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Problem using Partially-Premixed Combustion > G-Equation model

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Old   November 2, 2015, 12:40
Default Problem using Partially-Premixed Combustion > G-Equation model
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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?
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