Premixed Turbulent Combustion Modeling PhD student: Ehsan Yasari - - PowerPoint PPT Presentation

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Premixed Turbulent Combustion Modeling

PhD student:

Ehsan Yasari

yasari@chalmers.se

Department of Applied Mechanics Chalmers University of Technology

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Outline

• Project Description
• Tools and Solver
• Problems and Difficulties
• Possible Solutions

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• Premixed Turbulent Combustion Modeling
• Supervisor: Andrei Lipatnikov
• PhD student: Ehsan Yasari
• Project start date: 2010-01-01

Project Description

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• Implementing new combustion models.
• Simulation different premixed turbulent

flames.

• Link this project to internal combustion

engine simulation.

Project Goals

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• OpenFOAM
• XiFoam solver: compressible premixed/partially-

premixed combustion with turbulence modeling

• Combustion model: based on Weller model

Tools and Solver

|-- UEqn.H |-- XiFoam.C |-- bEqn.H |-- createFields.H |-- ftEqn.H |-- hEqn.H |-- huEqn.H |-- pEqn.H `-- readCombustionProperties.H

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   

c U x c D x c u x c t

t u k t k k k

~ ~ ~ ~ ~

, ,

                   

 

   

 



~ ~2

,

k C D

c t



 4 1 2 4 1 4 1 4 1 ,

' ' 5 . ' ' 5 . ' 5 . ' 5 .                            

 u L c c t t

u LS u u L u u Da u U    

Implementing the Chalmers Model

               



L t u D D

t t

exp 1

, 2 1 ,

exp 1                   



L t u t u L t u L U U

t t

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7 of 17 fvScalarMatrix bEqn ( fvm::ddt(rho, b) + mvConvection->fvmDiv(phi, b) + fvm::div(phiSt, b, "div(phiSt,b)")

• fvm::Sp(fvc::div(phiSt), b)
• fvm::laplacian(turbulence->alphaEff(), b)

);

Problems and Difficulties

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• Negative value of b
• Temperature Calculation in OpenFoam

Problems and Difficulties

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• Finer Mesh- Smaller time-step
• Schemes for strictly bounded scalar fields:
• limitedLinear
• vanLeer
• Gamma
• Different fvSolution
• Limit the b when solve the bEqn.H ?!

Possible solution for negative b problem

2 1 : 1 , 2 :     

• ld
• ld

b b b if b b b if

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Temperature Calculation Method

r u r u r u r u r u r r

a T a T a T a T a T a R W h

6 5 5 4 4 3 3 2 2 1

5 4 3 2 ~      

p b p b p b p b p b p p

a T a T a T a T a T a R W h

6 5 5 4 4 3 3 2 2 1

5 4 3 2 ~      

T R P ~  

) ~ 1 ( ~ ~ b T b T T

b u

  

• Transport equation for regress variable .
• Transport equation for enthalpy .

b ~ h ~

1 , ) ~ 1 ( 1     

u b u

T T b    

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Problem in Computation

• Mean density and Favre averaged temperature yielded by

OpenFOAM library differs significantly from well-known equations:

1 , ) ~ 1 ( 1 , ) ~ 1 ( ~ ~        

u b u b u

T T b b T b T T    

T ~

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         

  

  

) ( ) (

6 , , 5 1 1 1 l k k l k l l N l l l l N l

a T k a W Y R H W Y W H h

Multi Component Mixture

         



 6 , , 5 1 m k k m k m

a T k a W R h

l l k l N l m k m

W Y a W a

, 1 ,







l l N l m

W Y W







1

1

• Multi Component Mixture

OpenFOAM Approach

• OpenFoam Approach

 

b W b W W

b u m

~ 1 1 ~ 1 1   

 

b W a b W a W a

b k b u k u k m

~ 1 ~

, , ,

  

) ~ 1 ( , ~

2 1

b Y b Y             



 6 , , 5 1

~ ~

m k k m k m

a T k a W R h

homogeneousMixture.C specieI.H homogeneousMixture.C janafThermoI.H hhuMixtureThermo.C janafThermoI.H

b u

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What is the problem in this Approach?

• Mean state of burning mixture should not considered as

super-mixture(multi-component mixture).

• Non-linearity problem

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Super-mixture Problem :

• Mean state of burning mixture should not considered as

super-mixture(multi-component mixture).

p r

T T 

I. Two totally different phenomena II. Mean density

) ~ 1 ( 1 b

u

     







N l l 1

 

b u

    

b u

    

 

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Correct Temperature Calculation Method

r u r u r u r u r u r r

a T a T a T a T a T a R W h

6 5 5 4 4 3 3 2 2 1

5 4 3 2 ~      

p b p b p b p b p b p p

a T a T a T a T a T a R W h

6 5 5 4 4 3 3 2 2 1

5 4 3 2 ~      

T R P ~  

) ~ 1 ( ~ ~ b T b T T

b u

  

b

T

u

T

• Transport equation for regress variable in bEqn.H
• Transport equation for enthalpy in hEqn.H

b ~ h ~

1 , ) ~ 1 ( 1     

u b u

T T b    

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Results: Modification the

• Mean density and Favre averaged temperature yielded by

OpenFOAM library differs significantly from well-known equations:

1 , ) ~ 1 ( 1 , ) ~ 1 ( ~ ~        

u b u b u

T T b b T b T T    

T ~

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Thank you for your attention