Blade Drag Resistance in Windage Operating of Low Pressure Steam Turbines

On the basis of previous experimental and numerical studies, the windage operation of low-pressure turbine rear stage is investigated. The state of the steam within the rotor channel was correlated to measurements carried out downstream of the blades for different ventilation regimes. Considering very-low-volume flow conditions, the ventilation power was related to the drag force acting on the moving blades. A correlation was identified between the drag coefficient and a Reynolds number relative to the reverse flow height. This correlation can be used in order to predict the power loss of a last-stage moving blade operating at low load.