Simulation of Transitional Flow on Low Pressure Turbine Blade With Unsteady Downstream Potential Interaction

This paper numerically investigates the transitional flow on a LPT (low pressure turbine) blade with fluctuating downstream potential field. A linear T106 cascade is subjected to an oscillating potential field generated by downstream moving bars. Previous experimental results in open literature showed that the unsteady downstream potential field has an obvious influence on the transitional boundary layer of LPT blade. For the numerical simulations in this paper, the unsteady Reynolds-Averaged Navier-Stokes equations are solved using the commercial software FLUENT. The transition model used in this paper is the γ-Re_θ model, which has been validated against a number of transitional flows previously, including the influence of upstream wakes on the transitional boundary layer of T106 turbine blade. The simulation results are first compared to the experimental results in open literature to validate the numerical methods. Two different FSTI (free stream turbulence intensity), 1.6% and 4.0% are investigated with axial spacing between the blade and the downstream bar varying from 50% axial chord to 25% axial chord. To investigate the influence of flow compressibility, two different inlet Mach numbers, 0.02 and 0.2 are simulated. Results show that decreasing the axial spacing has an influence on the unsteady boundary layer separation and transition and the influence is enhanced at elevated inlet Mach number.