【作者】 王岳；

【导师】 张孝谦；

【作者基本信息】 中国科学院研究生院（工程热物理研究所） ， 工程热物理， 2002， 博士

【摘要】 湍流和火焰不稳定性对弱湍流预混火焰的影响具有可比性，因此在预测和控制这类火焰时需要考虑更多的因素，例如重力的影响。本文研究重力对稀燃弱湍流预混V形火焰的影响，目的是为发展弱湍流预混火焰理论提供基础数据。 本文利用落塔和OH-PLIF技术在正常重力和微重力下探测甲烷-空气预混V形火焰，记录了火焰锋面的动态特征。经过图像处理，从OH-PLIF图像中提取了平均反应度(?)、火焰锋面密度∑和湍流火焰传播速度S_T等特征量，以评价重力的影响。研究表明，微重力下火焰皱褶增大并且S_T加快。同时，重力对火焰皱褶的影响随着湍流的增强而减弱，对∑的影响集中在靠近燃烧产物一侧。对于一些火焰，重力的影响与湍流或火焰放热的影响处于同一量级，这意味着重力影响在燃烧模型中不能忽略。重力压制火焰皱褶的原因是Rayleigh-Taylor机理和斜压机理。 本文对V形火焰进行了数值模拟，目的是研究重力对流场的影响。计算结果显示，浮力加速了燃烧产物的上升，而这又加强了燃烧器出口附近的向上气流。重力的影响随来流速度的增大而减弱，但与火焰放热没有明显的关系，原因是火焰放热除了增强浮力也增大了燃烧产物的惯性力，两种效应相互抵消。 重力对预混火焰的影响表现为界面效应(对火焰锋面的影响)和体积效应(对流场的影响)，二者之间相互耦合。进入微重力后火焰总体特征(如火焰张角)发生的变化同时包含这两种效应。更多还原

【Abstract】 For the premixed flames of weak turbulence,the influence of turbulence and that of flame instability are comparable. Thus more influences,such as that of gravity,should be taken into consider when predicting or controlling these flames. The present study is focused on the influence of gravity on premixed V-flames of weak turbulence. The purpose is to provide basic data for the development of the theories about the premixed flames of weak turbulence.Methane-air premixed V-flames were detected under both normal gravity and microgravity by using drop tower facility and OH-PLIF. The dynamical behavior of flame fronts was recorded. To evaluate the influence of gravity,mean progressvariable c,flame surface density S and turbulent flame speed ST were extractedfrom the OH-PLIF images through image processing. The results show that wrinkles of the flames were enlarged and the values of ST were increased under microgravity.Also,the influence of gravity on flame wrinkles was weakened with the increase of turbulence intensity and the influence of gravity on ?was concentrated at the product side of flame brushes. For some of the flames,the influence of gravity was of the same order as that of turbulence or heal release. This implies that the influence of gravity should not be neglected in models of these flames. Rayleigh-Taylor mechanise anu baroclinic mechanism account for the suppression of flame wrinkles by gravity.To study the influence of gravity on flow field of the flames,numerical simulation was performed. The results show that buoyancy accelerated the rising plume of product and that the accelerated flow of the product in turn enhanced the rising flow near the burner exit. Also,the influence of gravity on flow field of the flames was weakened with increasing momentum of the coming flow,but no apparent correlation was found between the influence of gravity and heat release. The reason is that heat release also increased inertia force of product besides increasing buoyancy and these two effects were opposite to each other.As a whole,the influences of gravity on premixed flames are exhibited as two different effects:interface effect,namely the influence on flame fronts,and bulky effect,namely the influence on flow field,and the two effects couple with each other. Both of the two effects account for the change of overall features,such as flame angles,of the flames under microgravity.更多还原