基于CFD模拟的甲烷裂解太阳能管式反应器结构优化

doi:10.11949/0438-1157.20210322

摘要/Abstract

摘要：

太阳能裂解甲烷具有产物纯度高且环保的优点。对湍流条件下的甲烷高温裂解太阳能管式反应器进行计算流体力学（CFD）模拟，为提高太阳能甲烷裂解反应器的转化率，通过调节反应器结构对流场进行优化。为了更加准确计算太阳能辐射的加热效应，在湍流反应扩散模型中引入碳颗粒的生成和聚集模型，并采用离散坐标（DO）模型进行辐射模型求解。然后，在太阳能管式反应器中引入射流及挡板进行流场调节，并对挡板高度、射流流速及角度进行优化，达到强化反应过程的目的。优化后的反应器中，甲烷转化率可以提高约8%。以反应转化率和代表强化成本的黏性耗散为指标，筛选出不同离散条件下的Pareto最优解，并用支持向量机回归（SVR）算法对离散的Pareto最优解进行插值，得到操作曲线和与之相对应的最优射流角度及流速。

关键词: 甲烷, 太阳能反应器, 湍流, 结构优化

Abstract:

Solar cracking of methane has the advantages of high product purity and environmental protection. In this paper, flow field in a solar tube reactor for high-temperature cracking of methane is optimized through computational fluid dynamics (CFD) simulation by adjusting structure of the tube reactor under turbulent conditions. The carbon particle generation and aggregation model were introduced to calculate the heating effect of solar radiation more accurately. And the discrete-ordinates method (DO) model was used to solve radiation model. A jet flow and baffles were introduced to adjust and optimize the flow field. The baffle height, jet velocity and angle were optimized to enhance the reaction process. The Pareto optimal solution is screened through the definition method, and the Pareto optimal solution is encrypted with the machine learning prediction algorithm to obtain the actual operation encryption curve and corresponding operation parameters. As a result of the optimization, the conversion rate of methane is increased by about 8%. On the basis of the conversion rate, the viscosity dissipation, which represents the increase in strengthening costs, is used as an indicator to filter out the discrete Pareto optimal solution. The support vector regression (SVR) algorithm is used to interpolate the discrete Pareto optimal solution to obtain the operating curve, the corresponding jet angle and jet velocity.

Key words: methane, solar reactor, turbulence, structure optimization

中图分类号:

TQ 037⁺.1

肖凡,贾胜坤,罗祎青,袁希钢. 基于CFD模拟的甲烷裂解太阳能管式反应器结构优化[J]. 化工学报, 2021, 72(10): 5053-5063.

Fan XIAO,Shengkun JIA,Yiqing LUO,Xigang YUAN. Structural optimization of methane cracking solar tube reactor based on CFD simulation[J]. CIESC Journal, 2021, 72(10): 5053-5063.

图/表 14

图1 太阳反应器单元模型

Fig.1 Schematic diagram for a cell of solar reactor

表1 模型验证数据

Table 1 Model validation data

温度/K	转化率/%
温度/K	实验值	模拟值
1608	72	71.45
1693	95	95.03
1778	99	100
1793	99	100
1928	100	100

图2 太阳能反应器单元结构优化

Fig.2 Optimization schematic diagram for a cell of solar reactor

图3 无优化(a)和优化后(b)太阳能反应器内的流线图

Fig.3 Streamlines in the solar reactor for the base case (a) and optimization case (b)

图4 无优化(a)和优化后(b)太阳能反应器内的温度分布

Fig.4 Temperature profile in the solar reactor for the base case (a) and optimization case (b)

图5 无优化(a)和优化后(b)太阳能反应器内的甲烷质量分数分布

Fig.5 CH4 mass fraction profile in the solar reactor for the base case (a) and optimization case (b)

图6 无优化（直管）和优化后反应器内的温度分布对比

Fig.6 Comparison of temperature distribution for the base case(straight tube) and the optimization case in the reactor

图7 无优化（直管）和优化后反应器内的甲烷摩尔分数分布对比

Fig.7 Comparison of CH4 mole fraction distribution for the base case(straight tube) and the optimization case in the reactor

表2 不同挡板高度在不同射流流速下甲烷增加的转化率

Table 2 The increase of methane conversion rate for different baffle heights at different jet flow rates

H/mm	增加的转化率/%
H/mm	1 m·s^-1	2 m·s^-1	3 m·s^-1	4 m·s^-1	5 m·s^-1	6 m·s^-1	7 m·s^-1	8 m·s^-1	9 m·s^-1
1.0	0.14	0.15	0.20	0.31	0.42	0.51	0.61	0.68	0.80
1.5	0.31	0.31	0.37	0.51	0.68	0.81	0.90	0.98	1.05
2.0	0.31	0.32	0.39	0.53	0.70	0.84	0.93	1.01	1.11

图8 不同角度及不同射流流速下甲烷增加的转化率（相同流速下，以1.5 mm挡板、0°夹角结构下甲烷转化率为基准进行比较）

Fig.8 Increase of methane conversion rate in different angles and different jet flow rates

图9 流速5 m·s-1下无优化（0°）和优化后（30°,45°,60°）反应器内的温度分布对比

Fig.9 Comparison of temperature distribution in the reactor without optimization(0°) and after optimization(30°,45°,60°)at a flow rate of 5 m·s-1

图10 不同射流角度和射流流速下黏性耗散云图

Fig.10 Contour of viscous dissipation under different injection angles and injection flow rates

图11 甲烷增加的转化率与黏性耗散关系

Fig.11 Relationship between increased methane conversion rate and viscous dissipation

图12 甲烷增加的转化率与黏性耗散Pareto最优解

Fig.12 Pareto optimal solution of increased methane conversion rate and viscous dissipation

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