[executor]

Dear combustion modelers,

I'm trying to model dual fuel (not simultaneous combustion) burner attached on hot water boiler (ca. 20 MW of burner output). As for light oil, i have managed to get adequate results in comparison to measured values on boiler plant. I have used WD2 NO PDF reaction and EDM. The results (temp. field) are shown in first attached picture. All predicted values (temp, CO, NO) have been accurate.


The problem I'm having now is with combustion of natural gas. I'm using same mesh (burner geometry stays the same). I have specified the same reactions as for the first case (difference is that for NG I'm using Methane Air mixture - Methane Air WD2 NO PDF; all in gaseous state). Combustion model is still EDM with coefficient B of 0,5. The case converges, but as for Post, I'm getting some silly results (picture 2). Either the temperature is way too high (I've run this case with two different EDM settings) and flame fills only 50% of domain, or domain is on "constant" temperature. As for cold flow; streamlines are O.K.

I'm modeling this case as pure CH4 - Air mixture (Natural gas E consists 97% of CH4) as an easy case (later will upgrade to NG - Air).

Do you have some suggestions on where my errors are??

Oh, and I'm using mass flow for air and fuel inlets. Outlet is on static pressure; wall has a Heat transfer option (hot water temp is on ca. 363 K).


Marko