湍流模型在NexGen燃烧器出口流场模拟中的应用

Application of Turbulence Models to the Simulation of the Exit Flow Field of the NexGen Burner

Nex Gen燃烧器是美国联邦航空管理局(federal aviation administration,FAA)指定用于开展防火试验的燃烧器。采用商用Ansys Fluent软件对NexGen燃烧器进行三维定常数值模拟,研究其出口流场,为防火试验试验方案的设计提供参考和指导。首先,分别利用冷态流场和燃烧反应的实验数据验证计算模型的有效性;其次,由于燃烧问题和NexGen燃烧器结构的复杂性,为寻求一种能够捕捉其流场变化特性的湍流模型,研究不同湍流模型对出口流场的影响。分别选用Standard k-ε模型、RNG k-ε模型和Realizable k-ε模型进行数值模拟。结果表明,采用不同湍流模型时,计算得到的速度场和温度场不同;而Realizable k-ε模型计算得到的燃烧器出口下游101.6 mm处校准面上的温度分布、七点平均温度和平均热流密度与实验值吻合较好,因此更适用于防火试验的模拟研究。

NexGen burner is specified by FAA for fire test,Ansys Fluent is used for three-dimensional steady numerical simulation to study the exit flow field of NexGen burner,which provides the reference and guidance for the design of fire test scheme.First,the experimental data of cold flow field and combustion reaction was used to verify the validity of the calculation model,then studied the effects of turbulent models on the exit flow field of NexGen burner,to seek a proper turbulent model that can capture the variation characteristics of flow field,due to the complex of combustion problem and NexGen burner structure.Standard k-εmodel,RNG k-εmodel,and Realizable k-εmodel were adopted to numerical simulate.The results show that the velocity profiles and temperature distributions is different when compute with different turbulent model,and Realizable kεmodel is reasonable to the fire test simulation,with its simulation results is good agreement with experimental data,such as temperature distribution at monitor plane,average temperature and heat flux of seven points.