大幅面SLM成型仓结构优化及其流场特性

doi:10.12141/j.issn.1000-565X.220832

摘要/Abstract

摘要：

为探析激光选区熔化（SLM）成型仓内部的烟尘颗粒分布规律及排烟效率，本研究基于所建立的大幅面多孔风墙成型仓模型，采用Fluent离散相模型分析保护气体和烟尘颗粒在成型仓内部的流动规律，进而通过ANSYS中的多目标优化模块，基于多目标遗传算法（MOGA）对多孔风墙成型仓结构进行了优化。分别以成型仓进气口长度P₁、风墙孔半径P₂、锥形护板长度P₃和风墙孔轴长P₄作为优化变量，以成型仓内部中间截面保护气体的平均流动速度、成型仓进出口烟尘颗粒的质量浓度差以及整个成型仓内烟尘颗粒质量浓度的最大值作为优化目标，从而获得各个优化变量与优化目标的响应面及敏感性分析结果，并对优化前后的优化目标进行对比。结果表明：针对所优化的4个变量，对成型仓内中间截面保护气体流速影响的大小顺序是P₂>P₄>P₃>P₁，对进出口颗粒质量浓度差影响的大小顺序是P₂>P₄>P₁>P₃，对多孔风墙成型仓内最大颗粒质量浓度影响的大小顺序是P₂>P₁>P₃>P₄，多孔风墙的孔径大小对烟尘颗粒在成型仓内的流动起到最关键的作用。通过多目标遗传算法，得到优化后成型仓进气口长度为358 mm，风墙孔半径为20 mm，锥形护板长度为589 mm，风墙孔轴长为6 mm。与成型仓结构优化前进行对比，优化后成型仓内部中间截面保护气体流速提升了11.3%，进出口颗粒质量浓度差降低了16.8%，空间最大颗粒质量浓度降低23.9%，烟尘颗粒向外扩散的趋势有所减小，成型台面上方30 mm处通过的保护气体流速增加了21%，保护气体可以更加高效地将烟尘颗粒携带出成型仓。

关键词: 计算流体动力学, 结构设计, 烟尘, 激光选区熔化, 多目标优化

Abstract:

To study the distribution of soot particles and the efficiency of fume extraction inside the SLM (selective laser melting) forming bin, this research analyzed the flow law of shielding gas and soot particles in the forming bin with Fluent discrete phase model (DPM) based on the established model of the large-format porous wind wall forming bin. Then multi-objective genetic algorithm (MOGA) was used to optimize the structure of the porous wind wall forming bin. The length of air inlet P₁, the radius of wind wall hole P₂, the length of conical protection plate P₃ and the shaft length of wind wall hole P₄ were taken as optimization variables, and the average flow velocity of shielding gas in the middle section of the forming bin, the concentration difference of smoke particles at the inlet and outlet of the forming bin and the maximum concentration of smoke particles in the entire forming bin were taken as optimization objectives. The response surfaces and sensitivity analysis results of each optimization variable and optimization target were obtained, and the optimization target before and after optimization was compared. The results show that for the four optimized variables, the order of influence on the flow velocity of the shielding gas in the middle section of the forming bin is P₂>P₄>P₃>P₁; the order of influence on the concentration difference of inlet and outlet particles is P₂>P₄>P₁>P₃; the order of influence on the maximum particle concentration in the porous air wall forming bin is P₂>P₁>P₃>P₄; the pore size of the porous wind wall plays a key role in the flow of dust particles in the forming bin. Through multi-objective genetic algorithm, the optimized length of gas inlet is 358 mm, the radius of wind wall hole is 20 mm, the length of conical protection plate is 589 mm, and the shaft length of wind wall hole is 6 mm. Compared with that before the optimization of the structure of the forming bin, the flow velocity of the shielding gas in the middle section of the forming bin after the optimization increases by 11.3%; the concentration difference between the inlet and outlet particles decreases by 16.8%; the maximum particle concentration in space decreases by 23.9%; the trend of outward diffusion of soot particles decreases, and the flow velocity of the shielding gas passing 30 mm above the forming table increases by 21%, indicating that the shielding gas can carry the soot particles out of the forming bin more efficiently.

