A CFD–DEM study of bubble dynamics in fluidized bed using flood fill methodby Youjun Lu, Jikai Huang, Pengfei Zheng

Chemical Engineering Journal

Similar

Simulations of Reacting Fluidized Beds Using an Agent-Based Bubble Model

Authors:
S. Pannala, C.Stuart Daw, John Halow
2003

From Bubbles to Clusters in Fluidized Beds

Authors:
B. J. Glasser, S. Sundaresan, I. G. Kevrekidis
1998

DYNAMIC RESPONSE OF FLUIDIZED BEDS

Authors:
DONALD E. BEASLEY, LAWRENCE P. GOLAN
1989

Bubble properties in large-particle fluidized beds

Authors:
L.R. Glicksman, W.K. Lord, M. Sakagami
1987

Text

fly, Xi the correlations and experimental data. ble beh  2015 Elsevier B.V. All rights reserved. tribution of bubbles and their physical properties in the bed such as position, dimensions, rise and velocity [1,3]. Therefore, an indepth understanding of bubble characteristics is essential to the efficiency operation of fluidized bed.

A large number of investigations focusing on bubble characteristics in fluidized bed, mainly experiments, have been carried out. bble characterisvestigated al image an d bubble v are proposed. These correlations estimated their experi results quite well. Busciglio et al. [1] studied the fluid dynamics of a lab-scale two-dimensional bubbling bed using a

CCD camera. The images were processed by developing a digital image analysis method based on Matlab Image Processing

Toolbox, and various significant bubble properties such bubble size and velocity distribution were obtained simultaneously. Their results were compared with relevant literature correlations and sound agreements were found. Hulme et al. [6] studied the bubble ⇑ Corresponding author. Tel.: +86 29 82664345; fax: +86 29 8266 9033.

E-mail address: yjlu@mail.xjtu.edu.cn (Y. Lu).

Chemical Engineering Journal 274 (2015) 123–131

Contents lists availab ne w.at minimum fluidization conditions flows through the bed, bubbles and through flow are formed [2]. The natural phenomena of bubbles break-up and coalescence potentially worsen the scenario.

The fluidization quality of a bed is highly dependent on the disand the results showed that each of these two bu tics follows normal distribution. Shen et al. [5] in properties by developing a new method of digit and new correlations about bubble diameter anhttp://dx.doi.org/10.1016/j.cej.2015.03.117 1385-8947/ 2015 Elsevier B.V. All rights reserved.bubble alysis, elocity mental izationFlood fill method 1. Introduction

Fluidized bed has been employed extensively in numerous gas– solid contacting processes, such as coal-fired power plants, coal gasification and many other chemical industries. Bubbles often exist in these beds, and their characteristics govern hydrodynamics and efficiency of the operation for which the bed is used [1]. When the gas flow in excess of that required to maintain the dense phase

The experimental method includes intrusive technology such as inductance, capacitance or thermal probes, and non-intrusive technology such as CCD camera photographing and X-ray, which mainly based on digital imaging technology [1,4–6]. Imaging technology is based on different degree of attenuation of light or ray after passing through the bubble and emulsion. Caicedo et al. [4] studied the distribution of bubble aspect ratio and shape factor under different operating conditions using digital image analysis,Bubble

Discrete element method The results are in good agreement with  It has a great potential in studying bub a r t i c l e i n f o

Article history:

Received 17 October 2014

Received in revised form 20 March 2015

Accepted 24 March 2015

Available online 31 March 2015

Keywords:

Fluidized bedavior of fluidized bed. a b s t r a c t

Bubble dynamics are very important in the design of fluidized beds because they govern hydrodynamics and efficiency of the operation for which the bed is used. A numerical simulation work of two-dimensional gas–solid fluidized bed based on discrete element method (DEM) was carried out in this paper.

In order to study bubble statistical properties of a large number of bubbles, the flood fill concept was introduced in this paper to search the bubbles, which used the simulated voidage data directly.

Various bubble properties i.e. bubble size and velocity distributions, bubble shape factor and aspect ratio, can be obtained simultaneously using this analysis method. The calculated results of bubble properties are in sound agreement with previous empirical correlations and experimental data in literature. A new flood fill method was applied using DEM simulated voidage data.  Various bubble properties in fluidized bed were calculated.A CFD–DEM study of bubble dynamics in method

Youjun Lu ⇑, Jikai Huang, Pengfei Zheng

State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong Universit h i g h l i g h t s

Chemical Engi journal homepage: wwuidized bed using flood fill ’an 710049, Shaanxi, China le at ScienceDirect ering Journal elsevier .com/locate /cej ringdiameter and velocity characteristics in a cylindrical fluidized bed via X-ray fluoroscopy. All these investigations about the bubble characteristics are based on statistical analysis of a big number of bubbles in fluidized bed. Most imaging technology such as CCD camera photographing or X-ray employ the Image Processing

Toolbox in commercial software to detect bubbles in many RGB images [1], and bubble properties such as equivalent diameter, centroid coordinates and aspect ratio are obtained simultaneously.

Bubble velocity is calculated by tracking the bubble centroid coordinates in subsequent frame.

In recent years, thanks to the rapid development of computer

Nomenclature

A0 catchment area of distributor (m2)

Ab area of the bubble (m 2)

AR bubble aspect ratio (–)

Cd drag coefficient db bubble equivalent diameter (m)

Fc impact force (N)

Fd particle–fluid drag force (N)

F fp volumetric fluid–particle interaction force (N) g, g gravity acceleration (m s2)

H0 initial bed height (m) h distance of the bubble centroid from the distributor (m)

Ii moment of inertia (kg m2) ly vertical maximum of the bubble dimensions (m) lx horizontal maximum of the bubble dimensions (m) mi particle mass (kg)

P fluid pressure (Pa)

Pb bubble perimeter (m)

Re Reynolds number t time (s)

Ti torque (N m1) u superficial velocity (m s1) ub bubble rising velocity (m s1) 124 Y. Lu et al. / Chemical Engineetechnology, numerical simulation is becoming a more and more important and powerful tool to study fluidized bed. Hulme et al. [7] simulated the fluidization dynamics of bubbling fluidized bed using Eulerian two-fluid model via commercial software FLUENT.