Measurement and Analysis of an Efficient Turbine Rotor Pump Work Reduction System Incorporating Pre-Swirl Nozzles and a Free Vortex Pressure Augmentation Chamber

Abstract

Measurements and analysis of an efficient turbine rotor pump work reduction system is presented. The system features; a “low” radius pre-swirl nozzle comprised of cascade vanes with a radial orientation, equal radius seals downstream of the nozzle, “jumper” tubes across the nozzle, and a free vortex chamber. A scaled experimental rig was utilized to measure and compare with predictions the following; rotor pump work, average tangential velocity exiting the nozzle, tangential velocity variation in the axial and radial direction, free vortex chamber static pressure rise, effect of relative velocity pressure losses, and effect of “pollution” by seal flow. The effort focused on measuring pump work reduction and the efficiency of the pressure augmentation system. In contrast to aero-engines where the main objective of pre-swirl is to reduce cooling air temperature to the blades, the main objective for this industrial gas turbine is to reduce pump work and increase output. An external pre-cooler is utilized to achieve the large cooling air temperature reduction required to maintain disk material limits. The analytical results and rig test data are presented and compared. The results substantiated the following: the level of reduced rotor pump work due to pre-swirl, the static pressure rise in the free vortex chamber, the effect of eliminating “pollution”, and relative velocity pressure losses. CFD analytical results are compared with the rig data.

A new design of vane-shaped hole pre-swirl nozzle

“…where is actual outlet flow angle. By equations (3) and (5), together with ignoring the difference between id and act , can be expressed as…”

“…There have been a large number of experimental and numerical studies on the pre-swirl nozzle as well as the pre-swirl system [1][2][3][4][5][6][7] to understand their flow and heat transfer processes. Meierhofer and Franklin 1 analyzed the influences of nozzle number, vane height and other factors on the flow characteristics in the pre-swirl nozzle, and they were the first to use the pre-swirl effectiveness to characterize the nozzle.…”