Effects of Turbulence on Droplet Evaporation and Combustion: Droplet-Resolved Direct Numerical Simulation

湍流对液滴蒸发和燃烧的影响：液滴解析直接数值模拟

• 批准号: 1824617
• 负责人: Seung Hyun Kim
• 金额: $ 29万
• 依托单位: Ohio State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-01 至 2022-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1824617&HistoricalAwards=false
• 关键词: Effects; Turbulence; Droplet; Evaporation; Combustion

In most combustion engines used in automobiles and airplanes, fuel is injected in the form of the liquid. The evaporation of liquid fuel droplets and subsequent mixing with the surrounding air determine how fuel is ignited and burned. Turbulent fluid motions in the combustion engines enhance the rates of evaporation, mixing and burning. Better understanding of these processes will lead to more efficient engines. In this project, the effects of turbulence on the evaporation and combustion of fuel droplets will be investigated using a new computational method. Numerical simulations that resolve all relevant processes around and inside the droplets will be performed to advance the fundamental understanding of the droplet-turbulence-chemistry interactions under engine-relevant conditions. The advanced fundamental understanding will guide the improvement of engineering models and accelerate the development of combustion engines that meet future standards for fuel efficiency and pollutant emissions. The educational component includes the training of undergraduate and graduate students in computational combustion research and the K-12 outreach through an established program in the college.The project is to characterize the effects of turbulence on droplet evaporation rates, inter-droplet scalar mixing, ignition, and flame structures, when the size of droplets is comparable to or larger than the Kolmogorov scale, the smallest turbulence length scale. A new computational method, which can enable the accurate and stable computation of droplet evaporation and combustion in turbulent flows under engine-relevant conditions, will be developed. Direct numerical simulation (DNS) of the evaporation and combustion of single-component and bi-component fuel droplets in homogeneous isotropic turbulence and in temporally developing mixing layers will be performed using the developed method. The DNS data will be analyzed to delineate the conditions under which the existing laminar theory for the droplet evaporation rates can be used. The emphasis of the analysis will also be placed on identifying the key parameters that characterize the turbulence effects on the evaporation rates. The small-scale mixing statistics in the vicinity of evaporating and burning droplets will be analyzed to help improve spray combustion modeling.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在汽车和飞机上使用的大多数内燃机中，燃料以液体的形式喷射。液体燃料液滴的蒸发以及随后与周围空气的混合决定了燃料如何被点燃和燃烧。内燃机中的湍流运动提高了蒸发、混合和燃烧的速率。更好地理解这些过程将导致更高效的发动机。在这个项目中，湍流对燃料液滴蒸发和燃烧的影响将使用一种新的计算方法进行研究。将进行解决液滴周围和内部所有相关过程的数值模拟，以推进对发动机相关条件下液滴-湍流-化学相互作用的基本了解。先进的基本理解将指导工程模型的改进，并加速内燃机的开发，以满足未来的燃油效率和污染物排放标准。教育部分包括培训本科生和研究生在计算燃烧研究和K-12推广通过一个既定的计划在学院。该项目是表征湍流对液滴蒸发速率，液滴间标量混合，点火和火焰结构的影响，当液滴的大小是可比的或大于Kolmogorov尺度，最小的湍流长度尺度。一种新的计算方法，它可以使准确和稳定的计算液滴蒸发和燃烧的湍流在发动机相关的条件下，将开发。直接数值模拟（DNS）的蒸发和燃烧的单组分和双组分燃料液滴均匀各向同性湍流和在时间上发展的混合层将使用开发的方法进行。DNS数据将进行分析，以描绘的条件下，现有的层流理论的液滴蒸发率可以使用。分析的重点还将放在确定表征湍流对蒸发率影响的关键参数上。在蒸发和燃烧液滴附近的小尺度混合统计数据将被分析，以帮助改善喷雾燃烧model.This奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。