The effect of rotating receiver hole shape on a gas turbine pre-swirl system

Abstract

The life assessment and the efficiency of turbine cooling blades and vanes are seriously affected by the cooling air delivery system of a gas turbine. The pre-swirl system in a gas turbine plays an important role between the stationary and rotating parts to supply enough cooling air at the appropriate temperature at the expense of pressure drop. In the stationary part, the pre-swirl nozzle creates the flow angle in advance of the rotating orifice, called the receiver hole, to minimize energy loss. However, because of the sudden change of direction and area of the flow path, an energy loss occurs at the inlet of the receiver holes. The circumferential velocity at the receiver hole inlet decreases even though the circumferential velocity at the pre-swirl outlet is equal to the tangential velocity of the turbine rotor system. To reduce the energy loss at the pre-swirl system, various shape parameters can be applied to the receiver hole, and the area ratio between the pre-swirl nozzle throat area and the receiver hole cross-sectional area can also be varied considering the structure problem, mass flow rate, and pressure drop. In this study, the shape of the receiver holes and its effects were analyzed using a 3D CFD method that was validated by previous studies including experimental data. The edge shape, inclined angle, area ratio, and number of receiver holes were analyzed with the discharge coefficient, adiabatic effectiveness, and pressure drop. The pre-swirl system perform-ance increased as the area ratio increased, and under fixed area ratio, a large number of smalldiameter receiver holes showed better performance. The receiver hole edge fillet was the most influential shape parameter in pre-swirl performance.