Simulation study of screw extrusion forming die for complex propellant grains with uniform arc thickness

doi:10.11949/0438-1157.20250133

Abstract

Abstract:

The screw extrusion process of solid propellant has the advantages of continuous process flow, stable product quality and strong self-control. The propellant grain produced is suitable for large-scale promotion and application. To fully enhance the combustion efficiency of screw-extruded propellants, this paper focuses on four complex grain geometries with equal arc thickness. Different screw extrusion die structures were designed, and the screw extrusion process of solid propellants was simulated based on numerical simulation methods. The flow characteristics and extrusion swelling phenomena of the propellant material during the extrusion process with different die structures were analyzed. The simulation results were compared with experimental data to explore the main factors influencing the precision extrusion quality of complex grain geometries. The results indicate that the flow state of the propellant material at the die outlet is largely determined by the pressure-building capability of the screw. Different die structures can improve the non-uniform flow of the material within the cross-section. By analyzing the flow balance coefficient during the screw extrusion process, it was found that the die structure matching the wheel-type grain geometry resulted in the smallest flow balance coefficient at the material outlet, with the flow velocity in the low-speed region being approximately 42%—56% of the maximum velocity. Additionally, the extrusion swelling ratio was relatively small at 1.095, indicating optimal grain formation quality.

Key words: numerical simulation, propellant grain die, screw extrusion, complex grain geometry, flow balance, extrusion swelling

摘要：

固体推进剂的螺压成型过程具有工艺流程连续、产品质量稳定、自控性强等优点，所制备的推进剂药柱适合大面积推广应用。为了充分提高螺压推进剂的燃烧利用率，针对4种等弧厚复杂药型，设计了不同的螺压挤出模具结构，基于数值模拟的方法，对固体推进剂螺压成型过程进行模拟研究，分析了药料在不同模具结构挤出成型过程中的流场特性和挤出胀大现象，并与实验结果进行对比分析，探究了影响复杂药型精密挤出成型质量的主要因素。研究结果表明：模具出口药料的流动行为很大程度上由模具内的压力分布决定，不同模具结构能够改善药料在横截面内的不均匀流动；分析药料在螺压成型过程的流动平衡系数发现，匹配车轮型药柱的模具结构使药料出口处的流动平衡系数最小，低速区流速为最大流速的42%~56%，且挤出胀大比较小，为1.095，此时药柱成型质量最佳。

关键词: 数值模拟, 药柱模具, 螺压成型, 复杂药型, 流动平衡, 挤出胀大

CLC Number:

TQ 320.66

Chenglong XU, Guo LI, Yu WANG, Linsheng XIE, Guohui ZHANG, Pengfei LIANG. Simulation study of screw extrusion forming die for complex propellant grains with uniform arc thickness[J]. CIESC Journal, 2025, 76(8): 3954-3963.

徐成龙, 李果, 王玉, 谢林生, 张国辉, 梁鹏飞. 等弧厚复杂药型螺压成型模具的模拟仿真研究[J]. 化工学报, 2025, 76(8): 3954-3963.

Figures/Tables 14

Fig.1 Cross-sectional schematic diagram of the 3D flow channel model in screw extrusion forming process

Fig.2 Schematic diagram of the four grain geometries

Fig.3 Rheological characteristic curve of the propellant material

Table 1 Flow boundary conditions

边界位置	边界代号	边界条件
入口	inlet	f_n=f_s=10⁴
螺杆机筒内壁	outwall_1	v_n=v_s=0
螺杆表面	inner_1	v_x,v_y,v_z
模具机筒内壁	outwall_2	v_n=v_s=0
模具模针表面	inner_2	v_n=v_s=0
出口	outlet	f_n=f_s=0

Fig.4 Curve of extrusion pressure variation along the axial direction of the die

Fig.5 Comparison cloud diagram of extrusion pressure in the cross-section of dies for different grain geometries

Fig.6 Curve of extrusion velocity variation along the axial direction of the die

Fig.7 Comparison cloud diagram of extrusion velocity in different cross-sections

Fig.8 Comparison cloud diagram of extrusion velocity in different cross-sections

Fig.9 Flow balance state of different grain geometries

Table 2 Extrusion swelling ratios of different complex grain geometries

药型	挤出胀大比B
梅花型	1.09
六边型	1.16
车轮型	1.09
蚊香型	1.08

Fig.10 Comparison diagram of extrusion swelling deformation for different grain geometries

Fig.11 Sample strips of formed propellant material

Table 3 Parameters related to extrusion swelling under different conditions

出口截面	面积S/mm²	挤出胀大比B
设计截面	790	—
模拟截面	865	1.09
实验截面	939	1.19

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