Modern heavy-duty gas turbines operate with high turbine inlet temperatures and thus require complex secondary air systems to ensure that blades and vanes are supplied with the necessary amount of cooling air. Low-emission gas turbines with a high thermal efficiency require minimum amounts of cooling and sealing air which means that secondary air systems must be designed with extreme accuracy.

In previous papers, the secondary air system of Siemens Vx4.3A gas turbines and the calculation method used for their design were introduced. This paper deals with the calculation of the flow in cooling air passages in rotating hollow shafts with axial throughflow. The paper starts with a derivation of basic equations and a brief review of the work on this topic described in the literature. Then on the basis of these basic equations a simple one–dimensional model is described to predict the three–dimensional flow (losses, flow deflection) in the rotating hollow shafts for different massflow rates. The calculation system is completed by matching the correlations of the simple one–dimensional model to the results of the numerical simulations.

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