species transport model with volumetric reaction
 

I have attached case file and reaction UDF here.
When I simply solving the species transport (multicomponent diffusion only) it solves perfectly but when I include volumetric reaction in model, temperature fluctuates and it diverges, I have put the operating temp as 1073 and operation pressure as 101325 Pa. Do I need to put something there more parameters for energy balance ? why its not solving ?
If anybody could give some suggestions, would be great help.