摘要
燃烧油滴/颗粒的曳力和尾涡造成的湍流变动反映了燃烧油滴/颗粒和气体湍流的相互作用.关于燃烧对颗粒曳力的影响,文献中曾报导,燃烧的煤粒增大了曳力,但是燃烧的焦炭粒减小了曳力.至于燃烧油滴的曳力,文献中报导了增大或减小曳力的相反结果.在液雾燃烧数值模拟中往往采用无燃烧的固体颗粒的曳力规律.关于颗粒尾涡导致的湍流变动,众所周知,大颗粒的尾涡效应会增强湍流.但是燃烧油滴的尾涡造成的湍流变动至今不清楚.本文给出了气体绕过燃烧的单油滴和油滴群的数值模拟研究.结果指出,单个燃烧油滴的曳力比等温流动中固体颗粒的曳力小得多,而且燃烧油滴群的曳力比单个燃烧油滴的更小.与固体颗粒尾涡增强湍流效应相反,本文发现燃烧的单个油滴的尾涡效应是降低湍流.同时,随着气体相对速度的增大,燃烧油滴群的尾涡效应一开始是降低湍流,但是后来却是增强湍流的.
The drag force and wake-affected turbulence modification of combusting droplets/particles reflect the interaction between combustion droplets/particles and gas turbulence. For the effect of combustion on the particle drag force, it has been reported that combusting coal particles increase their drag force and combusting char particles reduce their drag force. For the drag force of combusting droplets, opposite experimental results of combustion enhancing or reducing the drag force have been reported, and in numerical simulations of spray combustion, the drag law for non-combusting solid particles is frequently adopted. As for the wake-affected turbulence modification, it is well known that larger solid particles enhance gas turbulence due to their wake effect, but the wake-affected turbulence modification of combusting droplets is still not clear. In this work, numerical studies are conducted for turbulent gas flows passing a single and multiple combusting droplets. The results indicate that the drag force of a combusting droplet is much smaller than that of a cold solid particle in isothermal flows, and the drag force of the combusting droplet group is also smaller than that of a single combusting droplet. In contrast to the enhancement of turbulence caused by the solid particle’s wake effect, it is found that the wake effect of a single combusting droplet is turbulence reduction, and as the relative velocity of gas increases, the wake effect of the combusting droplet group first results in turbulence reduction and later turbulence enhancement.
作者
周力行
李科
Zhou Lixing;Li Ke(Department of Engineering Mechanics,Tsinghua University,Beijing 100084,China;School of Energy and Environment,Inner Mongolia University of Science and Technology,Baotou 014010,China)
出处
《燃烧科学与技术》
EI
CAS
CSCD
北大核心
2019年第4期283-288,共6页
Journal of Combustion Science and Technology
基金
国家自然科学基金资助项目(51390493
51266008)
关键词
曳力
油滴燃烧
湍流
尾涡效应
drag force
droplet combustion
turbulence
wake effect
