about udf(s) to modify SurfaceCombustionLaw

Jiaqi Chen

Hi, Could anyone help me with my problem?

I'm using 2-mixture-fraction approach(2f for coal: one for char, the second for volatiles) and equilibrium chemistry to model the pyrolysis of coal particles in hydrogen plasma(about 3000K, after mixing, the gas temperature will drop to about 2600 K) in a reactor chamber. The SurfaceCombustionLaw embeded in FLUENT is not so suitable to describe the reaction between char and hydrogen at such high temperatures after devolatilization. So I need to write udf(s) to take place of the SurfaceCombustionLaw. Is it possible?

Should I use the macro 'DEFINE_DPM_LAW' to define my own rate of particle-mass-loss in the surface reaction process?

Since I've defined the change of particle mass in 'DEFINE_DPM_LAW', should I update the source term by the macro 'DEFINE_DPM_SOURCE'? And what species should be updated? I don't know how FLUENT works with this.

And since the char is represented as the mixture fraction, do I need to write a udf using 'DEFINE_SOURCE' to update mixture fraction in 'define-->boudary conditions-->fluid-1-->source term-->mean mixture fraction'?

The last question is : do I need to write a udf using 'DEFINE_DPM_SWITCH' to take place of the default switch law since I implement an user-defined SurfaceCombustionLaw.

I'm using non-premixed combustion model to model my process. The process is similar to coal gasification to some extent. However, the char reaction is different from that of gasification.

Could anyone give me some hints or example udf(s)? Your help will be very appreciated.

Jiaqi Chen