{"id":431083,"date":"2025-05-08T13:29:41","date_gmt":"2025-05-08T13:29:41","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/combustion-modelling-swirl3d-edm-steady-state-energy-residual-need-help\/"},"modified":"2025-05-08T13:31:47","modified_gmt":"2025-05-08T13:31:47","slug":"combustion-modelling-swirl3d-edm-steady-state-energy-residual-need-help","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/combustion-modelling-swirl3d-edm-steady-state-energy-residual-need-help\/","title":{"rendered":"Combustion Modelling – Swirl,3D, EDM, Steady-state. Energy residual need help!"},"content":{"rendered":"<p><p style=”text-align: justify;”>Hi,<br><br>I have been running a combustion case but the energy equation appeared to be stuck indefinitely at ‘3e-5’ and struggle to go down. Would be very helpful if I could get some insights from you.<br><br>This is my problem specification: <\/p><\/p><\/p>\n
\n- Mesh 6 million cells<\/li>\n
- There are 16 ‘swirl’ holes to inject air and one fuel hole in the middle. <\/li>\n
- Hybrid mesh, predominantly hexahedral mesh + tetra in bridging zone (converted to poly)<\/li>\n
- Flame developed (looks very logical shape)<\/li>\n
- <div>-Aspect Ratio: Average 5.8142 (below 35 guideline)<\/div><div>- Orthogonal quality: Average 0.8973<br>- Skewness: Average 0.1377 (below 0.33)<\/div><\/li>\n
- Case ID: 1 (methane-air), Eddy Dissipation Model<\/li>\n
- Steady-state simulation, coupled, pseudo time-scale factor 1 (now reduced to 0.8)<\/li>\n
- Turbulence: K-e realizable, Standard Wall Function<\/li>\n
- Radiation Model: Discrete Ordinates 3,3,2,2, default 10 interval<\/li>\n
- Gas absorption: wsggm-domain-based<\/li>\n
- Currently switched DO and Energy to 2nd order.<\/li>\n
- Gradient scheme: node-based <\/li>\n
- Shape of furnace, very uniform, burner in the centre of a rear square face and extruded square face that minimic a rectangular furnace, then the rectangular face entering a pyramid shape converging section and then exit via a rectangular slot. <\/li>\n
- Total iteration achieved on 67000 <\/strong>iterations. <\/li>\n
- Heat of Reaction source around 65kW now (according to the experimentalist, it should be higher based on fuel and air value supplied)<\/li>\n
- Net result (W): 15242 !<\/strong> (can’t find a way to get it down to 1 – 2% error). That explain why the energy is e-5. For other projects, I have reached -7 to -9 before<\/strong><br><br>I attached a snapshot of the temperature field to show you that my flame is developed (it is only a quadrant). I can’t understand why is this burner with swirl hole so much harder to get lower energy compared to my past projects (different burners)? I also attached a convergence monitoring plot to show you that I have been very careful with the simulation progress.<br><br><br>
![\"\"](\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2025\/05\/08-05-2025-1746709890-Image_1_CFD.png\")
<br><br>![](\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2025\/05\/08-05-2025-1746710694-mceclip1.png\")
<br>Would be very helpful to hear from you, how I can bring my simulation to ‘next level’.<br><br>Thanks again.<br>J<br><br><br><br><br>![\"\"](\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2025\/05\/08-05-2025-1746711103-Image_3_CFD.png\")
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