No abstract

The large swirling flow downstream the lean burn premix combustor significantly impacts on the aerothermal performance of the first stage turbine vane endwall. The effects of the anticlockwise swirling inflow on the aerothermal performance of the turbine vane endwall with film cooling layouts was numerically investigated using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and SST turbulence model. The heat transfer characteristics and film cooling effectiveness of the turbine vane endwall with three rows film holes along the axial direction at three kinds of inlet swirl number 0.6, 0.8 and 1.0 was analyzed and compared. The obtained results show that the anticlockwise swirling inflow leads to the horseshoe vortex of the vane endwall migrate to the downstream and generate the recirculation vortex of the mainstream by comparison to the uniform inflow condition. The anticlockwise swirling inflow changes the Nusselt number distribution of the vane endwall and results in the high heat transfer coefficients regions. The high heat transfer regions at the vane endwall increases with the swirling inflow strength increases. The anticlockwise swirling inflow enhances the Nu downstream the first row film holes at the x/Cax=0.31 and suppresses the coverage of the coolant jet from the film holes migration to the suction side. Comparison to the uniform flow condition, the averaged film cooling effectiveness of the first row film holes increases up to 27% and the third film holes decreases about 9%.

The turbine vane inlet downstream of the lean premixed combustor presents nonuniform distributions of velocity and temperature. For obtaining swirling inflow profiles close to reality, the simulated non-reacting combustor is designed firstly. Applying these profiles as inflow boundary conditions, the effects of realistic swirling inflow on the turbine vane endwall aerothermal characteristics and film cooling performance are numerically investigated through solving the three-dimensional Reynolds-Averaged Navier-Stokes equations coupled with the shear stress transfer ([Formula: see text]) turbulence model. Two swirling orientations (anticlockwise and clockwise) and five swirling core pitch-wise positions (aligned with vane 1 to vane 2) are considered in the current work. The results indicate that the residual vortices in the vane passage are strengthened and move with the swirling core along the pitch-wise direction. The migration of the horseshoe vortex is controlled by this movement. The shrinkage or expansion of the separation line of the horseshoe vortex can be observed under the anticlockwise and clockwise swirling inflow conditions respectively. The anticlockwise swirling inflow results in a larger aerodynamic loss by a 10%–35% increase of the laterally [Formula: see text]. The high Nu region near the pressure side surface enlarges and the area-averaged Nu at [Formula: see text] increases from 2337.9 to 2878.3. For the cases with clockwise swirling inflow, the area of the hot ring is enlarged and the Nu downstream of the row 3 film holes is decreased. As for the film cooling performance, the endwall coverage area shrinks and the phantom cooling area enlarges when the anticlockwise swirling core is aligned with vane 2. The endwall loses the protection from the row 3 film holes and the cooling failure ([Formula: see text]) occurs at [Formula: see text] when the swirling core is aligned with the vane passage. This is an extremely bad phenomenon that should be avoided. Among all cases, the highest endwall area-averaged [Formula: see text] (0.122) is obtained when the clockwise swirling core is aligned with vane 1. The largest endwall coverage area is achieved when the clockwise swirling core is aligned with vane 2.