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| 2. |
- Farzaneh, Meisam, 1982, et al.
(författare)
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A novel multigrid technique for lagrangian modeling of fuel mixing in fluidized beds
- 2011
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Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509. ; 66:22, s. 5628-5637
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a novel Lagrangian approach to model fuel mixing in gas-solid fluidized beds. In the mixing process, fuel particles are considerably larger than the inert bed material and therefore, the present work proposes three grids to account for the difference in size between the fuel particles and inert solids. The information between the grids is exchanged using an algorithm presented in the paper. A statistical method has been developed to analyse the distribution of the fuel particles in the bed. The results for the preferential positions, velocity vectors and horizontal dispersion coefficients are compared with experimental data in a bed applying simplified scaling relationships for different operating conditions. The effects of initial bed height and inlet gas velocity on the fuel mixing are investigated.It is found that the proposed Lagrangian modeling can capture the complex pattern of the movement of the fuel particles, in spite of the large difference in diameter between inert and fuel particles.
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| 3. |
- Farzaneh, Meisam, 1982, et al.
(författare)
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A Study of Fuel Particle Movement in Fluidized Beds
- 2013
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 52:16, s. 5791-5805
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Tidskriftsartikel (refereegranskat)abstract
- Lagrangian simulations are performed to investigate the process of fuel mixing in fluidized-bed energy converters. The computations are carried out for a narrow (0.4 m) and a wide (1.2 m) bed. Movement of a limited number of large and light particles in a bulk of heavy and small particles is studied using a multigrid technique proposed by Farzaneh et al. Preferential positions and the dispersion coefficient of the fuel particles are obtained under different operating conditions. In addition, detailed information on the motion of the fuel particles in the form of upward and downward velocity is obtained. Furthermore, in an attempt to investigate the effect of the inlet boundary conditions on the process of fuel mixing, two boundary conditions are employed: a uniform velocity profile at the air distributor and a non-uniform velocity profile obtained by including the air supply system in the computational domain.It is observed that the numerical simulations which include the air supply system in the computational domain, improve the prediction of the hydrodynamic behavior of the bed. However, regarding the averaged movement pattern of the fuel particles, the effect of the boundary condition employed is not significant in the 0.4 m bed. As for the wide 1.2 m bed, the simulation results differ substantially from the experiments when the uniform velocity profile is employed as inlet boundary condition. Including the plenum in the simulations considerably improves the results, but they are still not in a perfect agreement with the experiments.
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| 4. |
- Farzaneh, Meisam, 1982, et al.
(författare)
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Eulerian-Eulerian-Lagrangian Simulation of Fuel Mixing in Fluidized beds
- 2013
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Ingår i: 8th International Conference on Multiphase Flow ICMF 2013, Jeju, Korea, May 26 - 31, 2013.
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Konferensbidrag (refereegranskat)abstract
- In this paper, we combine Eulerian-Lagrangian and Eulerian-Eulerian frameworks to track a limited number of fuel particles in a bulk of inert particles in a gas-solid fluidized bed. The gas and the inert phase are treated as interpenetrating continua and resolved within the Eulerian-Eulerian framework, whereas the fuel particles are regarded as a discrete phase. In the method, the forces acting on a fuel particle are calculated by using the velocity and pressure fields of the mixture of the inert solid particles and gas.. To validate the numerical method, the results are compared with experimental data in the form of preferential positions, velocity vectors and dispersion coefficient of the fuel particles. The effects of a number of operating parameters (e.g. the fluidization velocity and the amount of bed material) on the mentioned properties of the fuel particles are studied. In addition, to accurately formulate the inlet boundary condition the air supply system is included in the computational domain. It is observed that the proposed numerical technique is able to correctly capture the behaviour of fuel particles in fluidized beds.
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| 5. |
- Farzaneh, Meisam, 1982, et al.
(författare)
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Simulation of Fuel Mixing in Fluidized Beds using a Combined Tracking Technique
- 2013
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Ingår i: Fluidization XIV, 2013, Noordwijkerhout, The Netherlands.
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Konferensbidrag (refereegranskat)abstract
- This paper presents an Eulerian-Eulerian-Lagrangian (E-E-L) numerical method to track a limited number of fuel particles in a bulk of inert particles in a gas-solid fluidized bed. The gas and the inert phases are treated as the interpenetrating continua and resolved within the Eulerian-Eulerian framework, whereas the fuel particles are regarded as a discrete phase. To validate the numerical method, the results are compared with experimental data in the form of preferential positions, velocity vectors and the dispersion coefficient of the fuel particles. It is observed that the proposed numerical technique is able to capture the behavior of fuel particles in fluidized beds.
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| 6. |
- Farzaneh, Meisam, 1982, et al.
(författare)
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The crucial role of frictional stress models for simulation of bubbling fluidized beds
- 2015
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Ingår i: Powder Technology. - : Elsevier BV. - 1873-328X .- 0032-5910. ; 270:Part A, s. 68-82
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we combine Eulerian-Lagrangian and Eulerian-Eulerian frameworks to simulate the behavior of a limited number of fuel particles in a bulk of inert particles in a bubbling gas-solid fluidized bed. The gas and the inert phase are treated as interpenetrating continua and resolved within the Eulerian-Eulerian framework, whereas the fuel particles are regarded as a discrete phase. The forces acting on a fuel particle are calculated by using the velocity and pressure fields of the inert solid and gas phases. We assume that the hydrodynamics of the bed are predominantly governed by the motion of the inert solid and gas phases. Therefore, emphasis in this work is on a correct description of the stress tensor of the inert particulate phase and, in particular, on the modeling of frictional stresses, which is of primary importance for continuum simulations of bubbling fluidized beds. Performance of two of the traditionally used frictional stress theories (Schaeffer [12] and Srivastava and Sundaresan [13]) and of the one more recently proposed (Jop et al. [18]) is investigated and the corresponding results are compared with experimental findings in the form of position and velocity of the fuel particles. In addition, preferential positions, the dispersion coefficient, and the average cycle time of the fuel particles motion are obtained by the simulations and compared with experiments. It is observed that the results of the visco-plastic model proposed by Jop et al. [18] are in good agreement with the experiments for prediction of the bed hydrodynamics and the movement of the fuel particles. The other two models underestimate the frictional stresses in the inert solid phase, leading to erroneous predictions of the stress tensor of the inert particulate phase and thus of the entire system.
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