The flow field inside a rotating smooth radial channel with a triangular shaped cross section is investigated. Test conditions resemble those pertaining to the passages used for the internal cooling of the gas turbine blade's leading edge. Heat transfer data are also available from the literature on the same geometry and at comparable working conditions and have been profitably used for a combined aerothermal analysis. The model consists of a straight smooth channel with an equilateral triangle cross section. The rotation axis is aligned with one of the triangle bisectors. Two dimensional particle image velocimetry (PIV) and stereo-PIV were used in order to characterize the inlet flow (in static conditions) and the rotation-induced secondary flow in the channel cross section at Re = 20,000, Ro = 0.2 and Re = 10,000, Ro = 0.4. A wider range of working conditions (Re = 10,000-40,000, Ro = 0.2-0.6) was explored by means of Reynolds averaged Navier-Stokes (RANS) simulations carefully validated by the available PIV data. The turbulence was modeled by means of the shear stress transport (SST) model with a hybrid near-wall treatment. The results show that the rotation-induced flow structure is rather complicated and show relevant differences compared to the flow models that have been considered thus far. Indeed, the secondary flow turned out to be characterized by the presence of two or more vortex cells, depending on channel location and Ro number. No separation or reattachment of these structures is found on the channel walls but they have been observed at the channel apexes. The stream-wise velocity distribution shows a velocity peak close to the lower apex and the overall flow structure does not reach a steady configuration along the channel length. This evolution is fastened (in space) if the rotation number is increased while changes of the Re number have no effect. Finally, due to the understanding of the flow mechanisms associated with rotation, it was possible to provide a precise justification of the channel thermal behavior

The present work considers the aero-thermal characterization of a rib-roughened cooling channel for the trailing edge of gas turbine blades, and is based on previous findings from a smooth channel configuration. The passage is characterized by a trapezoidal cross section with high aspect-ratio, radial inlet flow, and coolant discharge at both model tip and trailing side, where seven elongated pedestals are installed. In this study, heat transfer augmentation is achieved by placing inclined squared ribs on the channel central portion. RANS simulations with a SST turbulence model were performed using the commercial solver ANSYS CFX®v14. The numerical tool was first validated on the available experimental data and, subsequently, its capabilities were exploited in a wider range of working conditions, namely at higher rotation speed and different channel orientation. In this way it was possible to highlight the effects that ribs and working conditions have on the development of both flow and thermal fields. The results show that rotation and channel orientation produce contrasting effects. On the rib-roughened wall, rotation/orientation generates an increase/decrease of the heat transfer; conversely, on the trailing side region rotation/orientation has a negative/positive effect on the thermal field.

The flow field inside a cooling channel for the trailing edge of gas turbine blades has been numerically investigated with the aim to highlight the effects of channel rotation and orientation. A commercial 3D RANS solver including a SST turbulence model has been used to compute the isothermal steady air flow inside both static and rotating passages. Simulations were performed at a Reynolds number equal to 20000, a rotation number (Ro) of 0, 0.23, and 0.46, and channel orientations ofγ=0∘, 22.5°, and 45°, extending previous results towards new engine-like working conditions. The numerical results have been carefully validated against experimental data obtained by the same authors for conditionsγ=0∘and Ro = 0, 0.23. Rotation effects are shown to alter significantly the flow field inside both inlet and trailing edge regions. These effects are attenuated by an increase of the channel orientation fromγ=0∘to 45°.

The flow field inside a trailing edge (TE) cooling channel for gas turbine blades has been numerically investigated with reference to the effects of channel rotation and orientation. The channel consists of a single passage with high aspect ratio cross-section. The flow entering from the hub is discharged through both the channel tip and inter-pedestal passages at the TE. A commercial 3D RANS solver including a κ–ω SST turbulence model has been used to simulate the isothermal steady airflow at 20000 Reynolds number in the case of static channel and for two rotation numbers (Ro = 0.23, 0.46) at varying the channel orientation with respect to the rotation axis (γ = 0°, γ = 22.5°, γ = 45°). The present work extends a previous experimental analysis performed by the authors on the same channel geometry, the results of which are used to validate the numerical model. Rotation effects are shown to alter significantly the distribution of both the mass flow in the inlet duct and the velocity along the channel height. This causes remarkable modifications of the 3D flow structures in the inter-pedestal passages and, in particular, the disappearance of the horseshoe vortices from the pedestal upstream face. Changing the channel orientation results in an attenuation of the rotation effects in the inlet duct and in the hub region of the TE.