TCN CAE Lecce 2005TCN CAE Lecce 2005
UNIVERSITY OF CATANIA
Department of Industrial and Mechanical
Engineering
Author: M. ...
TCN CAE Lecce 2005TCN CAE Lecce 2005
PROBLEM FACED :
CFD
COMPUTATIONAL FLUID DYNAMIC
ADVANTAGES:
•Reduction of
planning ti...
TCN CAE Lecce 2005TCN CAE Lecce 2005
OBJECTIVES OF THE STUDY:
FEM modelling of the “cold” fluid-dynamics
of a swirl burner...
TCN CAE Lecce 2005TCN CAE Lecce 2005
SWIRL EFFECT:
““SSwirlwirl” is defined as the spiral rotational motion imparted to a ...
TCN CAE Lecce 2005TCN CAE Lecce 2005
THE SWIRL BURNER:
The modelled burner is used in several industrial applications:
TCN CAE Lecce 2005TCN CAE Lecce 2005
The anterior side is characterized by the following devices:
Holes for the fuel injec...
TCN CAE Lecce 2005TCN CAE Lecce 2005
CFD SOFTWARE : Comsol Multiphysics
TCN CAE Lecce 2005TCN CAE Lecce 2005
MODELLING STEPS:
Construction of the
geometrical model
Comsol Multiphysics module
cho...
TCN CAE Lecce 2005TCN CAE Lecce 2005
EQUATIONS AND MODULE
CHOICE:
FLOW HYPOTHESES :
INCOMPRESSIBLE
(Ma<0.3)
TURBULENT
(Re>...
TCN CAE Lecce 2005TCN CAE Lecce 2005
PHYSICS SETTINGS:
•Density: 1 kg/m3
•Kinematic viscosity: 1 E-5 m2
/s
•Volume forces ...
TCN CAE Lecce 2005TCN CAE Lecce 2005
COMPUTATIONAL GRID AND USED SOLVER
Used
solver:
DIRECT (UMFPACK), NON LINEAR
Finer me...
TCN CAE Lecce 2005TCN CAE Lecce 2005
PLOTTING E POST-PROCESSING OF THE
RESULTSCross sections: velocity field
It is possibl...
TCN CAE Lecce 2005TCN CAE Lecce 2005
Longitudinal section:
When the fluid enters the reactor, it expands with the classica...
TCN CAE Lecce 2005TCN CAE Lecce 2005
Streamlines of the fluid:
Spiral motion inside the “core”, typical of
“swirling jets”.
TCN CAE Lecce 2005TCN CAE Lecce 2005
“SWIRL NUMBER” AND LITERATURE
RESULTS
( )
( )
3
2
12
tan
3 1
h
x h
R RG
S
G R R R
ϑ
α...
TCN CAE Lecce 2005TCN CAE Lecce 2005
Radial distribution of the axial velocity
close to the burner’s outlet:
The negative ...
TCN CAE Lecce 2005TCN CAE Lecce 2005
Iso-surfaces of axial velocity:
The bulb, located in the central core, corresponds to...
TCN CAE Lecce 2005TCN CAE Lecce 2005
Radial distribution of the axial velocity
close to the burner’s outlet and 10 cm and
...
TCN CAE Lecce 2005TCN CAE Lecce 2005
CONCLUSIONS AND FURTHER
DEVELOPMENTS:
1. A three-dimensional simulation of a low NOx ...
TCN CAE Lecce 2005TCN CAE Lecce 2005
ACNOWLEDGEMENTS:
This work has been developed at theThis work has been developed at t...
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Numarical simulation of a &quot;Swirling jet&quot; expanding inside a combustion reactorTcn Cae 2005

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Numarical simulation of a &quot;Swirling jet&quot; expanding inside a combustion reactorTcn Cae 2005

