Read "Reaction zone structures and mixing characteristics of partially premixed swirling CH4/air flames in a gas turbine model combustor" by Meier et al. (2005). This paper shows experimental results from an experiment very similar to this tutorial, with CH4 injected and an air co-flow.
Create a new mesh (20 mm x 57 mm) that corresponds to the geometry of the combustor used and adjust boundaries/species inflow amounts according to the experiment values. Compare your results to those of the experiment, using the PDF mixing table and the premixed Zimont flame speed model.