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CCAST“颗粒物理”研讨会

作者： Y.L.Ding J.P.K.Seville R.Forster D.J.Parker School of Chemical Engineering . Positron Imaging Centre University of Birntingham Edgbaston Birmingham B15 2TT. UK School of Chemical Engineering . Positron Imaging Centre University of Birntingham Edgbaston Birmingham B15 2TT. UK School of Physics and Astronomy. Positron Imaging Centre. University of Birmingham. Edgbaston Birmingham B15 2TT UK School of Physics and Astronomy. Positron Imaging Centre. University of Birmingham. Edgbaston Birmingham B15 2TT UK

＜正＞ The industrial-scale rotating drums are usually operated in the rolling or slumping mode. For the rolling mode, the granular material bed can be divided into two regions, namely, a ’passive’ region where particles are carried up by the drum wall, and an ’active’ region where particles cascade down. As solids mixing mainly occurs in the active region, solids motion in this region and solids exchange between the active and passive regions are of prime importance for the overall performance of the drum. This paper reports some observations on particle motion in the transverse plane of a three-dimensional rotating drum operated at low and medium rotational speeds. The non-invasive PEPT （positron emission particle tracking） technique is used to follow particle trajectory and velocity. A mathematical model based on the thin-layer approximation is proposed to describe solids motion in the active layer. Reasonable agreement between the model predictions and experiments is obtained. A new parameter termed the ’solids exchange coefficient is proposed to characterise particle exchange between the passive and active regions. A theoretical expression for this parameter is also derived. This expression, upon application of the thin-layer approximation, is reduced to give an explicit relationship between the solids exchange coefficient and drum operating parameters such as rotational speed and fill percentage. as well as the bed material rheological properties. The solids exchange coefficient is also shown to give a possible scale-up rule for rotating drums operated in a rolling mode, 2001 Elsevier Science Ltd. All rights reserved.

关键词： Solids motion Solids mixing Rotating drums rolling mode PEPT

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Segregation of granular flow in the transverse plane of a rolling mode rotating drum

Segregation of granular flow in the transverse plane of a ro...

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CCAST“颗粒物理”研讨会

作者： Y.L.Ding R.Forster J.P.K.Seville D.J.Parker School of Chemical Engineering. University of Birmingham Edgbaston. Birmingham B15 2TT UK Positron Imaging Centre. University of Birmingham. Edgbaston Birmingham B15 2TT. UK School of Physics and Astronomy University of Birmingham. Edghaston. Birmingham B15 2TT UK Positron Imaging Centre. University of Birmingham Edgbuston. Birmingham B15 2TT. UK School of Chemical Engineering. University of Birmingham. Edgbaston. Birmingham B15 2TT UK Positron Imaging Centre University oj Birmingham Edgbaston Birmingham B15 2TT. UK School of Physics and Astronomy University of Birmingham. Eagbaston. Birmingham B15 2TT UK Positron Imaging Centre. University of Birmingham. Edgbaston. Birmingham B15 2TT. UK

＜正＞ This paper reports some observations on the behaviour of a segregated particle bed consisting of a mixture of small and large particles in the transverse plane of a rolling mode rotating drum. A non-invasive positron emission particle tracking （PERT） technique was used to follow the trajectories of different sized particles. A two-dimensional mathematical model based on the Eulerian approach and the thin layer approximation was developed to simulate solids motion and concentration distribution of different sized particles. It is shown that the bed structure for a binary mixture is similar to that for mono-sized particles, i.e. two-region structure consisting of a relatively thin ’active’ region and a ’passive’ region near the drum wall where particles move as a rigid body. At low rotational speeds, the velocity difference between small and large particles of a binary system is negligible in both the active and passive regions. At relatively high rotational speeds, the velocity difference is small in the active region and negligible in the passive region. Radial occupancy data suggest that small particles tend to concentrate in the core region, whereas large particles tend to occupy the shell region, in good agreement with model predictions. Axial occupancy data reveal that the axial particle mobility increases with drum rotational speed, and the mutual diffusivity of small particles is higher than that of large particles. It is also shown that the turnover time ratio of small to large particles is almost independent of concentrations of small particles under the conditions of this work. 2002 Elsevier Science Ltd. All rights reserved.

关键词： Particle segregation Solids motion Rotating drum rolling mode Bed turnover time Mathematical modelling PEPT

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Sand particle dislodgement in windblown sand

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Acta Mechanica Sinica 2014年第6期30卷 910-916页

作者： Tian-Li Bo Zheng Li Xiao-Jing Zheng Key Laboratory of Mechanics on Western Disaster and Environment Lanzhou University Department of Mechanics Lanzhou University School of Electronical and Machanical Engineering Xidian University

The incipient motion of sand particle from sand bed plays a very important role in the prediction of windblown *** this paper,we proposed a new method for predicting the incipient motion of sand particle based on wind speed fluctuation as follows,when the wind speed is larger than the critical wind speed,if the total impulse on sand particle is larger than the critical impulse,incipient motion of sand particle would take place,otherwise if ***,from the analysis of entrainment in the rolling and lifting modes,we come to the following *** the average wind speed is smaller than the critical wind speed,if the average wind speed is used to judge the incipient motion of sand particle,one will underestimate the number of sand particles jumping from the bed,if the instantaneous wind speed is used to judge incipient motion of sand particle,one will overestimate the number of sand particles jumping from the bed;When the average wind speed is larger than the critical wind speed,either the average or the instantaneous wind speeds is used to judge the incipientmotion of sand particles,one will overestimate the number of sand particles jumping from the bed.

