Numerical Simulation of the Dynamic Mixing Process of HTPB/Al/AP/RDX Solid Propellant

doi:10.12382/bgxb.2024.0611

Abstract

Abstract:

The mixing process,as a crucial step in the fabrication of solid propellants,typically involves the incorporation of particulate phases such as aluminum (Al),ammonium perchlorate (AP),and RDX into a polymeric binder matrix.The binder slurry is applied onto the solid particles through mechanical kneading and stirring.The dispersion accompanied by dynamic blade kneading during the co-mingling of solid particulate phases in a mixer is simulated based on the Mixture solid-gas-liquid multiphase flow model.Dynamic rheological measurements of slurries with varying solid contents (0%-95%) are performed to construct a rheological model of propellant slurry.Considering the dynamic changes in granular concentration and their impact on local rheological properties,the mixing dynamic processes at different granular injection flow rates are simulated.The analysis focuses on the temporal patterns of granular concentration,pressure fields,and torque under various operating conditions.The results indicate that the proposed numerical simulation method is in good agreement with experimental results in Ref.[39] with an average error of less than 15%.The study reveals that the greatest pressure occurs at the tips of the near and far blades,while a low-pressure zone exists in the middle of the blades.During mixing,the blade torque exhibits a serrated fluctuation,and gradually increases with the addition of the particulate phase.A slight increase in the granular injection flow rate results in a minimal torque change.However,a significant increase in flow rate could lead to a torque increase of up to 90%.In the continuous feeding mixing process,the torque value at the farthest blade from the axis of rotation continues to rise,eventually reaching an average value 19 times that at the initial stage.This research provides insights for enhancing the efficiency and safety studies of solid propellant mixing processes.

Key words: solid propellant slurry, planetary impeller, dynamic particle injection process, mixture multiphase flow model

CLC Number:

V512

HU Mulin, WUYi, WANG Xingyuan, GUO Songlin, YU Junyi. Numerical Simulation of the Dynamic Mixing Process of HTPB/Al/AP/RDX Solid Propellant[J]. Acta Armamentarii, 2025, 46(7): 240611-.

Figures/Tables 25

Table 1 Composition and content of rheological experimental propellant slurry

组别	Al粉/%	AP/%	RDX/%	HTPB/%	固含量 /%
a	0	0	0	100	0
b	18	7	0	75	25
c	18	42	0	40	60
d	18	46	31	5	95

Fig.1 The variation in viscosity with shear rate for different solid content levels

Fig.2 The values of K and n at different solid contents

Fig.3 Modeling diagram of the vertical kneader

Fig.4 The movement path of two paddle blade tips

Table 2 Working condition settings

序号	入口数	粉末加注速度mm/s	工序
1	15	12.5	加注+混合46.8s
2	15	15	加注+混合39s
3	15	17.5	加注+混合33.43s
4	15	20	加注+混合29.25s
5	7	32.5	加注+混合39s
6	15	15	加注+混合Al粉7.45s
			混合直至均匀
			加注+混合AP 24.89s
			混合直至均匀
			加注+混合RDX 6.66s
			混合直至均匀

Table 3 Composition and content of solid propellant slurry

组成	黏合剂 (液相)	AL颗粒相 (d=10μm)	AP颗粒相 (d=100μm)	RDX颗粒相 (d=100μm)
含量%	24	18	46	12

Fig.5 Mesh reconstruction process

Fig.6 The changes in grid settings over time

Table 4 Time averaged values of centrifugal propeller torque with different grid numbers

组别	网格数	远心桨扭矩/(N·m)	偏差/%
网格1	2×10⁵	0.000295	-8.3
网格2	3×10⁵	0.000321	-0.3
网格3	4×10⁵	0.000324	0.6
网格4	7×10⁵	0.000322	0

Fig.7 Schematic diagram of plate stirring device

Fig.8 Relationship between power number and Reynolds number of non-Newtonian fluid model

Fig.9 Cloud map of pressure and solid powder concentration distribution at different times

Fig.10 Change of torque over time in the control group

Fig.11 Distribution of pressure and particle concentration in the mixing pot at 20s at different injection speeds:in the mixing pot,at the cross section with a height of 20mm

Fig.12 The change of torque with time under different injection speeds

Fig.13 Particle distributions in the mixing pot and at the cross section with a height of 20mm with 7 inlets and 15 inlets at 32s,34s,and 36s

Fig.14 Pressure distributions in the mixing pot and at the cross section with a height of 20mm with 7 inlets and 15 inlets at 32s,34s,and 36s

Fig.15 Torque over time at different inlet positions

Fig.16 Torque over time during the complete injection process

Table 5 I-VI curve average value of centrifugal propeller torque

曲线编号	扭矩平均值/(N·m)	与曲线I相比增幅/%
I	0.033299
II	0.091416	174.5
III	0.175965	428.4
IV V VI	0.506172 0.489363 0.639475	1420.1 1369.6 1820.4

Fig.17 Three-dimensional cloud map of AP particle distribution in Stage III (upper) and plane distribution cloud map at a height of 20mm(below)

Fig.18 Three-dimensional cloud map of Al particle distribution in Stage III (upper) and plane distribution cloud map at a height of 20mm(below)

Fig.19 Three dimensional cloud map of AP particle distribution in Stage V (upper) and plane distribution cloud map at a height of 40mm(below)

Fig.20 Three-dimensional cloud map of RDX particle distribution in Stage V (upper) and plane distribution cloud map at a height of 40mm(below)

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