The Effect of Turbulence on the Heat Transfer in Closed Gas-Filled Rotating Annuli

Abstract

Higher turbine inlet temperatures are a common measure for increasing the thermal efficiency of modern gas turbines. This development leads not only to the need for more efficient turbine blade cooling but also to the requirement for a more profound knowledge of the mechanically and thermally stressed parts of the rotor. For determining thermal stresses from the temperature distribution in the rotor of a gas turbine, one has to encounter the convective transfer in rotor cavities. In the special case of an entirely closed gas-filled rotating annulus, the convective flow is governed by a strong natural convection. Owen and other researchers have found that the presence of turbulence and its inclusion in the modeling of the flow causes significant differences in the flow development in rotating annuli with throughflow, e.g., different vortex structures. However, in closed rotating annuli there is still a lack of knowledge concerning the influence of turbulence. Based on previous work, in this paper the influence of turbulence on the flow structure and on the heat transfer is investigated. The flow is investigated numerically with a three-dimensional Navier–Stokes solver, based on a pressure correction scheme. To account for the turbulence, a low-Reynolds-number k–ε model is employed. The results are compared with experiments performed at the Institute of Steam and Gas Turbines. The computations demonstrate that turbulence has a considerable influence on the overall heat transfer as well as on the local heat transfer distribution. Three-dimensional effects are discussed by comparing the three-dimensional calculation with a two-dimensional calculation of the same configuration and are found to have some impact.