Investigation on use of turbulators in internal cooling channels and simulation with rans based turbulence models

Turbulators are the turbulence forming mechanisms used in turbine blade internal cooling channels to improve heat transfer in gas turbine engines. In this study, firstly general cooling issues in gas turbine engines have been discussed and later specifically the use of turbulators in cooling channels of turbine blades have been studied in detail. Then, numerical methods in turbulence modeling and RANS based turbulence models have examined. Finally trapezoidal cooling channels have been modeled, meshed and simulated numerically in ANSYS Fluent. Square cross-section ribs have been placed in upper and lower surfaces of designed two-pass trapezoidal smooth channel. Rib pitch to rib height has taken 12 and blockage ratios (e /Dh) of narrow channel, bend section and large channel have taken respectively 0.078, 0.066 and 0.07. Ribs have been positioned orthogonal to the main flow (90o), then transverse (60°) and V-shaped. Heat transfer enhancements, friction losses and thermal performance comparisons of the rib configurations have been made for three different Reynolds numbers (16.800, 31.800 and 57.200). In addition to this, heat transfer characteristics of 180o bend flow in two-pass channel and extraction-contraction of channel flow with turbulators have also examined due to unequality of channel widths. Four kinds of RANS based turbulence models (RKE model, the SST k-ω model, V2F model and Reynolds stress model) have been used as a tool of numerical simulation. As a result, screenings of secondary flows, velocity vectors, turbulence intensities and distributions of Nusselt numbers have performed for each cooling channel configuration. Furthermore, the obtained results have been compared with the experimental data and the studied turbulence models have been identified in terms of accuracy and convergence whether give similar results with experimental data.