引用格式:

梅潇, 吴苇荣, 刘祥伟. 颗粒缩放理论标定未筛选烟煤离散元仿真参数[J]. 中国粉体技术, 2024, 30(2): 67-81.

MEI X, WU W R, LIU X W. Discrete elemental simulation parameters of unscreened bituminous coal calibrated by particle scaling theory[J]. China Powder Science and Technology, 2024, 30(2): 67-81.

收稿日期: 2023-11-08,修回日期:2023-11-30,上线日期:2024-01-14。

摘要: 【目的】为了给未筛选烟煤的仿真研究提供参数依据, 分析未筛选烟煤的离散元仿真参数, 保证仿真与实际颗粒的几何、 材料及运动学相似, 实现未筛选烟煤的可靠仿真研究。 【方法】采用实验和仿真相结合的方法, 测得未筛选烟煤的粒径分布、 密度、 静摩擦因数、 堆积密度、 休止角等基本参数; 基于颗粒缩放理论, 建立不同粒径范围内典型颗粒的放大模型,通过 Plackett-Burman、最陡爬坡、 Box-Behnken 试验对未筛选烟煤的泊松比、 切变模量、 滚动摩擦因数、 恢复系数、 Johnson-Kendall-Roberts(JKR)表面能等仿真参数进行标定。 【结果】以实验和仿真休止角相对误差最小为优化目标, 得到最优参数组合下的未筛选烟煤的仿真休止角为 37. 59°, 与休止角实验值 37. 81°的误差为 0. 58%; 仿真堆积密度为 717 kg / m³, 与堆积密度实验值 722 kg / m³ 的误差为 0. 69%。 【结论】煤-煤恢复系数与休止角呈负相关, 煤-煤和煤-钢滚动摩擦因数与休止角呈正相关,溅射现象会阻碍颗粒堆积。

关键词: 烟煤; 离散元; 休止角; 颗粒缩放理论; 参数标定

Abstract

Objective In recent years, the proportion of coal in port traffic has been increased. Unscreened bituminous coal, as an important fuel for power plants or industrial boilers, is one of the widely utilized coal types. Therefore, conducting simulation studies on the transport process of unscreened bituminous coal holds extreme importance. However, according to different simulation conditions,it is usually necessary to scale the particle size of unscreened bituminous coal to meet various simulation requirements. The validity of setting particle discrete element simulation parameters directly affects the accuracy of the simulation results. To obtain discrete elemental simulation parameters for unscreened bituminous coal particles after scaling processing, the simulation parameters should be calibrated to ensure that it meets the geometric similarity, material similarity and kinematic similarity with the actual particles.

Methods In this study, optimal parameter combinations for the discrete element simulation of unscreened bituminous coal were determined through a combination of physical experiments and simulation. Firstly, the basic parameters of bituminous coal, such as particle size distribution, density, static friction coefficients, bulk density, and angle of repose, were determined through physical experiments. Subsequently, typical particle models within different particle size ranges were established and the particle sizes were magnified by a factor of five using particle scaling theory principles. This approach aimed to shorten simulation time and reduce the computational demands on the computer performance during simulations. Following this, the Plackett-Burman (P-B) test was employed to analyze the significance of calibration parameters, including Poisson's ratio, shear modulus, rolling friction coefficient, restitution coefficient and Johnson-Kendall-Roberts (JKR) surface energy. The steepest ascent test was then utilized to quickly determine the range of optimal parameter combinations for the simulated angle of repose. Subsequently, a quadratic regression equation linking the significance parameters to the angle of repose was established by Box-Behnken (B-B) test.

Results and Discussion With the optimization objective of minimizing the relative error between the experimental and simulated angle of repose, the optimal parameter combinations are as follows: density at 1 326 kg / m³, Poisson's ratio at 0. 4, shear modulus at 0. 67 GPa, coal-coal static friction coefficient at 0. 72, coal-steel static friction coefficient at 0. 41, coal-coal rolling friction coefficient at 0. 107, coal-steel rolling friction coefficient at 0. 095, coal-coal restitution coefficient at 0. 5, coal-steel restitution coefficient at 0. 15 and the JKR surface energy is 14 J/ m². The simulated angle of repose under the optimal parameter combination is determined to be 37. 59°, with a mere 0. 58% relative error from the experimental value of 37. 81°. Additionally, the simulated bulk density is 717 kg / m³, with a mere 0. 69% relative error from the experimental value of 722 kg / m³.

Conclusion 1) Among the calibrated parameters, the parameters that have a significant influence on the angle of repose are:coal-coal restitution coefficient, coal-coal rolling friction coefficient and coal-steel rolling friction coefficient in sequence. The influence of the coal-coal rolling friction coefficient on the angle of repose is particularly significant. 2) The primary terms of the three significant parameters, the quadratic terms of coal-coal restitution coefficient and coal-coal rolling friction coefficient, and the interaction terms of coal-coal restitution coefficient and coal-coal rolling friction coefficient have significant influence on the angle of repose. The influence of the primary terms of the coal-coal restitution coefficient and coal-coal rolling friction coefficient on the angle of repose are particularly significant. 3) The coal-coal restitution coefficient is negatively correlated with the angle of repose, while coal-coal and coal-steel rolling friction coefficients show a positive correlation with the angle of repose. Additionally,sputtering phenomena are observed to hinder particle packing. 4) The above simulation parameter combinations are only applicable to the simulation study of unscreened bituminous coals at a 5-fold enlargement of particle size. Since the primary terms of the coal-coal restitution coefficient and coal-coal rolling friction coefficient are known to have a particularly significant influence on the angle of repose, only the coal-coal restitution coefficient and coal-coal rolling friction coefficient need to be recalibrated using the same method when determining the simulation parameter combinations for unscreened bituminous coal at the remaining multiples of the particle size.

Keywords: bituminous coal; discrete element; angle of repose; particle scaling theory; calibration of parameter

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