Computational Simulation of Complex Turbulent Diffusion Flames
复杂湍流扩散火焰的计算模拟
基本信息
- 批准号:0133925
- 负责人:
- 金额:--
- 依托单位:
- 依托单位国家:美国
- 项目类别:Continuing Grant
- 财政年份:2002
- 资助国家:美国
- 起止时间:2002-09-01 至 2007-08-31
- 项目状态:已结题
- 来源:
- 关键词:
项目摘要
Although the principles and fundamental equations that describe turbulent combustion are known, their direct numerical solution (DNS) remains impossible for practical problems. The usual approximations are to either time average or to spatially filter the fundamental equations. The first approach involves full time averaging (Reynolds averaged Navier-Stokes equations, or RANS), while the second filters only for the smaller scales, allowing the larger scales to be resolved in space and time (Large Eddy Simulation, or LES). In either case, the semi-empirical modeling assumptions associated with the averaging process are critical, and have been the focus of much debate. These approaches have had substantial successes in the modeling of many flames, principally those dominated by boundary-layer-like flows such as free jets and shear layers, and combustion that is uninterrupted by local extinction. Most practical flames are, however, stabilized by recirculation or swirl, and exhibit extinction events, e.g., standoff from the burner. These phenomena are not well captured by the present models. To improve the modeling one must consider issues such as strongly curved streamlines, buoyancy, strongly varying density, dilatation due to heat release and its influence on the overall dynamics of the flow, and local extinction and reignition of the flame chemistry in regions of high shear rates. In this study, the bluff-body laboratory flames of the University of Sydney are used as a prototype for the study of the modeling of these phenomena. A bluff body at the base establishes a recirculation zone that stabilizes the flame. This experimental work has covered a wide range of conditions between fast chemistry and close-to-blowout behavior. These experiments therefore exhibit many of the challenging phenomena occurring in more complex, practical flames. They are, however, of a simple axisymmetric configuration and have been experimentally well characterized. Thus, these flames are excellent targets for fundamental investigations into the modeling of complex flame behavior. The following research activities are proposed: (a) DNS and theoretical work towards better understanding of (1) the mechanisms of extinction/reignition in recirculation-stabilized jet flames, and (2) the physics and stability of flames dominated by large density differences, dilatation, curved streamlines, and buoyancy; (b) investigation/evaluation of LES subgrid-scale models that incorporate the new information gained on extinction/ reignition and on fluid-mechanics issues specific to recirculating flames; and (c) comparison of LES computations with laboratory data on bluff-body stabilized jet flames to test the performance of the subgrid-scale models developed in this project.
虽然描述湍流燃烧的原理和基本方程是已知的,但它们的直接数值解(DNS)仍然不可能用于实际问题。 通常的近似是对基本方程进行时间平均或空间滤波。 第一种方法涉及全时间平均(雷诺平均Navier-Stokes方程,或RANS),而第二种过滤器仅适用于较小的尺度,允许在空间和时间上解决较大的尺度(大涡模拟,或LES)。 在任何一种情况下,与平均过程相关的半经验建模假设都是至关重要的,并且一直是许多争论的焦点。 这些方法在许多火焰的建模中取得了实质性的成功,主要是那些由边界层样流动(如自由射流和剪切层)和不受局部熄灭影响的燃烧所主导的火焰。 然而,大多数实际的火焰是通过再循环或旋流来稳定的,并且表现出熄灭事件,例如,与燃烧器的距离 目前的模型没有很好地捕捉到这些现象。 为了改善建模,必须考虑的问题,如强烈弯曲的流线,浮力,强烈变化的密度,膨胀由于热释放及其对整体动态的流动,局部熄灭和重燃的火焰化学在高剪切速率的区域的影响。 在这项研究中,悉尼大学的钝体实验室火焰被用作这些现象的建模研究的原型。 底部的海崖体建立了一个稳定火焰的回流区。 这项实验工作涵盖了快速化学和接近井喷行为之间的广泛条件。 因此,这些实验展示了许多在更复杂、更实际的火焰中发生的具有挑战性的现象。 然而,他们是一个简单的轴对称配置,并已实验良好的特点。 因此,这些火焰是复杂火焰行为建模的基础研究的极好目标。 建议开展下列研究活动:(a)DNS和理论工作,以便更好地了解(1)再循环稳定射流火焰中熄灭/重燃的机制,和(2)以大密度差、膨胀、弯曲流线和浮力为主的火焰的物理和稳定性;(B)研究/评估LES亚网格尺度模型,该模型结合了关于熄灭/重燃和关于循环火焰特有的流体力学问题的新信息;(c)大涡模拟计算结果与实验室关于钝体稳定射流火焰的数据的比较,以检验本项目中开发的亚网格模型的性能。
项目成果
期刊论文数量(0)
专著数量(0)
科研奖励数量(0)
会议论文数量(0)
专利数量(0)
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George Kosaly其他文献
George Kosaly的其他文献
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{{ truncateString('George Kosaly', 18)}}的其他基金
Investigation of Nonpremixed, Reacting Turbulent Flows
非预混反应湍流的研究
- 批准号:
9415280 - 财政年份:1994
- 资助金额:
-- - 项目类别:
Continuing Grant
Investigation of the Laminar Flamelet Model of Turbulent Diffusion Flames
湍流扩散火焰层流小火焰模型的研究
- 批准号:
9021928 - 财政年份:1991
- 资助金额:
-- - 项目类别:
Continuing Grant
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