Developing CFD Software For Simulating Gas-Solid Riser Flow

Suryo, Is Bunyamin (2022) Developing CFD Software For Simulating Gas-Solid Riser Flow. Doctoral thesis, Institut Teknologi Sepuluh Nopember (ITS).

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Abstract

Fluidization process is widely used in commercial operation or industrial reactors. One of the reactor types which implement fluidization process is fluidized bed. The study of hydrodynamics behaviour of fluidized bed has been exercised for many years. By the development of advance numerical technique and high performance computing, computational
fluid dynamics (CFD) become an important tools to analyse the gas-solid hydrodynamics behaviour. There are two different approaches in simulating gas-solid two phase flows, Two-Fluid Model (TFM) or Eulerian-Eulerian approach and Eulerian-Lagrangian approach. In this study, Two-Fluid Model alongside with the kinetic theory of granular flow (KTGF) is
implemented into the developed CFD code, AIOLOS. AIOLOS is a CFD software which has been developed by Institut f ¨ur Feuerungs- und Kraftwerkstechnik (IFK), Stuttgart University, Germany. It is originally dedicated for simulating pulverized coal combustion and solid fuel gasification. The solution algorithm used in the simulation is adopted from Syamlal et al. [69] with some modifications. For dealing with pressure-velocity coupling problem, the
Semi-Implicit Method for Pressure Linked Equations (SIMPLE) is used. The k-epsilon turbulent model is used to calculate the gas phase turbulence viscosity.

The first test case in this study is based on the experiment of K.M. Luo [49]. The case is a 3D cylindrical riser with height of 5.5 m and diameter of 0.076 m. Two different meshes with the number of cells of 168600 and 948480 are employed. The simulation was carried out at transient
condition from 0-40 s with two different time step, namely 0.0001 and 0.00015 s. The simulation results from 30-40 s are time-averaged and its result is analysed and evaluated.
Three different drag models, namely Wen-Yu model, Syamlal et al. model, and Gidaspow model, are employed to calculate the momentum transfer between gas and solid phases. The radial distribution function models proposed by Carnahan-Starling and Syamlal et al. are utilized in the simulation. For the coefficient of restitution, two different values of 0.7
and 0.84 are set up. The inlet boundary condition is determined as a uniform inlet velocity and phase volume fraction for both gas and solid phase. The solid diameter and the solid density are 520 micron-m and 2620 kg/m3, respectively. The zero gradient at outlet for any properties is set up as the outlet boundary condition. Furthermore for wall boundary conditions, no-slip boundary condition is utilized for both phases. Preliminary simulation shows that the standard mesh is more appropriate to be used for the simulation. For laminar flow simulation of the first test case, 13 combinations of the simulation parameter are simulated. Using drag model of Syamlal et al., restitution coefficient of 0.7, and radial distribution function of Syamlal et al., the simulation obtains the best agreement to the experimental data, either using time step of 0.0001 s or of 0.00015 s. Using this combination of the simulation parameter, the turbulent flow simulation achieves slightly a different result comparing with the laminar simulation.

The second test case is based on the experiments of J. Zhuo et al. [81]. The case is a 3D rectangular riser with dimensions of 0.146x0.146x9.0 m. The computation grid consists of 146168 cells. The simulation was carried out at transient condition from 0-40 s with time step of 0.00015 s, Syamlal et al. drag model, the radial distribution function of Syamlal et al., and the restitution coefficient of 0.7. The inlet boundary condition is determined as a uniform
inlet velocity and phase volume fraction for both gas and solid phase. The solid diameter and the solid density are 213 micron-m and 2640 kg/m3, respectively. The zero gradient at outlet for any properties is set up as the outlet boundary condition. Furthermore for wall boundary conditions, no-slip boundary condition is utilized for both phases. Examining the lateral profiles of the solid velocity and the gas volume fraction, the simulation result shows a poor agreement with the experiment.

In order to improve the results of the current simulation, the implementation of the Johnson and Jackson wall boundary condition and the energy minimization multi-scale (EMMS)
drag model into the developed code are recommended. The use of a finer mesh and a parallel computer are also suggested to achieve a better result and an efficient and fast simulation.

Item Type:	Thesis (Doctoral)
Uncontrolled Keywords:	Gas-Solid Flow, Numerical Simulation, Drag Model
Subjects:	T Technology > TJ Mechanical engineering and machinery > TJ935 Pipe--Fluid dynamics. Tubes--Fluid dynamics
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21001-(S3) PhD Thesis
Depositing User:	Is Bunyamin Suryo
Date Deposited:	10 Feb 2022 01:27
Last Modified:	10 Feb 2022 01:27
URI:	http://repository.its.ac.id/id/eprint/93428

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