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要开展凝胶推进剂液滴燃烧特性的实验研究,必须首先形成凝胶推进剂液滴,在毛细管末端形成液滴是常用的液滴生成方法之一。为了揭示毛细管末端凝胶推进剂液滴的形成过程,求解了轴对称坐标系下的N-S方程,采用VOF(volume of fluid)方法捕捉液滴形成过程中气液交界面的演化规律,研究了无量纲液滴颈部直径DN/D0和无量纲液滴高度L/D0随时间的变化规律,并且与实验结果进行比较,验证了数值模型的可靠性。计算结果表明:在液滴形成过程中,液滴不是一直处于稳态;液滴颈部存在较大的剪切率,导致粘度下降,进而加快了颈部的断裂和自由液滴的形成;颈部断裂后,与液滴相连的部分迅速与液滴融合,出现很大的正向速度,而与毛细管末端相连的部分迅速收回,出现很大的负向速度。
To carry out experimental research on the characteristics of droplet combustion of gel propellant, it is necessary to form gel propellant droplets first, and droplet formation at the capillary end is one of the commonly used droplet generation methods. In order to reveal the formation process of droplet of capillary gel propellant, the NS equation in axisymmetric coordinate system was solved, and the VOF (volume of fluid) method was used to capture the evolution of liquid-gas interface during droplet formation. The diameter of the neck DN / D0 and the dimensionless droplet height L / D0 change with time, and compared with the experimental results verify the reliability of the numerical model. The calculation results show that the droplet is not always in the steady state during the droplet formation. The droplet neck has a large shear rate, which leads to the decrease of the viscosity, which accelerates the fracture of the neck and the formation of free droplets. The neck After the rupture, the part connected with the drop quickly fused with the droplet, a great positive velocity appeared, while the part connected with the capillary end rapidly recovered with a great negative velocity.