湍流燃烧的动态自适应直接数值模拟

Direct Numerical Simulation of Turbulent Combustion with Dynamic Adaptive Mesh Technology

关键词:  湍流燃烧  低温机理  直接数值模拟  动态自适应 

Key words:  Turbulent combustion  Low temperature chemistry  Direct numerical simulation  Dynamic adaption

摘要:

为了能以较低的计算成本分辨多尺度的湍流燃烧过程,发展了基于动态自适应网格技术的湍流燃烧直接数值模拟方法。在氢气/空气层流预混火焰传播的模拟中,准确计算出了火焰传播速度,表明该方法具有直接求解火焰以及精确捕捉火焰传播过程的能力。在衰减的各向同性均匀湍流的模拟中,借助FFT分析获得了合理的湍动能谱线随湍动能衰减的变化规律,表明该方法能够直接求解湍流。由于在实际应用中,点火发生的位置与低温机理的速率相关,因此在氢气/空气湍流预混火焰中研究了湍流对低温机理的影响,发现湍流输运以及湍流涡团间强烈的拉伸和剪切对低温机理有明显的加速作用,能显著增强放热。 

Abstract:

In order to resolve multi-scale processes in turbulent combustion with acceptable computational expenditure, a method for directly simulating the turbulent combustion was developed based on a dynamic adaptive mesh technology. The flame propagation velocity of a hydrogen/air laminar premixed flame can be simulated precisely by this method, showing that this method is capable of directly resolving the flame and its propagation. A reasonable variation of the energy spectrum with the decay of the turbulent kinetic energy in an isotropic homogeneous turbulence can also be simulated and it indicates the capacity of this method for directly resolving the turbulence. As the location where the ignition occurs in practical application is related to the rate of the low temperature chemistry, a numerical simulation is conducted to study the effects of the turbulence on the low temperature chemistry in a hydrogen/air turbulent premixed flame. It is found that the turbulent transport and the stretching and shearing effects between turbulent eddies can accelerate the low temperature chemistry significantly and thus intensify the heat release. 