【作者】 杨帆；

【导师】 叶桃红；

【作者基本信息】 中国科学技术大学 ， 动力工程及工程热物理， 2021， 硕士

【摘要】 本文在混合欧拉-拉格朗日框架下,基于湍流诱导一次雾化机理,将同时受液体湍流和空气动力学影响的横向射流一次雾化过程拆分为两个过程:湍流诱导一次雾化过程与空气动力学修正过程,并将新发展的一次雾化模型植入到OpenFOAM计算流体力学平台,研究了低液气密度比下的横向射流雾化和高频正弦脉冲激励下的横向射流雾化。具体工作如下:(1)开展液气密度比为312的横向射流雾化模拟,此时一次雾化同时受液体湍流和空气动力学影响,计算结果表明,修正模型所模拟的液滴直径和液滴速度分布均与实验测量值基本吻合,模型预测的喷嘴下游20mm处D32、D10的最大平均误差为10.3%。基于k-Omega SST的RANS、DES和VLES湍流模型对于雾化结果的影响研究表明,相较于RANS模型,DES和VLES湍流模型能够捕捉到流场的瞬态小尺度涡旋结构。总体而言,VLES湍流模型在液滴的速度分布和液滴大小分布预测上均优于DES湍流模型。(2)针对不同雾化破碎点高度系数Cb进行模拟,计算结果表明,对长径比为10的喷嘴,选择Cb为3.3最合理。此外,研究了 KH-RT、Reitz-Diwakar和TAB二次破碎模型对雾化结果的影响,发现当计算域没有明确的二次雾化现象时,不宜采用二次雾化模型。(3)开展射流高频脉动工况下的横向射流雾化模拟,计算结果表明,在高频正弦脉动下,随着射流脉动幅值的增加,射流穿透深度提升,主要液滴速度逐渐提高,液滴直径减小。随着射流脉动频率的增加,Sr数从0.25增大到1.0的过程中,当Sr数小于等于0.75时,射流穿透深度逐渐增大,主要液滴速度降低,直径降低,当Sr数大于0.75后,射流穿透深度降低,主要液滴速度增大,直径增大。更多还原

【Abstract】 In this paper,based on the turbulence-induced primary atomization mechanism in the hybrid Euler-Lagrange framework,the transverse jet primary atomization process,which is affected by both liquid turbulence and aerodynamics,is split into two processes:the turbulence-induced primary atomization process and the aerodynamic correction process,and the newly developed primary atomization model is implanted into the OpenFOAM computational fluid dynamics platform to study low liquid-to-gas density ratio transverse jet atomization and transverse jet atomization under high-frequency sinusoidal pulse excitation.The specific works are as follows:(1)The simulation of transverse jet atomization with liquid-to-gas density ratio of 312 is carried out,where the primary atomization is affected by liquid turbulence and aerodynamics at the same time.The droplet diameter and velocity distribution predicted by the new model are generally in agreement with the experimental results.And the maximum average error of D32 and D10 at 20 mm downstream of the nozzle predicted by the model is 10.3%.Three different k-0mega SST based turbulence model is used in the simulation.The result shows that the DES and VLES turbulence models are able to capture the transient small-scale vortex structure of the flow field compared to the RANS model.In general,the VLES turbulence model outperforms the DES turbulence model in respect of droplet velocity distribution and droplet size distribution prediction.(2)Simulations are performed for different atomization breaking point height coefficients Cb.Simulation found that for a nozzle with length to diameter ratio of 10,Cb of 3.3 is the most reasonable choice.In addition,the influence of KH-RT,Reitz-Diwakar and TAB secondary fragmentation models on the atomization results is studied,and it is found that when there is no clear secondary atomization phenomenon in the computational domain,the secondary atomization model should not be used.(3)The simulation of transverse jet atomization under high-frequency pulsation of the jet is carried out.The results showed that under high-frequency sinusoidal pulsation,with the rise of the jet pulsation amplitude,the jet penetration depth enhanced,the main drop velocity gradually raised and the drop diameter reduced.The Sr number increases from 0.25 to 1.0 with the rise of pulsation frequency,when the Sr number is less than or equal to 0.75,the jet penetration depth gradually enhanced,the main droplet velocity decreases and the droplet diameter becomes smaller,and when the Sr number is greater than 0.75,the jet penetration depth decreases,the main droplet velocity increases and the droplet diameter becomes larger.更多还原