当前位置: X-MOL 学术Flow Turbulence Combust. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Effect of Unsteadiness and Scalar Dissipation Models on Flamelet Modeling of Differential Molecular Diffusion in Turbulent Non-Premixed DNS Flames
Flow, Turbulence and Combustion ( IF 2.4 ) Pub Date : 2022-01-10 , DOI: 10.1007/s10494-021-00311-9
Chao Han 1 , Haifeng Wang 1
Affiliation  

Prediction of differential molecular diffusion remains a great challenge for flamelet modeling of turbulent non-premixed combustion. This work addresses this challenge through a priori and a posteriori testing of flamelet models by using DNS databases to enable a detailed examination of the model capability and limitation for the prediction of differential molecular diffusion under different combustion conditions characterized by different Reynolds numbers and Damköhler numbers. The emphasis is on the effect of unsteadiness and scalar dissipation models on the flamelet modeling. Two sets of Sandia DNS of temporally evolving turbulent non-premixed jet flames are used for the study, including six different cases. Three of the DNS cases are based on the CO/\(\hbox {H}_2\) fuel with different Reynolds numbers, and the other three cases are based on the \(\hbox {C}_2\hbox {H}_4\) fuel with different Damköhler numbers. The unsteady effect is examined by considering both steady and unsteady flamelet models in the context of Reynolds averaged Navier–Stokes simulations for the model examination. Different differential molecular diffusion models are incorporated in the flamelet models such as the linear differential diffusion model and the non-linear differential diffusion model (Wang, Phys Fluids 28:035102, 2019). It is found that the use of unsteady flamelet models can generally improve the model prediction for differential molecular diffusion when compared with the steady flamelet models. This suggests the importance of considering the unsteady effect in flamelet modeling of differential molecular diffusion. In the unsteady flamelet modeling, different models for the representative scalar dissipation rate are examined and compared. It is found that, in order to adequately capture differential molecular diffusion, an appropriate model for the scalar dissipation rate is needed in addition to the consideration of unsteadiness.



中文翻译:

非定常和标量耗散模型对湍流非预混 DNS 火焰中微分分子扩散小火焰模型的影响

微分分子扩散的预测对于湍流非预混燃烧的小火焰建模仍然是一个巨大的挑战。这项工作通过使用 DNS 数据库对小火焰模型进行先验后验测试来解决这一挑战,从而能够详细检查模型的能力和在以不同雷诺数和 Damköhler 数为特征的不同燃烧条件下预测差异分子扩散的限制。重点是不稳定和标量耗散模型对小火焰建模的影响。研究使用了两组随时间演变的湍流非预混射流的桑迪亚 DNS,包括六个不同的案例。其中三个 DNS 案例基于 CO/ \(\hbox {H}_2\)不同雷诺数的燃料,其他三种情况基于\(\hbox {C}_2\hbox {H}_4\)具有不同 Damköhler 数的燃料。在模型检查的雷诺平均 Navier-Stokes 模拟的背景下,通过考虑稳态和非稳态小火焰模型来检查非稳态效应。在小火焰模型中加入了不同的微分分子扩散模型,例如线性微分扩散模型和非线性微分扩散模型(Wang, Phys Fluids 28:035102, 2019)。研究发现,与稳态小火焰模型相比,使用非稳态小火焰模型通常可以改进对微分分子扩散的模型预测。这表明在微分分子扩散的小火焰模型中考虑不稳定效应的重要性。在非定常小火焰建模中,对代表标量耗散率的不同模型进行了检查和比较。研究发现,为了充分捕捉微分分子扩散,除了考虑非定常性外,还需要一个合适的标量耗散率模型。

更新日期:2022-01-11
down
wechat
bug