煤油超燃冲压发动机两相流场数值研究 (Ⅲ)煤油在超燃流场中的多步化学反应特征

Combustion flow of kerosene-fueled scramjet with 3D cavity (Ⅲ) Multi-step chemistry characteristics of kerosene

关键词:  冲压喷气发动机  煤油  超音速燃烧  导流型凹槽+  模型

Key words:  Scramjet  Kerosene  Supersonic combustion  Cavity with flow-usher slot~+  Model

摘要:

深入分析了煤油代用燃料C12H23的17组分30步反应模型在超燃冲压发动机流场内的细观化学反应动力学特征, 结果表明: (1) 该化学反应模型比较合理地描述了煤油在超燃流场内的裂解、点火、裂解产物的燃烧以及和NOX的生成等基本规律和特征, 其中对于OH分布特征的预示和文献的利用PLIF的物理观测结果一致。不过, 其单步裂解机制对温度场的预估偏高。(2) 对导流型凹槽内的化学动力学特征分析表明, 导流槽由于加强了凹槽外氧气向凹槽内的输运, 使得凹槽内的燃烧得以强化, 生成的CO2 偏多。(3) 煤油的化学反应动力学过程对于准确预示和评价煤油在超燃发动机内的燃烧状况及发动机整体性能有重要影响。

Abstract:

The chemistry mechanism of kerosene is key to numerical simulations of kerosene’s supersonic combustion flow field. The chemical dynamic characteristics of surrogate fuel’s (C₁₂H₂₃) reduced chemistry model were analyzed in detail. It was concluded that: （1） the cracking, ignition, combustion and NO_X emission characteristics are properly described by this chemistry model, in which the predicted distribution of OH is in consistent with the PLIF observation of literature, but the temperature flow field was over-predicted by one step cracking mechanism to some extent. （2） The production of CO₂ in 3D cavity is relatively high, which reveals more combustion enhancement in 3D cavity. Besides, the OH distribution in 3D cavity’s transverse vortex proves its flame stabilizing mechanism in microcosmic view. （3） The description of kerosene’s reacting dynamics plays an important role in exact numerical prediction of kerosene’s supersonic combustion flow field and evaluation of kerosene-fueled scramjet’s performance.