[Daveo643]

Hello, I hope someone would be able to help me. I'm doing a plane-2D transient simulation of hydrogen injected into a combustion chamber. The injector is modeled with a pressure inlet boundary condition. Air simultaneously enters through a separate sets of channels also with profile-defined pressure inlet boundary condition that mimics an in-cylinder compression following a polytropic.

My problem is that when I try to use the G-Equation premixed model (Peters), following spark ignition, the residuals for the G-Equation and G-Variance remain at zero and combustion does not take place. When I monitor Damkohler number and Turbulent flame speed, these also yield zero values throughout the simulation.

C-Equation works as long as "Non-Laminar Flame Speed" option is not checked in the Properties tab. I conclude this compromises the quality of the results because of the nature of the problem I am investigating (wall heat transfer and compressive heating). From the Help 10.3.5 Laminar Flame Speed: "For non-adiabatic simulations, such as heat transfer at walls or compressive heating, the unburnt mixture temperature may deviate from its adiabatic value. The piecewise-linear function of mixture fraction is unable to account for this effect on the laminar flame speed. You can include non-adiabatic effects on the laminar flame speed by enabling Non-Adiabatic Laminar Flame Speed, which tabulates the laminar speeds in the PDF table by evaluating the curve fits from [149] at the enthalpy levels in the PDF table. Note that the tabulated mean laminar flame speed accounts for fluctuations in the mixture fraction."

Motivation also to try the G-Equation model is that I find heat release rate and completeness of combustion to be far below experimental ranges. My model involves high-swirl, highly-stretched flame and C-equation does not take into account flame curvature.

Any other suggestions from you resident experts?

[lx882211]

Originally Posted by Daveo643

Hello, I hope someone would be able to help me. I'm doing a plane-2D transient simulation of hydrogen injected into a combustion chamber. The injector is modeled with a pressure inlet boundary condition. Air simultaneously enters through a separate sets of channels also with profile-defined pressure inlet boundary condition that mimics an in-cylinder compression following a polytropic.

My problem is that when I try to use the G-Equation premixed model (Peters), following spark ignition, the residuals for the G-Equation and G-Variance remain at zero and combustion does not take place. When I monitor Damkohler number and Turbulent flame speed, these also yield zero values throughout the simulation.

C-Equation works as long as "Non-Laminar Flame Speed" option is not checked in the Properties tab. I conclude this compromises the quality of the results because of the nature of the problem I am investigating (wall heat transfer and compressive heating). From the Help 10.3.5 Laminar Flame Speed: "For non-adiabatic simulations, such as heat transfer at walls or compressive heating, the unburnt mixture temperature may deviate from its adiabatic value. The piecewise-linear function of mixture fraction is unable to account for this effect on the laminar flame speed. You can include non-adiabatic effects on the laminar flame speed by enabling Non-Adiabatic Laminar Flame Speed, which tabulates the laminar speeds in the PDF table by evaluating the curve fits from [149] at the enthalpy levels in the PDF table. Note that the tabulated mean laminar flame speed accounts for fluctuations in the mixture fraction."

Motivation also to try the G-Equation model is that I find heat release rate and completeness of combustion to be far below experimental ranges. My model involves high-swirl, highly-stretched flame and C-equation does not take into account flame curvature.

Any other suggestions from you resident experts?

Hi,
I am interesting in the G-equation combustiom model, could you please give me some code or papers about this model, thanks very much.

[tang-100]

Dear Sir/Madam:

Could I use the partially premixed combustion model in Fluent for compressible flows?

Thanks and have a nice day,
leiyong

[lishengnan]

Originally Posted by Daveo643

Hello, I hope someone would be able to help me. I'm doing a plane-2D transient simulation of hydrogen injected into a combustion chamber. The injector is modeled with a pressure inlet boundary condition. Air simultaneously enters through a separate sets of channels also with profile-defined pressure inlet boundary condition that mimics an in-cylinder compression following a polytropic.

My problem is that when I try to use the G-Equation premixed model (Peters), following spark ignition, the residuals for the G-Equation and G-Variance remain at zero and combustion does not take place. When I monitor Damkohler number and Turbulent flame speed, these also yield zero values throughout the simulation.

C-Equation works as long as "Non-Laminar Flame Speed" option is not checked in the Properties tab. I conclude this compromises the quality of the results because of the nature of the problem I am investigating (wall heat transfer and compressive heating). From the Help 10.3.5 Laminar Flame Speed: "For non-adiabatic simulations, such as heat transfer at walls or compressive heating, the unburnt mixture temperature may deviate from its adiabatic value. The piecewise-linear function of mixture fraction is unable to account for this effect on the laminar flame speed. You can include non-adiabatic effects on the laminar flame speed by enabling Non-Adiabatic Laminar Flame Speed, which tabulates the laminar speeds in the PDF table by evaluating the curve fits from [149] at the enthalpy levels in the PDF table. Note that the tabulated mean laminar flame speed accounts for fluctuations in the mixture fraction."

Motivation also to try the G-Equation model is that I find heat release rate and completeness of combustion to be far below experimental ranges. My model involves high-swirl, highly-stretched flame and C-equation does not take into account flame curvature.

Any other suggestions from you resident experts?

Hi, dear Daveo
8 years had passed, I don't know if you can still see this message.
You said "C-Equation works as long as "Non-Laminar Flame Speed" option is not checked in the Properties tab.". But, I am using partially premixed combustion model(FGM) to simulate air/methane flame. Non-adiabatic & diffusion flamelet. Spark is used to model ignitor, but C and C-var remain 0 while the temperature rises up to 2000K, the ignition process is failed since C equals to 0. Why this difference occur between us? Is the spark parameters?

Look forward to your reply.

[LuckyTran]

You need to also patch the progress variable. Simply patching a high temperature just makes the region hot, it doesn't 'ignite' it.

[lishengnan]

Originally Posted by LuckyTran

You need to also patch the progress variable. Simply patching a high temperature just makes the region hot, it doesn't 'ignite' it.

Do you mean I need to patch a region with c=1 at the same time activate the spark model?