Abstract: In order to better understand the turbulent premixed combustion in aero-engine combustors, the turbulent premix flames in model combustors were studied by direct numerical simulations based on the relevant characteristic parameters. The calculation model is simplified from annular combustors that contains two adjacent lean premixed swirls with high inlet temperature and pressure to meet the aero-engine combustor conditions. In the simulation, the simplified kerosene reaction mechanism was used and different Karlovitz numbers (Ka) were designed corresponding to high and low loads. The simulation results show that the flame thickness under high pressure is extremely thin, so the flame surface is strongly affected by small scale turbulence. The turbulent premixed flame is located at thin reaction zone, which is distributed bilaterally along the shear layer, and a relatively broken flame structure is generated in the downstream due to the interaction of adjacent swirls, which is especially obvious when the Ka is high. From the upstream to the downstream, the average radial velocity increases due to the combustion expansion, while the average azimuthal velocity decreases due to the conservation of angular momentum. Turbulence pulsation in the downstream recirculation zone is stronger than that in the upstream. When the Re and Ka are larger, the downstream recirculation effect caused by the swirling shear action is more significant, and the turbulent disturbance effect in the shear layer is stronger. In addition, due to the limited space between the adjacent swirls, the expansion effect of the downstream flame of the double swirls is weaker than that of the single swirl. The correlation analysis of scalar flux and gradient shows that the main reactants and products basically satisfy the gradient transport, and the gradient transport effect is more significant when the number of Ka is large. However, for the intermediate products, the gradient diffusion hypothesis is not valid near the flame surface, which challenges the models based on the gradient diffusion hypothesis.