超声速横侧射流混合特性的大涡模拟  

Large eddy simulation of mixing characteristic of jet in supersonic crossflow

作　　者：曹长敏 赵马杰 周涛涛[1] 叶桃红[1] 

机构地区：[1]中国科学技术大学热科学和能源工程系,安徽合肥230027

出　　处：《中国科学技术大学学报》2015年第8期665-673,共9页JUSTC

基　　金：国家自然科学基金(51176178);国家重点自然科学基金(50936005)资助

摘　　要：采用大涡模拟方法研究了Gamba超声速燃烧室内的横侧射流流场中大尺度涡旋结构以及当地混合特性.超声速来流受到音速射流流体的阻碍,形成了复杂的激波和涡旋结构.由计算结果中的平均马赫数分布图可以清楚地看到激波结构,包括弧形激波、λ激波、桶状激波以及马赫盘;采用Q准则表征三维涡旋结构,可以看到稳态的反向旋转涡对(CVP)、尾迹反向旋转涡对(TCVP)、马蹄涡以及非稳态的射流剪切层涡等结构;此外,由平均流线图可以看到,TCVP结构与CVP结构的旋转方向相反,不对称的CVP结构导致燃料质量分数展向分布不均匀.引入概率密度函数方法分析当地混合特性,结果表明射流近场混合主要发生在射流出口上游回流区以及桶状激波下侧和射流剪切层下侧的射流尾迹区内;射流远场混合分数的概率密度分布从β分布逐渐过渡为高斯分布.研究射流浓度衰减特征,结果表明氢气质量分数沿射流浓度最大迹线呈指数-0.7衰减.Large eddy simulation was performed to study the large scale vertical structures and the mixing characteristic of supersonic transverse injection flow in the Gamba combustor.The supersonic flow is obstructed by the sonic jet,resulting in very complex three dimensional shock waves and vertical structures.All of the shock waves,including bow shock,λshock,expansion shock,barrel shock and Mach disk,can be seen in the mean Mach number contour.The three-dimensional vertical structures,such as steady counter-rotating vortex pairs(CVP),trailing counter-rotating vortex pairs(TCVP),horseshoe vortices and unsteady jet shear layer vortices,can be visualized by the iso-surface of Q-criterion.The TCVP structure rotates in the opposite direction of the CVP,which can be characterized by the averagestreamline.Moreover,the asymmetric CVP structure leads to non-uniform distribution of fuel mass fraction in span-wise direction.The probability density functions(PDFs)were introduced to study the mixing characteristic in the near field,far field and the recirculation regions in the upstream of the jet.The results show that significant mixing occurs in the recirculation regions,the bottom of the barrel shock and the wake below the jet shear layer.The PDFs of mixture fraction obeyβdistribution in the near jet flow-field and develop into Gauss distribution in the downstream.The study of the concentration decay shows that the H2 mass fraction obeys exponential decay along the maximum centerline with the index being about-0.7.

关 键 词：超声速横侧射流 大涡模拟 大尺度涡旋结构 混合特征 概率密度函数 

分 类 号：O358[理学—流体力学]