选择性激光熔化成形点阵结构及其沸腾传热特性

doi:10.16085/j.issn.1000-6613.(2)2018-1842

摘要/Abstract

摘要：

选择性激光熔化（selective laser melting，SLM）技术具有高度的加工灵活性，能够成形高表面积-体积比的点阵结构，用于强化池沸腾传热。本文主要研究单胞构型、梯度以及SLM成形特性对点阵结构样品强化传热效果的影响。使用CuSn10粉末成形出尺寸为15mm×15mm×15mm、孔隙率为59.82%～62.10%、侧表面轮廓算术平均偏差（R _a）为11.6～15.5μm的点阵结构样品，样品表面存在粉末黏结，可提供大量潜在汽化核心；使用去离子水进行池沸腾传热实验，得出两种单胞构型点阵结构的起始沸腾点（104～105℃）和临界热流密度（86.7～110.2W/cm²），发现不同单胞构型的点阵结构在沸腾传热过程中有不同的气泡逃逸和液体补充通道；成形出两种下层孔小、上层孔大的梯度点阵结构，将其沸腾传热曲线与均匀点阵结构进行对比，结果表明梯度结构对不同阶段沸腾传热的传热条件有着不同的影响。

关键词: 选择性激光熔化, 点阵结构, 梯度结构, 沸腾传热

Abstract:

Selective laser melting (SLM) provides great geometrical freedom for forming lattice structure, which can be applied to pool boiling heat transfer enhancement with its high surface area-volume ratio. This paper aims to explore the effect of cellular unit, gradient and SLM formability on the heat transfer of lattice structure samples. Lattice structure samples are formed using CuSn10 powder with size of 15mm×15m×15mm, porosity of 59.82%—62.10% and side surface arithmetic mean deviation (R _a) of 11.6—15.5μm. There is powder adhesion in surface of the samples, which can provide a large number of vaporized cores. Pool boiling heat transfer of water is investigated for samples and boiling point of 104—105℃ and critical heat flux(CHF) of 86.7—110.2W/cm² are obtained, which shows the cellular unit has important influence on bubble departure and liquid replenishment pathways during boiling heat transfer. Two kinds of gradient structures are formed with small holes in the lower part and large holes in the upper part. In comparison with uniform lattice structures, the gradient structures show different heat transfer curves, which reveals that gradient has different effects on the heat transfer conditions of boiling heat transfer at different stages.

Key words: selective laser melting (SLM), lattice structure, gradient structure, boiling heat transfer

中图分类号:

TF124
TK124

李培, 钱波, 张池, 张莉, 魏青松. 选择性激光熔化成形点阵结构及其沸腾传热特性[J]. 化工进展, 2019, 38(07): 3028-3037.

Pei LI, Bo QIAN, Chi ZHANG, Li ZHANG, Qingsong WEI. Selective laser melting forming lattice structures and their boiling heat transfer characteristics[J]. Chemical Industry and Engineering Progress, 2019, 38(07): 3028-3037.

图/表 24

图1 SLM成形的微结构表面

图2 使用拓扑优化获得最大有效热导率

图3 SLM成形的铝热管

图4 CuSn10粉末SEM图片

表1 CuSn10粉末化学成分

元素	质量分数/%
Sn	9.88
O	0.039
Cu	余量
杂质	≤0.2

表2 CuSn10粉末参数

项目	数值
球形度/%	96
氧含量/mg?kg^-1	398
粒度D ₁₀/μm	23.56
粒度D ₅₀/μm	31.62
粒度D ₉₀/μm	52.83
0～53μm粉末质量分数/%	95.50

图5 点阵结构设计过程

图6 点阵结构模型

图7 阶梯梯度点阵结构

表3 点阵结构参数

序号	单胞构型	支柱直径/mm	孔隙率/%	表面积/mm2
C1-1	C1型	0.6～1.2	66.86	4175
C1-2		0.885	67.02	4331
C1-3		0.895	67.02	4279
C2-1	C2型	0.6～1.2	66.86	4191
C2-2		0.895	66.88	4306
C2-3		0.895	67.06	4280

图8 选择性激光熔化成形设备

表4 SLM成形工艺参数

激光功率

扫描速度

/mm·s^-1

扫描间距

/mm

层厚

/mm

图9 沸腾传热实验装置

图10 SLM成形的点阵结构样品

图11 点阵结构样品的SEM图片

图12 区域1粗糙度的测量

图13 样品侧表面粗糙度测量结果

表5 点阵结构样品的孔隙率

序号	设计孔隙率/%	实际孔隙率/%	孔隙率相对误差/%
C1-1	66.86	60.82	9.0
C1-2	67.02	61.49	8.3
C1-3	67.02	61.39	8.4
C2-1	66.86	61.69	7.7
C2-2	66.88	62.06	7.2
C2-3	67.06	62.10	7.4

图14 不同倾斜角度支柱的截面

图15 点阵结构和平面样品的饱和沸腾曲线

图16 均匀点阵结构样品的饱和沸腾曲线

图17 点阵结构样品的饱和沸腾曲线

图18 C1型单胞点阵结构的核态沸腾过程

图19 C2型单胞点阵结构的核态沸腾过程

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