旋转爆轰燃烧室内煤油裂解气冷流掺混特性研究

Research on Cold Flow Mixing Characteristics of Kerosene PyrolysisGas in Rotating Detonation Combustor

为研究旋转爆轰燃烧室内煤油裂解气的冷流掺混特性,使用OpenFOAM对小孔-环缝喷注结构下煤油裂解气的喷射掺混过程进行了二维大涡模拟研究。根据数值模拟结果,系统描述了燃烧室内冷流场的流场结构和可爆轰区域位置,对比分析了喷注压力(保持当量比不变)、裂解气喷注位置及喷注角度对掺混效果的影响,并用掺混不均匀度定量评价了裂解气与空气的掺混程度。研究结果表明:由于Kelvin-Helmholtz(K-H)不稳定性产生的大尺度湍流涡结构的卷带作用是煤油裂解气与空气混合的主要机制。采用有限速率模型和一步化学反应机理计算得到的煤油裂解气/空气一维可爆轰当量比上、下限分别为2.9和0.4。在空气和裂解气喷注温度分别为300 K、720 K时,增大喷注压力,掺混效果降低;裂解气喷注位置远离燃烧室入口,掺混效果提高;裂解气与空气喷注角度由同向到逆向,掺混效果提高。

In order to study the cold flow mixing characteristics of kerosene pyrolysis gas in the rotating detonation combustor,the injection and mixing process of kerosene pyrolysis gas in the small hole-annular slot injection structure was studied by two-dimensional large eddy simulation using OpenFOAM.According to the numerical simulation results,the flow field structure of the cold flow field in the combustor and the location of the area which is capable of detonation were systematically described.The effects of different injection pressure(keeping the equivalence ratio unchanged),different injection position and injection angle of pyrolysis gas on the mixing effect were compared and analyzed.The mixing degree of pyrolysis gas and air is quantitatively evaluated by the mixing non-uniformity.The results show that the entrainment of large scale turbulent vortex structure caused by Kelvin-Helmholtz(K-H)instability is the main mechanism for the mixing of kerosene pyrolysis gas and air.The upper and lower limits of one-dimensional detonation equivalence ratio of kerosene pyrolysis gas/air calculated by the finite rate model and one-step chemical reaction mechanism are 2.9 and 0.4 respectively.When the injection temperature of air and pyrolysis gas are 300 K and 720 K respectively,the mixing effect decreases with the increase of injection pressure.The injection position of pyrolysis gas is far away from the inlet of combustor,the mixing effect is improved.The injection angle of pyrolysis gas and air changes from the same direction to the opposite direction,the mixing effect is improved.