Laminarization Mechanism of Near-Wall Turbulence in Premixed Natural Gas Combustion Investigated by Direct Numerical Simulation

In this study, we clarified the characteristics of flame propagation during combustion and the mechanism of laminarization resulting from the attenuation of turbulence structures in the flow field under the influence of the flame. We performed three-dimensional simulations of the wall turbulence in the combustion of premixed natural gas and premixed hydrogen. We adopted a direct numerical simulation method for compressible flow with combustion using a reaction model. Premixed natural gas and premixed hydrogen combustion have different laminarization mechanisms in turbulent combustion fields. The heat of the flame affects the velocity streaks and vortices of the turbulence structures differently, and changes in the wall shear stress and wall heat flux exhibit different tendencies. Depending on the thermal Péclet number, defined using the maximum local intensity of turbulence as a parameter for classifying the characteristics of the laminarization mechanism of the flow field, the wall shear stress may change before the wall heat flux, or both may change simultaneously, under the influence of combustion. The aforementioned results provide insights into the prediction and control of turbulent combustion for future applications.