  1. 1. TCN CAE Lecce 2005TCN CAE Lecce 2005 UNIVERSITY OF CATANIA Department of Industrial and Mechanical Engineering Author: M. ALECCI Co-Authors: G. CAMMARATA, G. PETRONE NUMERICAL SIMULATION OF A “SWIRLING JET” EXPANDING INSIDE A COMBUSTION REACTOR
  2. 2. TCN CAE Lecce 2005TCN CAE Lecce 2005 PROBLEM FACED : CFD COMPUTATIONAL FLUID DYNAMIC ADVANTAGES: •Reduction of planning time and costs. •Availability to study systems for which the experimentation is difficult and expensive. •Availability to study systems in conditions of extreme safety . DISADVANTAGES: •Discretized models present inevitable PDE approximation . •In the linear systems solution iterative methods are used. These allow to obtain only solutions close to the exact ones.
  3. 3. TCN CAE Lecce 2005TCN CAE Lecce 2005 OBJECTIVES OF THE STUDY: FEM modelling of the “cold” fluid-dynamics of a swirl burner. Evaluation and analysis of the velocity and pressure fields. Comparison of the obtained results with those coming from literature.
  4. 4. TCN CAE Lecce 2005TCN CAE Lecce 2005 SWIRL EFFECT: ““SSwirlwirl” is defined as the spiral rotational motion imparted to a fluid” is defined as the spiral rotational motion imparted to a fluid upstream of an orifice. This spiral develops in a direction parallelupstream of an orifice. This spiral develops in a direction parallel to the injection one.to the injection one. Then, a tangential velocity component and high pressure gradients (axial and radial) develop. The low pressure zone inside the spiral core is characterized by toroidal vortexes: (Precessing Vortex Core phenomenon PVC) This results (for strong degree of swirl) in the setting up of a Reverse Flow Zone (RFZ) where the fluid is recirculated towards the burner’s outlet. 1) Good mixing of reactants. 2) A decrease in flame temperature. 3) Flame stabilization. 4) High performance combustion for several carboneous materials. NOx REDUCTION
  5. 5. TCN CAE Lecce 2005TCN CAE Lecce 2005 THE SWIRL BURNER: The modelled burner is used in several industrial applications:
  6. 6. TCN CAE Lecce 2005TCN CAE Lecce 2005 The anterior side is characterized by the following devices: Holes for the fuel injection Duct for the flame revelation probe Axial swirler
  7. 7. TCN CAE Lecce 2005TCN CAE Lecce 2005 CFD SOFTWARE : Comsol Multiphysics
  8. 8. TCN CAE Lecce 2005TCN CAE Lecce 2005 MODELLING STEPS: Construction of the geometrical model Comsol Multiphysics module choice and physics settings. Meshing the model Plotting e post-processing of the results. Problem solving
  9. 9. TCN CAE Lecce 2005TCN CAE Lecce 2005 EQUATIONS AND MODULE CHOICE: FLOW HYPOTHESES : INCOMPRESSIBLE (Ma<0.3) TURBULENT (Re>2000) NEWTONIAN FLUID (homogeneous gases mixture) ( ) ( )T Fu u p uρ ν ν ρ  ∇ = −∇ + ∇ + ∇ +  r r r g g 0u−∇ = r g ( ) i T ij j k u u k k x ν τ ε ν σ   ∂ ∇ = − +∇ + ∇  ÷ ∂     r g g ( ) 2 1 1/ /i T ij j u u c k c k x ε ε ε ν ε ε τ ε ν ε σ   ∂ ∇ = × − + ∇ + ∇  ÷ ∂     r g g Momentum balance Mass balance (continuity) Turbulent Kinetic energy (K) equationDissipative turbulent (e) energy equation K-e Turbulence module
  10. 10. TCN CAE Lecce 2005TCN CAE Lecce 2005 PHYSICS SETTINGS: •Density: 1 kg/m3 •Kinematic viscosity: 1 E-5 m2 /s •Volume forces neglected Inlet flow with axial velocity: u=20 m/s. No slip conditions: U=0. Pressure: p=3 bar SUBDOMAIN SETTINGS: BOUNDARY CONDITIONS:
  11. 11. TCN CAE Lecce 2005TCN CAE Lecce 2005 COMPUTATIONAL GRID AND USED SOLVER Used solver: DIRECT (UMFPACK), NON LINEAR Finer mesh close to the swirler zone
  12. 12. TCN CAE Lecce 2005TCN CAE Lecce 2005 PLOTTING E POST-PROCESSING OF THE RESULTSCross sections: velocity field It is possible to observe how in the first duct the fluid accelerates when it goes through the swirler.
  13. 13. TCN CAE Lecce 2005TCN CAE Lecce 2005 Longitudinal section: When the fluid enters the reactor, it expands with the classical cone course, up to velocity of 1-2 m/s.
  14. 14. TCN CAE Lecce 2005TCN CAE Lecce 2005 Streamlines of the fluid: Spiral motion inside the “core”, typical of “swirling jets”.
  15. 15. TCN CAE Lecce 2005TCN CAE Lecce 2005 “SWIRL NUMBER” AND LITERATURE RESULTS ( ) ( ) 3 2 12 tan 3 1 h x h R RG S G R R R ϑ α  − =   −   ;“Swirl number”: S<0.6S<0.6 WeakWeak swirlswirl 0.6<S<10.6<S<1 MediumMedium swirlswirl S>1S>1 StrongStrong SwirlSwirl LDV (Laser Doppler Velocimetry) Swirl number of the analyzed system: S=0.77
  16. 16. TCN CAE Lecce 2005TCN CAE Lecce 2005 Radial distribution of the axial velocity close to the burner’s outlet: The negative values correspond to the RFZ development according to the literature results.
  17. 17. TCN CAE Lecce 2005TCN CAE Lecce 2005 Iso-surfaces of axial velocity: The bulb, located in the central core, corresponds to negative values of axial velocity. That means the fluid is recirculated towards the burner outlet section. (RFZ development)
  18. 18. TCN CAE Lecce 2005TCN CAE Lecce 2005 Radial distribution of the axial velocity close to the burner’s outlet and 10 cm and 20 cm from it: RFZ results stronger close to the burner’s outlet and it decreases as soon as the fluid reaches a certain distance from it.
  19. 19. TCN CAE Lecce 2005TCN CAE Lecce 2005 CONCLUSIONS AND FURTHER DEVELOPMENTS: 1. A three-dimensional simulation of a low NOx “swirl burner” is reported in this study. The analysis has been focused on the swirl device by the evaluation of the velocity and pressure fields of the jet entering the combustion reactor. 2. The model reflects, with good approximation, the real behaviour of the system, and finds a good correspondence with literature. Thus, it may be used to simulate different operative conditions (such as other fluids or other inlet velocities), avoiding expensive experimentation. 3. In a further development the combustion reaction will be introduced into the model, analyzing how it may influence the velocity and pressure fields. 4. A complete thermal characterization of heat exchanges will complete the entire model.
  20. 20. TCN CAE Lecce 2005TCN CAE Lecce 2005 ACNOWLEDGEMENTS: This work has been developed at theThis work has been developed at the DepartmentDepartment of Industrial and Mechanical Engineering ofof Industrial and Mechanical Engineering of thethe University of CataniaUniversity of Catania AUTHOR REFERENCES: marco.alecci@libero.it

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