Discrete elemental simulation parameters of unscreened bituminous coal calibrated by particle scaling theory
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 valid-ity of setting particle discrete element simulation parameters directly affects the accuracy of the simulation results.To obtain dis-crete 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 quad-ratic 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 modu-lus 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 combina-tion 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 applica-ble 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 multi-ples of the particle size.
bituminous coaldiscrete elementangle of reposeparticle scaling theorycalibration of parameter
万方数据
维普
