growth factor is 1.2, yes I use chemkin mechanism but I don't know if it encrypted or no, is there a  method to check it?, the Under-relaxation factors that I use is: 0,3 pressure, 0,6 density, 1 body forces, 0,55 momentum, 0,6 swirl,  0,8 Tur kinetic enrg, 0,8 tur dissipation rate, 1 turb viscosity, 0.95 species, and 0,95 energy is there any suggestion to play in this factor?

courant number i set up C <0.8 and the time step is 4e-6