CFD Simulation of Showerhead Jet Impingement at Leading Edge of a Gas Turbine Blade

Abstract

The performance of gas turbine improves with increase of turbine inlet temperature and leading edge of the turbine blades are subjected to the highest temperatures. To decrease the temperature, jet impingement technique is used for the leading-edge blade cooling. In this present study, showerhead arrangement is used for the jet impingement cooling. This showerhead arrangement consists of a central jet and it is surrounded by four jets resembling a shower. As the area/region of influence in the showerhead arrangement is hemi-spherical, an improved heat transfer is expected. The cross-section of the jet impinging holes is circular. The study is carried out by varying the Reynolds number from 11000 to 50000 for a jet impinging length of R/2. Steady-state simulations are carried out using commercial CFD code, ANSYS Fluent and turbulence model used is kω-SST. Wall temperature distribution decreases with increase in Reynolds numbers and it is observed to be minimal at the jet impingement point (i.e., stagnation point). Wall temperature distribution of the showerhead arrangement with straight impingement tubes is lesser compared to showerhead arrangement with bended impingement tubes. Mixing of jets prior to impingement on the wall is visualized for showerhead arrangement with bended impingement tubes leading to ineffective cooling for this arrangement. Nusselt number of the showerhead arrangement with straight impingement tubes are higher compared to showerhead arrangement with bended impingement tubes indicating better convective heat transfer.