Effect of Extended Surfaces on Stator and Rotor Heat Transfer

Rotating machinery like the gas turbine engines consist of surfaces such as the gas turbine disk rotating in presence of stationary surfaces. These stator-rotor spaces are subject to harsh environments due to the high operating temperatures of the engines and the ingress of hot turbine gases. The present study experimentally investigates the heat transfer over the stator and the rotor when cooling air is impinged on the rotor disk to counter the hot gas ingress and cool the stator-rotor assembly. Effect of addition of extended features in form of radial and inclined ribs on the rotor surface has also been studied. The rotor consists of an aluminum disk on which steady state heat transfer measurements have been used to study the heat transfer characteristics. Three different Reynolds numbers (Re) – 3000, 5000 and 8000 for rotation speeds of the disk corresponding to rotational Reynolds numbers (Re¬R) – 7315 and 14630 have been used for the study. Nusselt numbers (Nu) based on the disk diameter were been obtained for the rotor. The Nusselt number increased with the addition of the extended features. It also increased when rotation was imparted to the disk with ribs, however, no enhancement was obtained on further increase in the rotation speed. Also, the maximum enhancement was observed in the case of radial ribs and the Nusselt number decreased with the increase in the inclination angle of the ribs with the radial direction.