|November 2, 2015, 12:40||
Problem using Partially-Premixed Combustion > G-Equation model
Join Date: Mar 2013
Posts: 21Rep Power: 4
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  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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