laminat flame propagation

Araz Banaeizadeh

For one_dimensional laminar flame propagation,I've solved non_dimensionalized unsteady convection-reaction-diffusion equation by finite volume method.The coefficient of diffusion term is one over peclet number.I've used central scheme in discretisation of this term.For pure convection where the peclet number is infinity I get correct answers but for low peclet numbers the answers are very very diffusive and incorrect. I will be most grateful if some body could help me.

Banaeizadeh