关键词： Incipient motion rolling mode Average wind speed Total impulse Windblown sand

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CFD Simulation of Particles Mixing and Segregation in a Rotary Coating Disk: Influence of Drag models and Restitution Coefficient

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Open Journal of Applied Sciences 2022年第3期12卷 267-283页

作者： Salma Awad Nouh Ku Zilati Bt Ku Shaari Lau Kok Keong Shafirah Bt Samsuri Tigabwa Yosef Ahmed Department of Chemical Engineering Universiti Teknologi PETRONAS Seri Iskandar Malaysia

In this paper, the dynamics of a transverse plane of a rotary coating disk of a binary mixture system comprising sand and urea particles were simulated using the two-fluid model along with the kinetic theory of granular flow in Fluent 19.1. Although some parameters relating to the material properties and size of the rotary coating disk have been researched, the effects of both drag force and restitution coefficient on the flow characteristics have yet to be examined. Thus, this paper numerically examines the effect of the inclusion of drag models and particle-particle restitution coefficients on particle dynamics in a rotary disk operating in the rolling regime of the granular bed. Three particle-particle drag models were considered: the Schiller-Naumann, Syamlal-O’Brien, and Gidaspow. The Syamlal-O’Brien and Gidaspow models were both able to successfully simulate particle segregation in a perfect rolling regime, whereas the Schiller-Naumann drag model appeared to be unable to predict the segregation of the particles and the rolling flow regime under the assumed conditions. Four different values of the restitution coefficient were also investigated: 0.7, 0.8, 0.9, and 0.95. The higher restitution values of 0.9 and 0.95 were found to substantially affect flow characteristics, ensuring suitable rolling regime behaviour for the bed during the rotational movement. The lower restitution coefficients of 0.7 and 0.8, on the other hand, indicated that irregular velocity vectors could be obtained in the active region of the granular bed.

关键词： rolling mode Drag model Restitution Coefficient CFD

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Scaling relationships for rotating drums

Scaling relationships for rotating drums

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CCAST“颗粒物理”研讨会

作者： Y.L.Ding R.N.Forster J.P.K.Seville D.J.Parker School of Chemical Engineering. University of Birmingham Edgbastoh Birmingham B15 2TT. UK School of Physics and Astronomy University of Birmingham.Edgbaston Birmingham B15 2TT. UK School of Chemical Engineering University of Birmingham EdgbastonBirmingham B15 2TT. UK School of Physics and Astronomy University of Birmingham. Edgbaston Birmingham B15 2TT. UK

Rotating drums are extensively used in the chemical and process industries as kilns, mixers, dryers and reactors. Despite challenges from the development of newer and more specialised technologies such as fluidised beds, rotating drums continue to find applications. This is mainly due to their ability to handle varying feed stock’s, in particular granular materials with broad particle size distribution and significant difference in physical properties. However, the scale-up methodology tor such devices is still largely empirical and no general and systematic method has been established. This work is therefore devoted to the development of a set of scaling relationships which can be used to properly design rotating drums. The sealing relationships are obtained by non-dimensionalising the differential equations governing the behaviour of solids motion in rotating drums. The derived dimensionless groups include Froude number, pseudo-Reynolds number, pseudo-Euler number, drum geometric ratios, drum inclination, drum fill percentage, size distribution of particles, and physical properties of the particles and drum wall such as restitution coefficient and elasticity modulus. At relatively low pseudo-Reynolds numbers, the effect of velocity fluctuation and hence the granular temperature can be neglected, the granular Hows are thus in the quasi-static regime. At relatively low pscudo-Euler numbers, the effect of the frictional contribution to the total stress tensor is negligible and the flow is in the rapid granular flow regime. The upper limit of the quasi-static regime is evaluated and the adequacy of the application of granular flow kinetic theory to rotating drums is discussed. It is shown that granular flows in large drums operated at low to medium rotational speeds are often in Ihe quasi-static regime, whereas those in small drums operated at medium relational speeds may be in the transition How regime. Preliminary experiments have been carried out with the aim of re

关键词： Rotating drum Scaling relationships Solids mixing Granular flow rolling mode

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Granular motion in rotating drums: bed turnover time and slumping-rolling transition

Granular motion in rotating drums: bed turnover time and slu...

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CCAST“颗粒物理”研讨会

作者： Y.L.Ding R.Forster J.P.K.Seville D.J.Parker School of Chemical Engineering. University of Birmingham Edgbaston. Birmingham B15 2TT. UK Positron Imaging Centre. University of Birmingham Edgbaston. Birmingham B15 2TT UK Positron Imaging Centre. University of Birmingham. Edgbaston. Birmingham B15 2TT. UK School of Physics and Astronomy University of Birmingham. Edgbuston. Birmingham B15 2TT. UK School of Chemical Engineering. University of Birmingham Edgbaston. Birmingham B15 2TT. UK Positron Imaging Centre. University of Birmingham. Edgbaston. Birmingham B15 2TT. UK Positron Imaging Centre. University of Birmingham. Edgbaston. Birmingham B15 2TT. UK School of Physics and Astronomy University of Birmingham. Edgbuston Birmingham B15 2TT. UK

＜正＞ Theoretical models are presented tor calculation of the bed turnover time in both the slumping and rolling modes and the slumping-to-rolling transition in rotating drums with less than 50% volumetric fill of free-flowing granular materials. It is suggested that the transition from slumping to rolling occurs when the two turnover times arc equal. The model for the bed turnover time in rolling beds is compared with the data reported in the literature. Very good agreement has been obtained. The bed turnover time is also employed to define a new Froude number for constructing the bed behaviour *** is shown that the bed behaviour diagram based on the new Froude number brings the data points for sand and limestone into single curves. The implications of the bed turnover time for solid mixing and heat transfer within particle beds are also discussed. 2002 Elsevier Science B.V. All rights reserved.

关键词： Rotating drums Bed turnover time Solids motion rolling mode Slumping mode Transition Bed behaviour diagram

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