基于VOF-DPM模型的离心喷嘴中的燃油流动及雾化特征研究

Study on Fuel Flow and Atomization Characteristics in a Centrifugal Nozzle based on VOF-DPM Model

针对燃油在离心喷嘴中的内部流动及其外部雾化过程,采用VOF-DPM模型对其进行了数值模拟研究。分析了压力对喷嘴出口处空气芯大小和液膜厚度的影响,得到了液膜破碎长度和雾化锥角等雾化特性,应用实验测试结果对数值模拟进行了验证,并与流体体积函数法(VOF)和离散相追踪法(DPM)进行了对比。结果表明:VOF-DPM模型可以真实反映离心喷嘴的内部流动和外部雾化特性,研究发现了与实际雾化过程符合的液膜破碎存在孔洞破碎和边缘破碎两种形式;捕捉到了在液膜表面的波动及气动力共同作用下液膜失稳破碎形成液滴的过程;燃油流动及雾化特性随着压力增加发生变化,喷嘴内空气芯直径增大,出口处液膜厚度减小,液膜的破碎长度下降。

For the internal flow of fuel in the centrifugal nozzle and its external atomization process,the VOF-DPM model was used for the numerical simulation study.The effect of pressure on the air core size and liquid film thickness at the nozzle outlet was analyzed,and atomization characteristics such as liquid film breaking length and atomization cone angle were obtained.The numerical simulations were validated by applying experimental test results and compared with the volume of fluid(VOF)and discrete phase model(DPM).The results show that the VOF-DPM model can truly reflect the internal flow and external atomization characteristics of the centrifugal nozzle.The existence of two forms of liquid film fragmentation in accordance with the actual atomization process,namely pore fragmentation and edge fragmentation,is found;the process of droplet formation is captured by destabilizing and breaking the liquid film under the combined effect of fluctuations on the surface of the liquid film and aerodynamic forces;the fuel flow and atomization characteristics change as the pressure increases,the diameter of the air core in the nozzle increases,the liquid film thickness at the outlet decreases,and the breaking length of the liquid film decreases.