情况和实验数据进行比较。模拟的统计数据与完全绝热情况下获得的结果相似。获得了近壁区域温度的改进统计数据。非绝热小火焰情况显示火焰根部的平均反应速率值比绝热小火焰情况小约 50%。这导致抬离高度被高估。升空高度和体积积分放热率的时间序列表明，包括非绝热小火焰会导致火焰高度不稳定。当火焰根不存在并经历一些抬升时，在近场区域会看到更高的焓差，这表明在包括热损失时火焰更具动态性。这导致抬离高度被高估。升空高度和体积积分放热率的时间序列表明，包括非绝热小火焰会导致火焰高度不稳定。当火焰根不存在并经历一些抬升时，在近场区域会看到更高的焓差，这表明在包括热损失时火焰更具动态性。这导致抬离高度被高估。升空高度和体积积分放热率的时间序列表明，包括非绝热小火焰会导致火焰高度不稳定。当火焰根不存在并经历一些抬升时，在近场区域会看到更高的焓差，这表明在包括热损失时火焰更具动态性。