Combustion with injection
 

Hello everyone. I have a combustion chamber with a combustion with injection from an inlet and air from the other. in boundary i have inlet verlocity fuel 0.04 and for air 0.25. the geometry is 0.25xo.25x0.25 (3D). i have reduce a lot the under relaxation factors. i use the option->define injection where i choosetype of injection -> group with zero velocities in x,y,z and total mass flow rate 0.3. i follow the instruction from a tutorial for injection coal mv volatiles for all the other options.
I initialize from none condition. when i run calculation(500 iterations) the residuals are fine up to 40 iterations and then diverge all the equations! the error the appears above the divergence is invalid cp (0.00000J/kgxK) for coal volatiles air but i have follow the instructions of the tutorial and i define the cp=1000. i use also simple as a solver.
Any idea?
thank you