贫油预混预蒸发燃烧室回火现象的大涡模拟

Large Eddy Simulation of Flashback Phenomenon in a Lean Premixed Prevaporized Combustor

为研究贫油预混预蒸发(LPP)燃烧室的回火现象及形成机理,基于大涡模拟(LES)及部分预混燃烧模型,对Schneider试验进行数值计算,分别将冷态及燃烧温度场与试验结果进行对比,验证了模型的准确性。将该模型应用于LPP燃烧室,并利用详细的化学机理对航空煤油火焰传播速度进行修正,成功重现了回火现象的发生并向主燃级上游传递的动态过程,通过流场分析发现局部形成的不规则涡结构在回火现象中扮演着重要角色。进一步从涡量方程的角度对涡结构进行分析,发现燃烧引起的斜压及体积膨胀是诱发回火现象的主要原因。

To study the flashback phenomenon and formation mechanism in a lean premixed prevaporized （LPP） combustor, large eddy simulation （LES） and partially premixed combustion model are employed to study the flashback phenomenon based on an experiment conducted by Schneider. The cold flow field and combustion temperature are compared with experiment results, the accuracy of the model is verified. It is then used in the simulation of the occurrence and propagation of flashback within an LPP combustor. Detailed chemical mechanism is employed to predict the kerosene laminar and turbulent flame speed. The onset and propagation of the flashback is reproduced successfully. According to the observation of the flow field, the complicated vortex in the flow field plays an important role during the flashback onset and propagation. Further analysis of the vorticity equation for the structure of the vortex shows that the baroclinic torque and volume expansion induced by combustion may be the main cause of the flashback phenomenon in a gas turbine combustor.