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Problems bout CFD model of biomass gasification, Downdraft gasifier |
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November 17, 2009, 21:50 |
Problems bout CFD model of biomass gasification, Downdraft gasifier
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New Member
Wang Long
Join Date: Sep 2009
Posts: 5
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I am a Master student study in biomass gasification in Korea. I am trying to make a CFD model of downdraft gasifier using FLUENT 6.3. I have lot problems. I hope you give me some advice about it. Thank you very much.
I tried 2 ways to simulate this gasification process: one phase and multiphase. In one phase case, wood determined as very small carbon particles. So the carbon particles and air determined as fluid phase. The details you can see in the fluent case file. The model was run in a computer which has 3G RAM and Q6600 cpu for more than 12 hours and iterated about 26,000 times. The problem is: 1.The simulated result presented that nearly no reactions occurred in the gasifier. 2.If I use a injection of wood inlet, the injection rate will be very small because the wood is drop down very slowly, I cannot simulate the right case use a injection. In 2 phase case, carbon determined as solid phase and details of model setting as below: The problem is : 1.In the simulated result, temperature is too high (highest is 5000K), the temperature range in experiment is from 293K~1600K. 2.No reactions occurred in the gasifier as the simulated results. **Setting of Multiphase (2 phase) Slover Slover -Pressure Based Formulation -implicit Space -3D Velocity Formulation -Absolute Gradient Option -Green-Gauss Cell Based Porous Formulation -Superficial Velocity Multiphase Multiphase Model -Eulerian Number of phase -2 Energy -Energy Equation Viscous Model Model -k-epsilon (2 eqn) k-epsilon Model -Realizable Near-Wall Treatment -Standard Wall Functions k-epsilon Multiphase Model -Mixture Model Constants C2-Epsilon: 1.9, TKE Prandtl Number: 1, TDR Prandtl Number: 1.2, Disperion Prandtl number: 0.75, Energy Prandtl Number: 0.85, Turb. Schmidt Number: 0.7, Species Model Model -Species Transport Reactions -Volumetric & Particle Surface Options -Inlet Diffusion & Diffusion Energy Source Turbulent -Chemistry Interaction -Finite-Rate/Eddy-Dissipation Operation Condition Pressure: Operating Pressure(pascal)-101325 Gravity: Gravity- Gravitational Acceleration Z(m/s2)=-9.8 Boussinesq Parameters: Operating Temperature (k)=288.16 |
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biomass gasification, cfd model, downdraft gasifier |
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