Key words: CFD, structural design, soot, selective laser melting, multi-objective optimization

中图分类号:

TG665

刘国勇, 张文鹏, 张铜鑫, 等. 大幅面SLM成型仓结构优化及其流场特性[J]. 华南理工大学学报(自然科学版), 2023, 51(12): 53-63.

LIU Guoyong, ZHANG Wenpeng, ZHANG Tongxin, et al. Structural Optimization and Flow Field Characteristics of Large Format SLM Forming Bin[J]. Journal of South China University of Technology(Natural Science Edition), 2023, 51(12): 53-63.

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参数	速度/（m∙s^-1）	质量流量/（kg∙s^-1）	压力/Pa	温度/K	湍流强度/%	水力直径/mm
速度入口	3		0	300	2.62	132
压力出口			0	300	5.00	120
壁面				300
质量流量进口		3×10^-15	0	300	5.00	500

网格样本	网格最小尺寸/mm	网格数	平均流量/（kg·s^-1）
1	2.5	865 837	0.075 6
2	1.5	1 467 309	0.088 9
3	1.0	2 426 338	0.091 2

序号	P₁/mm	P₂/mm	P₃/mm	P₄/mm	G₁/（mm∙s^-1）	G₂/（10^-19 kg∙mm^-3）	G₃/（10^-18 kg∙mm^-3）
1	5.0	19.0	1.2	2.9	265.8	0.9	3.6
2	9.4	18.6	8.4	2.3	255.1	0.9	2.0
3	4.6	11.4	17.2	3.7	173.5	2.0	4.0
4	5.4	19.8	12.4	3.5	280.2	0.9	5.4
5	1.4	14.2	6.8	0.5	227.0	1.1	2.1
6	5.8	15.0	0.4	0.9	221.2	1.2	2.8
7	7.4	18.2	18.8	1.5	242.0	1.2	6.0
8	9.0	12.6	11.6	4.1	175.3	2.3	4.6
9	9.8	13.4	6.0	1.3	209.4	1.4	3.7
10	3.4	15.8	19.6	2.5	215.7	1.4	3.8
11	1.8	14.6	3.6	4.7	192.9	1.7	6.9
12	7.0	17.4	9.2	0.1	249.9	1.3	1.3
13	6.6	12.2	2.8	3.3	181.8	2.0	6.1
14	8.6	13.0	18.0	1.7	190.0	1.9	5.3
15	3.0	19.4	10.8	0.7	272.5	1.0	2.5
16	0.2	17.8	14.0	3.1	245.5	1.1	3.5
17	7.8	16.2	4.4	4.5	211.6	1.6	8.6
18	8.2	16.6	16.4	4.3	220.5	1.5	5.2
19	2.2	10.6	7.6	3.9	176.5	2.0	5.1
20	1.0	17.0	5.2	2.7	231.6	1.3	3.0
21	0.6	11.8	14.8	2.1	189.5	2.1	4.0
22	3.8	15.4	13.2	4.9	203.9	1.6	3.1
23	4.2	13.8	15.6	0.3	226.5	1.5	4.7
24	2.6	11.0	2.0	1.9	186.9	1.7	2.8
25	6.2	10.2	10.0	1.1	169.2	1.9	2.5

序号	P₁/mm	P₂/mm	P₃/mm	P₄/mm	G₁/（mm∙s^-1）	G₂/（10^-20 kg∙mm^-3）	G₃/（10^-18 kg∙mm^-3）
Ⅰ	357.5	20.0	589.3	6.1	286.8	8.51	2.38
Ⅱ	357.6	19.8	589.8	6.2	285.4	8.63	2.27
Ⅲ	357.6	19.9	589.6	5.6	283.7	8.68	2.39

优化对比	G₁/（mm∙s^-1）	G₂/（10^-19 kg∙mm^-3）	G₃/（10^-18 kg∙mm^-3）
优化量/%	11.3	16.8	23.9
优化前	254.40	1.02	3.12
优化后	286.81	0.85	2.38