李潇,王佔元,刘宗宽,等.超临界喷雾中涡的演化过程数值研究[J].内燃机工程,2022,43(3):71-78.
超临界喷雾中涡的演化过程数值研究
Numerical Study of Vorticity Evolution in Spray Under Supercritical Condition
DOI：10.13949/j.cnki.nrjgc.2022.03.010
关键词:超临界  射流扩散  涡的演化  大涡模拟
Key Words:supercritical  jet diffusion  vorticity evolution  large eddy simulation
基金项目:国家自然科学基金项目（51921004）；天津市自然基金项目（20JCYBJC01110）
作者单位E-mail
李潇* 天津大学 内燃机燃烧学国家重点实验室，天津 300072 lixiao3716@tju.edu.cn 
王佔元 天津大学 内燃机燃烧学国家重点实验室，天津 300072  
刘宗宽 天津大学 内燃机燃烧学国家重点实验室，天津 300072  
周磊* 天津大学 内燃机燃烧学国家重点实验室，天津 300072 lei.zhou@tju.edu.cn 
卫海桥 天津大学 内燃机燃烧学国家重点实验室，天津 300072  
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摘要:针对Sandia国家实验室关于正十二烷喷雾的试验数据，基于开源软件平台OpenFoam，采用大涡模拟方法对以正十二烷为燃料喷入超临界和亚临界环境中的喷雾过程进行了三维数值模拟。该喷雾模型使用Peng–Robinson状态方程及真实流体的热物性和输运系数计算方法。将计算得到的喷雾贯穿距和燃油质量分数与试验结果进行对比，证明所构建的喷雾模型能准确地捕捉超临界状态下喷雾的特征。通过对超临界和亚临界两种环境下喷雾过程的比较，重点研究了不同环境下燃油扩散混合过程的差异和涡的演化过程。计算结果表明，超临界环境下的射流扩散率和扩散角度均大于亚临界，在超临界环境下燃油射流与环境气体间的扩散混合效率更高。射流在超临界状态下会加速涡的形成，从而促进射流与周围气体的混合。射流与周围气体间的速度梯度是决定高速射流中涡演化过程的主要因素。超临界环境下大密度梯度的存在会使斜压转矩增大，从而促进涡的发展，密度梯度对射流发展有着重要影响。
Abstract:Taking the n-dodecane spray test of Sandia National Laboratory as the research object， based on the open source software platform OpenFoam， the large eddy simulation method was used to simulate the spray process of n-dodecane in supercritical and subcritical environments. The Peng–Robinson equation of state and calculation methods of thermophysical properties and transport coefficients of real fluid were used. The spray penetration distance and fuel mass fraction were compared with experiment results to prove that spray model can accurately capture spray characteristics. Through the comparison of the spray process， the differences of the fuel diffusion and mixing process and the evolution process of the vortex in different conditions were researched. The results show that jet diffusivity and the diffusion angle under supercritical condition are both greater than subcritical condition， and diffusion and mixing efficiency of fuel in the supercritical environment is higher. In supercritical state， the jet will accelerate the formation of vortex and promote mixing of jet with surrounding gas. The velocity gradient is the main factor that determines evolution of vortex in high-speed jet. The existence of a large density gradient under supercritical condition will increase baroclinic torque， thereby promoting the development of vortex. Density gradient has an important influence on jet mixing.
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