基于MAC方法的膏体推进剂管道流动特性

Pipe flow characteristics of pasty propellant based on MAC method

针对膏体推进剂管道内流动与挤出胀大问题,开发了基于标志网格(MAC)法和压力耦合方程组的半隐式方法(SIMPLE)的非牛顿不可压流体求解器,膏体推进剂本构方程采用剪切稀化幂率(power-law)模型。通过膏体推进剂管道出口挤出形态数值仿真结果与实验结果的对比,验证了数值计算方法的可靠性和准确性。在此基础上,对膏体推进剂在管道内的流动与挤出过程进行数值计算,详细分析了不同时刻下膏体推进剂的流动过程与挤出胀大形态,研究了入口速度和管道直径对膏体推进剂管道流动特性的影响。结果表明:膏体推进剂在挤出过程中,自由表面随时间变化,稳定阶段呈半球形,在管道出口存在明显的挤出胀大现象,当管道长度和直径不变时,压降和挤出胀大比都随入口速度的增加而增大;当入口速度相同时,压降和挤出胀大比随管径的增加而减小。

Targeting the problem of the pasty propellant flow in the pipe and extrusion swell,a non-Newtonian incompressible fluid solver based on the mark and cell(MAC)method and the semi-implicit method for pressure-linked equation(SIMPLE)was developed.Shear-thinning power-law model was used in the constitutive equation of the pasty propellant.The reliability and accuracy of the numerical method were verified by comparing the numerical result of the extrusion morphology of the pasty propellant at the pipe outlet with the experimental result.On this basis,the flow process and extrusion swell of the pasty propellant were numerically calculated and analyzed in detail.The influences of inlet velocity and pipe diameter on the flow characteristics of the pasty propellant were investigated.Results showed that the free surface of the pasty propellant changed with time during the extrusion process.In the stable stage,the free surface of the propellant was hemispherical,and there was obvious extrusion swelling at the outlet of the pipe.When the pipe length and diameter were constant,the pressure drop and the extrusion swell ratio both increased with the increase of the inlet velocity.However,when the inlet velocity was constant,the pressure drop and extrusion expansion ratio decreased with the increase of pipe diameter.