A new rotational flamelet model with inward swirling flow through a stretched vortex tube is developed for sub-grid modelling to be coupled with the resolved flow for turbulent combustion. The model has critical new features compared to existing models. (i) Non-premixed flames, premixed flames, or multi-branched flame structures are determined rather than prescribed. (ii) The effects of vorticity and the related centrifugal acceleration are determined. (iii) The strain rates and vorticity applied at the sub-grid level can be directly determined from the resolved-scale strain rates and vorticity without a contrived progress variable. (iv) The flamelet model is three-dimensional. (v) The effect of variable density is addressed. (vi) The inward swirl is created by vorticity combined with two compressive normal strain components; this feature distinguishes the model from counterflow flamelet models. Solutions to the multicomponent Navier–Stokes equations governing the flamelet model are obtained. By coordinate transformation, a similar solution is found for the model, through a system of ordinary differential equations. Vorticity creates a centrifugal force on the sub-grid counterflow that modifies the molecular transport rates, burning rates, and flammability limits. Sample computations of the inward swirling rotational flamelet model without coupling to the resolved flow are presented to demonstrate the importance of the new features. Premixed, nonpremixed, and multi-branched flame structures are examined. Parameter surveys are made with rate of normal strain, vorticity, Damköhler number, and Prandtl number. The centrifugal effect has interesting consequences when combined with the variable-density field. Flow direction can reverse; burning rates can be modified; flammability limits can be extended.

开发了一种新的旋转小火焰模型，该模型具有通过拉伸涡流管的向内旋流，用于子网格建模，以与湍流燃烧的解析流耦合。与现有模型相比，该模型具有重要的新功能。(i) 非预混火焰、预混火焰或多支火焰结构是确定的而不是规定的。(ii) 确定涡量和相关离心加速度的影响。(iii) 在子网格级别应用的应变率和涡度可以直接从解析尺度应变率和涡度确定，而无需人为的进度变量。(iv) 小火焰模型是三维的。(v) 解决了可变密度的影响。(vi) 向内漩涡是由涡量与两个压缩法向应变分量相结合产生的；这一特征将该模型与逆流小火焰模型区分开来。获得了控制小火焰模型的多分量 Navier-Stokes 方程的解。通过坐标变换，通过常微分方程系统为模型找到了类似的解。涡量在子网格逆流上产生离心力，从而改变分子传输速率、燃烧速率和可燃性限制。给出了不与解析流耦合的内旋旋转小火焰模型的示例计算，以证明新特征的重要性。检查预混、非预混和多支火焰结构。使用法向应变率、涡量、Damköhler 数和 Prandtl 数进行参数测量。当与可变密度场结合时，离心效应会产生有趣的结果。流向可以反转；可以修改燃烧速率；可燃性限制可以延长。