微滴喷射工艺参数与液滴形态关系的数值模拟

Numerically Simulating Relationship of Process Parameters Between Droplet Ejection and Droplet Morphology

以微滴喷射的增材制造技术为研究对象,采用守恒水平集方法建立了液滴喷射过程的数值仿真的物理数学模型。通过仿真实验分析了液滴喷射的流场分布,采用曲面响应法的中心复合设计建立了拟合模型并进行了修正,提出了液滴喷射过中液滴成球距离和断裂高度分别与入口处压强脉冲的幅值与脉宽的拟合关系式。模拟结果表明:在液滴喷射过程中喷嘴入处的压强脉冲的幅值与脉宽和液滴形态之间有密切的关系,压强幅值与脉宽之间存在一个临界关系,当不满足这个关系时液滴无法从喷嘴口喷出,只有当压强幅值与脉宽满足这个临界条件时,液滴才能够克服喷嘴口处的表面张力顺利喷出;在满足喷射条件的情况下压强幅值与脉宽时间越大,喷出的液滴成球距离越远;压强幅值与脉宽时间越小,喷出的液滴成球距离越近。

This paper studies the additive manufacturing technology based on droplet ejection.The numerical calculation of the droplet ejection process was carried out with the level set method.After analyzing the flow field distribution of droplet ejection,the response surface method(RSM)is used to establish and then correct the fitting model.The fitting relations between the distance of droplets that form a ball and the fracture height under different parameters are put forward.According to the fitting relations,the morphology of the ejected droplets under different inlet pressure pulse conditions is predicted,and the reliability of the fitting relations is verified by comparing the prediction results with the simulation results.The simulation results show that the amplitude and pulse width of the pressure pulse at the nozzle inlet and the droplet morphology during the droplet ejection are closely related.There exists a critical relationship between the pressure amplitude and the pulse width.When this relationship is not satisfied,the droplet cannot be ejected from the nozzle.Only when the pressure amplitude and pulse width satisfy this critical relationship can droplets be ejected smoothly to overcome the surface tension.In the case of meeting the ejection conditions,the greater the amplitude and pulse width of the pressure pulse is,the farther the droplet is formed into a ball.The smaller the amplitude and pulse width of the pressure pulse is,the closer the droplets are to the ball.